No Spark or Fuel During Engine Crank

[Torxhead]

One thing that seems odd with this is that it happened all at once. A pick up coil going bad should be a gradual issue instead of quitting all at once. It seems that there is a lot of gas going down the throttle body before it stalls. There could be some damaged e.f.i. wiring harness somewhere. Like from melted or frayed wiring in the engine area. A close inspection might be a good idea, especially where heat can get close to the harness. Just a thought.

 

[Posi]

As I previously mentioned I didn't think it was the tach filter, but it was worth trying seeing you already purchased it.
I'm thinking it isn't the ecm as well typically you would see a code 52 or 55.
The TPS is out of adjustment, and sending a signal to the ecm for more fuel then it may need.
This may be the reason why you had sooty plugs.
Adjust the TPS, I posted instructions somewhere on the previous page.

If there is improvement but still not running as it should pinch the fuel feed line behind the TB to restrict the flow.

No change, try the same with the return line.

There could be another issue, but lets start with the TPS and fuel.

When you removed the plugs were they all sooty, or were a couple plugs whiteish?

Try not to get frustrated, if the TPS adjustment helps but doesn't cure your problem we'll move onto checking ecm pin readouts.

 

[Lumpy Grits]

That engine is flooding out from too much fuel.
LG

 

[thundley57]

One thing that seems odd with this is that it happened all at once. A pick up coil going bad should be a gradual issue instead of quitting all at once. It seems that there is a lot of gas going down the throttle body before it stalls. There could be some damaged e.f.i. wiring harness somewhere. Like from melted or frayed wiring in the engine area. A close inspection might be a good idea, especially where heat can get close to the harness. Just a thought.

Thanks, as much as I was trying to avoid it, it might be time to start pulling all the wires out of their covers and start inspecting. I haven't done this yet.

 

[thundley57]

As I previously mentioned I didn't think it was the tach filter, but it was worth trying seeing you already purchased it.
I'm thinking it isn't the ecm as well typically you would see a code 52 or 55.
The TPS is out of adjustment, and sending a signal to the ecm for more fuel then it may need.
This may be the reason why you had sooty plugs.
Adjust the TPS, I posted instructions somewhere on the previous page.

If there is improvement but still not running as it should pinch the fuel feed line behind the TB to restrict the flow.

No change, try the same with the return line.

There could be another issue, but lets start with the TPS and fuel.

When you removed the plugs were they all sooty, or were a couple plugs whiteish?

Try not to get frustrated, if the TPS adjustment helps but doesn't cure your problem we'll move onto checking ecm pin readouts.

All of the plugs were sooty. I'll try the TPS adjustment and the fuel hose pinch, Thanks

 

[Torxhead]

One area where the harness can get cooked is where it runs from the firewall to the throttle body along the valve cover. The harness should not be too close to the exhaust manifold. Make sure the oxy sensor is far enough away from it also.

 

[Posi]

Thanks, as much as I was trying to avoid it, it might be time to start pulling all the wires out of their covers and start inspecting. I haven't done this yet.

Totally up to you what you do with your Jeep, but that would be a waste of time IMO. Especially when you can get the same results in 5 mins at the ecm.

Feel free to inspect any wires that may be near the exhaust as Torx posted, but I would recommend not touching or moving them at this point. Doing so could change voltage at the emc giving faults reading.

If there is a loose connection and you move the harness and the engine now runs as it should then you would have to dig through the harness to inspect each wire. By not touching the wires or harness, you can then pinpoint the exact wire to be repair at the ecm if in fact it was a faulty wire.

First the TPS adjustment

 

[thundley57]

Totally up to you what you do with your Jeep, but that would be a waste of time IMO. Especially when you can get the same results in 5 mins at the ecm.

Feel free to inspect any wires that may be near the exhaust as Torx posted, but I would recommend not touching or moving them at this point. Doing so could change voltage at the emc giving faults reading.

If there is a loose connection and you move the harness and the engine now runs as it should then you would have to dig through the harness to inspect each wire. By not touching the wires or harness, you can then pinpoint the exact wire to be repair at the ecm if in fact it was a faulty wire.

First the TPS adjustment

Yeah, all my harnesses are neatly zipped tied up at the firewall and I know I don't have any baking near the exhaust manifold but obviously don't know what is going on inside the harnesses unless I look. It was going to be my last resort thing to do?

What do you think about the IAC solenoid? If it were bad and not letting enough air in during idle wouldn't that cause the condition I'm seeing? Would a good test be to start it up and pull a vacuum hose below the throttle plate off to see if it runs better? I'm a little hesitant to mess with the TPS since according to that link you sent me was in spec although maybe a little on the higher end of the spec.

