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Unread 08-02-2010, 01:01 PM   #1
brentd711
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YJ No Start w/o Priming

Howdy...new to Jeeps and started with a '90 YJ 2.5L that I bought 2 weeks ago. It's been rode hard & put away wet but has run fairly well until this weekend. It will crank but refuses to fire until I pour a dash of fuel in the throttle body. I can hear the fuel pump start when I turn the key. It will start w/o priming 95% of the time as long as its not shut down for longer than 15 minutes. Previous owner says he replaced the fuel pump just before I bought it, I think it may have a bad sending unit ground as the gas gauge works at times, other times it goes to full when the tank is not filled. I've searched the forum and seen plenty of "no start" threads but can't make a connection to my problem. Any help is appreciated.

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Unread 08-02-2010, 01:04 PM   #2
Ronnie-Evans
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It sounds like a fuel sending unit/pump problem. As much of a pin that it is you'll need to drop the tank. Ive dropped mine 4 times since ive owned mine. All beacuse of fuel pump issues. Your pick up tube may have fallen off as well.
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Unread 08-02-2010, 01:12 PM   #3
jdarg
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At least check the pressure to make sure its not in spec before droppign the tank. It needs to hit 30 psi at prime and needs to hold that pressure for a good while after shut-off, lets say 15-20 mins before it starts dropping a bit.

If you are sure its priming, its not the wiring. The gauge issue sounds like the sender inside the tank was probably manhandled a bit too hard last time it was serviced.
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Unread 08-02-2010, 01:22 PM   #4
brentd711
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If the fuel pump is bad would it stay running? I drove it 90 miles yesterday, had to prime it twice, it started on its own about 5 times.
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Unread 08-02-2010, 04:40 PM   #5
Mark05059
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I would sooner guess that its sucking air somewhere... once it gets running it has enough fuel to keep it running.
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Unread 08-02-2010, 05:44 PM   #6
brentd711
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New air filter and I can't find any vacuum leaks. Something's not right 'cause I'm getting about 12 mpg.
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Unread 08-02-2010, 06:28 PM   #7
laybackman
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Quote:
Originally Posted by brentd711 View Post
Howdy...new to Jeeps and started with a '90 YJ 2.5L that I bought 2 weeks ago. It's been rode hard & put away wet but has run fairly well until this weekend. It will crank but refuses to fire until I pour a dash of fuel in the throttle body. I can hear the fuel pump start when I turn the key. It will start w/o priming 95% of the time as long as its not shut down for longer than 15 minutes. Previous owner says he replaced the fuel pump just before I bought it, I think it may have a bad sending unit ground as the gas gauge works at times, other times it goes to full when the tank is not filled. I've searched the forum and seen plenty of "no start" threads but can't make a connection to my problem. Any help is appreciated.
Turn the ignition key to the ON position and wait for a full minute. If it then fires up, your fuel pump is probablyEDIT EDIT becoming tired and will be NG soon enough. Check the fuel tank to see if it was actually taken down since it needed to be when that fuel pump was 'changed' by the previous owner. Now some guys get 'creative' and cut a hole in the tub to remove the fuel pump. Check that also.

If it is not maintaining fuel line pressure after shuttting down, for very long, then it is possible that the fuel pressure regulator in the TB is also tired.

Keep in mind that this Jeep is 21 model years old. How many cars that old are still on the road! Not many....
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Unread 08-02-2010, 06:47 PM   #8
brentd711
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I'm full of questions and appreciate all the replies. No access hole in the tub, no luck with the key on for a minute (and more) or cycling the key several times (for multiple prime cycles).

Can you point me to the pressure regulator? I don't see a Schrader(?) valve anywhere to check fuel pressure. Any chance a crapped up fuel filter could cause this issue? Should I get a good shot of fuel when the filter is removed and I turn the key on?

EDIT...searched the net and found the same issue on another forum with a 4.2 Cherokee. The guy says he cured the problem with a new coil, claims he had an "intermittent fault". Cherokee no start w/o prime

Last edited by brentd711; 08-02-2010 at 07:22 PM.. Reason: new info
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Unread 08-02-2010, 07:54 PM   #9
laybackman
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Quote:
Originally Posted by brentd711 View Post
I'm full of questions and appreciate all the replies. No access hole in the tub, no luck with the key on for a minute (and more) or cycling the key several times (for multiple prime cycles).

