996TT vs. GT2 Fuel Pumps

[KPV]

Hello all,

My 2002 996TT has sat unused for 3 years. It is a modified car with 600 hp. It had very little gas in it at the time of its last use. The last tankful was 100 octane GT100 from Sunoco. The fuel light was on when it was last used. I decided to get it back on the road recently and found it will not start.

I did the following so far:

1. I added drygas and a half tank of 93 octane fuel.

2. I removed the air filter (modified cone filter) and sprayed starter fluid into the velocity stack where the MAF sensor is located. The car started and ran for 5 to 10 seconds.

3. I know I have spark since it ran briefly.

4. I cycled the key on and off about 20 times (not engaging the starter) thinking I would "prime" the system with the fuel pump. The car did not start.

5. I pulled the fuel pump relay and tested it. It is functioning properly.

6. I disconnected the fuel pump harness connector in the front trunk and connected it to a test light. I turned on the car as if to start it and the test light turned on. This means the fuel pump is receiving 12V.

7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise.

8. I am convinced the fuel pump is the culprit.

If you agree with my assessment, please respond. If you think I missed something, please enlighten me.

Doing further research, I found that there are three fuel pumps listed for the 2002 996TT and GT2 in Porsche PET.

There are two listings for the 996TT:

Part #99662010700 (Comment "/LL")

Part #99662010800 (Comment "/RL")

There is a single listing for the GT2:

Part #99662005790

It is my understanding that the GT2 fuel pump has a higher capacity.

So, I have two questions.......................

Q1:

Does the 996GT2 fuel pump have a higher capacity than the 996TT? If so, what are their comparison specs in XXX LPH (Liters per hour) at YY pressure? (Example 200 LPH at 5 bar) If it does, I would probably want to install the GT2 pump since I am already running the 5 bar Fuel Pressure Regulator (as compared to the factory 3.5 bar unit).

Q2:

What is the difference between the two 996TT part numbers listed above and what do "/LL" and "/RL" mean?

I would appreciate any help that anyone can provide.

Thanks,

Ken

[boldis_63]

Hello all,

My 2002 996TT has sat unused for 3 years. It is a modified car with 600 hp. It had very little gas in it at the time of its last use. The last tankful was 100 octane GT100 from Sunoco. The fuel light was on when it was last used. I decided to get it back on the road recently and found it will not start.

I did the following so far:

1. I added drygas and a half tank of 93 octane fuel.

2. I removed the air filter (modified cone filter) and sprayed starter fluid into the velocity stack where the MAF sensor is located. The car started and ran for 5 to 10 seconds.

3. I know I have spark since it ran briefly.

4. I cycled the key on and off about 20 times (not engaging the starter) thinking I would "prime" the system with the fuel pump. The car did not start.

5. I pulled the fuel pump relay and tested it. It is functioning properly.

6. I disconnected the fuel pump harness connector in the front trunk and connected it to a test light. I turned on the car as if to start it and the test light turned on. This means the fuel pump is receiving 12V.

7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise.

8. I am convinced the fuel pump is the culprit.

If you agree with my assessment, please respond. If you think I missed something, please enlighten me.

Doing further research, I found that there are three fuel pumps listed for the 2002 996TT and GT2 in Porsche PET.

There are two listings for the 996TT:

Part #99662010700 (Comment "/LL")

Part #99662010800 (Comment "/RL")

There is a single listing for the GT2:

Part #99662005790

It is my understanding that the GT2 fuel pump has a higher capacity.

So, I have two questions.......................

Q1:

Does the 996GT2 fuel pump have a higher capacity than the 996TT? If so, what are their comparison specs in XXX LPH (Liters per hour) at YY pressure? (Example 200 LPH at 5 bar) If it does, I would probably want to install the GT2 pump since I am already running the 5 bar Fuel Pressure Regulator (as compared to the factory 3.5 bar unit).

Q2:

What is the difference between the two 996TT part numbers listed above and what do "/LL" and "/RL" mean?

I would appreciate any help that anyone can provide.

Thanks,

Ken

I think the pumps have the same specification, but the fuel tanks are different. The tt has 4 WD and a 63l tank while the GT only 2WD and a 92l tank.