 

[Torxhead]

From what I have seen those black split looms are more temperature sensitive than the wires, so if you have nothing melted you are probably o.k. there. I don't think the problem is the iac valve, it seems to be just too much fuel from the injectors. I did have to replace my iac valve once, the symptoms were an incorrect idle speed at startup. You could unscrew it and clean it though. When the vehicle first starts up it is in a full rich condition, but I think yours is beyond that. Another thing that can cause excessive fuel through the injectors would be a clog in the fuel return line. Howell says you can use the 1/4" oem return line, but I think a 5/16" new one would work better. Anyway, an inspection might not be a bad idea. Other possibilities could be the engine coolant sensor, map sensor, and the tps. I have seen an adjustable type of tps, but a fixed version can be made adjustable. For future startups I would suggest using the clear flood mode startup to try and lean it out.

 

[Posi]

I'm a little hesitant to mess with the TPS since according to that link you sent me was in spec although maybe a little on the higher end of the spec.

The link I sent you was a random link off the net to give you testing instructions. I'm sure those specs whatever they were was not for your system. Your .713 reading is too high and out of spec for your system according to Howell (.5-.7). I previously explained the reasons why the TPS should be set at .54, or as close as you can get without going under .54 or over .64

 

[thundley57]

From what I have seen those black split looms are more temperature sensitive than the wires, so if you have nothing melted you are probably o.k. there. I don't think the problem is the iac valve, it seems to be just too much fuel from the injectors. I did have to replace my iac valve once, the symptoms were an incorrect idle speed at startup. You could unscrew it and clean it though. When the vehicle first starts up it is in a full rich condition, but I think yours is beyond that. Another thing that can cause excessive fuel through the injectors would be a clog in the fuel return line. Howell says you can use the 1/4" oem return line, but I think a 5/16" new one would work better. Anyway, an inspection might not be a bad idea. Other possibilities could be the engine coolant sensor, map sensor, and the tps. I have seen an adjustable type of tps, but a fixed version can be made adjustable. For future startups I would suggest using the clear flood mode startup to try and lean it out.

Thanks. Do you know of any procedures to test the coolant or map sensors? I have tried the "clear flood" method (wide open throttle) but usually get a pretty good engine "cough" or backfire.

The link I sent you was a random link off the net to give you testing instructions. I'm sure those specs whatever they were was not for your system. Your .713 reading is too high and out of spec for your system according to Howell (.5-.7). I previously explained the reasons why the TPS should be set at .54, or as close as you can get without going under or over .64

Ok got it...will attempt to adjust the TPS down to .54. Will get back with results in a few days as the damn kitchen remodel has once again taken priority (not by my choice)!

 

[Torxhead]

Come to think of it I have not had much luck with that "Clear Flood Mode" procedure either. If I have flooded the engine, I will just clean the fuel off the spark plugs with a rag. Looking up test procedures, there are lots of videos and instruction pages to choose from. You are looking for a test on a '86-'91 GM 4.3 engine, take your pic. Your Howell instruction manual does give GM part numbers to refer to and I just give those to the auto parts guy and cross reference them.

 

[Posi]

After the TPS is adjusted do a ecm pin readout if needed.

Made sure you have at least 12.6v at the battery (w/out charger connected to it).
If you charge the battery let it sit for an hour before testing.

Test and post the following results.
Post battery voltage.
Check the ecm fuse block with key on.
Check the ecm fuse block while engine is running.

Test ecm pins

Do not remove the two ecm plugs
If you remove the combs it will make it easier to back probe the pins.
Test with key on
Use the red lead to probe, black to ground.
Start at the A1 pin

Now do the test again with engine running
If the engine is running good enough let it warm up first then test.

Also measure between A11 and C13 in addition to the chart tests. Red probe at C13 black probe at A11 with key on and once again with engine runiing.

Attached you will find a ecm voltage check chart. Post your results in the column test with key-on and engine running, fill in the attached chart and re-post when done. Don't be concerned if there isn't a wire on selected pins it simply means your not running that component.

Another thought, I believe you tested the ignition module before the pickup coil was diagnosed as bad. if so the module wasn't tested again with new pickup coil installed. If you have another good working module swap it in.

 

[Posi]

thundley57, you will not be able to type on the document I posted. It makes it a lot easier when you can type in the results. If you PM me your email address I will send you a copy you can fill out and send back to me.

 

[thundley57]

Come to think of it I have not had much luck with that "Clear Flood Mode" procedure either. If I have flooded the engine, I will just clean the fuel off the spark plugs with a rag. Looking up test procedures, there are lots of videos and instruction pages to choose from. You are looking for a test on a '86-'91 GM 4.3 engine, take your pic. Your Howell instruction manual does give GM part numbers to refer to and I just give those to the auto parts guy and cross reference them.

Thanks, I will look up the procedures for testing the MAP and coolant sensors as well as the IAC, perform the tests and post the results...that is if I can break away from this kitchen anytime soon.

Now do the test again with engine running
If the engine is running good enough let it warm up first then test.

My engine will only run for a few seconds then dies. Is it still worth doing the "key on" tests?

