[thenodnarb]

first, I've read the post 4.0L swap/spark problems

so heres where i'm at...
I got the fuel pump to kick on and build pressure. I bypassed the computers control of the ASD relay and just hooked up the coil to power. I get spark at the coil, but not at the plugs.
the computer was kicking on the relays for 1 second then shutting them back down which is what led me to bypass those relays(fuel pump and ASD relay).
A friend was helping me and said that he could here the injectors working. this leads me to believe that the CPS and CMS are both working properly.
I do not have a battery temp sensor hooked up and I hear that if that is missing, the engine wont fire. Could the computer be disconnecting the voltage to the plugs until it recieves some sort of input that I have missed?
this is a 98 4.0L (OBDII).


A few other notes. The computer has its own park/neutral position switch. I grounded this wire so that the computer will always fire should it rely on this signal to start. Also, the harness I got with my engine was complete except for the computer plug C3 which controls the ASD relay control and output along with the fuel pump relay control and output. It also is responsible for the batter temp sensor(dont have it) and the voltage regulator signal(which I believe powers the computer). I hacked this plug from a junkyard harness and spliced in those critical sensors and such.

A few other things that i've hooked up are:
The generator field driver
generator field source
various grounds
fused ignition(for the computer)

A few things I HAVN'T hooked up:
VSS
o2 sensors
A/C Compressor clutch(no A/C)
A/C Compressor clutch relay
Tranny Solenoid Assembly(TF727 not stock)
Battery temp sensor
4wd switch
trany relay control
various other 4wd switch stuff
Speed control vacuum(and vent) solenoid control
Overdrive off lamp driver
vapor canister solenoid driver
speed control on/off switch sense
overdrive off switch sense
vapor conister pump switch driver
Evap emissions solenoid control
A/C pressure switch sense
Stop lamp switch sense
SCI recieve
CCd bus(-/+)
SCI transmit
Speed control switch signal

 

[sceep]

sounds like the same issues i had with my 5.2l into cj-7 swap. (non OBDII)

crank, fire, run for 1.5 seconds, shut down. over and over and over.

Mine was the ECM.

If your donor was equiped with an alarm. once you seperate the ECM from the alarm module the ECM goes into "panic" mode. On the factory alarms it allows the vehicle to fire, then shut down, then fire, shut down. over and over. Makes the thief think that it will start, when in actuallity it wont.

There is NO way to make the ECM think that its alarm module is there without swaping the module in also.

New ECMs are all the same, UNTIL they see their alarm module. If there is no module present the ECM cant see it.

Once i bit the bullet and bought a new ECM my swap fired right up. And what a glorious sounds it was

Might try and find a buddy that has a non alarm equipped 4.0 and borrow his ecm for a test start.

 

[Spike5421]

Sorry O/T What fuel pump/sending unit did you use for your swap???

 

[sceep]

Sorry O/T What fuel pump/sending unit did you use for your swap???

ford E2000 pump on my 5.2l no sending unit, 16 gal cell.

 

[ScottDeLano]

ODB-II Ignition

This might help out. If you're getting spark on the discharge side of the coil and not at the plug, it sound like an ignition (distributor) issue. This article might help.

Check each plug wire with a timing light. See if you get a spark on any Cyl.

I don't know alot about the ODBII system but I would not permanantly bypass the ASD relay. Also, FIRC, I THINK you have to have the O2 sensor installed for your engine to run.

 

[wiltech]

A couple other places to look:

My 4.0 Swap page

and

4.0 help on CJ-8.com

btw: I should be trying to fire mine this weekend ....

Tony W

 

[Herb in Tx]

Sounds just like what mine was doing. I swapped a 01 4.0 into my 83 CJ7 and all my relays would energize for about a second and then de-energize. Mine was the Crank sensor - changed that and it fired up.

I will agree with sceep said in that if your donor had the anti theft stuff - it wont crank without the SKIM module and the transponder key. If you have tried it more than 6 times without those it will have to be reset and reprogrammed by a dealer. I went to car-parts.com and found an ECM at a yard, got the VIN for the vehicle it came in and called Chrysler to determine if it had the anti-theft stuff from the factory. I found one that did not and paid $75 for it. Then swapped my crank sensor and it fired up.

