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Discussion Starter · #1 ·
VEHICLE: 98TJ, 2.5L, manual tranny (engine went bad. #1 piston disintegrated and blew a hole out of the side of the block)

DONOR ENGINE: 91YJ (don't know any more. vehicle owner supplied engine)


I did the engine swap. I used the 98 Intake, throttle body, sensors, flywheel, clutch and distributor. I double, tripple and quadrupple checked the rotor position (set for #1 @ TDC) and am 99.99% sure it's right. i have fuel, good fuel pressure and spark. it cranks, and sounds like it really really wants to start, but just won't. i've been trying to get it started for a whole day already, and now i'm completely out of ideas.

what am i missing???

PS: i'm doing a compression test as we speak.
 

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sim sim balla bim
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Is your timing advanced? I had the same problem when I swapped my 93 4.0. Everything went together really easy was getting spark, and was getting fuel just wouldn't fire. Finally after working on it for a couple days I had my buddy which is a mechanic look at it he had it running in 5 minutes. He said the timing has to be advanced. One tooth off on the gear, that was the problem. I dont know if the 2.5's are the same but it may be worth a shot. Good luck!!
 

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Discussion Starter · #6 ·
yeah i looked into that. like i said, i checked that a million times, and i'm sure it's on.

but i think it's time to call it GAME OVER

#1=60psi
#2=100psi
#3=115psi
#4=110psi
 

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eek, but shoot oil into the cylinders and do it again. You could have washed the cylinders down real bad.

Did ya block the throttle at WOT when you did the compression test?

In this weather it should still fire with 100psi. Try it with starting fluid. 100psi will fire that for sure.
 

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Discussion Starter · #9 ·
i could see it starting with 100psi since that's still within the "acceptable low range".

but the 60psi one i don't think will kick it.

yes. throttle wide open.
 

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on my 4.3L swap I had the pinched the fuel lines. I still had fuel pressure but not enough volume. something to check. I agree it should at least fire with 100psi. Try oil but not too much as oil for some reason does not compress.:sonicjay:
 

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i could see it starting with 100psi since that's still within the "acceptable low range".

but the 60psi one i don't think will kick it.

yes. throttle wide open.
Yea, but it's only one cylinder. It should still start, just run bad even if those are correct readings. Think about it, you can pull a plug wire off, or foul a plug and it still runs, just has a miss.
 

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Discussion Starter · #12 ·
Yea, but it's only one cylinder. It should still start, just run bad even if those are correct readings. Think about it, you can pull a plug wire off, or foul a plug and it still runs, just has a miss.

good point.

so what could i be overlooking that it won't start???
 

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You should still do a wet test to determine what is wrong with that cylinder. It may have a clue to what is going on with your engine.

IE: water jacket leak into the cyl will cause it to run like crap and never start.

A weak Ign. Coil or Module will also give you similar probs.
 

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Covered in mud...
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What coudl you be overlooking? The fact that the engine maybe hasn't run in a while, and doesn't have a good ring seal. Cranking it just washes the cylinders and it'll never fire.


On an engine like that, always squirt a little oil in each cylinder, and fire it on starting fluid. I've had no less than 4 engines that absolutely refused to start (talking days of trying), then oil + SF, then they ran perfect from there on out.
 

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Discussion Starter · #17 ·
What coudl you be overlooking? The fact that the engine maybe hasn't run in a while, and doesn't have a good ring seal. Cranking it just washes the cylinders and it'll never fire.


On an engine like that, always squirt a little oil in each cylinder, and fire it on starting fluid. I've had no less than 4 engines that absolutely refused to start (talking days of trying), then oil + SF, then they ran perfect from there on out.
:thumb: :thumb: :thumb: :thumb: :thumb:
 

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