RebelofMetal
NAXJA Forum User
- Location
- Lakewood, CO
I have been pretty competent and haven't really been stuck on a problem till now - I am hoping someone can see the error in my way here:
I have a '87 XJ 4.0L Auto that is now perched on a sweet custom hybrid Lift.
Now, that old '87 had well over 400K and never left me stranded. It finally had a #2 Intake stick, and the head had to come off.
Rather than putting the "old" stuff on, I took a '93 Cyl head and installed it.
I also took the engine compartment, AKA Engine electrical harnesses, all sensors and injection components.
I swapped the terminals and splices at the bulkhead connector, and all the lights/chassis accessories/guages/etc, are properly functioning and all the smoke is still installed in the harnesses. All fuses are replaced and new, and I have verified the mechanical and electrical ability of all my relays. I have perfromed a lot of professional electrical work, so I am pretty confident it is OK. None of the computer control circuits are sent thru the bulkhead as the computer and control wiring are all contained in the engine harness.
Ok - to the problem - The engine cranks, no start - I have 3 handy things - 1) compression 2) Spark 3) Fuel entering the combustion chamber. I also know that the new timing chain is properly lined up, and that when I take the #1 SP out, the timing mark is lining up with the 0 at TDC, just as the distributor rotor is approching the #1 tower on the cap.
There is +12V at the Injectors, and the computer seems to be switching them to ground, as they do inject fuel and I see the noid light flicker when cranking.
The Ignition appears to throw a syncronized spark output to all the plugs.
I put a fresh set in, and after the crank, I pulled the plugs. The engine tred to start, but only "burped".
All plugs were clean and wet with fuel, except #3 who had been blackened from a detonation, but was wet with fuel, and #4 who had detonated and black, but was not wet.
After several cranking attempts, the results remained the same. No other plugs detonated, but they would all spark when tested outside the cylinder. #3 & #4 were occasionally detonating.
So, this is what I think is happening:
Someting in the crank signal is causing erronious computer control of spark timing/fuel injecting.
a) I would repl the crank sensor, but it appears to be giving a clean signal consistently. I am using the '93 sensor.
b) And what I am afraid of - but I cannot find the parts avail to verify:
That I need to install a Flex plate from a '93 because the '87 flywheel had a different signal pattern, aka Confused computer.
Does anyone know if "b" is true - or experienced this swap?? Or do you happen to know something I dont see? Please help!!!
I have a '87 XJ 4.0L Auto that is now perched on a sweet custom hybrid Lift.
Now, that old '87 had well over 400K and never left me stranded. It finally had a #2 Intake stick, and the head had to come off.
Rather than putting the "old" stuff on, I took a '93 Cyl head and installed it.
I also took the engine compartment, AKA Engine electrical harnesses, all sensors and injection components.
I swapped the terminals and splices at the bulkhead connector, and all the lights/chassis accessories/guages/etc, are properly functioning and all the smoke is still installed in the harnesses. All fuses are replaced and new, and I have verified the mechanical and electrical ability of all my relays. I have perfromed a lot of professional electrical work, so I am pretty confident it is OK. None of the computer control circuits are sent thru the bulkhead as the computer and control wiring are all contained in the engine harness.
Ok - to the problem - The engine cranks, no start - I have 3 handy things - 1) compression 2) Spark 3) Fuel entering the combustion chamber. I also know that the new timing chain is properly lined up, and that when I take the #1 SP out, the timing mark is lining up with the 0 at TDC, just as the distributor rotor is approching the #1 tower on the cap.
There is +12V at the Injectors, and the computer seems to be switching them to ground, as they do inject fuel and I see the noid light flicker when cranking.
The Ignition appears to throw a syncronized spark output to all the plugs.
I put a fresh set in, and after the crank, I pulled the plugs. The engine tred to start, but only "burped".
All plugs were clean and wet with fuel, except #3 who had been blackened from a detonation, but was wet with fuel, and #4 who had detonated and black, but was not wet.
After several cranking attempts, the results remained the same. No other plugs detonated, but they would all spark when tested outside the cylinder. #3 & #4 were occasionally detonating.
So, this is what I think is happening:
Someting in the crank signal is causing erronious computer control of spark timing/fuel injecting.
a) I would repl the crank sensor, but it appears to be giving a clean signal consistently. I am using the '93 sensor.
b) And what I am afraid of - but I cannot find the parts avail to verify:
That I need to install a Flex plate from a '93 because the '87 flywheel had a different signal pattern, aka Confused computer.
Does anyone know if "b" is true - or experienced this swap?? Or do you happen to know something I dont see? Please help!!!
