Fuel pump issue? Maybe?

[JMadigan]

Happy Thanksgiving :D

This past week, I was driving I-70 eastbound from Grand Junction to Denver. Going up a large hill approaching the Eisenhower tunnel my Xj began to jump 4-5 times. At first I thought it was the transmission slipping, since this was near the top of the hill and the rest of the drive was downhill I chose to keep going.
The next day, I drove it around and it it only "jumped" once. Later in the day, going up another hill at about 45mph It just died. There was an instant loss of power and the rpms jumped around and then it died. I rolled into a parking lot and tried to restart it; the starter would turn the engine but it would not start and I noticed the fuel pump was not buzzing when i turned the key into ignition. After towing it home, I swapped in a relay for the fuel pump and she started right up!
Yesterday, I was driving up a similar hill at 45mph and it died again. This time, I had to leave it for a few hours before towing it due to traffic. about 4 hrs later when we towed it the battery was dead from just running the caution lights. This time I checked the power line for shorts using a multimeter and tested the relay. The relay tested good, so I'm assuming it's not a short killing the relays? Then I checked the battery, refilled it with distilled water (since it was a little low) and charged it for a few hours. It started right up after a charge so i went around the block a few times and parked it.
Today, I started it and let it run in the driveway and it sputtered and died. :bang: The battery has some juice and the fuel pump also runs. It shouldn't be the alternator since i replaced that less than a year ago.

Any ideas? I searched around and found things on the fuel pump shorting, but I checked all of the common spots. fuses are all good and I clean off the terminals real good. Any help is GREATLY appreciated!

EDIT: just went outside and started it, had to give it a lot of gas to get it going. Fuel pump/filter maybe?

[4.3LXJ]

The ting to do is verify fuel pressure with a gauge. But I suspect that since it died quickly that it is something else. The general culprit is the crank position sensor since it tells the injectors to fire.

[JMadigan]

I didn't think the pre-96 Xjs has a crank position sensor? But I can look into it.

[bigjim350]

Yes it has a CPS

[Showtime3492]

I didn't think the pre-96 Xjs has a crank position sensor? But I can look into it.

Pretty sure because that also influences timing.

[Carves]

X 2 on checking fuel pressure ... but crank sensor is a common problem.

The sensor in the distributor also controls injector timing and is known to fail also.


Both sensors are the ... "dont like hot, dirty environments" type ...

... which makes em, just perfect ... for car engine bays .. :rolleyes::rolleyes: .. :D

[JMadigan]

Thanks for all the quick replies! I tested the original CPS by performing the ohm test while it was cold, then running the engine until it died and quickly disconnecting the CPS and testing again. When cold, there was infinite resistance. when warm, there was a low resistance so I changed it.
Went to Autozone, bought a new one (when did these things get to be nearly $70 :out: ) and plugged it in. Tried to start it and nothing! Then I tested the one I just bought and got a reading of 2-4 Mohms. Went back and bought another; I tested this one before putting it in the Jeep and got the same reading as before.
It this a common issue? To have them not work right out of the box? or is Duralast just crap when it comes to these things? :confused:

Thanks!

[xjrev10]

Try a different battery. I've seen some crazy weird things happen with bad batteries. Even if I thought it was good.

[JMadigan]

I've been working on narrowing down the issue;
I replaced the CPS with a NAPA one since I couldn't get a good one from Autzone. I replaced the fuel pump/fileter/strainer after I checked all the wires and verifed I was getting spark (The filter was very dirty). The Jeep still dies but ALWAYS when going uphill. The rest of the time is drives fine. To ensure the CPS was not coming undone (since I read that was a common issue) I bound the connectors tightly together with e-tape.

When it does die on the road I only have to pull off to the side and it restarts with little or no effort. :confused:
I'm out of ideas :bang:

EDIT: in response to Carves post, apparently mine doesn't have a sensor in the distributor? or is this the pick up coil?

[4.3LXJ]

All of our distributors have a cam position sensor in them. It still sounds like you are being starved for fuel. It would be interesting to have a fuel pressure gauge on there when this happens.

[HarryHydro]

Hi Folks:
I see this is an old thread, but it fits my Jeep! 1990, Renix. Was running low on gas, stopped into a gas station, got $20 bucks worth, gauge came up to 3/4, normal.
Pulled out of there, a hundred yards later I'm pulling over and onto a side street because it's running rough. :crazy:
I feather the throttle and it's running, but will not take a poke. It slows and stalls. I drift into an open field. Mud puddles all over, of course..
It's cranking fine, no start. I can't hear the pump. I can usually hear it a little.. So I'm underneath tugging and jiggling the connector by the pump. turn the key, no start. I press that fuel pressure test valve, like the tire valve. I get just air. I hit the key a few times. Still just air.. No start. :crazy:
So, I get out my buck-knife and cut a length of coax, because I'm a Ham and have more wires and junk than anything.. I strip the splice I made years ago, when a mouse ate the B+ wire between that connector and the tank. I tapped into that, ran the wire inside, and connected it to a B+ wire that runs the ham radio. I can hear the pump running. I press that valve again, and get a bunch of vapor, I hold it a few seconds, then gas!:pray:
I turn the key and it starts! Runs fine! Disconnect that wire, and it stalls. So, I guess it's the relay. I seen a beautiful illustration here that I found with Google, which is why I'm here, now. I didn't know which relay feeds the pump.
Now, I have a brick resistor on the driver-side inner fender. Does this feed the pump? It's broke.. Well, it's broke from the fender, but the wires are still attached. It's been like this for a while. Kinda cold here, now, and I seen a post here on snow coming. Not a daily driven vehicle, so it can wait.
Thanks!
Hydro

[4.3LXJ]

Yes, that resistor is part of the pump circuit. Fix that and you will probably good to go

[HarryHydro]

Thank You, Sir. I was playing with it over the weekend. That resistor is 1 Ohm, so it's good. I polished up the terminals. I found the one side goes to another relay/solenoid next to the 4-relay bundle. An orange wire/plug. It was pretty corroded.. I polished that up too wth a brass brush..
The fuel-relay wasn't clicking though.. I wasn't getting voltage across the coil-terminals - with a meter - either. I was doubting the second relay from the firewall-end was the right one. I could hear something clicking though, even with that relay out. I poked with stuff, testing voltage at the fuel pump with my coax, still attached.. Then I could hear another relay clicking.. I had the wife work the key, and it was the second relay from the firewall clicking now.. It's not always a 1 second on-pulse, though. In fact, sometimes it doesn't close. But, this time it started without the coax..
Where might this pulse come from? Is it the computer under the glove box?
Thanks Folks!
Harry

[slvmart]

Here are a few diagrams from a '89 manual. I would think they should be close to a '90.

Hope this is of some help. I only have a '89 or '00 manual. But if you need parts of the wiring diagram, I can see what I can do for you.

[ArmyGuy45]

The ting to do is verify fuel pressure with a gauge. But I suspect that since it died quickly that it is something else. The general culprit is the crank position sensor since it tells the injectors to fire.

This. I replaced my pump and was still stuck. It was my CPS.

[4.3LXJ]

Glad you got it figured out