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steamboattj 07-21-2010 04:24 PM

Help with Fuel system problem!
I will try to keep this short and to the point. I have a 97 TJ with 120K miles, 4 liter engine When cold it starts right away, when hot it will crank for ever with out starting. If I cycle the key off/ on several times it seems to build up pressure (I can hear the fuel pump cycle) and then starts right up. When it is hot I suspect it is boiling the fuel away from the fule bar on the engine. (no pressure when I open the valve) What confuses me is that it does not seem to have a problem with losing pressure sitting over night. One other symption that is randomly, as i accelerate it loses power abruptly and then catchs up with itself. Any ideas?

my94wrangler 02-01-2011 09:58 PM

I am having sort of the same issue you are. I am lose power randomly but it then picks right back up. Just in the past few days, it's not picking back up unless I pull over, cut it off and restart but with in a few miles is loses power again but not picking back up like it once was. I have replaced everything you would normally do for a tune up, replaced the fuel regulater and oxygen sensor. I just put a fuel guage on it to check the fuel pump and that passed no problem. The only thing I can come up with now is maybe the computer or the map sensor. Did you ever find out your problem?

doclouie 02-01-2011 10:10 PM

This sounds like a classic check valve going bad on the fuel pump. Unfortunately you need to drop the tank as the fuel pump and check valve are one unit. I had that problem on my XJ and that fixed it. I am sure others will chime in too. It costs about $100 for the pump and about 4 hours of your time. Just make sure your tank is near empty.

my94wrangler 02-01-2011 10:15 PM

Even though I put the fuel guage on it when it was acting up and the guage read the correct pressure?

TexasT 02-01-2011 10:24 PM

I had a similar problem and it was my gas cap. Replaced and no problems since.

my94wrangler 02-04-2011 06:03 PM

A gas cap? wow! are you serious? It will cause it to loose power? How can that be?

rrich 02-18-2011 09:15 PM

Gas cap? Easy and not too unusual.

When you burn gas air has to replace the gas used in the tank. If the little vent on the cap gets plugged air can't get in. It eventually creates enough vacuum in the tank that the pump can't overcome it - so it stops running.
Try it with the cap loose - if it stops happening, replace the cap. It's a one way valve that lets air in but not out.

It can pull enough of a vacuum to collapse the tank! The plastic tanks are very susceptible to that. Fortunately they often bounce right back to shape,

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