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  #1  
Old March 2nd, 2004, 18:44
SilverMJ SilverMJ is offline
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'86 2.5L TBI MJ Won't start now (Get comfortable)

Okay, I did a search, and learned alot of new things, but not what I came here to learn.

On Friday, I drove the MJ to the store. When I came out and tried to start it, it nearly caught on about the 3rd rotation, but didn't. After which it took a good while of cranking (multiple attempts) before it started. Once it did, it ran...okay, it ran about as good as it usually did (don't get me started).

Then on Saturday, it did it again while I went to another store. Again took a while to start. This occurred twice again at a couple of stops I made. In between those, one time it cranked right up when I got in and turned the key.

After it not starting, then finally catching, it would rev like mad for a sec, I assumed as it burned up the gas that was in the TBI/manifold/cylinders?

I had a bottle of fuel injector cleaner I'd been meaning to put in this week, and decided to drop that in Sunday morning. I tried to start it and let it run for a bit, but it again nearly caught and then just cranked without starting. It's been that way ever since.

If I dump a couple tablespoons of fuel into the carb, it runs for the second or so until that fuel is gone.

So, we come to what I think is the logical conclusion that it's not getting fuel. Altho that doesn't explain why it revved outta control when it DID start.

But my question is, is there a way to find out whether it's the pump, filter, injector, or something else I haven't thought of without just throwing parts at it?

The Haynes manual says to connect a pressure gauge (which I don't have) to the TBI and let it run for 30-40 seconds.

Kinda hard to do right now...

Any ideas, oh great masters of the best Jeeps of all?
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  #2  
Old March 2nd, 2004, 20:26
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

First thing I woudl check is if the pump was priming. Key on dont start and listen for the wirrrrrrr sound.
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  #3  
Old March 2nd, 2004, 21:06
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Go to Autozone or Advanced and rent a fuel pressure gauge. Thats the first place to start and that will tell you what you need to check next.
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Old March 3rd, 2004, 10:34
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Okay, gonna try those things when I get home. Now that you mention listening for the pump, I recall that I never HAVE heard the pump on this thing. How loud is it? Do I need to be up by the tank to hear it?

And after thinking about it, why would it just not start, but run somewhat well once it DID start? Wouldn't it need the same, if not more, amount of fuel/pressure as when starting?

Now I'm completely confused!

Thanks for the help guys.
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Old March 3rd, 2004, 11:34
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Well, do you start your XJ with every thing on like most people do? Turn it all off and key it on. If it is FI you should hear a faint wirrrrring sound. If you do nto hear it then start with fuses then check volts to the sending unit outside the tank. If you have volts there pull the unit and see if anything is loose. There is a hose that goes from the sending unit to the bottow of the tank. Last year at Tellico Fore Wheeler's Father-in-Law (I think that is who it was) had that happen. Good luck let us knkow if we can help!
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  #6  
Old March 3rd, 2004, 11:59
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Well...there's nothing to have on.

A/C don't work, radio's gone. I don't use the CB unless I'm on the trails.

I'll listen for it tonight. The only noise I remember hearing when I turn the key is the momentary sound of the throttle position motor moving.

What fun! I love my MJ!!!
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  #7  
Old March 3rd, 2004, 15:33
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

And after thinking about it, why would it just not start, but run somewhat well once it DID start? Wouldn't it need the same, if not more, amount of fuel/pressure as when starting?

If the fuel pump was not working at all it would never start or run, however if it just on the fringe of going bad it may miss every now and then. If you test the fuel pressure it should be low if the pupm is not working to its full potential.
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  #8  
Old March 3rd, 2004, 16:49
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Okay, I got down under the truck and put my ear to the tank. There is no noise coming from that area.

But I swear in all the years this thing has been handed back and forth between my dad and I I've never heard the fuel pump running. Then again if it's a quiet pump...
I've never gotten under the truck to listen before. Never had to, it ran.

I'll stop by one of the parts places on the way home tomorrow night and see what they've got to rent.

Oh hey, Ghost, any idea which fuse runs the pump? I see nothin' labelled as such and I never had an owner's manual for this thing. Maybe after my daughter goes to bed I'll head out there with a meter.
If I decide I'm gonna keep this ornery beast, I'll have to invest in a FSM for it The Haynes manual is a bit vague in the fuse ID department.

Thanks again for the help guys. Y'all rock!

Last edited by SilverMJ; March 3rd, 2004 at 16:52.
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  #9  
Old March 3rd, 2004, 18:13
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Okay, so at the connector right before the tank... with it disconnected I get half a volt across the orange and black wires. I figure it takes more than .505 volts to run that pump!

The half-arsed circuit diagram in the Haynes manual shows a Fuel Pump Relay but the book doesn't tell me where it might be. In fact, the only relay I'm aware of that might be affiliated with this is the one sitting beside the battery in the engine compartment and I always assumed that was related to the starter, but now I dunno...
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Old March 3rd, 2004, 18:40
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

The fuse panel cover should tell you what fues is what. The fuel pump relay should be in the underhood relay center.
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  #11  
Old March 3rd, 2004, 18:44
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

This is an '86 MJ.

I'm afraid there isn't any fuse panel cover or underhood relay center.

It's just got miscellaneous crap strewn all over the fender wells and firewall.
I WISH it had such things. Methinks life would be so much easier....

Last edited by SilverMJ; March 3rd, 2004 at 18:50.
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  #12  
Old March 3rd, 2004, 19:09
SilverMJ SilverMJ is offline
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Okay, so I forgot about those little green Bosch cubes on the PS fender well. Swapped relay 2 and 3 and it started!

Unless this is a coincidence I'm gonna say that's the problem and buy a replacement tomorrow after work. (anyone know what the second relay was? )

Thanks again for all the input. I know I can always count on the guys to have the right answers.
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  #13  
Old March 3rd, 2004, 19:09
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Quote:
Originally Posted by SilverMJ
This is an '86 MJ.

I'm afraid there isn't any fuse panel cover or underhood relay center.

It's just got miscellaneous crap strewn all over the fender wells and firewall.
I WISH it had such things. Methinks life would be so much easier....
Not sure if its the same...but on my 88 the Haynes book calls it a B+ Latch relay....I tore my hair out one day cause i kept not checking it, cause I never heard of a B+ Latch...if it goes badf, it makes my elec fan go freaky too...
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  #14  
Old March 3rd, 2004, 19:10
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

one of them for the blower motor...
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  #15  
Old March 3rd, 2004, 19:36
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Re: '86 2.5L TBI MJ Won't start now (Get comfortable)

Could it be the horn relay?
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