walterlee06

I recently put the 4.0 from our rusted out '93 XJ into a clean '98 body after rebuilding the motor. It will not start unless I jump the 87 to 30 on the fuel pump relay. bought a new relay seems to only deliver half the required fuel pressure with relay. Also, It will not idle without depressing the pedal or jamming something in the linkage. The motor sounds good oil pressure is good but no charge to battery, which I keep charging. No power to power windows or locks, although when I take out the 50 amp fuse in the fenderwell block the locks do seem to do something. I have looked for unconnected wires, blown fuses, no smoking gun and turning the key on and off gives me no flasing codes. Any Ideas?

Topaz45

Just fought the same thing for a few weeks in my 98 but with out the motor swap and finally ended up taking to a friend to out on the computer and diagnose. And he found the ECM (little box beside the air cleaner box with three plugs in it) I also have a 95 and the ECM's are completely different maybe be the mix in models are not firing the sensors and such properly.

Mine would not crank but every once in awhile and when it would crank and run I had to keep my foot on the throttle to keep it running. With no knowledge to account for much I replaced the fuel pump thinking it was shot. No improvement. Finally sent it to my guy and he sold me an ECM off a junk 98 for 75.00 and it has been running perfect since. Try switching the ECM's if the plugs are the same and see if it makes a difference. They changed a lot between 93 and 98 Unless you just used the short block and put all of your 98 equipment on the 93 short block. If so then I have no clue.

Hope this helps

freegdr

check ppower to fuses in boxes?

walterlee06

Yes I did swap everything out from the '98 block Flywheel, distributor, intake on to the '93 block and head but I don't see how the computer could know that. The relay in the fuse block under the hood makes no difference if it is in or out the car will stumble like it is not getting quite enough fuel to start. only jumping the relay will start it. A couple of people insist it must be a bad ground somewhere. but I have looked at all visible grounds and found nothing so far