Can you point me to the pressure regulator? I don't see a Schrader(?) valve anywhere to check fuel pressure. Any chance a crapped up fuel filter could cause this issue? Should I get a good shot of fuel when the filter is removed and I turn the key on?

EDIT...searched the net and found the same issue on another forum with a 4.2 Cherokee. The guy says he cured the problem with a new coil, claims he had an "intermittent fault". Cherokee no start w/o prime
Yes you should get a good shot of fuel if the fuel line was off before fuel filter and someone else cranked the starter. I would change rthe fuel filter simply beccasue it is probably shot anyway.

Weak spark; pull a plug wire and then have a buddy turn the enggine over.

You must be holding the exposed metal end of the plug wire close to anything metal under the hhood. Look at the spark, is it bkue/white in color?

Did you hear the 'snap' when the spark arched? If the answer was yes then you have probably have a good spark.

Oh yeah....Make sure that you are insualted from the end of that plug wire!

The '90 2.5 had a fuel pressure regulator inside the TB.

It can have any number of things OR combination of things affecting its ability to start or run.

You could have a bad gas cap, lower than optimum fuel pressure, a bad regulator, a weak spark and bad plugs. And the list is not complete.

What you must do is eliminate the most likely item and work on the next most likely item.
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Unread 08-02-2010, 08:11 PM   #10
brentd711
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Saturday morning I picked up new plugs, distributor cap & rotor, tried to move the YJ into the garage to work on it and it wouldn't start. Replaced the parts in the yard, still wouldn't fire. All the cranking didn't flood it so I tried a shot of fuel in the TB and it started right up. It does seem logical that a weak spark would ignite a TB with a heavy charge of fuel but not a "normal" charge. I do know that the gasket on the fuel cap is sketchy and changing out the fuel filter is cheap insurance anyway. Anyone know what the coil resistance should be?
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Unread 08-03-2010, 07:04 AM   #11
laybackman
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Quote:
Originally Posted by brentd711 View Post
Saturday morning I picked up new plugs, distributor cap & rotor, tried to move the YJ into the garage to work on it and it wouldn't start. Replaced the parts in the yard, still wouldn't fire. All the cranking didn't flood it so I tried a shot of fuel in the TB and it started right up. It does seem logical that a weak spark would ignite a TB with a heavy charge of fuel but not a "normal" charge. I do know that the gasket on the fuel cap is sketchy and changing out the fuel filter is cheap insurance anyway. Anyone know what the coil resistance should be?
If it runs when you hit it with a dose of fuel down the throat of the TB you probably have good voltage. I would replace the fuel filter. If it does start then I would treat the fuel with SeaFoam or Marvel Mystery Oil for the next few fill ups.
I don't think the fuel pump is NG if it pumps fuel OK after you get the engine fired up. Your TB could be real dirty BUT try one thing at a time! Logic gets things fixed faster when coupled with knowledge.
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Unread 08-03-2010, 01:23 PM   #12
Que89YJ
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Clean the throttlebody, IAC, and TPS. Change the fuel filter. I am bettin' that it is somethin' else not mentioned. The fuel will drain down into the tank if the check valve in the fuel tank fails. My .02 would be to do a fuel pressure test and look at the bleed down.
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Unread 08-04-2010, 07:39 PM   #13
brentd711
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I don't have any way to check the fuel pressure. Replaced the filter, had to prime it once to start, then restarted it several times w/o priming about ten minutes apart. Engine never got warmed up so I thought I got lucky but now it's back to not starting when cold.
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Unread 08-04-2010, 08:21 PM   #14
93jeepyj
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The gauge and the the pump share the same ground and you say the gauge is funny, I would be checking that out.
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Unread 08-05-2010, 10:07 AM   #15
Que89YJ
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You can get the gauge from any of the bigger auto parts stores for a deposit that is refunded when you return it. You need to check the fuel pressure.
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