loss of fuel pressure

Alright, so I've searched and everything, just looking for some quick input.

So, I have 98 xj, auto, 6" lift. It's been having a voltage issue for the past week or so where the voltmeter will drop to 0. I'm pretty sure it's just a bad battery cable as when I wiggle it around and tightened the clamps, it seemed to be ok.

So, took it out Sunday wheeling in deep water. Most of it was 2-3' deep. Several spots over 4', so water over the hood for short periods. Jeep ran perfect through everything. I shut it down after prob. 1-2 hrs of wheeling. Started back up, but running very rough and loss of power unless you're really on the throttle. I figured somethings wet, been there before, it'll dry out.

Next, the voltmeter goes out again. Ok, mess with the cables, still nothing. We're leaving for the day anyway, I'll figure it out when I get home. So, I'm driving (still running rough) and then the jeep just dies. No fuel pressure at the rail, fuel pump isn't priming when you turn the key. I check the cps connection, fuel pump connection, relay, etc. Everything is dry and clean. Hit the gas tank a bit, still nothing. Spray some starter fluid into the intake and it'll fire up (still running rough). I figure I'll let it sit for a few days and let things dry out. Tried messing with things last night, still nothing. It'll still run with starting fluid, but still runs rough on that. Still no fuel pump.

So, before I drop the gas tank and go through that PITA of testing the fuel pump itself, any suggestions?

Before you drop the tank, check for voltage at the fuel pump plug. If you get 12V and the ground is good, but pump won't run, then it's the pump. If no 12V or ground is gone, your problem is outside of the fuel tank. (wires, fuel pump relay, etc.)

Ok, so check the voltage at the plug that's under the jeep back by the fuel tank?

Also, I was going to try jumping the terminals in the relay for the fuel pump to see if that does anything, but I forget which 2 terminals you jump. Anybody remember?

Also, what are they symptoms of water in the gas? Could that be a possible culprit for the running rough part? Although, I don't know why it would only start doing that after it was shut down and then restarted if it was water in the gas. Just a thought.

Agree with Winterbeater...check for voltage at the pump before you go to the trouble of pulling the pump out. Rough running sounds to me like moisture somewhere...distributer cap, sensor connectors, etc. And, since you were having trouble with the connections before the swim, I'd check them all, especially grounds. Get some dielectric grease and clean, grease, and re-connect all connectors you can find.

I would charge and test the battery, test the alternator, replace the bad cables, and then look at other issues.

Bad battery, bad alternator, bad cables--FIX the heart of your XJ first or you are P/ing into the wind.

battery and alternator are new. I know my cable clamps need to be replaced, which I'll be doing. I just happened to come across 2 Caterpillar High Output 1000 CCA heavy duty batteries that they use for cranes, excavators, etc. So, now I'm thinking of doing a dual battery setup. That's a project for another day though. First I need to fix this stuff.

Did you pop the cap on your distributor and wipe any moisture out of there? Spray start in there will dry it out to, but don't reassemble until it's all evaporated or the next start up try could blow off the cap. (Seen it happen. LOL)

yeah, the distributer was clean and dry. I had put dielectric grease in all my connections prior to this and siliconed my distributor cap to try and keep water out. Seems that part worked.

Haven't had time to mess with things yet. I have tomorrow off from work, so I think I'll tinker on it then.

so, it turns out it was the fuel pump. I tested the connection and it was getting 12V, so I dropped the tank (which was fully by the way, so I had to drain it first) and pulled out the pump and hitched it to the battery and nothing. I have a feeling water/sand got into the tank and seized up the pump.

And, for the first 1-2 min. after it started it was running rough like before, but after several min. it smoothed out, so that kind of reinforces my water in fuel theory I think.

Unfortunately, I thought the jeep was fixed. I let it idle for about 15 min. and it was running fine so I decided to go for a test drive. Thankfully I didn't go far because when I was returning, about 500 yards from my house it died. I had just enough momentum to roll it into the driveway. It would continue to start up, but would die immediately. I can hear the fuel pump priming, so I know that's working.

I let it sit for about 2hours, went out and it fired right up, so I let it idle and it ran for about 5 min then died and now dies immediately when started again.

Now, the fuel pump I swapped in was a used one, but I put it in to see if that was the problem. I may still get a new fuel pump and try that, but I'd like to get some input before I spend $125 on a new pump only to find out that's not the issue, considering I know the pump in there is working. The only thing I can think is maybe it's not supplying enough pressure, but that doesn't make sense it it will run for 10 min. or so only after sitting for a couple hours. I'm kind of stumped on this one.

One other thing is that after it died the time after I test drove it, I got underneath to see if maybe one of the fuel lines was disconnected or something. Everything was attached at the gas tank, but I did notice that the fuel supply line was not attached where it enters into a black box that's mounted underneath approx. under the rear, driver's side seat area. I'm not sure what the box is, but it had a couple other lines going into it. Anyway, I plugged it back in and it would still die immediately upon starting. Anybody know what that black box is? I wish I had a camera to take a picture.

When you drained the tank how much water did you find in the gas? Don't get mad, but did you check for sand/crud in the tank?

I didn't drain the tank completely because the siphon I have sucks. I left prob. 2-3 gallons in there. When I was draining the gas, it looked pretty clean coming out the siphon. The fuel pump assembly did have a little bit of sand in it though, which I cleaned out with some brake cleaner before I installed the other pump.

I'm starting to think it might be something electrical because I know it is getting fuel, at least initially. I'll just have to keep troubleshooting on this one.

pulled the cel codes:

P0463 - fuel sending unit sending too high voltage
P1282 - fuel pump relay control circuit shorted
P1494 - Leak Detection Pump
P1682 - Charging system voltage too low

Looks like i'm going to have to go through some wiring!

jeepster_259 said:

One other thing is that after it died the time after I test drove it, I got underneath to see if maybe one of the fuel lines was disconnected or something. Everything was attached at the gas tank, but I did notice that the fuel supply line was not attached where it enters into a black box that's mounted underneath approx. under the rear, driver's side seat area. I'm not sure what the box is, but it had a couple other lines going into it. Anyway, I plugged it back in and it would still die immediately upon starting. Anybody know what that black box is? I wish I had a camera to take a picture.

Click to expand...

Your black box is the charcoal cannister for recycling gas fumes. Your leak detection pump code is related to the line that was disconnected there. Sometimes this can even be from a loose gas cap.

Get rid of ALL of that bad gas.

thanks for clarifying what the black box is.

I found why my voltmeter was going out also. The connector for the ground cable to the alternator was completely corroded. When I happened to jiggle that wire to test connections, the connector snapped right off. So, it looks like that mystery is solved.

Now for the fuel part. I just ordered a new Bosch fuel pump with a lifetime warranty which should be here in a few days, as well as new strainers, etc.

jeepster_259 said:

thanks for clarifying what the black box is.

I found why my voltmeter was going out also. The connector for the ground cable to the alternator was completely corroded. When I happened to jiggle that wire to test connections, the connector snapped right off. So, it looks like that mystery is solved.

Now for the fuel part. I just ordered a new Bosch fuel pump with a lifetime warranty which should be here in a few days, as well as new strainers, etc.

Click to expand...

IMHO, I would completely remove the tank and sacrifice a few gallons of gas to ensure there is no sand or crud left in it.

yeah, I think i'm going to empty it all out when I put in the new fuel pump.