1996 Jeep Grand Cheorkee Fuel Pressure question

(1996 JGC 4.0L 6cyl)

OK folks, maybe I'm getting to the core of the problem. This still goes back to my orginal multi-post below:

http://www.automotiveforums.com/vbulletin/showthread.php?t=503585

.......but I needed an answer to what I checked today.

I measured the fuel pressure on the fuel rail today and it came in at 50 psi. The spec is 37-41 psi and the Haynes manual says to replace the regulator (which, of course, is part of the fuel pump, which REALLY sucks because I can't do that and it won't be cheap).

Can anybody give me a thumbs up as to whether this seems correct?

Also, any idea why didn't I see this problem before my CPS went out? As you can see, I have replaced quite a few other things as well, including the TPS today before I checked the fuel pressure. Just seems weird that now it has bead fuel pressure all of a sudden.

By the way, would high fuel pressure exhibit "misfires" as a symptom at higher speed rather than lower "around town" traveling? Just curious as if anyone knows...I confirmed today after I changed the TPS that I had the same symptoms as before.

Last thing, I had the last fuel pump installed about 3 years ago (supposedly non-aftermarket, but I am not certain).

Thanks for the help folks...

Bryan

Did some qucik checking and both Autozone and Advance have the same fuel pump listed for about 375.00.

http://www.partsamerica.com/ProductDetail.aspx?mfrcode=MST&mfrpartnumber=E7099M&parttype=52&ptset=A

I'm guessing that if I have to replace it, it's going to be that one.....

Bryan

Hold your horses on replacing the fuel pump.:nono:
Instead of replacing the fuel pump throw that haynes manual in the trash can and replace it with some good repair info. :grinyes: :lol: :rofl:
Mr Mitchell on demand says fuel specs for it is 47-51 lbs.
You are right on the money with 50 lbs.
Do not leave home without it.
But haynes is right on fuel pressure reg as part of fuel pump.

Man.....whew......that's great news.......

I was REALLY fretting over that for the past few minutes this afternoon.

I'm going back to the source and guessing my mechanic put on a piece of crap CPS. I'm going to put a MOPAR CPS on it and go from there.

It is just VERY strange to me that I had absolutely NO problems with my Jeep (vice the rattle in the Cat Converter, no replaced) before the CPS went bad. Now I can't get it to quit "misfiring" at high speeds for anything.

Thanks for the help....VERY much appreciated...

(If anyone else has thoughts or experience with a poor quality CPS too, let me know)

Bryan

I thing to keep in mind is when the cps is replaced a relearn sould be done on it with a good engine capable scanner.
Also a good scanner should say what cylinders are missfiring and how many times. That helps to know if it is any certain cylinder or all of them.
If you are going to try another crank sensor make sure to set it according to specs. Some use a felt dot under them to set the new sensor and be sure to run the relearn with a scanner after replacement.
Let us know how it goes.

His Jeep is 1996 which is still OBDI yes?

All 96 and up are federal mandatory OBD11 compliant

It is also required for you to be able to reach the diagnositc connector when sitting in the drivers seat.
But for some reason I have to bend streach and twist ever which way and stand on my head to find or reach some of them. :grinno: :grinyes: :lol:

That was my concern (regarding the replacement CPS) when I kept reading about this paper spacer on some of them. It just kept "digging" at me....."what if"...you know?

How about this though? Is there a way I can "re-learn" so to speak, the CPS that is on there now? Say, take it off and apply another "spacer" or pad or have someone take a dealership type scanner and try to re-calibrate it?

If not, the bad part is that I have no way of knowing what happened when it was replaced. Maybe it was done right, maybe not.

The good news is that I know a mechanic that works at a local dealership here and he has helped me before, I'm sure he will again. He helped me initially when I couldn't figure out what was going on, but I didn't know enough to bring up the possibility of the CPS.

I really appreciate all of the input. Very much appreciated I might add.

Bryan

All 96 and up are federal mandatory OBD11 compliant

Wasn't sure, looking online it appeared that the change was 97 and onward.

Can't Hoofan just disconnect the battery for awhile and force a full reset?

If the crank sensor on your jeep has a single bolt for mounting, it will have a paper spacer on it. If your's has 2 mounting bolts it will not have a spacer. Remove battery ground before changing sensors. Dale jeepman600@sbcglobal.net

I Just Had The Same Problem With Mine A Couple Weeks Ago. Took It Several Shops.some Said The Fuel Pump Was Going Out And It Would Cost $461.00 To Much For My Blood. So I Took It To A Old Friend Of Mine And He Checked It Out And Said That The Crankcase Sensor Was Going Bad And Also The Cam Sensor Was Also About To Go Out. He Replaced Both Of Them And It Is Running Great. Seems Like Everyone Is Having Problems With Jeep Products.

Wasn't sure, looking online it appeared that the change was 97 and onward.

Can't Hoofan just disconnect the battery for awhile and force a full reset?

Yes and no on reset.
Some systems retain memory and codes even with a battery disconnect.
There is several differnt PCM systms.
It is better on OBD 11 systems to use a scanner to clear codes and reset.
Alos some functions like the crankshaft relearn needs to be done with a scanner.
OBD 11 was mandatory in 96 up but you can find a few OBD 11 systems on some 94 and 95 models. And GM had the half/half systems on some 94-95. That required a special adpter and cabel and scanner to do anything witth them .

I have removed the Neg Battery cable quite a few times to clear the CE light and digital codes. However, I don't have a scanner.

I'm also not sure whether I have a one or two mount CPS, but I'm going to check.

Bryan

I have removed the Neg Battery cable quite a few times to clear the CE light and digital codes. However, I don't have a scanner.

I'm also not sure whether I have a one or two mount CPS, but I'm going to check.

Bryan

Like dale said the one bolt needs the green felt dot to set it.
If so make sure you use it or you will be in a world of trouble.:grinyes: :lol:
The battery disconnect is no the safest or best way to clear codes.
But if you do it that way be sure to unplug the neg cable first and hook it up last and always have the key in the off position.

I have a 1996 jeep grand Cherokee 4.0 it has 40 psi for fuel pressure it runs then stall out on me trying to get it fix.

I have a 1996 jeep grand Cherokee 4.0 it has 40 psi for fuel pressure it runs then stall out on me trying to get it fix.

That could be a lot of different things! Can you give more background on what has been done in the past?

Coil ECM new spark wires new pick up new fuel pump an filter

Putting a other fuel pump in it

Would wrong spark plug cause it to stall