Oh, and you should not need the battery temp sensor. From the FSM:

Ignition Switch (key-on) Mode
This is an Open Loop mode. When the fuel system is activated by the ignition switch, the following actions occur:


The PCM pre-positions the Idle Air Control (IAC) motor.
The PCM determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy.
The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based on this input.
Intake manifold air temperature sensor input is monitored.
Throttle Position Sensor (TPS) is monitored.
The Auto Shutdown (ASD) relay is energized by the PCM for approximately three seconds .
The fuel pump is energized through the fuel pump relay by the PCM. The fuel pump will operate for approximately three seconds unless the engine is operating or the starter motor is engaged.
The O2S sensor heater element is energized via the ASD relay. The O2S sensor input is not used by the PCM to calibrate air-fuel ratio during this mode of operation.
Engine Start-up Mode
This is an Open Loop mode. The following actions occur when the starter motor is engaged.

The PCM receives inputs from:


Battery voltage
Engine coolant temperature sensor
Crankshaft position sensor
Intake manifold air temperature sensor
Manifold Absolute Pressure (MAP) sensor
Throttle Position Sensor (TPS)
Camshaft position sensor signal
The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM through the fuel pump relay.

Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector ON and OFF.

The PCM determines the proper ignition timing according to input received from the crankshaft position sensor.

Good luck.

 

[thenodnarb]

after reviewing a lot of this information, I believe that the problem lies within the distributor. it COULD be the CPS because I am not entirely sure that it is mounted in there straight or at a proper distance. I replaced it last night when I was trying to get it to fire, but it still did not work. I do not believe that my computer is equiped with an anti theft device becasue there is no mention of it in the entire jeep service manual( the BIG manual) for my engine. besides, it would at least fire for a few seconds if that were the case.

Herb-
What else did you have hooked up that perhaps i'm missing. you seem to have had a very similar problem. any info on the position of the CPS( should the paper on the tip be flat and against the flexplate)?

I have a vss but it is not plugged in yet. would that help?
is it possible to rotate the distributor to set timing?
if I were getting absolutely NO spark at the plugs, what could be the cause?
What is causeing the computer to only energize the relays for only 1 second?

to quote from a previously mentioned article:
1. Pin # 8 sees voltage change from ASD relay.
2. Dst Sync (cam sensor) MUST be seen prior to crank signal.
3. Crank signal is x amount of degrees after cam signal.
4. Primary ignition signal is seen.
5. Injector signal is turned on.
6. Once in order, the PCM sees everyone is OK and allows the engine to run. Any other sequence and the PCM shuts down after two sparks!

according to #2,3 my cam sensor must be working along with my CPS because my injectors are working. the only problem I can see is that either
1.) my timeing is off due to an indexing problem(perhaps im not noticing the two sparks mentioned above) or
2.) there is a physical problem that is not permitting spark to travel to the injector plugs

anybody else have an assesment of this problem?

 

[DE Jeeper]

I would guess the dist is not set right. You have to set your engine to TDC on the compression cycle and position the oil pump and rotor correctly then insert the dist. You CAN NOT rotate the dist on a 4.0 FI. It is a PITA, but I do know it will run if it is one tooth off. I had mine set that way and it would only stall under heavy load. The set up and positioning is all in your FSM.

 

[Herb in Tx]

Yep, I agree with DeJeeper - sounds like your distributor is not installed correctly. My swap was an 01 - no distributor. I would pull the distributor and re-install exactly as the FSM instructions indicate.

As far as the crank sensor - mine just bolted right up, no setting to mess with.

The only other thing I would check is to check your manual for SKIM or Sentry Key Immobilizer Module - this is the anti-theft stuff that you don't want. You can call Chrysler ( 1-800-992-1997 ) with the VIN from you donor and they can tell you if it came with it. Believe me - they had it available in 98.

Best of luck.

 

[ScottDeLano]

What else did you have hooked up that perhaps i'm missing. you seem to have had a very similar problem. any info on the position of the CPS( should the paper on the tip be flat and against the flexplate)?

If you have tried to crank the engine and the paper is still on the CPS, it's not close enough. Loosen the two bolts and press the CPS against the flywheel then tighten the bolts. The paper is used to set the proper gap. It will come off after it runs for a few.

The easiest way to check the distributor is to knock (break) off the post for the #1 cylinder of the dist. cap with a hack saw and make certain that when at TDC the rotor arm is .020" (or so) from the node of the #1 cylinder. For $5.00 (cost of a cap) you get piece of mind to know you have the distributor indexed properly.

Good luck

 

[gripguru]

If you have tried to crank the engine and the paper is still on the CPS, it's not close enough.

Get it close enough and take the paper off. The paper does not belong on the sensor.

