Intermittent Fuel Pump Failure? 2000
 

2000 XJ 4.0L Auto

Full tank of gas. Driving down highway 3 hrs before no issues driving or starting.
Started highway again and it began sputtering and died.

Original fuel pump i believe. almost 200K miles (re-man engine)

Seems like everytime i start i hear the "whizzing" sound of the fuel pump start up and prime before firing.

This time i didnt hear it. Also 1 time while attempting i heard the pump but it sounded different, kinda more like a humming than a whizzing. i can hear a click in relay area and can feel fuel pump relay click with finger on it. Hit tank a couple times and jiggled wires on tap but nothing.

left jeep over night. went back and it started right up. had it towed just in case didnt want to break down in the middle of nowhere.

Thoughts?

also at roadside pressed on fuel rail valve. it sprayed gas. no sure if it seemed like high pressure or not.
new plugs, relatively new coil pack, etc

Also if needed, BEST brands of fuel pump to replace with?
(read negative things with airtex, carter, autozones brand, etc)

does CPS have anything to do with fuel pump from the off to on position? would it prevent priming?
(had cps worked on awhile back and i swear things weird after that)

Fuel pumps are known for intermittent failure when at end of life. 200k miles on the original fuel pump does seem reasonable for replacement time. It's hard to verify this for sure since you'd have to get a fuel pressure reading when it's acting up and make sure you have 49psi (-+ 5psi) steady pressure. Also a fuel pump is a rough thing to "fire the parts cannon" at since it's expensive and requires dropping the tank to get at (so usually you replace the straps as well due to rust), so it's both an expensive part and laborious to replace.

A flaky CPS definitely -can- exhibit the symptoms you're having.

If you've had CPS problems since it was replaced, the first question is did you use a Mopar part? These XJ's are super, super picky about CPS's and if you got anything but a Mopar, it's likely to be problematic. I've heard NAPA recently can be OK, but anything else, I'd suspect you have a flaky CPS (at least, it's less expensive and easier to get to). You can test the CPS for the most part, but true testing requires expensive equipment. I'd start with testing the CPS resistances and fuel pressure and see if that leads you to one or the other.

Fuel pumps are not as known to display thermal failure as CPS. What you describe sounds like something that failed when it got hot, then started to work again after cooling down. PatHenry is correct that that behavior (at least around here) is usually more associated with a CPS going out than a fuel pump. If the CPS is failing due to heat it will start to send bad signals to the computer (nonsense signals), the computer will accept that for a few moments, but if it doesn't self-correct within a few moments the PCM will stop providing ground to the ASD relay and the ignition system will stop firing. It may sputter a little before dying because the cylinders are hot and things are already in motion.


Did it sputter just briefly then die? or did it sputter for an extended period of time then die? (more than 10 seconds?)

i believe my mechanic put in a Mopar CPS because the big store brand would not work.

i sputtered for a little bit of time before shutting down while driving.

Sorry, forgot to answer your question on this in particular. No the CPS is not related in the fuel pump operation or priming.


Based on everything you have said and the fact that you have a recently installed Mopar CPS (by the way, are you sure?). The next logical test is a fuel pressure test with an actual pressure gauge at a range of RPMs. Though in the driveway in neutral/park it can be difficult to recreate the fuel demand that the vehicle sees when accelerating onto a highway. So a pump that fails under very heavy load, may not fail at home even at higher RPMs (high RPMS is not the same as a heavy load on the motor). But perhaps the test will show some pressure anomalies that are worth noting.


But also based on what you said, I'm more inclined to look at something temperature related. Which puts us back under the hood somewhere. For example, a fuel pump relay dying or producing a ton of resistance when it gets hot could produce very similar symptoms.

ok thanks. gonna snoop around then re-post

I agree with the others. Gotta get some fuel pressure readings. You could start with one in the driveway when it is not symptomatic as if the pump is tired, it might be out of spec while at idle, but it of course would be best to test it when it is acting up.

49 psi, plus or minus 5 psi is your bogey for fuel pressure reading.

This all being said and I am always in favor of a solid testing based strategy to determine root cause, if you truly have 200K on that fuel pump, even if this is not the root cause, and you plan on keeping the vehicle, replacing this fuel pump is certainly not money wasted. Not many fuel pumps go much past 200K.

I like Bosch pumps, Carter is my second choice. Under no circumstances would I install an Airtex pump or anything rebranded from that company. Bad track record.

Bad fuel pump. It was original with almost 200K on it. Low pressure to rail.
Replaced it with a Delphi.

We'll see how it goes. Thanks for all the info.

Glad to hear that you (hopefully) figured it out! Definitely keep us posted on how it goes.

That was pretty quick - did you do it yourself or take it somewhere?

Thanks for the follow up!

it broke down while i was camping 3 hrs away. had it towed (AAA thanks) to my mechanic. would've loved to do repair myself but did't have the time.

replaced those straps too of course.

Oh man, I hope it didn't ruin your camping trip!

Glad to hear you got it resolved quickly!