Fuel system nightmare! My Boxster used to run so well...

[mprowan87]

I have been dealing with fuel system issues now since day one. I purchased my 986 in November 2011. The very first day I heard a howl from the fuel filler area. For 6 months, I would occasionally hear the howl and also get a P0442 CEL for a minor evap leak. I read a bit about it during that time but never came to anything conclusive. It didn't affect performance, but I knew it would be something to be dealt with sooner than later.

Turns out it was sooner... The past 7 months now I have been having major fuel system issues. I have researched everything I can think of including Diagnostics manuals, Durametric, Pressure tests, etc. but I cannot figure out my problem. I feel I may have multiple problems in the fuel system.

List of symptoms:

-very rough idle most of the time, the whole car shakes, a little gas and it smooths out

-howl sound has moved from the fuel fill area to the area around the pump under dash (only howls when starting or turning off vehicle)

-gas mileage is terrible

-major loss in performance (sometimes it runs better than others but I haven't found a common denominator)

-occasionally engine will rev higher than input of the throttle. It's a sudden change and the DME quickly adapts the FT's

-CEL for Major Evap Leak (P0455)

So far I have done the following in trying to diagnose this. There are so many valves it could relate to, and I just hate to keep "throwing parts at it".:

-Replaced fuel pump relay

-replaced fuel pressure regulator

-cleaned injectors, manifold, etc

-replaced AOS

-replaced oil filler tube

-removed and inspected fuel pump

-removed and inspected charcoal canister/vent valves/vent lines

-removed and inspected fuel pump

-tested fuel pressure at rail (I have video footage of the gauge...)

-durametric- I have video footage of various readings like fuel pressure difference, fuel trims, etc, while it is idling poorly, but could find limited information regarding its meaning)

The fuel pressure diff will climb until it reaches 40ish and then drop to 5-8 and start building again. Is this normal? This was not listed on the nominal durametric values.

Fuel trim is -2.00 for the long term... This is way off of the nominal value.

I completely removed charcoal canister, valves, etc, and have been venting into the wheel well the past two days to narrow the problem. It seems to have not changed anything. It stills operates with as inconsistent performance as before. I read some post about boxster race cars just removing the system so I figured it couldn't hurt for a couple days... I plan on reinstalling it though for the sake of the CEL.

I hope I have covered everything. It's late and my mind is shutting down for the day so let me know if I missed anything. It's a 2000 2.7L. 5 speed. Thank y'all all for your insight. I am ready to have her running like a top again!

Link to durametric video https://www.dropbox.com/s/6a2p94usfyjuc50/summary.mov

Link to video of fuel pressure gauge (sorry it's a little dark) https://www.dropbox.com/s/uzmtog3c8nkn4n0/Fuel%20Pressure%20Gauge.mov

Thanks so much for your help!!

[bar10dah]

Starting out small, have you inspected your gas cap o-ring?

[JFP in PA]

I have been dealing with fuel system issues now since day one. I purchased my 986 in November 2011. The very first day I heard a howl from the fuel filler area. For 6 months, I would occasionally hear the howl and also get a P0442 CEL for a minor evap leak. I read a bit about it during that time but never came to anything conclusive. It didn't affect performance, but I knew it would be something to be dealt with sooner than later.Turns out it was sooner... The past 7 months now I have been having major fuel system issues. I have researched everything I can think of including Diagnostics manuals, Durametric, Pressure tests, etc. but I cannot figure out my problem. I feel I may have multiple problems in the fuel system.List of symptoms:-very rough idle most of the time, the whole car shakes, a little gas and it smooths out-howl sound has moved from the fuel fill area to the area around the pump under dash (only howls when starting or turning off vehicle)-gas mileage is terrible-major loss in performance (sometimes it runs better than others but I haven't found a common denominator)-occasionally engine will rev higher than input of the throttle. It's a sudden change and the DME quickly adapts the FT's-CEL for Major Evap Leak (P0455)So far I have done the following in trying to diagnose this. There are so many valves it could relate to, and I just hate to keep "throwing parts at it".:-Replaced fuel pump relay-replaced fuel pressure regulator-cleaned injectors, manifold, etc-replaced AOS-replaced oil filler tube-removed and inspected fuel pump-removed and inspected charcoal canister/vent valves/vent lines-removed and inspected fuel pump-tested fuel pressure at rail (I have video footage of the gauge...)-durametric- I have video footage of various readings like fuel pressure difference, fuel trims, etc, while it is idling poorly, but could find limited information regarding its meaning)The fuel pressure diff will climb until it reaches 40ish and then drop to 5-8 and start building again. Is this normal? This was not listed on the nominal durametric values.Fuel trim is -2.00 for the long term... This is way off of the nominal value.I completely removed charcoal canister, valves, etc, and have been venting into the wheel well the past two days to narrow the problem. It seems to have not changed anything. It stills operates with as inconsistent performance as before. I read some post about boxster race cars just removing the system so I figured it couldn't hurt for a couple days... I plan on reinstalling it though for the sake of the CEL.I hope I have covered everything. It's late and my mind is shutting down for the day so let me know if I missed anything. It's a 2000 2.7L. 5 speed. Thank y'all all for your insight. I am ready to have her running like a top again!Link to durametric video https://www.dropbox.com/s/6a2p94usfyjuc50/summary.movLink to video of fuel pressure gauge (sorry it's a little dark) https://www.dropbox.com/s/uzmtog3c8nkn4n0/Fuel%20Pressure%20Gauge.movThanks so much for your help!!

