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Unread 06-18-2011, 05:28 PM   #1
Plyj
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1990 YJ Wrangler 
 
Join Date: Feb 2010
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90 YJ Got spark, got fuel. No start

Okay... this is frustrating. Installed new 4.0L head (new valves, springs, retainers, headers, rocker arms, etc.) on my 4.2L block.
Got TDC on compression stroke (the way I checked this was by watching the valves open while manually turning engine... last valve open before TDC mark hit 0 was intake valve). Have GM HEI which ran great before head transplant.
In fact, everything ran great before transplant.

I'm getting spark (hung light off #1 & cranked engine). I'm getting fuel (looked down throat of Weber & see gas going in when I move throttle).

This should be simple... I've got spark, I've got fuel, and I'm on TDC.

Time to pull timing chain cover??? This thing has me baffled... help!

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Unread 06-18-2011, 05:51 PM   #2
giggityjeeper
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1990 YJ Wrangler 
 
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bad vac leak somewhere, taht would keep it from firing, if it was bad enough....

ground not hooked up somewhere...

dont know man frustrating fro sure this kind of ****
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Unread 06-18-2011, 08:46 PM   #3
laybackman
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Quote:
Originally Posted by Plyj View Post
Okay... this is frustrating. Installed new 4.0L head (new valves, springs, retainers, headers, rocker arms, etc.) on my 4.2L block.
Got TDC on compression stroke (the way I checked this was by watching the valves open while manually turning engine... last valve open before TDC mark hit 0 was intake valve). Have GM HEI which ran great before head transplant.
In fact, everything ran great before transplant.

I'm getting spark (hung light off #1 & cranked engine). I'm getting fuel (looked down throat of Weber & see gas going in when I move throttle).

This should be simple... I've got spark, I've got fuel, and I'm on TDC.

Time to pull timing chain cover??? This thing has me baffled... help!
That intake valve should have been closed (fuel air charge has to be in the cylinder before the compression stroke begins) as you were coming up on TDC of the compression stroke.
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Unread 06-18-2011, 09:07 PM   #4
Noltz
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^^ beat me too it. Your last valve to open before TDC, and it should close as you approach TDC. If there's a bit of overlap in the cam you might have both valves moving at the same time, @ TDC.

Sounds like you're 180 out.
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Unread 06-18-2011, 09:30 PM   #5
laybackman
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Pull #1 plug...stick finger in plug hole. Have a buddy bump engine until the compression wants to push your finger out of the #1 plug hole. Use breaker bar and large socket to findish bringing this engine up to TDC by sticking long thin stick in #1 hole to watch #1 piston come up to TDC checked against your timing marks. Once TDC on the compression stroke is attained, pull the distributer cap and check rotor position. Move rotor to just before #1 plug tower position on said disrtibuter. Enjoy!
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