2002 GTX DI fuel pressure drops

[clt1meb]

Big thanks to this forum and the members willing to troubleshoot issues. I have been able to bring my 97 GTI back to life by reviewing existing threads. I need help to get my wife's 2002 GTX DI back in shape. It would die after about 30 minutes of running well. Restarted with no problem, but will fail again very quickly. So I replaced the fuel pump with a Quantum Fuel System pump and all new filters. I made and attached a fuel pressure gauge and it registered 27 psi with the lanyard and hit 100 + when running on the trailer. I thought success! I put it in the water and it started great, I idled out through the no-wake zone in the cove, and all was good. Once I got out into the lake, I opened it up and it ran better than before. Great acceleration and maintained 100 + psi fuel pressure. I was celebrating on the way home with a cold beer at idle speed in the no-wake zone. It died once but restarted right away. But fuel pressure is now about 70 psi and idling rough. If I try to accelerate, it goes a little faster but the engine is running rough and sputtering. Fuel pressure stays down around 70 psi. It idles well and did not die again. Made it back to the dock, but now sure what to look into next. Should I replace the fuel pressure regulator on the fuel rail next?

 

[WaarrEagle]

Aftermarket DI fuel pumps are hit and miss, and lots of folks recommend staying away from them. Is it possible the fuel pump drained your battery? Another thing to check is air pressure. Fuel pressure is regulated by air pressure, so if your air pressure is low, your fuel pressure will be low too.

 

[clt1meb]

Aftermarket DI fuel pumps are hit and miss, and lots of folks recommend staying away from them. Is it possible the fuel pump drained your battery? Another thing to check is air pressure. Fuel pressure is regulated by air pressure, so if your air pressure is low, your fuel pressure will be low too.

All true. I was skeptical about after market pump, but I read some good reviews and decided to give it a try. The crazy thing was right off the bat the fuel pump worked like a champ. The fuel pressure measured a steady 105ish. Now it does the 27ish with the key, then holds a steady 70 psi when the engine is running. I suspect my problem is the air pressure regulator. Replacement one is on the way. I did try the soap spray all over to see if that would show an air leak. I will post results.

 

[POPPS]

I have yet to have an aftermarket pump work.

 

[clt1meb]

So the latest is I replaced the air regulator. It still holds at 70 psi??? I am baffled why it went to 105 psi the 1st outing with the new fuel pump, but now only holds at 70 psi. Argg! Any suggestions on what to try next? I can't wait to throw some more $ into this thing.

 

[WaarrEagle]

So the latest is I replaced the air regulator. It still holds at 70 psi??? I am baffled why it went to 105 psi the 1st outing with the new fuel pump, but now only holds at 70 psi. Argg! Any suggestions on what to try next? I can't wait to throw some more $ into this thing.

Check dead head pressure output on the air pump to make sure it is high enough. If that checks out, it points to a bad fuel pump, which is not surprising with an aftermarket unit.

 

[clt1meb]

Check dead head pressure output on the air pump to make sure it is high enough. If that checks out, it points to a bad fuel pump, which is not surprising with an aftermarket unit.

I am kinda thinking the same thing about the fuel pump. I will check the air pump output.