Let's start with the fuel pressure. What you are describing (I cannot see the gauge in your video) is not normal. At idle, the car should have a steady pressure reading in the 3.3 +/- 0.2 bar, or 47.9 +/- 2.9 PSIG. You are nowhere near that pressure.

A second critical fuel system test for these cars is delivery, or how much fuel volume is the pump putting out. In 30 seconds, your pump should deliver at least 850 cc of fuel. With the pressure you are describing, I’d be will to bet you are nowhere near that either.

Something is obstructing the fuel flow. When was the last time the fuel filter was changed, and have you pulled it and at least checked it to see if it is blocked?

[mprowan87]

Starting out small, have you inspected your gas cap o-ring?

Yes. Replaced the gas cap... Sometimes after it has been running poorly, There will be a long slow vacuum hiss when removing the gas cap. It lasts a long time compared to the usual "woosh" the pressurized system will normally make... Forgot to mention that... Thanks for your input!

[bar10dah]

Following JFP's recommendations (listen to him, smart guy, knows an awful lot on troubleshooting these cars), I can let you borrow my fuel pressure tester. But, you'd have to drive 70 miles south to pick it up. :) Or, since fuel prices are so high, just spend about $40 and get your own.

[mprowan87]

I have been dealing with fuel system issues now since day one. I purchased my 986 in November 2011. The very first day I heard a howl from the fuel filler area. For 6 months, I would occasionally hear the howl and also get a P0442 CEL for a minor evap leak. I read a bit about it during that time but never came to anything conclusive. It didn't affect performance, but I knew it would be something to be dealt with sooner than later.Turns out it was sooner... The past 7 months now I have been having major fuel system issues. I have researched everything I can think of including Diagnostics manuals, Durametric, Pressure tests, etc. but I cannot figure out my problem. I feel I may have multiple problems in the fuel system.List of symptoms:-very rough idle most of the time, the whole car shakes, a little gas and it smooths out-howl sound has moved from the fuel fill area to the area around the pump under dash (only howls when starting or turning off vehicle)-gas mileage is terrible-major loss in performance (sometimes it runs better than others but I haven't found a common denominator)-occasionally engine will rev higher than input of the throttle. It's a sudden change and the DME quickly adapts the FT's-CEL for Major Evap Leak (P0455)So far I have done the following in trying to diagnose this. There are so many valves it could relate to, and I just hate to keep "throwing parts at it".:-Replaced fuel pump relay-replaced fuel pressure regulator-cleaned injectors, manifold, etc-replaced AOS-replaced oil filler tube-removed and inspected fuel pump-removed and inspected charcoal canister/vent valves/vent lines-removed and inspected fuel pump-tested fuel pressure at rail (I have video footage of the gauge...)-durametric- I have video footage of various readings like fuel pressure difference, fuel trims, etc, while it is idling poorly, but could find limited information regarding its meaning)The fuel pressure diff will climb until it reaches 40ish and then drop to 5-8 and start building again. Is this normal? This was not listed on the nominal durametric values.Fuel trim is -2.00 for the long term... This is way off of the nominal value.I completely removed charcoal canister, valves, etc, and have been venting into the wheel well the past two days to narrow the problem. It seems to have not changed anything. It stills operates with as inconsistent performance as before. I read some post about boxster race cars just removing the system so I figured it couldn't hurt for a couple days... I plan on reinstalling it though for the sake of the CEL.I hope I have covered everything. It's late and my mind is shutting down for the day so let me know if I missed anything. It's a 2000 2.7L. 5 speed. Thank y'all all for your insight. I am ready to have her running like a top again!Link to durametric video https://www.dropbox.com/s/6a2p94usfyjuc50/summary.movLink to video of fuel pressure gauge (sorry it's a little dark) https://www.dropbox.com/s/uzmtog3c8nkn4n0/Fuel%20Pressure%20Gauge.movThanks so much for your help!!

