1993 Jeep Grand Cherokee fuel leakdown problem. - JeepForum.com
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Unread 06-14-2010, 12:58 PM   #1
Jess1256
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1996 XJ Cherokee 
 
Join Date: Jun 2010
Location: usa
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1993 Jeep Grand Cherokee fuel leakdown problem.

1993 JGC 5.2 Liter V8 Limited. Having issue with keeping the fuel pressure up in the fuel rail. Using quick start the engine can be made to run after a quite few tries, runs nice, too, though it won't start-up after sitting over night, but will keep fuel in the rail for only a few hours and starts right up in that time and will run endlessly. But if not started every few hours, all the fuel seems to drain from the rail and back to the tank. There doesn't appear to be any fuel leaks and no strong smell of fuel. I am hoping someone might have a suggestion that I have not thought of. Fuel pressure regulator , although I have no means to actually test it, and it's vacuum seems to be fine. It is a 1993 5.2 so the FPR is on the back end of the fuel rail and has a vacuum going to it from the intake manifold. Perhaps it is the fuel pump? Might it cause such a thing if it's on it's way out? Any advice or a point in some direction would be greatly appreciated.

Love the forum, by the way. Great resource and lots of great people. Thank you for any help you might offer. Have a nice day.

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Unread 06-14-2010, 03:54 PM   #2
Craft95ZJ
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It sounds like you have a possibility of leaky injectors leaking into the cylinders and flooding the engine. If it runs good then perhaps you have a good fuel regulator. On the other hand your check valve could have gone out, but it should start and run without a check valve. Something to check anyways.
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Unread 06-14-2010, 05:33 PM   #3
classicmetalman
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Originally Posted by Craft95ZJ View Post
On the other hand your check valve could have gone out, but it should start and run without a check valve. Something to check anyways.
Leaning towards the check valve. IIRC, check valve is supposed to hold pressure in line when off. Tried priming it before a cold start?
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Unread 06-14-2010, 10:24 PM   #4
-Joe-
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The fuel pump will run for ~1 to 2 seconds when your first turn the key to prime the rail. Even with a leak down situation it should still start after that.

Are you saying it wont start at all? Or just not within the first few cranks?
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Unread 06-15-2010, 05:34 PM   #5
Jess1256
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It will start after being primed, either with alot of tries with quick start of priming the line. And then, after many tries of it starting, idling for a few seconds, it will run normally, lots of power then and getting plenty of fuel, drives fine once it is running and does not stall. But after a few hours of sitting it will lose it's prime and the rail will have no pressure and the whole process must be done again for it to start and run again. Thanks for the suggestions. I am going out to check out the check valve in a bit. Thanks again and have a nice day and happy jeeping.
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Unread 06-15-2010, 06:01 PM   #6
Jess1256
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It will never crank over on it's own. Must be primed first, or quick started multiple times till fuel is sucked or pushed up to the rail
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1993 zj , 5.2l , fuel pressure regulator , fuel system , help please

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