[Diehardx]

Hey everyone!
I have a 97 Sport, Automatic. It's got a little over 200k miles on it and has been well taken care of by myself and the previous owner. I personally have put roughly 90k miles on it.

Over the past 6 months it has started shutting off on me while I am driving. At first it would only happen once a month for about 5 months and we couldn't figure out what was causing it. For the past month it has started to shut off on me every single day. At first it seemed to only happen when I was accelerating but the past couple times have been in turns or when I am sitting still. Battery is fine, radio stays on when it happens. Sometimes it will start right back up, but most of the time I have to let it sit for a couple of minutes before it will cut on. Has anyone else experienced this? Luckily my uncle owns a shop right down the road, just wondering if we can get a head start on where to look.

Thanks!

 

[Digger84]

Fuel pump till proven other wise and will get more and more frequent till leaves you stranded check the rail pressure or fuel trim when it is acting up

 

[Big Sarge]

Fuel pump till proven other wise and will get more and more frequent till leaves you stranded check the rail pressure or fuel trim when it is acting up

I second this!! The only way I figured it out was to monitor fuel trims while driving. Fuel rail pressure was 49 psi every time I checked it. Replaced the pump, no more shutting off.

 

[Diehardx]

Awesome, thank you guys!

 

[crallscars]

When my fuel pump was dieing, I found the engine would die more often when I had a 1/2 or less fuel tank. It didn't seem to do it as much when full.

 

[Big Sarge]

When my fuel pump was dieing, I found the engine would die more often when I had a 1/2 or less fuel tank. It didn't seem to do it as much when full.

that's because the pump is cooled by fuel in the tank. As the tank empties there is less "cooling capacity" around the pump thus allowing it to heat up.

 

[crallscars]

I have to agree with you on your diagnosis,
It also helps sometimes to diagnose a bad pump.

 

[c.d.c.]

Typically if a fuel pump failure was causing a stall the engine would gradually sputter to a stop as fuel pressure bleeds off. Is that what was happening when your fuel pump died Big Sarge, or was it a very sudden shut off such as turning off the key?

Diehardx, how sudden is your engine cutting off?

 

[Diehardx]

Diehardx, how sudden is your engine cutting off?

It is very fast, literally one second it's going fine then all of a sudden without warning, no shaking or sounds, it dies. Not really sure if it makes a difference, but once it shuts off I have to let it sit for a couple of minutes before it will start back up.

 

[Big Sarge]

Typically if a fuel pump failure was causing a stall the engine would gradually sputter to a stop as fuel pressure bleeds off. Is that what was happening when your fuel pump died Big Sarge, or was it a very sudden shut off such as turning off the key? Diehardx, how sudden is your engine cutting off?

mine was like somebody turning off the key! Only did it after driving for an hour straight. I could push in the clutch, turn the key off for a few seconds, turn it back on, let the clutch out and start the engine again and keep on driving. Once it happened the first time it was fairly quick to happen again. I changed every sensor in my jeep as well as the whole ignition system because I was convinced it wasn't the pump. I was convinced I was stupid after changing the pump and it was fixed!! The positive side is that I have all brand new sensors now!! Lol

 

[c.d.c.]

mine was like somebody turning off the key! Only did it after driving for an hour straight. I could push in the clutch, turn the key off for a few seconds, turn it back on, let the clutch out and start the engine again and keep on driving. Once it happened the first time it was fairly quick to happen again. I changed every sensor in my jeep as well as the whole ignition system because I was convinced it wasn't the pump. I was convinced I was stupid after changing the pump and it was fixed!! The positive side is that I have all brand new sensors now!! Lol

Interesting, you said you caught it by looking at fuel trims. Did the trims go positive just before the engine shut off?

 

[Big Sarge]

Interesting, you said you caught it by looking at fuel trims. Did the trims go positive just before the engine shut off?

yeah they spiked up around 30 IIRC

 

[c.d.c.]

Well that's a good place to start, Diehardx. If you have a smart phone or laptop you can get an OBDII cable or bluetooth transceiver and download a scan tool all for around $30. Then watch your fuel trims and see if they spike before it dies.

That said I once diagnosed an engine shutting off issue with a 4.0L Cherokee. That one turned out to be a bad PCM. If I recall correctly it was dropping ground to the ASD relay or something along those lines. Took several hours of driving with the scope hooked up to catch it.

 

[crallscars]

The only other problem I have had with my 97 that was similar to a pump failing was the plate in the distributor failing.

I was driving down the highway and she acted like I had a loose wire on the ignition coil, the engine never stalled out, but lost power at speed. then it would act fine. It did this several times over the next few weeks, Jeep service manager suggested the distributor plate and it fixed the problem.