Let's start with the fuel pressure. What you are describing (I cannot see the gauge in your video) is not normal. At idle, the car should have a steady pressure reading in the 3.3 +/- 0.2 bar, or 47.9 +/- 2.9 PSIG. You are nowhere near that pressure.

A second critical fuel system test for these cars is delivery, or how much fuel volume is the pump putting out. In 30 seconds, your pump should deliver at least 850 cc of fuel. With the pressure you are describing, I’d be will to bet you are nowhere near that either.

Something is obstructing the fuel flow. When was the last time the fuel filter was changed, and have you pulled it and at least checked it to see if it is blocked?

Yes, I felt the fuel pressure readings were askew as well. I could not seem to get consistent pressure readings in relation to key cycles... I did not jumper the relay though... Switching the key on and off should produce the same results as the jumper, correct?

Secondly, were do I go about disconnecting the fuel return line in order to measure flow? I need to do this...

I replaced the fuel filter about a month before these issues started occurring... Is it possible to get a bad fuel filter? It was from Pelican Parts... I suppose pulling it out and inspecting it would not hurt... I will do that when I measure fuel flow, hopefully tonight...

IMO, if fuel filter is okay, it must be due to a bad fuel pump or vent valve that sits next to the fuel pump access hole...??? Thanks for your input!

[mprowan87]

Following JFP's recommendations (listen to him, smart guy, knows an awful lot on troubleshooting these cars), I can let you borrow my fuel pressure tester. But, you'd have to drive 70 miles south to pick it up. :) Or, since fuel prices are so high, just spend about $40 and get your own.

Thanks for the offer! I rented one from O'Reilly's this time, but plan on purchasing the next one, now that I have experience with the necessary valves. 70 miles south eh; I always enjoy hearing from some Porsche folks from Alabama! Thanks for all your help!

[bar10dah]

Ah crap, I just noticed you did check for fuel pressure already. Sorry. Thought I was helping.

If you can't figure it out, I read some other folks had good experiences at http://momentummotorworks.com/.

[JFP in PA]

I have been dealing with fuel system issues now since day one. I purchased my 986 in November 2011. The very first day I heard a howl from the fuel filler area. For 6 months, I would occasionally hear the howl and also get a P0442 CEL for a minor evap leak. I read a bit about it during that time but never came to anything conclusive. It didn't affect performance, but I knew it would be something to be dealt with sooner than later.Turns out it was sooner... The past 7 months now I have been having major fuel system issues. I have researched everything I can think of including Diagnostics manuals, Durametric, Pressure tests, etc. but I cannot figure out my problem. I feel I may have multiple problems in the fuel system.List of symptoms:-very rough idle most of the time, the whole car shakes, a little gas and it smooths out-howl sound has moved from the fuel fill area to the area around the pump under dash (only howls when starting or turning off vehicle)-gas mileage is terrible-major loss in performance (sometimes it runs better than others but I haven't found a common denominator)-occasionally engine will rev higher than input of the throttle. It's a sudden change and the DME quickly adapts the FT's-CEL for Major Evap Leak (P0455)So far I have done the following in trying to diagnose this. There are so many valves it could relate to, and I just hate to keep "throwing parts at it".:-Replaced fuel pump relay-replaced fuel pressure regulator-cleaned injectors, manifold, etc-replaced AOS-replaced oil filler tube-removed and inspected fuel pump-removed and inspected charcoal canister/vent valves/vent lines-removed and inspected fuel pump-tested fuel pressure at rail (I have video footage of the gauge...)-durametric- I have video footage of various readings like fuel pressure difference, fuel trims, etc, while it is idling poorly, but could find limited information regarding its meaning)The fuel pressure diff will climb until it reaches 40ish and then drop to 5-8 and start building again. Is this normal? This was not listed on the nominal durametric values.Fuel trim is -2.00 for the long term... This is way off of the nominal value.I completely removed charcoal canister, valves, etc, and have been venting into the wheel well the past two days to narrow the problem. It seems to have not changed anything. It stills operates with as inconsistent performance as before. I read some post about boxster race cars just removing the system so I figured it couldn't hurt for a couple days... I plan on reinstalling it though for the sake of the CEL.I hope I have covered everything. It's late and my mind is shutting down for the day so let me know if I missed anything. It's a 2000 2.7L. 5 speed. Thank y'all all for your insight. I am ready to have her running like a top again!Link to durametric video https://www.dropbox.com/s/6a2p94usfyjuc50/summary.movLink to video of fuel pressure gauge (sorry it's a little dark) https://www.dropbox.com/s/uzmtog3c8nkn4n0/Fuel%20Pressure%20Gauge.movThanks so much for your help!!

