986 Boxster S cranks but no start

[Andrew Howell]

Hello,

 

I have a 2001 Boxster S 6-speed that left me stranded a few times and now refuses to start.  There were two incidents where the car refused to start after running for a while so I first thought it was crank position sensor but then it refused to start at all so I thought maybe fuel pump.  I have now replaced both the fuel pump and cps in the past two weeks but the car still refuses to start, just cranks.

 

When i took out the old crank position sensor, it had a good amount of fine metal filings stuck to the end.  Any thoughts where those came from?  I'm quite sure the pressure plate has a crack in it but the clutch hasn't started slipping yet.

 

When I installed the new crank position sensor, the car seemed to want to start and sort of puffed a few times but then just went back to cranking.  When I turn the key to the on position I do see the tach raise up to about the 100 rpm marker and sit there while the car cranks, so I assume that is the "tach bounce" I've read about.  

 

I do have a durametric cable but I'm not seeing any obvious codes.  I did see a message at one time while cranking saying the immobilizer was not in a ready state but I havn't been able to reproduce that message again.

 

Any ideas or suggestions would be much appreciated.  I'm feeling a bit defeated by this issue.  Thank you in advance!

 

 

[JFP in PA]

"I did see a message at one time while cranking saying the immobilizer was not in a ready state but I haven't been able to reproduce that message again."

 

That is very concerning, that unit will paralyze the car if it is unhappy, so I would start there, pulling the unit and looking for evidence of corrosion, water damage, and check the glass fuse in the unit itself.

[Andrew Howell]

Thanks for the quick reply, JFP.  I have examined the immobilizer closely and there is no visible damage and both the fuses appear to be in tact.  I still have the seat unbolted so I can check again but I even cleaned the connections with sand paper and alcohol just to be sure.

 

I strongly suspect that the fuel pump is not getting power but I have not been able to confirm this.  I have tried to jump the relay but I never hear any noise from the fuel tank when i turn the ignition to the on position.  I tested the original pump that I removed from the car and confirmed it runs fine when I hook it directly to a battery.  

 

Perhaps there is another sensor that is keeping the immobilizer from sending power to the fuel pump?  I have read about bad cam position sensors but I'm unsure if they will cause these symptoms.  I'm thinking of looking there next maybe?

 

Thanks again for the suggestions!

[JFP in PA]

The immobilizer shuts off both the fuel and ignition systems to prevent theft of the car.  The CPS does the same thing if it does not sense the engine rotation.

 

When you jump the fuel pump relay, the immobilizer is out of the picture, so if you do not hear the pump running when it is jumped, you have a fuel pump issue.  Using a multi meter or Power Probe, you can test the fuel up connector at the tank to see if it goes hot when cranking the engine.

[Andrew Howell]

Just got the car started! 

 

I didn't realize that jumping the fuel pump relay bypasses the immobilizer.  That makes a lot of sense now and got me thinking about what else could be cutting power to the fuel pump.  Not much else in that equation so I went back over the basics again.  I first checked for voltage at the fuel pump relay and confirmed that I did not see any voltage when cranking the car. 

 

Next down the line would be the fuse box so I looked at the fuse box again and went to pull the fuel pump fuse, a 25 amp fuse in position C4.  I was shocked when I looked and it was completely missing!  DOH!  I did pull all the fuses about a week ago in a fit of desperation so perhaps I walked away with it to check for continuity or something and put it down somewhere?  I have no idea where it went as its nowhere to be found in the car (apparently cannabis can effect the memory.)

 

And that doesn't explain why it wasn't starting before I pulled the fuses.  Perhaps the original CPS was bad as well?  I tested the old fuel pump and it seems fine so my money is on that CPS.  I guess I could put it back in the car to see if goes back to crank no start but at this point I'm very glad to have the car running.  I have a car friend arriving tomorrow for a visit from across the country and the weather is perfect for some mountain and costal road carving with the top down.  I was really worried that he was going to miss the opportunity to experience this amazing car that I've really been enjoying for the past few years.  

 

Thank you very much for the prompt responses, JFP.  I couldn't have done it without your added info and I can't tell you how much I appreciate it!