Got my 1991 XJ put back together last weekend and everything is plugged in and timing is correct but the motor will not start and run... it spudders and dies... theres fuel / air / spark ... only thing I can think of is the Crank pos. sen. When I removed the flex plate I did not mark it and im not honestly sure you need to or not but I know the CPS reads the flex plate. If anyone has any ideas or suggestions that would be super helpfull.. Thanks

 

The crank sensor went bad on my 98, but it would just crank and crank but never even sputter. I think if it was the crank sensor that went bad you would get no signs of life.

 

my main question is would the possition of the flex plate effect the cps reading?

 

not sure what you mean by the position of the flex plate, the cps tells the ecm if the engine is spinning, how fast etc. so it should read basically at all positions. I have heard of people who were getting a weak signal so they tapped on the sensor to get it closer to the plate, but if it breaks that's bad news bears. Mine was $75 for a new one.

 

When I put a new flex plate in mine,I could only bolt it in one spot. I got it wrong the first time and my bolts did not line up when I got to the third bolt. I think if you have all the bolts in it, then it should be in the correct spot.

 

Well, there's this...

1991-1995 are OBD-I (Chrysler)


The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

 

The flex plate only can go on one way - the right way. The offset holes in the crankshaft index it.

 

Define "put back together". What all did you do? It's not the flexplate.

 

x2 the flexplate will only go on one way - the holes are not evenly spaced. So if you got all 6 bolts in, you got it right.
You can double-check, if you like:
- remove the starter.
- rotate the crank to 0 degrees (TDC) at the timing marks at the front of the engine.
Check in the hole for the starter:
- there should be no notches right at the starter hole. If you reach down in the hole with your finger, you should be able to reach one notch down lower. You may be able to reach one up higher, if you have long fingers, but there should not be any staring you in the face.
I'm talking about the notches the CPS picks up, not the starter ring gear teeth. The notches (actually square holes in a ring on the flexplate) are behind the ring gear teeth. The notches are in 3 groups of 4, groups are spaced 120 degrees apart.

 

Well I bought this jeep with no motor , I bought a long block and put it in the jeep. Got the trans rebuilt and bolted everything together and plugged everything in .... I have replaced a few sensors ( coolant temp , maps , crank sensor ... ) I got spark air and fuel ... when the jeep turns over it pops a lot but no running... checked the codes this morning ... nothing came up that means anything ... 12 , 33 , 55 ....

 

Check the ballast resistor and your timing its either a bad ballast or your timing is off a couple teeth on the distributor

 

firing order wrong some manuals have it wrong according to the screw on dist which most of us use as reference point!

 

My money's on an improperly indexed distributor and/or messed up firing order as freegdr suggests.

 

ill take timing issue for a hundred...lol...

 

Sooo, Guys, is #1 at 5:00, (viewed from the side), on all 4.0's? (except 00 & 01)