Let's start with the fuel pressure. What you are describing (I cannot see the gauge in your video) is not normal. At idle, the car should have a steady pressure reading in the 3.3 +/- 0.2 bar, or 47.9 +/- 2.9 PSIG. You are nowhere near that pressure.

A second critical fuel system test for these cars is delivery, or how much fuel volume is the pump putting out. In 30 seconds, your pump should deliver at least 850 cc of fuel. With the pressure you are describing, I’d be will to bet you are nowhere near that either.

Something is obstructing the fuel flow. When was the last time the fuel filter was changed, and have you pulled it and at least checked it to see if it is blocked?

Yes, I felt the fuel pressure readings were askew as well. I could not seem to get consistent pressure readings in relation to key cycles... I did not jumper the relay though... Switching the key on and off should produce the same results as the jumper, correct?

Secondly, were do I go about disconnecting the fuel return line in order to measure flow? I need to do this...

I replaced the fuel filter about a month before these issues started occurring... Is it possible to get a bad fuel filter? It was from Pelican Parts... I suppose pulling it out and inspecting it would not hurt... I will do that when I measure fuel flow, hopefully tonight...

IMO, if fuel filter is okay, it must be due to a bad fuel pump or vent valve that sits next to the fuel pump access hole...??? Thanks for your input!

Believe it or not, there is even a spec for fuel pressure in these cars when they are not running: 3.8 +/- 0.2 bar; which is even higher than the idle fuel pressure.

Normal method to check fuel delivery is to disconnect the fuel line under the car at the fuel filter or at the return line (which is under one of the removable panels near the front of the engine; if you have access to a Bentley manual, it has pictures) so that you can catch the fuel in a measuring container. As your problems started just after installing a new filter, I would start there. It is also possible to check fuel delivery volume at the fuel rail by disconnecting it and routing it to a line that runs to the collection container, but the under the car method works fine and does not require a special routing line to run the test.

And yes, there are bad filters, right out of the box……

I would also try running the fuel pressure test with the gas cap off; yes, that may throw a “large vacuum leak” code, but I would want to see if the fuel pressure changes when the cap is removed.

[mprowan87]

Less than 300 cm^3 in 30 seconds!!!!Fuel filter seems ok. I removed it and blew through it in direction of flow... I could blow steady through it. There was some restriction - I couldn't blow full force through it... I know this is a rudimentary way of testing it but its my best option at the moment...300 cm is a lot less than the nominal 850!!!! Bad pump? I collected from the return line under car. Thanks

[mprowan87]

Update. I tested flow from connection before filter. It put over 1 L in 30 sec!!!!I went back and tested at the return line again and got about 275 ml again!!!Advice? Is there supposed to be loss in flow throughout the system or does this sound like a blockage? Thanks

[JFP in PA]

It sounds like a blockage of some sort, the return line should also be at least 850 cc in 30 seconds.

[mprowan87]

It sounds like a blockage of some sort, the return line should also be at least 850 cc in 30 seconds.

Just to verify... The engine should be off while measuring the flow, correct? I know the pressure regulator is not operating without vacuum...I am in the process of pulling the intake manifold, fuel rails, etc so I can track down this issue.I also have a new fuel pump and filter ordered to be on the safe side of things.Where are the likely places that a blockage might be besides the filter?I am under the impression that the fuel routes from the pump to the filter, then up the drivers side of the engine bay and around the back to Bank 1 (passenger) fuel rail, then across the front of the motor to Bank 2 fuel rail. From there the regulator releases fuel to the return line to the point where I measured insufficient flow from. Am I missing anything important in my understanding of the path the fuel takes?Thank you very much for taking the time to assist me with this!

