Cranking but not catching (1 Viewer)

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Joined
Aug 21, 2011
Threads
19
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82
Location
Huntsville AL
Evening fellow LC enthusiasts,

My 91 is cranking but not running. I have checked and the fuel pump is working fine. Tried a new igniter (that I hopefully can return) to no avail. I ran across this EFI flow chart that I have seen around here http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf and I believe I might have a bad coil. Ohm meter showing 0 resistance on the positive and negative but it is showing proper resistance between positive and high tension terminal. CEL light IS on when the switch is on. Someone mentioned a start relay, but I'm not familiar with that one. Any advice? Thanks
 
Do a search for the @jonheld start-up procedures for this. For that matter, any posts he's done.....except for the 7-pin mod. :flipoff2:
 
Spray starting fluid into the intake for two to three seconds, immediately try to start the engine. If it lights off and idles until the starting fluid is consumed then you have just verified your ignition system and air flow.
 
Look at Jonheld' "No Start" troubleshooting chart under the FAQ's....step by step flow chart from the best in the business! Good luck!
 
Evening fellow LC enthusiasts,

My 91 is cranking but not running. I have checked and the fuel pump is working fine. Tried a new igniter (that I hopefully can return) to no avail. I ran across this EFI flow chart that I have seen around here http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf and I believe I might have a bad coil. Ohm meter showing 0 resistance on the positive and negative but it is showing proper resistance between positive and high tension terminal. CEL light IS on when the switch is on. Someone mentioned a start relay, but I'm not familiar with that one. Any advice? Thanks
The primary of the ignition coil is a very low resistance. Unless you have a good meter and know how to use it, it's difficult to see 1/2 ohm. It will read as a short (0 ohms) on most meters.
A very simple diagnostic is to check for spark.
 
Spray starting fluid into the intake for two to three seconds, immediately try to start the engine. If it lights off and idles until the starting fluid is consumed then you have just verified your ignition system and air flow.

Tried the starting fluid in the air I take....... nothing. No go.
 
Look at Jonheld' "No Start" troubleshooting chart under the FAQ's....step by step flow chart from the best in the business! Good luck!

Thanks, @Marine7

Can't find that chart. I'm not so good at navigating this site yet. You have a link? Thanks!
 
Update and summary: The 91 LC ran yesterday again but not today.:bang: Very unpredictable and unreliable at this point. Not sure if weather is a factor but it seems like the run to no-run ratio is getting worse. When she runs she runs smooth with no skipping or going dead.

CEL is lit when switch is on but never been lit while running.

Don't know if it's relevant but The exhaust smells strong when idling.The odor reminds me of a bad codolitic converter.
Also the LC was recently parked and was not driven much.

I've checked and fuel IS being delivered to the intake. The spark plugs are NOT firing. I pulled one, put it back in the SP wire and touched it to the motor while my kid hit the ignition. No spark. I even tried spraying some starting fluid in the air intake but she wouldn't fire up.
Cleaned the cold start injector.
Replace igniter with new one.
The primary coil resistance was too low to register on the meter but the secondary coil read correctly.

Is there a start relay on this thing!?!?

Thanks y'all! :flipoff2:
 
There are no secret "start" relays, at least not in the OEM setup.
Have you gone to the next step in the flowchart and checked distributor coil resistance? You should also make certain that the distributor coils are making it back to the ECU.
Have you checked the simple things like the making sure the distributor rotor/cap are in good shape internally?
 
There are no secret "start" relays, at least not in the OEM setup.
Have you gone to the next step in the flowchart and checked distributor coil resistance? You should also make certain that the distributor coils are making it back to the ECU.
Have you checked the simple things like the making sure the distributor rotor/cap are in good shape internally?

The primary coil resistance read 0 or it was too low to register on the meter but the secondary coil read correct resistance. Haven't checked inside the distributor cap due to the fact that the truck seems to be running smoothly when it decides to run. I've always heard that a bad distributor will make the engine misfire.

