I just put the engine back in, got everything connected nice and neat and she cranks but doesnt fire. I rebuilt the engine, machined, rebuilt head, new pistons, cam, lifters, bearings.... the whole deal.
While the engine was out I did loosen the crank position sensor mounting bolts and re tighten them just in case. I guess I should have replaced that sensor then....
I also took the cam pos sensor apart just to see how it works. It's a hall effect sensor - not much to it. I don't think I could have messed that up?

Is there a test procedure to check these to see if they are working?

Any and all thoughts are appreciated.
Thanks,
Brian

 

Which is it missing, fuel, spark or both?

 

When I rebuilt the engine on my chevy (haven't done a jeep yet) and put it back in, it was just like trouble shooting an engine that doesn't work...

I just stated the obvious huh?

Really, check if it starts with some ether (starting fluid) first, check the spark, check the fuel.

THEN start worrying about issues with sensors.

Chances are, it's just not getting enough gas. If it runs on the ether, you'll have a place to start. Plus, what an easy check of your stuff.

 

Was the CPS installed to bellhousing when you dropped the engine back in and bolted up? Most guys that do that report that they broke the CPS by hitting it with the flexplate.

But yes, see if you have fuel and spark.

 

There is pressure at the fuel rail (remove cap and depress valve - fuel squirts out). This is a MY2000 so I have the long coil pack. not sure how to check for spark. I guess I can remove the coil pack, plug in a spark plug and use a cable to ground it? then turn over the engine... I'll try that.

Ok... I have spark. But i did notice that the new plugs (bosch platinums) were fouled with a black oily substance. It hasnt really fired so my guess is that it is fuel and engine assy lube (black graphite). Maybe i went a little heavy on the lube when I slide the pistons in. I coated the cylinder walls.... like I've done before? Also the fuel is old (from last fall - 1/8 tank). I guess I should pull the plugs, clean them and add some fresh gas to the tank.
I should probably dribble a little fresh gas down the intake as well to see if it will fire?

Also, yes the CPS is mounted to the bell housing. It could have been bumped? But since I'm getting spark would it be logical to assume the CPS is functioning???

I have to go help my son install a stove.... so this will have to be continued later. You guys are great and so is this site!
I'll pick up some starting fluid....

Thanks.... any other thoughts.

 

Black moly on the cylinder walls? Never heard of that. a little motor oil maby, but i bet the black gunk coated Bosch(hopefully not +2 or +4 platinum or Iridiumz) are the problem. Plain ol Champions like from the factory or Autolites are what these engines like. Ive seen many, many missfiring cylinders because of these blasted german multi spark plugs blowing the ceramic electrode insulator apart. Mmmm, internal flying ceramic!

 

Put a cheap set of plugs in it, don't get suckered and be a victom of advertising. Platinum plugs, and multi electrode plugs are a scam in odrer to take your hard earned cash.

 

I hope you guys are right. I'll get some champions and give it a shot tomorrow. I ran out of day light today...

I've been running the Bosch plugs in my other 2 Cherokees with out problem tho. Maybe I should swap those out as well?

And I guess I got carried away with the assembly lube. I kinda give every friction surface a light coat of it as it goes back together. Cylinder walls could have gone with out. Live and learn.....

Thanks for the help and I'll update tomorrow.

 

So I put a set of champion plugs in.
I swapped coil rails with one of my other Cherokees.
The other jeep runs fine with this rail in it (just a check...).
Still no start.

So i compared fuel rail pressure between this one and the one I had parked next to it (was using it for jump start). What i found was the other Cherokee with the key turned on had a steady spray of fuel coming out of the test port when I depressed the valve with a screw driver. This one did not.... when I push the valve i just get a little squirt / dribble (with the key in the on position).
I checked all the fuses with an ohm meter and swapped fuel pump relays with the running jeep. Again the running jeep ran fine with this relay.
Has the fuel pump gone bad from just sitting in the drive way?
Fuel pump in in the tank??? If so, it wont be fun

Any other ideas.... how to test a fuel pump?
Air in the fuel line? I hold the fuel rail valve in and nothing seems to come out. I turn the engine over a bit and pressure builds up a but depressing the valve only yeilds a small amount of fuel.
Thoughts?
Thanks

 

Check your PM's...Tj

 

are you not hearing the pump prime the system when you first turn the key? if not, pull htep ump out and spray the crap out of it with carb cleaner. like through the pick ups and the outlet and everything and then put power to it with some jumper wires. if it doesn't break, reverse the wires back and forth a few times. still no go then soak the pump in a 1 gallon can of carb cleaner over night. it'll fire after that.

i buy broken down bmws and rebuild them and lots of time the pumps are frozen from sitting for so long. this is how i clean them and they last for as long as i know the people who get htem from me have had them. i put a junkyard frozen pump into my autocross bmw after cleaning it the way i put above here and it still runs, 5 years later for the guy who bought it from me. he uses it as a daily driver, so you know that cleaning it works and hte pump won't crap out on you in a few weeks.

 

I can hear the fuel pump run. Comparing it to a running cherokee.... it sounds the same.
I guess i need to buy a fuel gauge to measure the fuel pressure.

I can't find any vacuum leaks. I pulled a line off the back of the throttle body and sucked on it (don't laugh). it seems to hold a vacuum - one way valves seem to be working....

"Check your PM's" what is a PM? Power module?

Thanks again...

 

private messages


do you have the fuel lines on right or is the return and inlet lines backwards? no idea if you can do that, just throwing out ideas

also, did you set the tps properly

 

MY2000... there is only one fuel line?
TPS? throttle position sensor? Set up? cant find any info on that....

I replaced the Crank Position sensor.... still nothing.

I swapped Cam Position Sensors with one from a running Cherokee. I started the running cherokee with the Cam pos sens from the nonrunner and CEL started flashing. Running cherokee ran rough. Non runner was popping and hissing like it wanted to start. I swapped them back and now i cant get the runner to start???? Has that good cam position sensor gone bad just from me swapping them?
I guess I'm off to buy 2 new cam position sensors.

 

Got it running today.
I discovered that the camshaft pos sensor shaft has to be aligned properly. The cps controls the fuel injector timing. Once aligned it fired right up. too bad i learned this when i swapped cps between this xj and a running one. in the end the runner no longer ran and I had 2 non runners parked in the drive. I swapped the cps by swapping shafts and all.... not good. the position of the shaft is critical.
Thanks for all the responses.... Time to order a lift and get this thing out.