Engine not firing

YJJPWrangler87

YJJPWrangler87

New Member
Joined
Mar 12, 2006
Location
Raleigh
So this past weekend, we pulled the head of my 87 YJ to fix a small gasket leak, took it got it magnafluxed/resurfaced brought it back and started buttoning everything back up. We get to go start it and it will not fire at all..it will just sit there and crank and crank, it IS getting Fuel/Air and Spark to every cylinder. So we finnally got it to crank but it runs like crap now...raw gas is shooting back out the TBI Setup(its got a Howell TBI on it) and it seems like the valves aren't closing/opening all the way. What do we need to look for?

Zack
 
Did you pull the dizzy?
1st thought here is a tooth (or more ) out of time...
 
YJJPWrangler87 said:
So this past weekend, we pulled the head of my 87 YJ to fix a small gasket leak, took it got it magnafluxed/resurfaced brought it back and started buttoning everything back up. We get to go start it and it will not fire at all..it will just sit there and crank and crank, it IS getting Fuel/Air and Spark to every cylinder.
Click to expand...
Did you check the compression?
 
i don't think timing would be an issue cuz the jeep did not move after we pulled the head off, it does backfire through the intake, it spits out raw gas. compression is good cuz it will run now, it just runs like crap...no we did not pull the distributor off..all we did was replace the rotor button..

Zack
 
At least take the valve cover off and check that all of the rocker nuts are torqued down properly. How much was taken off of the head?
 
If you didn't move the Distributor and you didn't turn the engine over and move the timing, and you have spark and fuel. My guess is the the valves are the issue. How much did they take off on the resurface job?
Check compression on all cylinders. Sounds like valves are not closing all the way, or not opening up.
Is this a 258? 4.0? 2.5?
 
258 4.2...im gonna pull the valve cover off and look at the rockers..i took it to loop road...second time taking a jeep head to them...i don't know how much they took off..not much..the engine is only 2 1/2-3 yrs old.

Zack
 
sounds like valves are adjusted wrong or the valve stem height is wrong. However, you usually dont see that problem on just a resurface. Did you get a valve job done or did they lap the valves in..or do you know? One more thing to check..I know this sounds stupid, but I've seen it done before ..are the wires in the correct order?
 
yes the rockers were off when they resurfaced it...they were put back in the correct order...bigwoody wires are in correct order...numbered them actually to prevent it...all i had done was magnafluxing and resurfacing...no valve job done whatsoever

Zack
 
like everyone said, recheck the valves/rockers. The 258 has non adjustable rockers, and they are only something like 12 ft/lbs
 
Just for a tempory thing to try it, loosen up the rocker bridges a little bit, so the valves can close all the way, after you have checked compression, and found you dont have a min. of 90 lbs. It takes that to run at all normally.
 
I'm kinda agreeing with Bob here.

you surfaced the head, but made no allowance for the removed material in the push rod length, so now the valves are held open ever so slightly.

You need to know how much has been removed, and then replace the pushrods with a set that much shorter.

Have fun
 
we didn't have to do that for amandas xj when we got her head resurfaced...now when i installed the rockers and everything...after i had torqued them down...i could wiggle two of the rocker arms...is this cuz the piston was all the way down or all the way up? if thats not right then thats my problem.

Zack
 
Yo,
Bring #1 up to TDC and ready to fire. Both intake and exhaust should have some slack relative to one that is pushed down. If not, valves are being held open and I would assume the rockers are adjustable to correct the effects from the valve job at the shop? I bet if you search Google you will find the valve adjustment procedure for that motor. When valves are ground they are pushed up into the head this erasing any clearance they may of had prior to the work UNLESS the technician measured the stem heights and restored those original values before releasing the head to you.

:beer:
 
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