So the pumps have different installations, the tt having one piece with the tank level sensor included and the GT2 is separated.

[KPV]

Hello all,

My 2002 996TT has sat unused for 3 years. It is a modified car with 600 hp. It had very little gas in it at the time of its last use. The last tankful was 100 octane GT100 from Sunoco. The fuel light was on when it was last used. I decided to get it back on the road recently and found it will not start.

I did the following so far:

1. I added drygas and a half tank of 93 octane fuel.

2. I removed the air filter (modified cone filter) and sprayed starter fluid into the velocity stack where the MAF sensor is located. The car started and ran for 5 to 10 seconds.

3. I know I have spark since it ran briefly.

4. I cycled the key on and off about 20 times (not engaging the starter) thinking I would "prime" the system with the fuel pump. The car did not start.

5. I pulled the fuel pump relay and tested it. It is functioning properly.

6. I disconnected the fuel pump harness connector in the front trunk and connected it to a test light. I turned on the car as if to start it and the test light turned on. This means the fuel pump is receiving 12V.

7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise.

8. I am convinced the fuel pump is the culprit.

If you agree with my assessment, please respond. If you think I missed something, please enlighten me.

Doing further research, I found that there are three fuel pumps listed for the 2002 996TT and GT2 in Porsche PET.

There are two listings for the 996TT:

Part #99662010700 (Comment "/LL")

Part #99662010800 (Comment "/RL")

There is a single listing for the GT2:

Part #99662005790

It is my understanding that the GT2 fuel pump has a higher capacity.

So, I have two questions.......................

Q1:

Does the 996GT2 fuel pump have a higher capacity than the 996TT? If so, what are their comparison specs in XXX LPH (Liters per hour) at YY pressure? (Example 200 LPH at 5 bar) If it does, I would probably want to install the GT2 pump since I am already running the 5 bar Fuel Pressure Regulator (as compared to the factory 3.5 bar unit).

Q2:

What is the difference between the two 996TT part numbers listed above and what do "/LL" and "/RL" mean?

I would appreciate any help that anyone can provide.

Thanks,

Ken

I think the pumps have the same specification, but the fuel tanks are different. The tt has 4 WD and a 63l tank while the GT only 2WD and a 92l tank.

So the pumps have different installations, the tt having one piece with the tank level sensor included and the GT2 is separated.

Thank you very much for the reply, however, I am not sure that is the only reason for the different pumps. The GT2 pump is $549 retail and the TT pump is $349 retail. That is quite a disparity for it just to be a different pump. I also read references of tuners changing the pump for modified cars to add extra pumping capacity with higher horsepower and greater fueling needs.

So, any definitive answers to both questions???

[Loren]

RL is for RHD (Right Hand Drive) cars and LL is for LHD (Left Hand Drive) cars.

The TT is a 4WD car and the GT2 is 2WD - the gas tanks are different shapes so most of the parts are different.

[KPV]

RL is for RHD (Right Hand Drive) cars and LL is for LHD (Left Hand Drive) cars.

The TT is a 4WD car and the GT2 is 2WD - the gas tanks are different shapes so most of the parts are different.

Loren,

Thanks for your response! Are you the same Loren that is friends with Cary (ERP)? I think he actually chatted with you about this.

Anyway, I realize the TT vs. GT2 tanks are different and therefore, some of the parts, however, is the pump capacity different too? It is conceivable due to the GT2's higher HP value from the factory. They may have upsized the pump. I have read they have a higher capacity, but don't necessarily trust the source. I wanted to somehow get a definitive answer with flow rate specs. Can you help? Do you have this info or know where to get it?

Best regards,

Ken

[Loren]

I don't recall having any conversations with Cary (ERP).

The only thing the GT2 Tech Book says is "The fuel delivery rate of the sucking jet pump/in-tank fuel pump combination has been adapted to the requirements of the 911 GT2 engine."

None of the volume tests in the service manual indicate any difference.

Perhaps RFM knows?

[wross996TT]

My first guess is the hose has ruptured...so the pump is fine, but it is pumping the fuel back into the tank. Do a search as I have posted on this several times.

