Sudden Stall

[apache5g]

Hey everyone. I am looking for some trouble shooting ideas. I completed an oil pan gasket and rear main seal replacement yesterday. I let the new gasket sit for 24 hours with the RTV in the corners of the gasket as recommended. I refilled the oil and ran it for about 20 minutes. No leaks, no stutters, good idle. I drained the oil and replaced it as well as the filter. When I put the Jeep back on the floor and tried to start it, I got combustion and then it died after about 1-2 seconds. Eventually, I lost combustion all together and the motor won't turn over. I have a TBI, that I did not install, so I am not really familiar with the workings of it. Please keep in mind that I am learning mechanics on this Jeep as I go, so I may not be familiar with some of the obvious solutions. Any insight would be appreciated.

 

[mtnwhlr]

I don't see how what you did could have anything to do with it. It takes two thing to make a motor run, spark and gas. Take the air cleaner off and see if it is spraying gas when you hit the gas and make sure your plugs are firing.

 

[apache5g]

Thanks for the response, it is truly a weird scenario. I have fuel spray, however I did not check the spark plugs because initially I got the motor to turn over and run even if for only a few seconds. Even still, I can't see how any part of replacing the seals would interfere with the ignition or fuel systems.

 

[Torxhead]

I would suggest on finding out what aftermarket products you might have installed on your CJ to help you with finding out just how to repair them if they are causing your stall issue. Like a problem with the tbi it would help to know what system it is, like is it a Howell or Mopar unit. Your distributor could be an original Motorcraft, it could also be modified to "Team Rush" specs or a GM HEI type. Your stalling problem could be from something that got bumped during your recent repair work. Mtnwhlr has some good suggestions to start with.

 

[hole]

If its Mopar MPI, it likely has a CPS (crank position sensor) on a bracket mounted off the front of the oil pan, and if not set correctly engine will not run. Not familiar with TBI, so not sure if it uses a CPS or not

 

[jafo]

When you say the motor won't turn over, do you mean it's not firing over as in loss of spark? Or the engine literally won't turn over as in you lost power to the starter?

Depending on how the electric fuel pump is incorporated into the system, either in tank or external, if you starve them too much they can lock up. If that happens, replacement of the pump is required. Depending on the answer to the first paragragh, can you here the pump run when the ignition key is turned on? If you can't then have someone turn the key on for you and watch the tbi injectors to make sure there is fuel coming out. If not, you could have a bad fuel pump. Also check any relays and fuses. Those can pop anytime for various reasons. Make sure you didn't pinch any wires or lines etc. TBI or (throttle body systems) are really not that complicated. They still need the same essential elements as a mechanical system to run. They just require sensor information for engine management requirements.

Again it all depends on what you mean by "turn over".

Now, if the engine is not turning over, that could be a whole different set of issues.

 

[Lumpy Grits]

Try starting with a known, fully charged battery.
LG

 

[apache5g]

When I say "turn over", I mean not getting any spark. When the problem first presented, I was atleast getting idle for a couple of seconds before it died. During that time I did have a buddy observe fuel spray in the TBI. I have not yet checked it since I started losing combustion. I checked all fuses and the battery is fully charged and reading at just north of 12 Volts. I have also lost power to some components that are wired directly to the battery through a stand alone fuse box. (stereo, CB, LED lights, and aux power supply). I still have power to the dash lights, head lights, turn signals, blower motor etc. Just those components. All those fuses are good. It is just so weird that this happened after running just fine not 30 minutes earlier. I guess that's the Jeep life.

 

[Torxhead]

Losing power to componets that are wired directly to the battery sounds like there is a bad connection somewhere. Losing fire after ignition consistently sounds like another problem. Time to determine whether you are losing spark or getting too much/too little gas.

 

[WHATROAD]

I'm leaning with LG .... battery and cables, loose, broken, dying (in the case of the battery).

 

[jafo]

Yep. I agree. Start tracing wires and checking connections. I personally would start at the distributor and check for voltage there, obviously there is probably none, but check it anyway and go backwards from there, or you could pick any one or all of the components that has lost voltage and go backwards from those. There may be a junction you didn't know about. Wiring problems are not impossible but they do suck especially when you're dealing with modifications.

