New Member, Fuel Pressure Question

It's my first day on the site, and I've got a question. 93 Grand Cherokee w/ 318. My fuel pump went out a while back. I changed it and the filter, and I'm still getting the same symptoms. About 3/4 of the time I have to crank for about five seconds to get the thing to start, and when I run around 45-50 mph the Jeep drops into overdrive and feels like it's stumbling, not getting enough fuel. If I push the pedal down it will downshift and everything is fine. It only does this in OD at that speed range.

My question is, is there a way to increase the fuel pressure, because it doesn't seem like it's getting enough, or what else should I check?

Thanks,
Nathan

Thats a good question, my 1993 I6 engine has the same problem, I have been looking for some answers also. It seems to be that the pressure is not the problem but the engine timeing. I read on the net about another person hvaieng the same problems, I had the window open to look at it, but since I had so many windows open with a few pop ups I closed it by mistake.

I went as far as getting a big $$ cap and rotor and Bosh plugs and good wires, however it helped for a while but it seemed to come back.

I'm going to change the fule pump this summer (My mothers useing it in PA) as soon as she drives it back to my place. I have her run injector cleaner every fill up to try to combat the problem and all around good thing to do.

I would like to think since it's on both the 318 and I6 that it might be a PCM problem?!

If you find the problem please let me know
also if you can post what you do trying to solve it that would be cool.
Good luck.

First off, I think that the rough running between 43-53 mph and the occasional hard (prolonged cranking) starts are related. It seems to me that the engine is not getting enough fuel. I've changed the plugs. Even tried gapping them a little bigger for a little more power. Two fuel filters, new fuel pump (original died ~160K miles), fuel injector cleaner, octane booster, premium gas, and a new air filter. Nothing got rid of it.

My questions: What controls the fuel pressure? And is it adjustable? What keeps the fuel in the engine when it's turned off? Seems like I crank and crank just to get the fuel to the injectors.

If anyone know, please share the info.

Thanks,
Nathan

I'm not directly familiar with the '93s but if memory serves, there is a standard fuel pressure regulator on the return line which is vacuume operated. There are three things which can lead to the loss of pressure when the pump is off: 1) a bad check valve in the pump 2) one or more leaking injectors 3) a bad fuel pressure regulator.

Generally, low pressure would be more prone to cause loss of power with higher engine RPMs and load. The fact that you downshift and get better performance is kinda counter indicative of a pressure issue. You really need to put a gauge on it and test drive to find out for certain.

I just got done reading "Things to know about JGCs"thred, and it looks like what steve is talking about, try turning the key till the fuel pump truns on, but don't start it, hold on for about 40 seconds then start it, it it fires right up it's most likely the regulator.

If you find the problem write in...