[KPV]

My first guess is the hose has ruptured...so the pump is fine, but it is pumping the fuel back into the tank. Do a search as I have posted on this several times.

Wross,

"7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise."

When I applied 12V directly to the fuel pump terminals, right from the battery, there wasn't any noise from the fuel pump. I was in a quiet garage and expected to hear a "whir" or some other mechanical noise. Trying repeatedly with direct 12V gave zero response.

Loren,

Thanks for the excerpt. So, it seems it is not totally clear if the pump is more powerful, more efficient, pumps more volume. What is the source you referenced? I am not familiar with that acronym.

Best,

Ken

[wross996TT]

Ken, I read through your post too quickly, sorry....yes quite possible the fuel pump is bad. I have been through 3 of them.

[Loren]

My first guess is the hose has ruptured...so the pump is fine, but it is pumping the fuel back into the tank. Do a search as I have posted on this several times.

Wross,

"7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise."

When I applied 12V directly to the fuel pump terminals, right from the battery, there wasn't any noise from the fuel pump. I was in a quiet garage and expected to hear a "whir" or some other mechanical noise. Trying repeatedly with direct 12V gave zero response.

Loren,

Thanks for the excerpt. So, it seems it is not totally clear if the pump is more powerful, more efficient, pumps more volume. What is the source you referenced? I am not familiar with that acronym.

Best,

Ken

Every year Porsche publishes a technical book that is the changes from the previous model year. These are usually called Service Technik or Service Information books.

When a new model comes out (i.e. the first model year of the new model) the book is very thick and has a great deal of technical detail on the new model.

Many of these books are available here for our Contributing Members.

[KPV]

My first guess is the hose has ruptured...so the pump is fine, but it is pumping the fuel back into the tank. Do a search as I have posted on this several times.

Wross,

"7. I applied direct 12V from battery to the fuel pump terminals on the top of the gas tank and there wasn't any noise."

When I applied 12V directly to the fuel pump terminals, right from the battery, there wasn't any noise from the fuel pump. I was in a quiet garage and expected to hear a "whir" or some other mechanical noise. Trying repeatedly with direct 12V gave zero response.

Loren,

Thanks for the excerpt. So, it seems it is not totally clear if the pump is more powerful, more efficient, pumps more volume. What is the source you referenced? I am not familiar with that acronym.

Best,

Ken

Every year Porsche publishes a technical book that is the changes from the previous model year. These are usually called Service Technik or Service Information books.

When a new model comes out (i.e. the first model year of the new model) the book is very thick and has a great deal of technical detail on the new model.

Many of these books are available here for our Contributing Members.

Loren,

Thanks. You actually misunderstood my question though. I meant the acronym RFM! LOL I found out that RFM is a person! LOL

Anyway, I look forward to RFM's insight if he is available to shed some light on the differences between the TT and GT2 fuel pumps.

Best regards,

Ken

[RFM]

KPV

The pump UNIT is different towards connections in a different fuel tank, the best option is to replace the PUMP itself, you can order a pump in a ROBERT BOSCH service center, the Bosch # is stamped on the pump body. The total cost is 50% lower than the complete Porsche unit, just some work to pull out the faulty pump and push in the new one. There is no manual for this job since it's not a official and approved Porsche accomplicement. Hope it's help.

[KPV]

KPV

The pump UNIT is different towards connections in a different fuel tank, the best option is to replace the PUMP itself, you can order a pump in a ROBERT BOSCH service center, the Bosch # is stamped on the pump body. The total cost is 50% lower than the complete Porsche unit, just some work to pull out the faulty pump and push in the new one. There is no manual for this job since it's not a official and approved Porsche accomplicement. Hope it's help.

RFM,

Thank you for your reply, however, my original questions are still unanswered.

First and foremost, I would like to know if the GT2 pump has a higher capacity, what is the higher capacity, and would it be appropriate to move to the GT2 pump in my 600hp, 5 bar fuel pressure regulated twin turbo car.

Knowing if the GT2 pump has better flow characteristics will allow me to make the right decision.

I hope you can help.

Best regards,

Ken

[RFM]

I have no technical info available here, so i cant give no conclusive answer about the possible different flow characteristics of both pumps. Contact your dealer or Bosch for that info.