Fuel pump runs constantly
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From: The Redneck Riviera
Fuel pump runs constantly
'92 Flareside.
What would cause the fuel pump to start running constantly at initial startup, instead of stopping after a few secs like it should?
There is no fuel pressure sensor on this truck so it's not trying to acheive a certain level of fuel pressure. I understand that the computer controls the pump relay, so what conditions would cause it to act like this?
It doesn't do it all the time and seems to effect whether the truck will start or not. If the pump doesn't stop, then the truck is hard to start. If it does stop like it should, then it fires right up.
I also noticed while trying to get the codes that if the pump continues running the code reader will not work. If it stops, then things work fine, usually. I did have an instance this morning where the pump started in mid scan and stopped the scan.
???
Rob
What would cause the fuel pump to start running constantly at initial startup, instead of stopping after a few secs like it should?
There is no fuel pressure sensor on this truck so it's not trying to acheive a certain level of fuel pressure. I understand that the computer controls the pump relay, so what conditions would cause it to act like this?
It doesn't do it all the time and seems to effect whether the truck will start or not. If the pump doesn't stop, then the truck is hard to start. If it does stop like it should, then it fires right up.
I also noticed while trying to get the codes that if the pump continues running the code reader will not work. If it stops, then things work fine, usually. I did have an instance this morning where the pump started in mid scan and stopped the scan.
???
Rob
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Joined: Mar 2002
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From: Bonita Springs FL
You need a new PCM. Yours is fried. You'll need one from a speed density truck with a 5.8 and an E4OD.
Fuel pump running constantly and not being able to pull codes are two dead giveaways of a bad PCM.
Fuel pump running constantly and not being able to pull codes are two dead giveaways of a bad PCM.
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From: The Redneck Riviera
Thanks, guys.
I suspect that you're right. Along about the time it began this intermittant poor running, the tranny started shifting hard also.
I've examined the vac lines until I know them by heart, the wiring and grounds too. All seem servicable. I tested the TPS and the IAC. There is no EGR or AIR anymore, so I was running out of stuff to look at.
Rob
I suspect that you're right. Along about the time it began this intermittant poor running, the tranny started shifting hard also.
I've examined the vac lines until I know them by heart, the wiring and grounds too. All seem servicable. I tested the TPS and the IAC. There is no EGR or AIR anymore, so I was running out of stuff to look at.
Rob
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From: The Redneck Riviera
Just checked the codes again (KOEO) and got three,
637 - TOT - trans oil temp sensor, sig too high
624 - EPC - electronic pressure control solenoid - circuit failure
And one Continuous Memory code,
512 - ECA - electronic control assembly problem - keep alive memory test failure
The first two look like trans codes, while the last looks like a computer code.
Are the first two also part of the PCM or are there some problems within the tranny?
637 - TOT - trans oil temp sensor, sig too high
624 - EPC - electronic pressure control solenoid - circuit failure
And one Continuous Memory code,
512 - ECA - electronic control assembly problem - keep alive memory test failure
The first two look like trans codes, while the last looks like a computer code.
Are the first two also part of the PCM or are there some problems within the tranny?
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Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
Basic troubleshooting 101: If you find a problem, fix it. Then re-evaluate the whole problem. In this case replace the PCM and then check the codes. You may be pleasantly surprised to find that all your problems have disappeared.
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From: The Redneck Riviera
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From: The Redneck Riviera
I do have the 5.0 one that was in the truck originally. Don't know about the firing order thing tho.
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From: The Redneck Riviera
Yeah, it was an E4OD originally.
But I never drove the truck after I bought it except to get it home. It was in pretty bad shape mechanically. Ran poorly like it was in limp mode, the tranny didn't seem to have 1st gear or OD. So I don't know if the PCM is any good or not. I was thinking I might try it and see, might show if the tranny is OK. At least until I decide what to do. Whether to scrounge up another 15 - 20 year old computer from the junkyard (<$50), buy a reman (which will be a refurbished 15 - 20 year old computer, about $100), or go for the expensive aftermarket chip and Baumann controller (about $1000 total).
In the interests of reliability I suppose I should go for the new parts, or else hit every junkyard I come across and amass a stockpile of old PCM's, keep 2 or 3 in my toolbox.
But I never drove the truck after I bought it except to get it home. It was in pretty bad shape mechanically. Ran poorly like it was in limp mode, the tranny didn't seem to have 1st gear or OD. So I don't know if the PCM is any good or not. I was thinking I might try it and see, might show if the tranny is OK. At least until I decide what to do. Whether to scrounge up another 15 - 20 year old computer from the junkyard (<$50), buy a reman (which will be a refurbished 15 - 20 year old computer, about $100), or go for the expensive aftermarket chip and Baumann controller (about $1000 total).
In the interests of reliability I suppose I should go for the new parts, or else hit every junkyard I come across and amass a stockpile of old PCM's, keep 2 or 3 in my toolbox.
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