Hey guys,

So I have been troubleshooting an issue with my EVO IX not running for a few months now. The car would start at every turn of the key, run for 10 seconds and die. I figured out that there was no fuel pressure being delivered.

I don't throw any codes at all, what I can do is run a jumper in the harness for fuel pump relay #3 (the one on the firewall) which basically bypasses that relay and the resistor that controls the changes in voltage to the fuel pump when at idle/throttle changes. This sends about 13.8V directly to the pump.

Now I tried replacing that relay, no change. I'm waiting on a used resistor thats on the firewall but I have doubts its going to be my problem.

With my jumper in place I start the car and it will run, however it starts off at 13.8 AFR then just gets progressivley richer, past 11.0 which is as far as my AEM will read. Now I know I'm sending more voltage to the fuel pump that it would normally see at idle but should the fuel pressure regulator not be enough to dump excess back into the tank?

Could my problem be something with the regulator and when the relay is plugged in the car is turning itself off to protect it?

Anyway thanks for any input, this problem is driving me crazy!

 

Try to disconect your MAF. You will have a check engine for that but possibly you should be able to start and rev the car.

Somebody i know had to troubleshot that he could only run with de maf (he did try to swap it)disconnected. He tried a lot of thing but never found the true cause of that. Maybe you could check your IAC too.

 

If the regulator is bad it can cause a low pressure condition which will keep the car from running very long. Basically the pump will prime and build pressure but once the engine is running it can't maintain it. No pressure = no fuel being injected = stall. First make sure you don't have any loose or damage vacuum lines at the fuel pressure regulator. If there are (of course) replace them. Easy and cheap the hose is common.

If that doesn't work it might be a good idea to hook up a fuel pressure gauge to the rail and see what pressure your getting. Stock should be 43.5 psi I believe. Have someone turn the ignition to the 'on' position (not start) and watch the gauge, it should build pressure. If the regulator is going bad the pressure won't be maintained (or build as much as necessary).

Fuel pumps control flow/pressure off voltage and when you jump it, it's basically going to flow as much as possible, which is why your going rich at idle.



hope this helps.

 

I've already been down this road, yes the car will run with the MAF unplugged (not very well although). I've tried changing the MAF and the IAC already.

 

This does help, I think this is closer to where my problem is, I will have to check those vaccum lines. Is there a good way to pressurise that system? I've done a boost leak test but that obviously doesn't hit this fuel system with pressure.

 

When checking the vacuum lines the best way would just be to remove them and inspect them. The lines for the FPR are very short since it is right next to the intake manifold and any damage should hopefully be obvious. Im still leaning towards maybe a bad FPR ......but check the easy /cheap stuff first.

 

I will be checking the hoses tonight for damage, what is the recommended aftermarket FPR for our cars? I was thinking I should get one with a guage output too. My guage pod on the dash has an opening

 

Well, checked over all the vaccum lines again no issues. Replaced the FPR but still having the same problem.

I have the fuel relay resistor coming in hoping that will be the problem, otherwise I really have no idea.

Strange thing I noticed when bypassing the fuel relay #3 and resistor is the car will idle just a bit rich 14.3ish for a while but as soon as it warms up and reaches normal idle it goes to 11.0 and richer and I just shut it off.

What all would be changing with the car hitting normal temp?