TJ spluttering
 

Hi guys hopefully someone has had this issue because I cannot seem to figure it out, what’s happening is after running for 5-10 minutes it starts sputtering and cracking at 3500 rpm and it won’t rev past that it loses power and is a pig to drive, I’m getting 42 psi of fuel pressure at the fuel rail (both before and after changing the fuel pump) since changing the fuel pump it takes longer for the problem to occur, now here’s the weird part, when it’s having a problem and you put a fuel pressure gauge on the fuel rail the problem is gone, hopefully someone has had the same issue

Thanks


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Do you reckon it could be crud in the tank being shaken up as you drive then being sucked onto the filter in the tank? When you stop the crud falls away and the pressure tests as good when you're stationary.

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Can also have good pressure but not so good flow.
System will pressure to the correct level but something could be blocking flow.

No when I changed the pump I cleaned the tank out, my Cherokee has 50 psi of fuel pressure at the rail and my wrangler only has 42 psi, the Cherokee only drops 5 psi of pressure when you rev it however the wrangler drops between 15-25psi when revving it and the Cherokee will hold 45-50 psi after switching the engine off however the wrangler just loses all pressure, I’ve never heard of an issue like this with anything so I’m stumped


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42 psi is a little below spec (44.2-54.2 psi), and pumps should flow 1/4 litre of fuel in seven seconds, which I'd have thought enough to maintain pressure when revved. You should also have at least 30 psi for at least five minutes after turning the ignition off.

Have you checked fuel lines for kinks/damage?

Did you swap out the whole fuel pump assembly or just the actual pump?

If you just did the pump, the filter/regulator on the top of the tank might need changing. The pressure regulator will also act as a check valve and if defective can allow fuel to drain back into the tank when the engine is off. I had a long crank problem many years ago and it was fixed by swapping only the filter/regulator.

I think it is the regulator as I didn’t have this problem before and I changed it, which is when I believe the problem started I couldn’t hear the fuel pump prime which led me to believe that was the problem, I will be ordering a new filter/regulator tomorrow and changing it as soon as I get it, hopefully that’s all it is


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Well I finally found the issue, there was 1 O-ring missing off the fuel pressure regulator, put a new regulator on it and runs so much better now


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