 

[Lumpy Grits]

When I say "turn over", I mean not getting any spark. When the problem first presented, I was atleast getting idle for a couple of seconds before it died. During that time I did have a buddy observe fuel spray in the TBI. I have not yet checked it since I started losing combustion. I checked all fuses and the battery is fully charged and reading at just north of 12 Volts. I have also lost power to some components that are wired directly to the battery through a stand alone fuse box. (stereo, CB, LED lights, and aux power supply). I still have power to the dash lights, head lights, turn signals, blower motor etc. Just those components. All those fuses are good. It is just so weird that this happened after running just fine not 30 minutes earlier. I guess that's the Jeep life.

You need to look hard at that 'stand alone fuse bx'.
Unless that battery reads (under a no-load condition) at least 12.5 vdc. The battery needs to be put on a charger.
Did you check these fuses for continuity, with a meter?
LG

 

[apache5g]

The battery tested out at 12.88. All fuses tested with a meter and checked out. The injection was not producing spray, however I tested the fuel pump, and it was supplying fuel to the TBI. The injectors were not spraying due to a loose connection. That issue is corrected and now I am getting fuel spray into the throttle body. So now I am getting combustion but then the motor dies. I have spent most of the night tracing wires and it turns out that my battery is grounded at least 6 times in six different locations! It is a total rats nest. I am going to start back up with trouble shooting the distributor because it seems like I get an initial spark, then nothing. Any helpful techniques for this task would be appreciated.

 

[PistolDave]

Having multiple grounds is ok. The grounds on GM TBI ECM's are absolutely critical. If you are running a 1227747 ECM (first gen 1988-1992) or similar look for the ground wires from pins A11 & A12 and D1 & D2 from the ECM. These must be grounded well for proper operation. What distributor are you running? If it is full timing control, the EST module from your distributor sends the timing signal to pin B5 (Dist Ref Hi - Purple/White). This is the signal from the EST that tells the ECM to fire the injectors. If you are running fuel only control like a lot of Howell setups, the signal will come into this pin from a filter I believe. A poor or intermittent signal here will keep it from running properly. Also make sure that all of your ignition circuits to the ECM, ignition, etc. are hot in both Crank & Run position. There is a cranking input on pin C9 (purple) from the starter solenoid that tells the ECM that the engine is cranking, if this wire has become detached it can also cause problems. I am not an expert on GM TBI, just what I learned from messing with my own stuff and those belonging to friends. There are probably some more things to check but this will give you some stuff to look at.

Dave


http://chevythunder.com/1227747 ecm diagram.JPG

1227747 ECM wiring

 

[Lumpy Grits]

Multi-battery grounds are a good thing. You want the main GND to be the top mounting bolt of the starter.
Sounds like you still have a intermittent connection, and those are the very hardest to track down.
LG

 

[Torxhead]

That stand alone fuse box could be the one came with the fuel injection unit, as I have one under the dash. Another thing that could cause your engine stall would be to much gas. Like from a clogged fuel return line or improper fuel pressure. Checking spark plug burn could determine that.

 

[apache5g]

I have been checking connections all day. I have replaced the ignition control module. It did not fix my issue, however looking at the state of it, it needed to be done. My question is, should I have electricity at the distributor on the volt meter with the key in the on and not run position?

 

[Lumpy Grits]

Yes in the 'on' position.
Have you ck'd and confirmed the fuel pump PSI?
If the injectors don't 'see' a certain psi. They won't function.
LG

 

[apache5g]

I have not checked the fuel pressure. I do not know how to check that, so any advice would be helpful. Today I checked the flow of electricity for the distributor. I was not able to get any volts out of the distributor at the terminal for the battery wire until the key was turned to "run". The same for the starter solenoid. I do have spark in the spark plugs. I replaced them today. The number 3 and 4 cylinder plugs were very fouled and had a lot of carbon/corrosion built up. These plugs were only about 2 months old. Does that point to any particular issue? Thanks again for all the help.

 

[apache5g]

here is what the middle plugs looked like. The outside cylinders were discolored as well, but no where near as bad. The outside plugs discoloration was also only on one side of the plug.