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<ABRUPTLY> Will Not Start

I

idahjo

NAXJA Forum User
Location
USA
Any help on this would be greatly appreciated:

Have a 1998XJ. New Battery and New Starter. Drove it a couple days ago and it had absolutely no issues. Tried to start it today in the garage and cranks over fast, but no 'fire in the hole'.

Just got home and have not had a chance to troubleshoot it but thought I would throw it out and hopefully get some words of wisdom before tackling it.

Thinking there may be a specific issue common to the effect I am having?! Maybe fuel pump... Is the electric pump in this rig fused?
Thanks in advance..
 
Follow the tutorial that Ecomike posted.

You must first determine what you are missing, fuel or spark. Or both.

Do not guess and do not throw parts at this.
 
Thanks guys.
It will be tomorrow before I tackle this/ hands-on.
The information looks great. Just what I was looking for. I will digest it tonight before I start checking things out.
In my case, there was NO maintenance/tinkering done. Just went out a couple days later and it was KAPOOT!
Will check back after I get into it..
 
Got on it this morning.

No fuel at the Shrader valve. Could not hear the fuel pump running with ignition switch ON. Smacked the tank a couple times with a rubber hammer, still didn't hear a pump noise, and STARTED it up. Apparently, the fuel pump had 'stuck' for some reason. Guess I am going to have to pull the tank down and change the pump unit as it probably cannot be trusted not to do it again...or not!

Does the fuel pump run with the ignition key in the ON position? I had the key ON after smacking the bottom of the tank and the Shrader produced only a brief dribble. Thought I'd just crank it for the devil of it and it started! And.. started again.

Any words of wisdom on pulling the tank and replacing the pump/sender unit? I see a plastic hose connector to the metal line that I am totally unfamiliar with.

As usual, I only come here when I have problems but you guys are GOLDEN when I need some ideas. THANKS!
 
When you turn the key to the "on" position the pump will run for a second or two till the system builds pressure. I'm not sure if it's timed or senses the pressure then shuts off. It's starts running again when the vehicle is running.
 
I would check the relay pin contacts, the FP ground, and connectors at the FP, for dirty contacts, and lastly, check the FP hose on the FP in the gas tank, to see if it is coming loose and leaking!!!! My 87 and 89 FP problems were old, corroded E-contacts.

Before buying and replacing anything.

Most aftermarket FPs are junk, go OEM if you do need one!
 
DrMoab said:
When you turn the key to the "on" position the pump will run for a second or two till the system builds pressure. I'm not sure if it's timed or senses the pressure then shuts off. It's starts running again when the vehicle is running.
Click to expand...
Do the later models like his have the ballast resistor?
 
Last year for the ballast resistor was 1993.

If you do end up replacing the fuel pump on a 98, you must drop the gas tank. I recommend you replace the ENTIRE fuel pump assembly while you have the tank down. That is the fuel pump, regulator, filter, etc. That way, everything is fresh.

I recommend Bosch replacements. Carter is okay. I will not install nor will I recommend an Airtex. Search if you want to know why; plenty of guys (including me) have been burned with their fuel pumps.

Good luck!
 
I have a similar problem but with a '91 4.0L Cherokee. In my case a place where the fuel tank had been patched started leaking, I bought a new tank & fuel pump (Airtex - didn't check recommendation here as it looks like it's not so reliable) and installed them both. Put about 4 gallons in and it started fine. Then it sat a week until my appt. to get a safety inspection (I was also "buying" it - basically free from a relative if I wanted to fix it). When I went to start it to drive to get the inspection it wouldn't start :-(. The pump didn't make any noise. There was no fuel pressure at the valve stem, though there was pressure when first checking it (pressure from the week before). I measured no voltage at any pin of the pump connector when the key was turned, although if it's timed, the time may have elapsed before I checked it. There was continuity to ground from the ground pin of the FP connector. This all happened about 8 months ago. I'm now in a situation with some time to work on it and would appreciate any ideas.

I just read the post from old_man linked above, which is great info and there are several things I haven't tried that should help me isolate my problem (e.g., ballast resistor, ignition switch, which doesn't hold the key anymore). Other suspicions specific to the '91 would be appreciated though. I suppose I could have started a new thread, but the topic is quite similar and opted to post here. Hope that's OK. I'm new to the site and haven't read lots of posts to have a feel for that. A friend recently recommended this site to help me figure out my problem and old_man's post on starting issue diagnosis is just what I was hoping to find.