I checked the pick up coil resistance (the plug coming off the bottom of the distributor) (while ignition was turned off) and got nothing.

How do I "make certain that the distributor coils are making it back to the ECU." Please forgive my lack of knowledge on the subject. I'm learning as I go. Thanks
 
The primary coil resistance read 0 or it was too low to register on the meter but the secondary coil read correct resistance. Haven't checked inside the distributor cap due to the fact that the truck seems to be running smoothly when it decides to run. I've always heard that a bad distributor will make the engine misfire.

I checked the pick up coil resistance (the plug coming off the bottom of the distributor) (while ignition was turned off) and got nothing.

How do I "make certain that the distributor coils are making it back to the ECU." Please forgive my lack of knowledge on the subject. I'm learning as I go. Thanks
Do not make assumptions when diagnosing a problem. It takes all of 5 minutes to check the simple things first and it can save you hours of frustration. A warn out center button on the distributor cap will cause impossibly long crank times. Once she catches and is running, the spark will jump the gap and things will appear normal. Don't assume, check it and move on.

What do you mean by "I checked the pick up coil resistance and got nothing". What does "nothing" mean? Please quantify your results.

The wires from the base of the distributor run back to the ECU above the glove box. Terminals NE; G1, G- should hit ECU connector E4 pins 4; 18; 17 respectively. You can see the ECU connector pinout on the bottom of page 1 of my troubleshooting procedure.
 
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I checked the pick up coil resistance (the plug coming off the bottom of the distributor) (while ignition was turned off) and it registered 0.

I will pull the distributor cap and have a look.

Thanks @jonheld for the help.
 
I checked the pick up coil resistance (the plug coming off the bottom of the distributor) (while ignition was turned off) and it registered 0.

I will pull the distributor cap and have a look.

Thanks @jonheld for the help.
You need to make sure your meter is set correctly to read low resistance. The distributor pick up coils should read between 140-1800 ohms. That's a pretty wide range and your meter should be able to register it correctly.
 
I checked the pick up coil resistance (the plug coming off the bottom of the distributor) (while ignition was turned off) and it registered 0.

I will pull the distributor cap and have a look.

Thanks @jonheld for the help.
This bothers me. I can see 1 of the 2 coils reading bad, but not both. Ignition on or off makes no difference here as you should reading the DISTRIBUTOR side of the connector, not the harness side.
Alternatively, you could leave the distributor connector plugged in and test resistance at the ECU connector with connector E4 removed from the ECU.
 
This bothers me. I can see 1 of the 2 coils reading bad, but not both. Ignition on or off makes no difference here as you should reading the DISTRIBUTOR side of the connector, not the harness side.
Alternatively, you could leave the distributor connector plugged in and test resistance at the ECU connector with connector E4 removed from the ECU.

Re-checked the pickup coils with the ohm meter today. When I touch probes to the pins I get a quick resistance reading of 180 or less and instantly the number disappears and the meter reads zero. This happens on both pickup coils every time I re-apply the probes. It may be a coincidence but at two different times today when the LC would crank but not run, I tested the pickup coils with the meter and got the flash readings and the truck would fire up when cranked immediately after. It has began randomly going dead when driving and idling.

I did get the new coil in today and it didn't fix the problem. I got a back up coil and igniter now! :(
 
I pulled the Distributor cap and had a look inside. nothing stood out as bad to my un-trained eye. Center button spring still appears to be working and everything looked pretty clean inside. With the funky pick-up coil readings in mind, do you guys think it could be just a bad dissy cap? Or...... Should buy the whole thing? thanks to you @jonheld
 
The cap has nothing to do with the resistance readings of the pick up coils. However, I'm uncertain as to what readings you're seeing and how proficient you are with a meter and electrical diagnostics in general.

A replacement distributor is certainly a possibility, but I would source a used OEM one from a reputable parts supplier like @arcteryx jason@cruiseryard.com.
Any 3FE distributor will do, from an FJ62 or FJ80.
 
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