2K1XJ

ok...I have just finished installing my freshly rebuilt 4.0L motor. It turns over and (nice solid cranks) will not start. During cranking, a loud burst of air can be heard in airbox (sounds like its blowing out not sucking in). I can smell fuel and I got fuel when I pressed the pressure release on the fuel rail. I have double checked the coil pack installation, all wire harness connections and all grounds. I have the distributorless ignition and have tried starting with the crank position synchronized (CPS) installed both directions (180). I hooked up a scan tool and it is not throwing any codes.

I cannot think of anything else. Any thoughts would be greatly appreciated!

revsxj

check all grounds .... idk what to say i threw my new motor in last week and first crank started suprisingly.....take airbox off n feel for suction on the tb

2K1XJ

I'm gonna re-re-check the grounds and give it another go. The engine was rebuilt at a very reputable machine shop...hopefully that means they did it all correctly

revsxj

do you have compression? all vacuum lines hooked up?

2K1XJ

All vacuum lines are and hooked up and as best as I can tell, not leaking. I cranked the engine with my hand over the throttle body and I can feel air rushing out of it. Thats prolly not supposed to happen...just a guess.

revsxj

definately suppose to be sucking in......ugh let me give it thought and ill get back to you

krzonic

Sounds like your distributor is 180 out. Same thing happened to my new rebuilt engine by a shop. All the stuff was going backwards. After I put the new motor back in myself I had to take it back to them to get it running. There was backfiring from the air box not right. Right? The Distributor had to be turned 180 to get all the gasses blowing the right direction.

DFlintstone

Is the alternator hooked up?

2K1XJ

tried again with the "distributor thingy" aka cam position synchronizer/cam position sensor installed in both positions (180). still no start and blowing out of the throttle body.

Alternator is connected.

I have no way of checking compression...may need to go rent one at AZ.

Still no start.

DFlintstone

I had a wacky idea it might be possible to crank backwards. (A DC motor WILL go backwards), but that bendix won't. I would think that if it is truly sucking in from the exhaust pipe, (and rotating clockwise), something is wrong with the cam. Also, your finger makes a fair compression tester, for this!

Cherockee

The cam is not lined up correctly with the crank, IMO. If it were backfireing out the intake I could see there being a problem with the sensor being 180* out, but if you're just feeling air then that's a cam misalignment problem. Get the shop that rebuilt the motor to come over and take a look at it. I'm betting the cam and crank are not lined up correctly.

1991Jeep_Man

x2. To my knowledge, no sensor or disconnected vacuum line would cause a throttle fart.

Only things I can suggest is either make sure the cam is lined up correctly (I imagine the timing cover and everything ahead of it needs pulled), or go to AutoZone and rent a compression tester. If the came is 180* off, then I'd think no cylinders would have compression since the intake valves seem to be open during the compression stroke.

homebuilt503

^ I was thinking the same thing. With the cam being misaligned, the intake valves could be open during compression/exhaust strokes. Have that shop look it over, that would be my first step.

1991Jeep_Man

This thread does make me wonder something else though. Is the 4.0 an interferance engine? If the shop who rebuilt the engine put the cam in 'backwards' relative to proper timing, couldn't this cause some valve damage?

Firestorm500

Guy said he has distributorless ignition.