fuel pump issues
01-12-2012, 06:48 PM
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fuel pump issues My fuel pump is not priming when i turn my key. While diagnosing the problem, I got the pump to prime and build fuel pressure by bypassing the fuel pump relay so I know the pump works. The fuel pump relay isn't getting a signal to turn on the fuel pump. Does anyone know what the possible causes might be?
01-12-2012, 10:33 PM
#4
Terminal A7 on the PCM (ASSuming you have a 94+) controls the fuel pump relay. So, it could be that the PCM isn't happy about something or the PCM is **** up or there is a bad connection or broken wire between the PCM and the FP relay.
01-13-2012, 07:26 AM
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01-13-2012, 01:20 PM
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Hahaha....so you can rule out an electrical short here and still not have any fueling issue's during start up.....hmmmm
??Hint: Wont start if switch doesnt get the minimum oil pressure!
Last edited by Uwilllosetomy93lt1; 01-13-2012 at 01:26 PM.
01-13-2012, 02:01 PM
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That is putting the cart before the horse.
The PCM has nothing to do with oil pressure, it's a gauge specific thing.
01-13-2012, 02:16 PM
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OK......guess I'll gtfo then
!!! I tried to help!!
01-13-2012, 02:34 PM
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It still plays no function even when cranking. Shbox is always right.
I just wired up a new engine, there is no oil psi to pcm, only gauges.
Besides, do you know what the crank speed is compared to a running engine? 60 rpm minimum, compared to 600-800 at idle.
Idle when warm psi is around 20-40 on average and depending on the engine specifics.
Now, divide that idle speed psi by 10 and what do we get? 2-4 psi. IIRC the minimum required pressure for everything to be lubed properly is around 8.
If you were correct the PCM would not let ANY engine run if it had a psi minimum required for start.
And to add to that, I've had non OEM pressure sensors that were cheap worthless crap and showed 0 at idle, yet everything still worked.
I just wired up a new engine, there is no oil psi to pcm, only gauges.
Besides, do you know what the crank speed is compared to a running engine? 60 rpm minimum, compared to 600-800 at idle.
Idle when warm psi is around 20-40 on average and depending on the engine specifics.
Now, divide that idle speed psi by 10 and what do we get? 2-4 psi. IIRC the minimum required pressure for everything to be lubed properly is around 8.
If you were correct the PCM would not let ANY engine run if it had a psi minimum required for start.
And to add to that, I've had non OEM pressure sensors that were cheap worthless crap and showed 0 at idle, yet everything still worked.
01-13-2012, 02:48 PM
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It still plays no function even when cranking. Shbox is always right.
I just wired up a new engine, there is no oil psi to pcm, only gauges.
Besides, do you know what the crank speed is compared to a running engine? 60 rpm minimum, compared to 600-800 at idle.
Idle when warm psi is around 20-40 on average and depending on the engine specifics.
Now, divide that idle speed psi by 10 and what do we get? 2-4 psi. IIRC the minimum required pressure for everything to be lubed properly is around 8.
If you were correct the PCM would not let ANY engine run if it had a psi minimum required for start.
And to add to that, I've had non OEM pressure sensors that were cheap worthless crap and showed 0 at idle, yet everything still worked.
I just wired up a new engine, there is no oil psi to pcm, only gauges.
Besides, do you know what the crank speed is compared to a running engine? 60 rpm minimum, compared to 600-800 at idle.
Idle when warm psi is around 20-40 on average and depending on the engine specifics.
Now, divide that idle speed psi by 10 and what do we get? 2-4 psi. IIRC the minimum required pressure for everything to be lubed properly is around 8.
If you were correct the PCM would not let ANY engine run if it had a psi minimum required for start.
And to add to that, I've had non OEM pressure sensors that were cheap worthless crap and showed 0 at idle, yet everything still worked.
Listen bud....just trying to help!! Not gonna get into a pissing contest with you or anyone else for that matter....OK?
01-13-2012, 03:02 PM
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How exactly? He is practically the end all be all of LT1 info.
Ok, here is where you are wrong. It is not about being a winner or loser, or getting into a pissing match over the biggest dick.
It is about giving correct info, seeing as how this is a TECHNICAL forum. Any wrong info should be immediately dismissed. It only hurts the OP by giving bad info.
It's already been shown that oil PSI has nothing to do with starting or the PCM.
How many times must it be said before you realize this?
I haven't wandered into the LT1 section for a year cause of all the ********* and I decide to start reading and posting and it's got even more of you guys than when I gave up.
It is about giving correct info, seeing as how this is a TECHNICAL forum. Any wrong info should be immediately dismissed. It only hurts the OP by giving bad info.
It's already been shown that oil PSI has nothing to do with starting or the PCM.
How many times must it be said before you realize this?
I haven't wandered into the LT1 section for a year cause of all the ********* and I decide to start reading and posting and it's got even more of you guys than when I gave up.
01-13-2012, 03:32 PM
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