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Discussion Starter · #1 ·
So recently my 1998 TJ with the 4.0 died going down the highway. I hit a bump all my gauges fell off and the car instantly died. I pulled over to the side of the road and crank the engine for about a minute and a half no start. I couldn't hear my fuel pump priming, and I know there was having fuel issues before this. I told it back and I've replaced the fuel pump. The fuel pump won't prime or engage when I turn the key to the run position. I've checked all the wiring with a multimeter from the ignition switch lock all the way down to the relay and the connection module that sits on the firewall that sends power back to the fuel pump, and it's all getting power. However, when I check the power down where the fuel pump plugs into the wiring harness there are only 1.3 volts at Max. The car will sit there and turn over and won't start. I've tried everything I know and I'm hoping one of you can help me.
 

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....I hit a bump all my gauges fell off and the car instantly died ...
This should be a big clue.
Do the gauges still work?
What fuel issues before this?
Did the new fuel pump ever work?
Its not clear, what is the 'connection module'?
The bump could of jarred something loose.

Assuming you checked or swapped out the fuel pump relay and any related fuses.
Have you swapped out the ASD relay?
If the ASD relay triggered, that could of possibly affected the gauges. Don't know for sure.
If the ASD relay jarred loose from the bump or bad it will also prevent voltage to the fuel pump.

I had a similar issue with my XJ's 4.0, turned out to be the CPS.
Not saying this is your issue because your TJ is a different vehicle and year but keep that in mind.

Other than that based on what you've said, i'd double check the fuel pump harness and all involved connectors from the pump to the engine bay where you get good fuel pump voltage.
 

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Discussion Starter · #3 ·
The gauges don't "come alive" when I turn the key to the run position. Before this, I had to prime the fuel pump 6-8 times before it would start, or it would crank for a very long time before it turned over. The new pump worked when I put it in, I checked it off the battery using some extra wire. I don't know what it's called but it's the connection up by the firewall that supplies power to the rear of the vehicle. The ASD relay worked when I swapped it out. I've checked for resistance on the CPS and there was no problem there. My CPS went out on my old jeep.
 

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If the gauges don't work at all in run position, if it were me i'd try to troubleshoot that first.
Was this always the case or did it happen when you hooked up the new fuel pump?
Could be possible its related to the fuel pump not turning on.

These old Jeeps had a lot of mods from PO'ers.
Is there a fuel pump kill switch or suspicious wiring anywhere?

By the new pump ever working, i meant when it was all hooked up.

If you had to prime the old pump 6 to 8 times that 'could' indicate there might of been nothing wrong with the old pump. Just an intermittent electrical problem that went permanent a possibly a connector, relay socket, flaky relay, etc.
I would double check each and every connector that you plugged/unplugged for bent or spread contact pins.

Can you can measure the voltages at both the relay's energizing coil and its output contacts to the fuel pump, both should be 12 volts. Depending on the relay socket could be tricky to get at those measuring points.

Far as that mysterious module on the firewall, could it be a big connector?
I don't believe they used TIPM's back in '98 and don't have one in my XJ but could be wrong seeing yours is a TJ.
Might want to research that module if it is module and see exactly what it is.

If you're positive you've got power at the fuel pump harness under the hood and not at the fuel pump, it could be only one thing a broken wire in the harness or a spread pin in a connector.
The 1.3 volts you measured at the pump would also show up at its harness wire under the hood that goes directly to the pump.
Are you sure you're measuring the pump voltage at the right spot under the hood.

If all else fails, might want to find an electrical schematic to trace out the entire fuel pump circuit.
I've trouble shot electrical problems with the Hayne's manual generic schematics.

I might not be able to pinpoint the problem but maybe give you some things to think about and offer some encouragement.
Electrical problems can be a beeach.
 

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Discussion Starter · #5 ·
So the gauges only stopped working after I put the new pump in. The new pump has never cycled on since I've put it in. That module is just a big connector I didn't know what it was called, but I had seen several other people had issues with it. Thank you for all the suggestions, I will work down this list you gave me and get back to you.
 

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Discussion Starter · #6 · (Edited)
So I followed your list and I got the fuel pump to come on by bypassing the relay. I pressurized the fuel rail, turned the key, and no start. I then went and checked the spark plugs. I am getting no spark, even from the coil. I went ahead and put a new CPS into it and nothing. So I have no power being sent to the fuel pump, spark plugs, and gauges when I turn the key, also my OBS II scanner says it cannot connect. Could this be a computer issue?
 

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I had a hunch the instrument gauges not working would lead you to the final solution.
If the CANbus is corrupted the engine could crank but will not start.
At this point i don't think its a computer issue but anything is possible.

Far as i can tell here's what you've got going so far:
-'the gauges only stopped working after i put the new pump in' is a giant clue.
-New CPS would of also been one my suspects but didn't fix the problem.
-There were prior problems priming the fuel system with the old pump
-Measuring 1.3 volts power at the pump but if the CANbus is dead the power relay likely wouldn't energize

Might try totally disconnecting the fuel pump's connectors then do a PCM reset.
See if the gauges come back and if your scanner can now connect to the computer's CANbus.
This should only take about 20 minutes or so with the PCM reset.

One other thing you can try after that if you still have the old pump is to disconnect the new pump's harness connector and plug the old pump into the harness and see if the gauges come back. But i'd do a PCM reset before that to be safe.
 

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I am a little confused by your terminology. When you say, "it took a long time for the engine to turn over", do you mean the starter motor spun but did not crank the engine over? Or do you mean it took a long time of turning the engine over until it fired up and ran? Normally saying an engine cranks over means the starter motor is turning the engine over and it fires up when it's running.

I am asking this because you could simply have a bad battery (or other electrical) connections or for some reason it's not charging and you have less than a fully charged battery. Three days ago I had to replace the battery in my jeep because it was running poorly, the gauges were acting screwy and the starter would not engage and turn the motor over properly all the time.

When you hit a bump that would leave me to believe a battery, electrical or changing system connection possibly power at the fuse box.

I would eliminate some basics before replacing a lot of expensive electronics.
 
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