06-5.7 mpi mag starts,, stalls, starts stalls. ran fine last fall

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svb165

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i just this morning had time to get back to it. i reinstalled the fuel pressure tester at the rail shrader valve and started it. it starts okat abot 40 and then fuel pressure drops to 30psi and it quits. re start, same thing. no vacume to call for fuel?? as i mentioned the old AND new iac valve did not move when turning on the key.. but has power to it (key on) when i test with a test light ?
 
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cwella

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svb165 said:
i just this morning had time to get back to it. i reinstalled the fuel pressure tester at the rail shrader valve and started it. it starts okat abot 40 and then fuel pressure drops to 30psi and it quits. re start, same thing. no vacume to call for fuel?? as i mentioned the old AND new iac valve did not move when turning on the key.. but has power to it (key on) when i test with a test light ?
Click to expand...
The fuel pressure drop is the main clue. Check if the pump is losing power or if pressure is falling due to a weak pump, clogged filter, bad regulator, or restricted supply.

The IAC may not visibly move with key-on on some vehicles. Since it has power, check for the ECU control signal and also inspect vacuum leaks, MAP sensor lines, and injector pulse.
 
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svb165

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its got a new fuel pump/cooler, press. regulator and the iac unit.
yep, i need to do a voltage test at the pump and see whats going on there. it seems t shut off, as it drops off right after starting. its got a recent pick up in the tank and a new water/fuel separator
not sure if it has an old style check ball in the top tank fitting or not? i will pull the hose at the seperator/ filter and see how the draw is there with a small pump.
 
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cwella

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svb165 said:
its got a new fuel pump/cooler, press. regulator and the iac unit.
yep, i need to do a voltage test at the pump and see whats going on there. it seems t shut off, as it drops off right after starting. its got a recent pick up in the tank and a new water/fuel separator
not sure if it has an old style check ball in the top tank fitting or not? i will pull the hose at the seperator/ filter and see how the draw is there with a small pump.
Click to expand...
Sounds like you’ve already covered a lot of the usual suspects. Checking the voltage at the pump while it’s running should give you a better idea of what’s happening. The separator/filter test sounds like a good next step too. Hopefully it turns out to be something simple and you’re getting close to having it sorted.
 
alldodge

alldodge

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svb165 said:
i just this morning had time to get back to it. i reinstalled the fuel pressure tester at the rail shrader valve and started it. it starts okat abot 40 and then fuel pressure drops to 30psi and it quits. re start, same thing. no vacume to call for fuel?? as i mentioned the old AND new iac valve did not move when turning on the key.. but has power to it (key on) when i test with a test light ?
Click to expand...
Since it's same time I think something is shutting the pump off (ground from ECM to FP relay, or fuel pump relay. Could hot wire the relay or fuel pump. A ground to the ECM side of the relay or go direct to FP by removing relay and connect direct to contact
 
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svb165

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whitling it down.. Its tough to do some of this stuff without a second set of eyes at times. and im still recovering from removing that frickin cool fuel pac !
another thing i was told to try is,, jumping the oil pressure switch and see if it isnt shutting the pump off after initial start up. that will have wait till the early AM when its cooler.
 
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cwella

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Messages
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svb165 said:
whitling it down.. Its tough to do some of this stuff without a second set of eyes at times. and im still recovering from removing that frickin cool fuel pac !
another thing i was told to try is,, jumping the oil pressure switch and see if it isnt shutting the pump off after initial start up. that will have wait till the early AM when its cooler.
Click to expand...
Whittling it down, it’s tough to troubleshoot some of this stuff without a second set of eyes sometimes. I’m still recovering from removing that darn fuel pump module!

Another thing I was told to try is jumping the oil pressure switch to see if it’s shutting the pump off after the initial startup. That’ll have to wait until early morning when it’s cooler and easier to work on.
 
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svb165

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alldodge said:
Since it's same time I think something is shutting the pump off (ground from ECM to FP relay, or fuel pump relay. Could hot wire the relay or fuel pump. A ground to the ECM side of the relay or go direct to FP by removing relay and connect direct to contact
Click to expand...
You know, i DID replace the dash this spring, so i had much of the wiring apart. i took many pictures and put it back the same way and re checked it over and over. could i have screwed something up there i wonder? EVERYTHING looks to be working fine there. all lights ect..
 

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alldodge

alldodge

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svb165 said:
i just this morning had time to get back to it. i reinstalled the fuel pressure tester at the rail shrader valve and started it. it starts okat abot 40 and then fuel pressure drops to 30psi and it quits. re start, same thing. no vacume to call for fuel?? as i mentioned the old AND new iac valve did not move when turning on the key.. but has power to it (key on) when i test with a test light ?
Click to expand...
Since it's same time I think something is shutting the pump off (ground from ECM to FP relay, or fuel pump relay. Could hot wire the relay or fuel pump. A ground to the ECM side of the relay or go direct to FP by removing relay and connect direct to contact

The oil pressure switch has nothing to do with your fuel pump, you have a MPI so the ECM controls the pump and everything else
 
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