No start after head swap, pushing air through TB

[9c1cap]

So I picked up an '01 recently with a cracked 0331 for 400 bones. Towed it home and pulled the head to verify the problem and, indeed, it was cracked in the same place they all do. Picked up an 0630 from the 'yard and dropped it off at the machine shop. They took .006" off the deck, did a three-angle job and installed new, taller beehive springs and new guides and seals. I also had them deck the new header I bought and throw everything in the cook tank and bead blast the intake. I bored the TB out myself to approx. 60mm (just enough to remove most of the lip without going too far or getting into the butterfly seal. To test the TB I ran it on my '95 XJ for a week with no issues other than a slight whistle (had to plug the port for the MAP sensor of course).
So I get everything together with a new w/p, new IAT sensor, new CTS, cleaned injectors and rail, and new battery, and crank her over for the first time in my possession, NO START and Im getting air intermittenly popping thru the throttle body. Not a backfire, just puffs of air(no intake installed). Pulled a p0122 (IIRC) and a couple of trans codes so I ignored the trans codes and replaced the TPS with an Advanced unit. Return to the jeep and with new TPS installed I get a repeat of first start attempt only now Im getting just a p1391 code.
I have a few things I want to verify concerning the p1391 next time I can get to the jeep (stashed it at my brothers house) but the air popping thru the TB is a concern for me. I pulled the VC to make sure all the pushrods were installed correctly and seated on the lifters and I see no issues there. Just looking for some advice on what to check next. I dont have access to a computer while Im at the jeep and all I have is a Haynes for reference so I m trying to put together a checklist next time I can make it up there (have a 3mo old baby so time is limited). Any input or suggestions is greatly appreciated!!

Craig

 

[birchlakeXJ]

P1391 is intermittent loss of either the camshaft position sensor signal OR the crankshaft position sensor signal.

If you have no spark, I'd suspect the crank sensor. If you have spark, the cam sensor is suspect.

The cam sensor can be tested with a meter and a manual. The crank sensor can be tested too, but testing is not always conclusive. If you buy a crank sensor, do yourself a big favor and buy a Mopar unit directly from Jeep. Aftermarket crank sensors are "hit and miss" with a whole lot of miss........

 

[9c1cap]

Yeah, thats why I noted that the TPS was an aftermarket piece. From here out Im goin Mopar on all electrical parts. Thats also why Im asking for trobleshoot procedures or paramaters on the sensors instead of just throwing expensive Moparts at it. Is there any links to an FSM in pdf or whats the best place to buy one?

 

[birchlakeXJ]

http://www.jeep4x4center.com/knowledge-base/index.htm#catalogs?utm_source=cj

http://www.pacificcoastmanuals.com/jeep_cherokee_service_manuals.html

 

[9c1cap]

Thanks! Next task is towin the jeep home so I dont have to run back and forth with what little free time i have!

 

[joe_peters]

How consistent is that "puff" of air?

Makes me suspicious of your timing--intake valve open on compression/exhaust stroke?

 

[RenegadeStang]

How consistent is that "puff" of air?

Makes me suspicious of your timing--intake valve open on compression/exhaust stroke?

What I was thinking...

 

[9c1cap]

Thats why I pulled the valve cover!! Thought maybe I torqued a pushrod off to the side of a lifter! But I ruled that out today. As I said the p1391 doesnt concern me as much as that air out of the TB. Havent touched anything below the water pump, let alone had the timing cover off. Hopefullly Ill get the thing yanked home by thursday or friday. I think first thing to check would be the cam sensor, setting the first cyl at TDC and doing the toothpick check. And even then Ill prolly pull the distro to check the teeth. Then checking sensors from there???

 

[8Mud]

TDC 1, turn the motor over by hand until the number one piston is building pressure. I usually use a compression gauge. See how close the timing marks are to "0".

To get it near exact, put a curved piece of wire into the spark plug hole and turn the motor over by hand, with the wire resting on the top of the piston, until the piston is all the way to the top. You can rock the piston up and down and feel with the piece of wire when it is all the way up. Just make sure the last time you turn the harmonic balancer, it is to the right as you are facing the motor (to take the slack up in the timing chain). You can get pretty darned close to a true TDC (top dead center) this way. Both the number one rockers should be all the way up and loose enough to wiggle the rockers sideways a little. The timing mark should be at "0". I'm not exactly sure how to check the timing of the sync sensor. In a typical distributor, the rotor should be near the number one pole, but won't be exactly on. I'm really not familiar with the late models.

My guess is something may be off a tooth or two. It is always better to check the basics before you move on to the exotic, especially after major engine work. Double checking the basic setup never really hurts anything and can save a lot of headache and grief in the long run. As will a basic compression test.

You can also use a degree wheel and a piston stop. But my way is good enough for a quick check and will let you know if something is assembled wrong.

If you take all the plugs out, you will likely be able to turn the motor over using the harmonic balancer bolt. Though it may loosen the bolt, when turning counter clockwise facing the motor. Trying to do it with the starter is unlikely to work out for you. Removing the electric fan and putting a piece of cardboard in there to protect the radiator (and your knuckles) if the socket skips off the bolt, will make things easier in the long run.

 

[Warlock1]

How many miles on that engine? Sounds to me like a stretched timing chain and the cam to crank timing is off a tooth or 2 or 3. To check, pull off distributor cap and turn crankshaft with socket on harmonic balancer bolt slowly first clockwise until distributor rotor starts to turn then turn counter clockwise until rotor starts to move. If any more than say 1/16 or so of a revolution of the crank turning and rotor not turning then your timing chain and gears are probably shot.

Only other thing it could possibly be would be an intake valve hanging slightly open but since this is a freshly rebuilt head, it's not too likely.

 

[Talyn]

The puff of air does sound like a timing issue or possibly too much preload holding the valves open. Of the lifters could just be pumped up make take a few minutes of running for them to bleed down. From the work that was done it doesn't sound like to much preload. I do question the longer springs they installed though. Did they use the stock valves?

It wouldn't be a stretched timing chain. It would have to be really stretched for this to happen and I doubt that.

The p1391 code is probably the cam sensor. I would check it out, the magnet may have fallen out of the or the drive could have locked up and sheered some teeth. If it checks out I would reindex it and see what happens.

 

[9c1cap]

Talyn- stock valves with a "3 angle" job.

Trailering the jeep home tomorrow. Hopefully I will have some new info before the weekend is over.

Thanks for all the suggestions. Gonna give a thorough goin over, just threw about a grand at her with this new top end so Im gonna take some time to diagnose instead of just throwin expensive mopar sensors at it. Would like to have this thing on the road under two grand...

 

[Warlock1]

Well, what happened? I'm very curious.

 

[9c1cap]

FINALLY got twenty minutes free to have a look. Oil pump drive was off a tooth. Pulled and reset with a toothpick and she fired up on the first rotation!!I know the previous owner had replaced the cam sensor as the old one was in a box in the right fenderwell. I had mistakenly assumed that this was done previous to the head failure, otherwise I would have paid it more scrutiny sooner. Wonder why he would have pulled the drive tho?? Teeth looked good on both the cam and the drive....

Still dont understand the puffs of air thru the tb tho. I have to pull the w/p to replace the metal inlet tube because it cracked at the threads. I'll pull the timing cover and check for excess slack in the timing chain. But otherwise it runs really strong with good throttle response, at least for the quick maiden test drive i took up the street, and fires over quickly after turning the key...