One of my final gremlins in my project jeep is this stumble/power loss when the engine is hot. when cool it runs like a scalded dog, but after about 20 minutes it loses power.

I hooked a fuel pressure tester up to it, it seemed OK at idle 29-32 psi, with the vac line disconnected its around 34 psi. when driving cold its great holds fuel pressure fine. But once its hot and you try to hit the skinny pedal the PSI drops. like below 20. loss of power, backfiring, you name it.

new parts- Fuel filter, fuel pump, four hole injectors, mopar TPS, bosh O2 sensor.

I have a new fuel pressure regulator coming tomorrow and I'm going to check the fuel pump ground in the morning.

if we can find a solution, i will post it. i wont leave the next guy hanging like the last 2 people who have had this same issue.

 

Try jumping the ballast resistor also.

Hate to say it, but new fuel pumps can be junk right outta the box.

but, continue on the path you outlined for yourself. Good plan.

 

Yep, already had the ballast jumped, and while I was checking grounds and connections, I sanded fresh metal on the little connectors.

I did all my morning tasks. I'm about to pull the pump and just make sure that all is kosher inside, before I commit to replacing the regulator.

What the heck could cause a pressure drop as the engine gets hot? It even gets worse as the heat builds.
It's almost like the fuel is vaporizing in the rail.

I tempted to remove the hood and go for a drive.

 

i pulled the pump. the the tank was full of rust. i suspected that the sock was getting covered with rust and starving the pump. so i siphoned out the gas with a big hose and sucked out a large amount of rust debris. i reached in and felt around, it seemed a lot better.

i also tested the pump in a bucket of water and it sprayed really well. i also made sure to clear out the water. i put everything back together and the problem is worse. now the problem presents almost immediately.

filled fresh fuel- no help

another new filter- no help

replaced pressure regulator- no help

i ordered a new pump. but after that, i have no idea what it could be.

 

Perhaps there is debris in the rail and injectors.

 

well I doubt the injectors are the issue since the pressure is low at the rail. I didn't see any debris in the rail when I removed the pressure regulator.

Are there any components between the pump and the rail?

 

Just the fuel filter. How did the last fuel filter look? Could you pour out rusty crap from it?

 

The old filter had rust in it. but it only had maybe 50 miles on it. Also, the new filter didn't help AT ALL.

If the pump doesn't help then I guess it's time to blow out the lines. I'm also going to try taking a pressure reading right off the pump and right after the filter.

Should I take a voltage reading at the pump? What values should it be?

 

Well, that rust went through the pump if there was rust in the new filter...
12 volts or so at the pump with the ballast resistor jumped.

 

I will be very happy if the new pump fixes the issue. It's possible that the sock fell off and sucked some larger rust chunks up in the pump and that might have exaggerated my already failing pump.

we shall find out in the morning!

 

Yup. How about disconnecting the fuel delivery line in the engine bay and the outlet side of the fuel filter and flushing that line just for fun?

 

I had thought of doing that, too but a few things are pushing me away from doing that.

1. What would be better at flushing it out than 30PSI Fuel?

2. I'm not good with those quick disconnect fittings, and the last time I fiddled with that particular one, it took me quite a few minutes to get it to stop leaking.

3. Fuel on the clean side of the filter has always looked pretty good.

I'll take a fresh look at it tomorrow and see how tough the quick disconnect fitting looks.

 

Don't mess with it then if the fuel filter outlet spits out clean fuel

 

Fuel pump did not fix it. It's quieter, and I think it's overall a healthier unit, but I still got the pressure drop 15 minutes down the road.

I pulled over and checked my voltage. It was 4.5v at the pump, and idling at 25psi.

Got home, ran to the PC to do some research, came back out, started her up, and now I'm getting 13v at the pump.

 

Wiring to the pump. Find a connector that's getting hot.

But all of that was not wasted effort. With that rust in the tank, it needed to be cleaned out.