4.0 issues please help.

skyhighZJ

skyhighZJ

Gov retirement < needs to live
Joined
May 31, 2012
Location
Aberdeen, NC.
Fractured the flex plate in my 97 XJ. Pulled the motor out to replace the Flex Plate. My old motor ran but was tired. I sourced a low mile motor that I was told was a good runner but while it was out I figured I'd tighten it up while it was easy access and on the stand. Question for you. I got the motor, put it on the stand and did oil pump, timing set, water pump and also did a new head gasket with ARP head studs (they were on sale so why not). While I had the head off I pulled the valve springs one by one and installed new valve seals too. I got everything buttoned up and torqued to spec. I primed the oil pump prior to firing it. Put the motor in and I can't get it to fire. I have ran through every connection and sensor and they are all good. Checked and rechecked the timing, ran a compression test and it averaged out to 74psi. Not sure where I went wrong. Have any thoughts?
 
Does it have fire? Possibly washed the cylinders from spinning it over alot causing low comp.
 
Do a wet compression test and see if the compression is in spec then. Like @Infamous1 said, your cylinders may be washed.
I copied the following from a reply I've made about a dozen times.
Then do this:
Here is how to MAKE SURE the distributor is indexed PROPERLY on a 4.0

1-Remove distributor and remove the distributor cap, cam sensor and rotor button
2- Remove #1 spark plug
3-rotate engine by hand until you feel compression coming out of the spark plug hole (3/4" or 19mm wrench on crank pulley)
4-continue to rotate until the timing mark on the harmonic balancer (crankshaft pulley) lines up with the "0" mark on the timing cover
5-Locate the hole on the bottom of the distributor housing. There is also a corresponding hole on the plate that spins inside the distributor housing. Line them up and drop a pin (screwdriver, drill bit, etc) into them. Now the distributor and pickup plate are indexed properly.
6-With a flat head screwdriver, rotate the oil pump (through the hole where the distributor sits) to approx the 11 o'clock position
7- With the pin still inserted in the distributor body, drop the distributor into the engine block. Do not remove the pin if it doesn't drop all the way in the first time. Rather, move the oil pump drive a little
8-When the distributor is fully seated and the retaining hole is lined up, remove the pin and bolt the distributor down to the block.

You are now timed/synced/indexed properly. Period.
 
Jody Treadway said:
Do a wet compression test and see if the compression is in spec then. Like @Infamous1 said, your cylinders may be washed.
I copied the following from a reply I've made about a dozen times.
Then do this:
Here is how to MAKE SURE the distributor is indexed PROPERLY on a 4.0

1-Remove distributor and remove the distributor cap, cam sensor and rotor button
2- Remove #1 spark plug
3-rotate engine by hand until you feel compression coming out of the spark plug hole (3/4" or 19mm wrench on crank pulley)
4-continue to rotate until the timing mark on the harmonic balancer (crankshaft pulley) lines up with the "0" mark on the timing cover
5-Locate the hole on the bottom of the distributor housing. There is also a corresponding hole on the plate that spins inside the distributor housing. Line them up and drop a pin (screwdriver, drill bit, etc) into them. Now the distributor and pickup plate are indexed properly.
6-With a flat head screwdriver, rotate the oil pump (through the hole where the distributor sits) to approx the 11 o'clock position
7- With the pin still inserted in the distributor body, drop the distributor into the engine block. Do not remove the pin if it doesn't drop all the way in the first time. Rather, move the oil pump drive a little
8-When the distributor is fully seated and the retaining hole is lined up, remove the pin and bolt the distributor down to the block.

You are now timed/synced/indexed properly. Period.
Click to expand...


Did this to a T about three different times thinking I was missing something and came to the same results. I have spark and fuel. Going to go back and try the "wet" compression and see if there are results.
 
I had issue similar when I put a 97 4.0 in my 96zj timing Was the culprit not allowing fire to hit at the right time to make any compression I thought I had installed a bad engine until i went through timing procedure that's given by Jody up there^
 
I will add that I have seen crank dampers spin and the marks on the damper be off. Screw driver or dowel in the cylinder will tell true tdc if all else has failed.
 
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