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Car Wont Stay Running

pittzy23

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Having an odd issue all of the sudden. came back from a short vacation and went to start my car (drove it before I left. changed nothing) and it turns over and dies pretty much immediately. Assuming a fueling issue, I watched fuel pressure during the starting process, which does build pressure and almost immediately drops to zero (0) psi. using a FPDM bypass module (used to empty fuel tank when putting the car in accessory mode) i confirmed that the fuel pumps are running / can hold fuel pressure. Just seems when hooking into the FPDM the car is not holding / demanding fuel? I plan to just buy another FPDM module just to rule that out, but thought it worth asking if anyone has any other recommendations / troubleshooting steps.
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Cory S

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So it primes, but pump(s) fail to turn on again after start-up….
 
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pittzy23

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So it primes, but pump(s) fail to turn on again after start-up….
yes that seems to be the case. when bypassing the FPDM the pumps run continuously.
 

Cory S

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pittzy23

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Well still no luck. swapped the FPDM and still getting the exact same result. fuel pumps prime, car turns over, and then dies right away. cant imagine an injector / spark plug issue (all of them bad at the same time very unlikely), car has half a tank in it so the pumps arent running dry. fuel shouldnt be old (ran fine on the first half of the tank. filled a few weeks ago.) I suppose I could check the MAF but it has been fine / untouched the whole year. will take another look at the vacuum lines but i know those are also unchanged. I will Venmo whoever suggests the correct fix 25 bucks so I dont have to stare at a 40+k decoration in my garage any longer lol
 

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Mike Pfeifer

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Mouse ate a crankshaft sensor wire while parked?
 
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pittzy23

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Mouse ate a crankshaft sensor wire while parked?
lol. that would have sucked, but no issues there. I finally got a hold of one of my Ford ASE buddies and have it narrowed down to an airflow issue (i was stuck on fueling in my head). had me unplug the MAF and start the car, which it did and would stay running (pretty well actually). the MAF appeared clean visually but will get some cleaner and try again tomorrow. otherwise possible faulty MAF. it sits right under my coolant reservoir which did have a leak sometime back so not sure if that worked its way info the MAF and got it all upset. At least I have a path moving forward.
 

Cory S

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Well still no luck. swapped the FPDM and still getting the exact same result. fuel pumps prime, car turns over, and then dies right away. cant imagine an injector / spark plug issue (all of them bad at the same time very unlikely), car has half a tank in it so the pumps arent running dry. fuel shouldnt be old (ran fine on the first half of the tank. filled a few weeks ago.) I suppose I could check the MAF but it has been fine / untouched the whole year. will take another look at the vacuum lines but i know those are also unchanged. I will Venmo whoever suggests the correct fix 25 bucks so I dont have to stare at a 40+k decoration in my garage any longer lol
Can you have someone probe the power wires going directly to the pumps and watch what happens when you start the engine? Going to guess they get voltage during prime, and after engine starts…. It drops to 0V.
 

saleen367

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I would be sure to check for vacuum leaks to as that would create a lean condition if the MAF sensor wasn't properly metering the incoming air volume. At idle that lean condition would likely create a stall. Just a guess
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