dave1123

Okay then.

635users

My ground to pins 1,3,4 were all about 125.0 when I plugged the good PCM to my bad Jeep. Not 55,11,11 like before. That bad PCM had some problems

dave1123

Funny story! My 81 Chevy Citation had a computer controlled carburetor and I needed a computer. I went to the junkyard and they had the same number one from a Z28 Camaro. When we swapped PROMs, we found a bent pin. The one counterguy turns to the other and says "That's why that freaking Z never ran right!"

635users

Great story! Now on to my next problem which is low oil pressure when it's supposed to be at 40 and it's only at 20. I just replace the Rings and a bad piston and the rod bearings which made no difference in my oil pressure. I checked out my oil pump and it seemed to be fine there were no bad teeth or pits in the gears. They seem to fit nice and tight but what you think about my situation?

dave1123

Did you check the rotor end clearance? The end plate and body cavity of the pump could be worn allowing pressure to bypass. I'm assuming you've checked pressure with a mechanical gauge?

Jeep says 10 psi it idle is okay as long as it increases with rpm. IDK, but that puts the fear of God in me! 40 psi at idle shows the pump is putting out all that the pressure relief valve will allow. Anything lower shows wear in bearings or lifters. In today's engines it's very unusual for the lifter bores to wear oversize so we can just about eliminate that. So all we have left is cam and mains. Oh..and thrust. Not being a standard transmission, thrust wear is also unusual, although it has happened.

IDK man. That just about covers all my brain has to offer. I know you just buttoned it up, but you could try a new pump. Argh!

635users

Yes, a manual gauge. I will have to read up to see how to check and see if there is wear in the parts you mentioned

635users

I replaced the old oil pump with a new high volume
one and I'm getting 35 pounds. That's just cranking the engine over because I'd haven't got my PCM back yet. The high-volume oil pump was about 3/8 inch longer so I had to make my oil pan work by cutting out part of the brace that's inside it and using an air chisel to push out the metal but now it's on there and all systems are go.

dave1123

BINGO! It's always nice to know I haven't lost my touch! Now to see if it holds at temp.

635users

Funny how you are the only one that has given me any insight about this problem. Where are all the other Jeep enthusiasts? Anyway, I will let you know how things turn out when I get the PCM back and get this thing running so thanks again for your help.

dave1123

Not to blow my own horn, but this comes from 60 years of working on cars and trucks, racing, and tearing them apart, putting them back together again. Unfortunately, the Grand is the bastard child of jeeps. Most of the hard core gearheads are into XJs and Wranglers, OH, and let us not forget MJs.

Just as an aside, I don't like or work on Fords! I've always been a Mopar and GM guy.