Engine dies randomly

Andresme

Andresme

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Jul 1, 2020
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45
Location
Santa Monica
My 4.0 keeps dying randomly. I threw a new mopar crankshaft positioning sensor at it a few weeks ago thinking that would fix it and forgot about it. This Sunday it happened again and got it towed to a mechanic. He said he checked all my grounds, relays, fuel pressure, and fuses. At first he wasn’t getting any fuel pressure and my gas gauge was at E so he thought I was out of gas.

He put in two gallons I had in a jerry can and the gauge went to half (so I wasn’t out of gas) and it started, but it keeps happening to me and I’m trying to get it fixed before I leave Moab. It seems to idle in place fine but the problem only happens when I’m moving.

Is it worth throwing a new fuel pump at or should I try something else? Is there any way I can test the fuel pump other than a pressure test?
 
What did he say the fuel pressure was?
Has it generally been low on fuel when it has died?
When it dies, is it like you turned the key off?, or does it struggle and die?
When it dies have you noticed any patterns, like you were on the free way, you were pulling a hill, you were off throttle and costing, ect., any pattern you may have noticed may be very helpful
 
He said it was at 49 when he got fuel pressure. It only seems to die when I’ve got my foot on the gas because I just idled it fine for around 10 minutes but it died 2 minutes into driving. It’s been at at least a half tank when it dies and when it dies I can hear the engine slowing to a halt and if I’m in gear as I get closer to zero it feels like it’s about to stall. Power steering is gone but gauges still read and radio a still going until I turn it off. If I can get it to start it usually takes a couple cranks unless I prime the pump a bit.

I’m right next to an oreillys right now so I borrowed a fuel pressure tester and hooked it up but it kept spewing fuel out of the other hose of the tester without the key even being in the ignition.
 
the tester you have from oreillys, the little hose that is spewing fuel should come back up to the base of the gauge and there you should see a little black button. make sure that button is not depressed, they do get stuck down so try and pop it back up.
try and verify the fuel pressure
 
Damn, I just returned it after it continuously spewing fuel every where. Do fuel pumps usually have a slow death like this though or do they just crap out and not work anymore?
 
I just had it idling for a solid 10 minutes and even gassed it a few times while in neutral. Decided to try and limp to the mechanic down the street and put it in first and it died not too long after so gassing it doesnt seem to be the problem but as soon as I gas it in gear that’s when it’s having trouble.
 
here's what I got for you from a far, so given all I got is what you have said.

If the tech saw a no fuel pressure condition, and assuming there way fuel (and that he really checked the relays) it would appear to me that you have an intermittent fuel pump failure. this would not be hard to verify, but may be inconvenient.

option #1: just replace the pump and the fuel pump relay, its a roll of the dice but does line up.

option #2: wait for it to die again. if and when it dies again (if you wanna buy one) put the gauge on it then, or listen for the fuel pump to prime. Warning: you may still here the pump but it may not be making enough pressure, you will only verify with a gauge

if you dont hear the pump prime, swap your horn relay (assuming your horn works) for the fuel pump relay and try again.
if that works use the horn relay for awhile and see if it happens again. if not buy a relay, otherwise buy a pump, but if you buy a pump, just based on age, spend 5 bucks and get a new relay as well

hope that helps
 
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