Fuel system problem/question

[Eternalsolitude]

This vehicle is not the one in my profile, this vehicle is a 1990 Talon Tsi Turbo FWD completely stock setup.

Here's the situation:

Initially when I got the car, it would intermittantly run really rich and choke out. Other times it would run so-so. I replaced the plugs, plug wires, battery, and o2 sensor and still the same symptoms. I made sure I had spark in all the cylinders and then tested the fuel pressure. The pressure reads really high, something like 55psi on average when I put the fuel pressure tester on the return nipple on the fpr. That would make sense then that it runs rich obviously. I figured I had a problem with my fuel return line so I cleaned that out and made sure it was flowing well. Still no fix. I checked my fuel pump, it has juice and works well. I replaced my fuel pump relay, and my fuel pressure regulator. I also put a new MAFS in. Still no fix.

Any suggestions or ideas are great thanks in advance.

 

[steve]

The pressure reads really high, something like 55psi on average when I put the fuel pressure tester on the return nipple on the fpr.

I'm not sure I follow how you checked the fuel pressure. You have to measure from somewhere before the regulator, since it's the FPR that creates the pressure by blocking the flow. If you were measureing 55psi at the return line you have a serious problem. There shouldn't be any sigificant pressure in the return and it would have to be less than the desired pressure in the rail or the regulator can't do it's job.

Steve

 

[Eternalsolitude]

Thanks for the quick response.

So ideally, where do you test the fuel pressure on DSMs?

 

[steve]

The most common place if you don't have an aftermarket FPR with a port for the gauge is via the B&M fuel filter bolt/gauge kit.

Steve

 

[NOMIEZVR4]

Or you can also mount a fuel pressure gauge with an adapter on top of the fuel filter

 

[Eternalsolitude]

Thanks a bunch for the prompt responses there guys, I really appreciate it.

It turns out we had a bad ECM, so after a series of tests, we decided to try another. The fact that the 90 ECMs differ from the 91-94 didn't help the availablitiy of them. Anyway, Car runs great.

 

[steve]

If I hadn't read the whole thread I might have suggested checking the ECU since it's such a common problem and causes the symptoms you described as you now know. Glad you got the problem solved.

Steve