accel dfi problem

[Jim Nilsen]

ok, i took the car out for a short run today.so i started it up and let it idle for a good half hour...got it to temp then took it out for a run...i got on it pretty good,spun the motor to about 4800rpm..first time i did that no stumble a couple of minutes later the stumble is there...so i bring it home and let it idle for a minute or two then all of a sudden the fuel pressure drops to like 25lbs..the motor starts to stumble and finally dies..now i let it cool down and start it up again i rap the throttle fuel pressure stays like a rock,after it warms up i rap the throttle again and the fuel pressure goes down when i do that..it comes right back up though..i tried three different fuel pumps and the same thing occurs..im thinking fuel pressure regulator??? what else would cause this only when the motor is warm?? also i have good voltage at the pump, about 13.5v..even when i rap the throttle the voltage stays at 13.5...the fuel pressure is supposed to go up when i stab the throttle,right?? where else should i look ??

My fuel pressure stays the same no matter what rpm or throttle position unless the pickup lost fuel. You may very well have a regulator problem, what kind of regulator do you have and how is your system configured? Is your bypass at the beginning of the rails or the end of the rails? Do you have a vacuum line connected to your regulator and where is the vacuum line connected to the engine if you have one? Is it an adjustable regulator?

It really does sound like a bad regulator. Erratic pressure levels definately can be directly related to a bad regulator most of the time. It would be highly unlikely that you could be continually getting a bad fuel pump.

It may sound like a bunch of work and I have been there with fuel problems so I understand the frustration.

Reconfiguring the the lines may be your best alternative in the long run. Going with a bypass regulator in the back and going with one line to the engine will solve a bunch of other problems that could arise later also. I will never regret redoing my system the way I did even though it cost me more money. The good thing is that you ususally don't need to buy any more line to do it. I really like the Aeromotive regulator and it has never once fluctuated more than a pound one way or the other unless the pickup starved.

It definately sounds like you found the problem, now you have to work on the solution and that can be found in several threads.

Goodluck and if you need anymore help just give a shout.