Cherokee fuel press

Guys, if You don't help, nobody will. I have a '92 Jeep Cherokee 4.0 which has had a stalling problem for a few years which no one can seem to fix. Any help would be greatly appreciated. Let's get started. When it comes to 2250 rpm (under load or acceleration) seems like someone pinched the fuel line and it just doesn't want to accelerate. After a while, 3-4 seconds, it accelerates like nothing was wrong. So, I've been writing to all you guys before and after all answers, I tried to check everything possible before ask again. It took some time because I'm seaman and mostly on a ship but after replacing part by part, here I am, back here. First, new fuel pressure regulator... nothing happened, then oxygen sensor (it seemed like it measures wrong values), still same. New fuel filter (yesterday), still same. In Haynes manual I found how to test fuel press and I have just done the same and found: With or without vacuum line attached, pressure is 22 psi. So, I tried to drive around with gauge connected and mounted inside the cabin. Happens that in the moment of "stalling" press drops to 18 psi (!?). When it comes to my 22, things goes fine. But nothing like in Haynes about 31 to even 39 psi!? I tried to pinch return hose (possible only down before tank, everywhere is a plastic hose) and nothing changed, it stays on 22. Few months ago, even a fuel pump was removed and I expected dirty inlet filter (one like a nylon bag) but nothing was wrong, clean and fine filter found. One more thing, it happens even with a full tank of gas. Please, this group is my only and last hope. I like this car but the damn thing just doesn't want to perform like it should. Many thanks and greetings from Croatia, Europe.

Reply to
Davey
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Weak fuel pump.

Spdloader

Reply to
Spdloader

I would be looking at the connection on the throttle position sensor first. I use a spray contact cleaner on the connections on mine. WD40 will work as a connection cleaner too.

They are a rheostat and can get a dead spot, but their electrical connection can cause hiccups like you describe too. You can use a multimeter on ohms and take the readings as you open the throttle with it unplugged and the engine off. It should change evenly. If the resistance bumps, you likely have found the trouble.

I hear you can clean the guts of the TPS too, but have never needed to.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Few months ago, Jeep was at authorised workshop and guy hooked it up on some kind a multitester for Chrysler/Jeep and complete test passed through all of electronic items and found nothing wrong. Guy told me he has no time to drive around with "tester thing" so we couldn't see what happens when it comes to loaded 2250 rpm. Mike, what about this fuel pressure, can it be just a damn pump? Logically, when you pinch return hose, pressure should jump very fast, right?

Reply to
Davey

Reply to
L.W.(Bill) Hughes III

Reply to
Will Honea

The first thing I do with a suspected fuel problem is change the filter, then blow the old one back into a cup to see what was in it, and how plugged it was. Shiny metal flakes are usually pump, but some is normal

Reply to
Stupendous Man

Reply to
Davey

Weak fuel pump.

Spdloader

Reply to
Spdloader

I live in the rust belt so usually look for bad connections first. They are cheap and easy fixes. Our 88's fuel pump is run via a ceramic ballast resistor that is out on the fender near the rad. That is open to the elements and gets bad connections now and then.

The ground for the fuel pump is the body and the mesh strap from the rear of the head to the firewall goes rotten easy not letting a consistent circuit happen, but that usually causes stalls at speed like a CPS going bad.

That TPS is known to give an acceleration hiccup though. It is cheap and easy to clean it's connections just for the heck of it. Mine need a clean it every two years or so.

I have seen fuel pump impellers come loose on Dodge and Chrysler vehicles though. The suckers hum and draw power right, but just a trickle comes out.

If you think you actually got the return line blocked, then that pump could be suspect. Low power to the pump can cause it too though.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

Reply to
Davey

The last one I bought was $139.00

Spdloader

Reply to
Spdloader

Reply to
Davey

Mike, please, one more thing. If I drop down to fuel pump connections, how many volts should I read? More or less than 12 Volts? After your reply, everything is suspicious now. I remember one time I washed engine in my Cherokee and after a while, problems started. Possible some connection somewhere is rusty.

Reply to
Davey

If you connect the two wires together, which I have done before to test it, they are both female but the 3/4 circle on each side will fit one on one with the other or you need a long spade connector loose to plug the the two together (I have snipped off or unsoldered dead headlight spades that I use for that purpose) should give you battery and alternator voltage at the pump. This shouldn't hurt anything. The volt drop is for noise reduction only.

I am not sure without my Jeep out there to check what the drop is after the resistor, but if I remember right you should have about 10 with the key in run and a spike up to battery voltage when the key is first clicked on start, then a drop with the starter cranking... I think it is a 1.3 ohm resistor or a stock 'chrysler' resistor.

Mike

Davey wrote:

Reply to
Mike Romain

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