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Discussion Starter · #1 ·
I think my regulator is out on my 90 5.2 tbi. I used to put the key on the on position and I could hear the fuel pump kick in, preassurize the line, then kick off until I turned the engine on. Now it doesn't turn off, it keeps running, like maybe the regulator is staying open. If i pinch the return line, the pump will kick off, like it used to do before. My questions are:

1) is the regulator out (seems like it to me)

2) what symptoms would I see with this? (the injectors are seem to be staying open for a long time at idle, 3.5-4;2 ms, and the engine runs rich through about 2000 rpm)

I would think that if the regulator is out, there would be insufficient preassure and there should be a lean condition. Any help would be great!

james

 

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Well, your description of the fuel pump running all the time is strange. The computer is supposed to turn off the fuel pump within 2 to 3 seconds after there is NO signal from the distributor. The pump will continue to run all the time when the computer sees the distributor turning using the pulses from the hall device(pick-up) in the distributor. I have posted some info(theory) from the service manual below. I would think that if the fuel pump continues to run then you have a sticky ASD relay, wiring problem or a bad computer. The fuel pump or computer have no way of knowing the fuel pressure so the pump is not controlled by the pressure regulator. Double check this fuel pump continuing to run and get back to us. In the mean time I would not replace the regulator.

Theory
The Auto Shut Down (ASD) Relay controls power to the ignition coil, fuel injectors, and electric fuel pump. Controlled by the Single Board Engine Controller (SBEC) the ASD supplies power to the ignition coil, fuel injectors, and electric fuel pump at all times when the ignition switch is in the START position. When the ignition switch is in the RUN position and the SBEC is receiving reference signals from the distributor, power will also be supplied. If there is no reference signal after two seconds the SBEC will de-energize the ASD and no power will be supplied to the ignition coil, fuel injectors, or electric fuel pump.
 
G

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your truck will idle fine but will fail when you accelerate if you have fuel pressure problems. I had a failure with my regulator. I went and got a fuel pressure tester to diagnose the problem. I'm not sure how the regulator correlates with the fuel pump's initial pressurization.
 

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Discussion Starter · #4 ·
Thanks Chump. I'll check the relay. Of course, I'll give you an update. Your theories are always welcome. I was thinking about getting a tester, but i'm not sure if it's one of the things you rent or have to buy.
 

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Hey Jaamz did you ever try and get that comp reprogrammed to work better with the new motor, maybe the comp is going nut's, see if it still does it if you pull the batt and reconnect
 

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Discussion Starter · #6 ·
Hey Marty,

I can't get the computer reprogrammed without pulling it out and sending it to JET. They say it's expensive, like $450 or something like that, because of the year model it's encased in gel. And there is no guarantee on it, if it didn't work, I would just have to send it back for re-reprograming. It might be a bad computer, but i'm not getting any bad codes on the scanner. I'll check a few more things on it. But a new computer would be nice, at least it would eliminate one more possibility.

james
 
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