[JFP in PA]

That is pretty much how the system functions. You should have as much fuel delivery at the return line as at the filter. While we are on the subject, have you checked your fuel pressure regulator for being involved in the noise you hear at start up? Reason I ask is your earlier comment about the fuel pressure swinging from high to low and then building back up sounds like it could be some sort of blockage, or it could also be related to the pressure regulator opening and abruptly closing when it should not be doing that:

While I hate to be throwing in more possibilities at the 11th hour, if the regulator were to "dump" the fuel rail pressure, nearly all the fuel volume would suddenly be passing into the return line, which could be the source of the sound you hear as it heads back to the tank. Unfortunately, there are very few tests to check the regulator, but one common rule of thumb is if If the operating pressure is below 35psi, or fluctuates wildly, and the fuel pump seems otherwise fine, it’s probably a good bet that the regulator is bad. If you pull off the vacuum connection and there is fuel dribbling from the nipple, the diaphragm inside has failed and the regulator must be replaced. The fuel pressure regulator could also explain why the return delivery rate is so low.

[mprowan87]

That is pretty much how the system functions. You should have as much fuel delivery at the return line as at the filter. While we are on the subject, have you checked your fuel pressure regulator for being involved in the noise you hear at start up? Reason I ask is your earlier comment about the fuel pressure swinging from high to low and then building back up sounds like it could be some sort of blockage, or it could also be related to the pressure regulator opening and abruptly closing when it should not be doing that:

While I hate to be throwing in more possibilities at the 11th hour, if the regulator were to "dump" the fuel rail pressure, nearly all the fuel volume would suddenly be passing into the return line, which could be the source of the sound you hear as it heads back to the tank. Unfortunately, there are very few tests to check the regulator, but one common rule of thumb is if If the operating pressure is below 35psi, or fluctuates wildly, and the fuel pump seems otherwise fine, it’s probably a good bet that the regulator is bad. If you pull off the vacuum connection and there is fuel dribbling from the nipple, the diaphragm inside has failed and the regulator must be replaced. The fuel pressure regulator could also explain why the return delivery rate is so low.

So is the regulator open or closed when no vacuum is on it? The engine is supposed to be off when measuring flow, correct?

I replaced the regulator with a dealer ordered part last month... The old one had a broken screen on it when I pulled it out... It seems like the car briefly ran a little better, but since performance seems to fluctuate so much, it is hard to tell... Hmmm, Maybe blockage around the area?? I am pretty sure I accounted for all the pieces of the old regulator (orings, screen bits, etc.) But I am about to go check out this area well!!!

What function does the valve that sits on top of the fuel pump access hole serve? It is either this or the pump/level sender that is making the audible noise at shut down and start up. Its like a slow pressure releasing howl, almost sounds like a police siren, coming from dead center of the dash... It happens every now and then, usually when tank is approaching low fuel light level or after fill up...

Thanks!

Edited January 16, 2013 by mprowan87

[JFP in PA]

The car should hold 3.8 bar pressure when it is not running, 3.2 at engine idle. All flow measurements are with the engine off for safety reasons, plus the engine would not run well, if at all, while doing a fuel delivery test as it would be fuel starved.

The regulator is vacuum operated, throttling back the fuel delivery and pressure (opening) under high vacuum signal (idle, cruise, or deceleration) and stepping up fuel delivery(closing) under low vacuum signal (open throttle for power) or during engine start. It essentially is bleeding off excess fuel to the return line when not required by the engine.

If you are referring to the round plastic "turret" where the fuel supply line connects, it is just part of the fuel level sender unit, which also includes the tank vent line and fuel return line, and extends down into the tank.

[mprowan87]

The car should hold 3.8 bar pressure when it is not running, 3.2 at engine idle. All flow measurements are with the engine off for safety reasons, plus the engine would not run well, if at all, while doing a fuel delivery test as it would be fuel starved. The regulator is vacuum operated, throttling back the fuel delivery and pressure (opening) under high vacuum signal (idle, cruise, or deceleration) and stepping up fuel delivery(closing) under low vacuum signal (open throttle for power) or during engine start. It essentially is bleeding off excess fuel to the return line when not required by the engine. If you are referring to the round plastic "turret" where the fuel supply line connects, it is just part of the fuel level sender unit, which also includes the tank vent line and fuel return line, and extends down into the tank.