Another thought, I believe you tested the ignition module before the pickup coil was diagnosed as bad. if so the module wasn't tested again with new pickup coil installed. If you have another good working module swap it in.

I swapped my module out the other night when my 1st attempt to start it after I replaced the tach filter resulted in zero improvement, same result after swapping the ign module.

 

[JR74CJ5]

My engine will only run for a few seconds then dies. Is it still worth doing the "key on" tests?

Not to speak for Posi, but I believe he's assuming after you adjust the TPS to his recommendation, the engine will probably stay running.

After the TPS is adjusted do a ecm pin readout if needed.

Here's hoping that's true

 

[Posi]

Adjusting the TPS "will' help the engine run better.
Hopefully enough to keep the engine running.
However, I believe there still may be another issue going on.
Yes, do the key-on test if that's all you can get.

The test below is important, key on and while running.
The engine now runs long enough to do the run test below.
You may need a helper at the ecm probing/reading while you feather the throttle to keep it going if that's the case.
As JR posted I'm hoping it stays running for the complete test.
Also could you can take a pic looking down at the throttle blades without the engine running?

Made sure you have at least 12.6v at the battery (w/out charger connected to it).
If you charge the battery let it sit for an hour before testing.

Test and post the following results.
Post battery voltage.
Check the ecm fuse block with key on.
Check the ecm fuse block while engine is running.

 

[Posi]

Thanks, I will look up the procedures for testing the MAP and coolant sensors as well as the IAC, perform the tests and post the results...that is if I can break away from this kitchen anytime soon.

FYI, the extended amount of time it takes to test each sensor isn't time well spent, especially when you can have the same results, plus more, in 5 mins by reading the ecm pins as I posted earlier.

 

[Posi]

Another option for testing the ecm fuse block.
Key in the run position w/out engine running
Check voltage at battery
Check ecm fuse block

Attach battery charger
Key in the run position w/out engine running
Check battery voltage
Check ecm fuse block

Post your 4 voltage readings

The battery charger will not work for the ecm pin readout the engine has to be running for the second half of that test.

 

[thundley57]

I finally got a short reprieve from kitchen remodel duties (and filing taxes) to continue troubleshooting my "starts but will not come up to full idle and immediately dies" issue. Sorry about prolonging this thread even longer but hoping those of you that have been hanging with me, namely Posi & Torxhead, will continue helping me troubleshoot this issue so I can get this thing out of the garage and back on the trails! Posi, I tried my best to perform your requested tests the results of which are below.

What is your throttle blades set at?

The throttle blades should just be slightly opened. You can use a 1/4" strip of paper as a feeler gauge to get an idea of how far their opened.

If the throttle blades are out of adjustment they must be adjusted “before” adjusting the TPS. Adjusting the throttle blades with change the TPS setting.

What I did was use feeler gauges to try and measure the throttle blade openings. I got about .003 when the blades are fully closed. Don't know what it should be but I do know that when it starts and I immediately crack the blades open just a little bit there is no improvement.

Adjust the TPS, I posted instructions somewhere on the previous page.

If there is improvement but still not running as it should pinch the fuel feed line behind the TB to restrict the flow.

No change, try the same with the return line.

There could be another issue, but lets start with the TPS and fuel.

When you removed the plugs were they all sooty, or were a couple plugs whiteish?

Pulled the TPS and elongated the mounting holes enough to where I could turn the unit to get with-in the desired range. Ended up with .56 volts by the time it was all said and done. Started the engine and although there may have been a slight improvement, it still barely idled for a few seconds then died.

Cleared the cylinders then started it again this time slowly pinching the fuel supply hose with a pair of needle nose vice grips. I watched the fuel spray from the injectors start to diminish at which time the engine died. This makes me wonder now if I'm too lean but based on the look of the plugs the last time I had them out I'm thinking not (very sooty).

Started the engine again and this time slowly pinched the fuel return line but noticed no change.

Another option for testing the ecm fuse block.
Key in the run position w/out engine running
Check voltage at battery
Check ecm fuse block

Attach battery charger
Key in the run position w/out engine running
Check battery voltage
Check ecm fuse block

Post your 4 voltage readings

Key in run position w/o engine running
Voltage at battery: 12.8
Voltage at ECM fuse block: 12.3

Key in run position w/o engine running and battery charger attached
Voltage at battery: 13.3
Voltage at ECM fuse block: 12.6

After the TPS is adjusted do a ecm pin readout if needed.

Test ecm pins

Do not remove the two ecm plugs
If you remove the combs it will make it easier to back probe the pins.
Test with key on
Use the red lead to probe, black to ground.
Start at the A1 pin

Now do the test again with engine running

Tested the ECM pins with the engine not running and key in the run position. Results attached. The engine will not remain running long enough for me to perform the running tests.

I pulled the ECM and mailed it off to Howell for them to install in their test Jeep and see if there are any issues with it. Other than shipping no charge according to Troy. I feel like I'm grasping at straws now but at least it will be one more component checked off the list.