Also, mine would not start because I forgot to plug in the o2 sensor. From earlier posts, it sounds like the o2 sensor serves a different purpose when trying to start the motor than air fuel ratio. I just know that it was the only thing that was missing when I first tried to start mine and it did not allow it to start.

 

[thenodnarb]

Success!!
I got it to turn over and run for a few seconds. the only changes i made were:
1.)I tried to get the CPS close to the flexplate but I believe it had nothig to do with it.
2.)We losened the distributer and was able to twist it slightly.
3.)the rotor in the distributor was WELL worn. we cleaned it up a bit and tried it and it fired!

now, its only running as long as I am cranking the engine. as soon as i let off the starter, it dies. if I leave it cranking too long, it dies. its almost like the coil stops getting power right after I stop cranking. I am not confident that I have my ignition hooked up right. can anyone assist me in troubleshooting this?

 

[Herb in Tx]

Sounds like you don't have a key on 12V supply and you are only getting 12V when the key moves to start. You should have two separate wires providing 12V one when the key is on and another for the starter relay.

 

[thenodnarb]

For anyone who wants to know...
I was mistaken. the engine does run even after I let off the starter...It just dies so rapidly afterward that it was hard to distinguish.
ALSO, i talked to the dealer and the wiring guru there said that it was my antitheft system in the PCM that was shutting down the engine. He lead me to believe that it couldn't be anything else. HE suggested to just use an older wiring harness(OBD I) and computer since the motors are the same physically. I'm going to buy a computer(OBD II) from the junkyard this weekend and see if that solves it. if it doesnt, I may resort to the OBD I comp and harness swap

BTW. i also found that there was no sentry key available in 98( at least for the GC). 99 is the year when they switch to that system. However, there still is an anti-theft system with an engine no-run feature that my computer must obviously have. i think i'll get a TJ 98 computer which I think will simplify the computer splicing process. anyone have the pages from the manual that show what each pin does on the computer for a 98 TJ?

 

[wiltech]

If you switch form ODB-II to ODB-I you'll have to swap out almost EVERY sensor on the engine.

Tony W

 

[Old Army]

I was the "electrical engineer" for the fellow in the 4.0L swap/spark problems thread. The complexity of the wiring leaves many places for things to go wrong. What helped us was a factory diagram of all the wire assignments and the great care we took in tracing all the wires for continuity as we assembled a custom harness from a couple of factory ones.

With that said, your problem sounds just like the problem we hit: a screwy CPS.

Missing VSS and O2 sensors won't keep it from starting.

-Old Army

 

[thenodnarb]

I was the "electrical engineer" for the fellow in the 4.0L swap/spark problems thread. The complexity of the wiring leaves many places for things to go wrong. What helped us was a factory diagram of all the wire assignments and the great care we took in tracing all the wires for continuity as we assembled a custom harness from a couple of factory ones.

With that said, your problem sounds just like the problem we hit: a screwy CPS.

Missing VSS and O2 sensors won't keep it from starting.

-Old Army

i was under the impression that it wouldnt even fire if it didnt recieve the CPS signal? all i need to know is would it fire and run for a second or two if the CPS was not in there correctly? i am buying the computer tomorrow and would like to avoid an expensive mistake.

 

[dorfs]

You need to break down and install a drb or generic scanner. The pcm will set a hard code it there is vtss problem. If when you start it, it runs good for a 2 or 3 second period, I would tend to agree. You can turn to the page that states if the security system is activated and tell that way. If the security system is activated, you will need a new pcm. If it isn't, don't activate it! There is no way to turn it off.

I would go back and re-stab the dist. The manual isn't real clear on this process. It dosn't take into consideration that when installing the dist. it will turn from the meshing of the cam gear. It is very easy to install it incorectly. It will give the same symptoms you discribe. Poor spark to the plugs, hard starting, and only run for a few seconds excpet for wide open throttle. You may even want to grind off the index on the dist. to allow you to turn the dist and put it back in sync. Don't grind it off all the way so you can't see where it was intended to go, but just enough to allow some expermenting.

 

[Old Army]

We got a scanner as well. All it showed us was that the second O2 sensor was not installed.

As to the engine firing and not starting, it was an all or nothing thing for us. We did run into a somewhat similar problem due to insufficient fuel pressure. The returnless nature of the OBD II system required us to construct an intank fuel pump with an external adjustable regulator. The first regulator we tried didn't work, and the engine would only sputter at idle then die. But with a little engine starter fluid sprayed down the throttle body, we could get it to run. This was easily diagnosed with a feul pressure gauge.

Hope this helps,
Old Army out...