The "turret" is directly on top but there is also a line with a valve on it that is right next to the sending unit. What does this valve do?Update: I have the entire intake manifold off. I have removed all the lines between the two points I measured flow (filter, long line to bank 2 rail, fuel rails/connecting hose, and short return line under the regulator). The lines seem to all have slight restriction, but I don't think it is abnormal, because I see a couple of restrictor holes built into the fittings. I blew about 80PSI through them and no debris of any type came out. Tomorrow I plan on measuring flow, by adding 1 part at a time from the pump and see where the losses are occurring. Also, the new fuel filter is a little less restrictive than the 3 month old one but has not had any fuel in it yet.So I have two more questions and hopefully I will conclude my diagnoses.1. The pressure regulator (recently replaced with OEM part), when uninstalled, seems to be closed. I cannot blow any air through the inside hole (hole that exits to the return line). Could the brand new pressure regulator be bad? Is there an underlying problem that would be ruining my pressure regulators? If I am understanding your last post correctly, the regulator should be opened when it is uninstalled (high vacuum, about 1 BAR absolute atmospheric pressure).2. Roughly what kind of fuel volume should I expect from the line before the filter. Mine was putting out over 1 liter in 30 sec (seemed high to me at first), but after seeing all the restrictions the fuel must travel through before the return line, I would guess that output at the filter location would have to be substantially higher than 850 cm^3.Thank you so much for your assistance and time. Some of the information you are providing is nowhere to be found online, so hopefully this thread will help some folks!

[JFP in PA]

The fuel pressure regulator is closed when the car is not running (no vacuum). This functions as a shut off or check valve for the return side of the system to maintain pressure in the fuel rails. If the regulator did not do this, fuel pressure would bleed off via the return line, and momentarily make the care hard to restart, particularly when hot. When you run the fuel delivery test (engine off), the fuel flow from the pump opens the regulator, allowing the fuel into the return line.

The fuel delivery rate out of the line leading to the fuel filter should be at least 850 cc or more. The “standard” delivery test (OEM service manual method) is done off the fuel return line, so you are seeing the entire fuel system delivery (pump, filter, regulator, fuel rails, fuel lines, etc.). If the return line flow is in bounds, everything else has to be OK by default.

You should see three lines coming off the top of the fuel pump, one is fuel out from the pump (the turret), and the other two are the fuel return line and the tank vent line to the EVAP canister system. The main out line also has a check valve at the top of the pump to hold pressure while the car is sitting, otherwise pressure would bleed backwards into the tank, and you would have the same hot start issues that a bad pressure regulator would cause.

On modern cars, the entire fuel system is a closed loop to prevent any hydrocarbon leaks to the atmosphere. When the engine is off, the system is entirely sealed. Any vapors generated in the tank are routed to the EVAP canister and stored in activated carbon. When the car starts, a small controlled amount of outside air is bled into the EVAP canister, across the carbon bed to pick up trapped vapors, to the tank vent, and into a purge line system that leads to a small valve at the intake manifold. When the car is running, these vapors are let into the intake at a controlled rate and burnt, so nothing escapes to the atmosphere. This EVAP purge system also acts as a fuel tank vent line to limit the vacuum level in the fuel tank, otherwise the pump would not be able to draw, and actually prevent excess vacuum from collapsing the plastic fuel tank. While somewhat overly complicated, the system is quite functional.

[mprowan87]

Update:After almost 2 months of downtime, I finally got the car back together last week (had several projects I was working on while it was down).In regards to the fuel system, I removed and tested all lines/rails/regulator, cleaned and rebuilt injectors, replaced fuel filter, replaced all crankcase vacuum lines/intake vacuum lines/sensor orings on block (knock, oil pressure, etc)/intake plenum boots/intake manifold gaskets.The car still runs lean. Through process of elimination, I have narrowed it down to the fuel pump. In correlation with what JFP in PA said, it now sometimes takes a long crank cycle to fire (hot or cold), and I suspect the pressure is leaking down at the check valve or internally. The new pump will be here tomorrow or Tuesday. I will have an entirely new fuel system by the time this is finished, but hopefully it will save me some trouble down the road and I have sure learned a lot. JFP in PA; thank you so much for all your advice. The detailed information you provided me has been invaluable in my endeavor. I hope this thread can help others, as there is not much comprehensive information on the fuel system online. I will verify that the fuel pump resolves my issue after I get it installed. I feel certain it will though because it is all that is left. Thanks!