Idahjo, good luck with your problem.
 
Well, IT's BaAAAAACK!

For sixteen days the rig did not miss a lick. Did maybe 500 miles with 30-40 starts and absolutely no problems. Today, in the garage again, NO START. Fast cranking but no' fire in the hole'. Fuel at the Schrader valve was a dribble... and, no ignition.
It would seem the rubber hammer on the bottom of the tank (which seemed to "fix" the problem) was no more than some kind of a 'fluke'.
Does anyone know if the Crankshaft Position Sensor has anything to do with the fuel pump? It appears to me that it is only for ignition. Hard as I tried I have never heard any fuel pump noise even when the vehicle was running. I get a dribble of fuel from the Shrader valve after I crank on it but I cannot see how it could charge the injectors!
Ideas anyone? Thanks
 
If you hit the bottom of the tank and it worked then but now it's doing it again and you don't have fuel pressure then it seems obvious to me you have a fuel pump problem.
 
If it had an ignition spark I would agree. But along with having no fuel pressure OR ignition spark there is NO low-fuel warning light "on" when the switch is turned to the on position (as in the normal light test sequence). I'm thinking more of some sort of electrical malady?!
Would'nt, for instance, a bad battery connection cause something like this ..BUT.. I would think a strong starter cranking should rule that out.
My problem is that I am from the 'old school' where engines and electrical systems worked straight forward and had NO micro-electronics to screw with your mind! I am not sure how it's little "brain" reacts in the electrical system and how it meddles in other functions.
I find it highly unusual to have two things like ignition AND fuel to go out at the same time unless there is something in it's computer that would cause that to happen.
Thanks
 
Fuse F-6 feeds the fuel pump, F-15 feeds the fuel pump relay and the ASD relay, which then feeds the ECU!

Check both fuses.

Check the ASD and fuel pump relays, and Fuse 15, F-6 and lastly the ignition switch could be bad on the power feed to the ECU.
 
Ecomike: Thanks for the feed back. I went through everything I could (with no wizard-ly electronic reader gizmos available). Checked all of the fuzes. Voltage and ohmeter check on the Crankshaft Position Sensor. Went back to the plug connector C200-C100, I believe it is called, at the fuel pump. Previously I had blown it out and cleaned it well -even though it was not really that grubby- and put some silicone grease on the female contacts. Unplugged it again and checked voltage to it and ground, OK. Pump side of the plug checked grounded on ohmeter. Plugged it back together and started the engine. Seems to be OK at this time and I have a Check Engine light on. Going to take it to the shop tomorrow and see what their equipment makes of all of it!
As fuses don't repair themselves, it would appear the culprit may well be the ignition switch (that you suggest) or the C100-C200 connector.
If this problem is POSITIVELY identified I will be sure to post it for others with similar problems.
Thanks
 
[Monday] Updated information. A local shop read out the 'check engine' status and obtained an error code of P-1694, a transmission error. After a little research I was informed that the code will be displayed if the PCM does not communicate with the TCM (transmission). Probably the error code would have resulted when the 5v signals were interrupted/or missing. As the 5v supply is also used for both ignition and fuel functions its absence would account for BOTH the no spark and no fuel conditions. From a technical website he accessed, he found the CPS (crankshaft position sensor) was the culprit in about 75% of something like 50 reported occurrences. Further, I was told that when the fail to start condition occurs, probably, the fuel and voltage gauges will not pop-up --they did not-- and the digital odometer will probably read "NO BUSS"--I didn't notice the 'no buss' indication myself, may have missed it (?).
With 75% odds, I ordered up a Jeep OEM crankshaft sensor as told to do and will put it in tomorrow. [note] Everything I did that 'appeared' to fix the fault had to have been a coincidence of the off and on again intermittent behavior. Meaning, it probably would have started at that point in time had I left it be and gone fishing or something!
Hopefully that will end this educational adventure!
I am only relaying what I was told. If anyone disagrees, I am not qualified to debate it, but would be interested in any other perspectives.
Thanks again for the interaction!
 
Last edited:
Jeep gremlins are very mobile, and have their own stealth methods, :laugh3: LOL. Let us know if it solves the current issue.

Don't forget it could still be wiring or a loose connector....
 
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