The fuel pressure regulator is closed when the car is not running (no vacuum). This functions as a shut off or check valve for the return side of the system to maintain pressure in the fuel rails. If the regulator did not do this, fuel pressure would bleed off via the return line, and momentarily make the care hard to restart, particularly when hot. When you run the fuel delivery test (engine off), the fuel flow from the pump opens the regulator, allowing the fuel into the return line. The fuel delivery rate out of the line leading to the fuel filter should be at least 850 cc or more. The “standard” delivery test (OEM service manual method) is done off the fuel return line, so you are seeing the entire fuel system delivery (pump, filter, regulator, fuel rails, fuel lines, etc.). If the return line flow is in bounds, everything else has to be OK by default. You should see three lines coming off the top of the fuel pump, one is fuel out from the pump (the turret), and the other two are the fuel return line and the tank vent line to the EVAP canister system. The main out line also has a check valve at the top of the pump to hold pressure while the car is sitting, otherwise pressure would bleed backwards into the tank, and you would have the same hot start issues that a bad pressure regulator would cause. On modern cars, the entire fuel system is a closed loop to prevent any hydrocarbon leaks to the atmosphere. When the engine is off, the system is entirely sealed. Any vapors generated in the tank are routed to the EVAP canister and stored in activated carbon. When the car starts, a small controlled amount of outside air is bled into the EVAP canister, across the carbon bed to pick up trapped vapors, to the tank vent, and into a purge line system that leads to a small valve at the intake manifold. When the car is running, these vapors are let into the intake at a controlled rate and burnt, so nothing escapes to the atmosphere. This EVAP purge system also acts as a fuel tank vent line to limit the vacuum level in the fuel tank, otherwise the pump would not be able to draw, and actually prevent excess vacuum from collapsing the plastic fuel tank. While somewhat overly complicated, the system is quite functional.

[4agdtym]

I know you removed the carbon canister. I've heard that sometimes the carbon pellets get out of the cannister and block the return line to the intake.

[griggsat]

This has been an excellent thread!  Can we get a final status on this?  Did the fuel pump solve the problem?  

Thanks!

[wvicary]

How did you test for a vacuum leak? It sounds to me like you have a leak in the EVAP control system.

[mprowan87]

The fuel pump did solve the problem.  Some of the other symptoms were caused by an intermittent vacuum leak on the lower portion of the oil filler tube (the end that goes into the engine).

 

I tested for the vacuum leak with a homemade smoke machine.

[1schoir]

How do you make a "homemade smoke machine" and how does it compare to the big $$ commercial units?

 

Regards, Maurice.

[mprowan87]

Parts needed to make a "homemade smoke machine":

 

-Fog machine (the type people use for halloween props)  (can be found on eBay for cheap)

-Aquarium Air Pump (Walmart or Amazon)

-Cooler ($5 bucks at the thrift store)

-Vacuum hose (about 13 feet)

-2x Metal fittings that will fit into the vacuum hose (needs to be somewhat heat resistant)

-1 Gallon of Fog Solution (eBay)

-Surge Protector (to plug fog machine and aquarium pump into)

 

I bolted the fog machine to the top of the cooler and ran some vacuum hose from the output of the fog machine to a fitting that I drilled and pushed into the side of the cooler.  I then bolted the aquarium air pump to the inside of the cooler with its air line running to another fitting which exits the cooler.  Attached to the outside of the second fitting, I ran about 10 feet of vacuum line which attaches to a vacuum line on the engine.

 

To use, I put ice in the bottom of the cooler to increase the density of the fog.  Run the fogger for about 30 seconds to fill the cooler with fog, then plug in the air pump and the fog is pumped into the intake system.

 

Obviously the car should not be running when conducting the test.

 

As far as how it compares to an expensive commercial unit, I cannot say, because I have never used one.  I would imagine the commercial units would put more pressure in the intake which would make finding leaks easier, but the fish tank air pump provided enough pressure for me to find my leak.

 

I would estimate this setup cost me about $75-$100 after it was all said and done with.  Much better than the $800 you would shell out for a commercial one.