What in the name of every single blasted fruit bat is going on here?!: my daughter's 86 2M4 (everything stock) starts and runs great 99% of the time, but occasionally will simply not start-- just cranks but won't fire. Several months ago when this happened, I stuck a timing light on it to see if it had spark and it fired right up!. Next time it didn't start, just for the heck of it, I stuck the timing light on it again and IT FIRED RIGHT UP! Thinking two trees aren't yet a row, I left the timing light in the trunk and the next time it happened, I again connected the timing light and it immediately started. I've repeated this at least 5-6 times now and each time it's exactly the same situation- car cranks over but won't fire- put the timing light on and it instantly starts and runs fine.
For what it's worth, my timing light is a vintage series-type (non-induction) with the spring that clips in between the plug tip and the plug wire. The last time this happened, I connected the timing light's trigger wire to the plug without connecting the leads to the battery and it would not start. Connected the battery leads and it fired right up. I don't even have to press the trigger on the timing light for this trick to work- somehow, the car just knows the light is connected and starts.
Im going to go with bad ground. And Somehow adding the timing light adds more grounding.
My first gut was that the fuel pump relay has failed and its kicking on due to oil pressure. You try to start build up a little oil pressure nothing then add the light try again and because things have pumped up it then starts. However it sounds like you are cranking more than a little.
If it hasn't been done for a while, a general ignition system service would be a good idea. Still, try removing and cleaning the bolts that hold the Ignition module to the distributor base first.
I pulled the distributor apart yesterday and cleaned the ignition module bolts/mounting holes and baseplate, but first time I tried starting it, she just cranked with seemingly no spark. Stuck the timing light on, and just like before, fired right up. However, after I did that, the check engine light came on so I ran the ECU diagnostic and it spit out codes 21 and 33, which would seem unrelated to the ignition system.
My guess is that you have high resistance somewhere in your high voltage system. Have you looked at your plugs, cap/rotor, or sparkplug wires? You may have oil/fuel fouled plugs.
Don't drive a car w/ problems like that. May have some no-start problems now turning into a big problem latter or even have a car fire when some E-part finally dies.
Old T-lights put extra load on High side of ignition. That can do odd thinks even "solving" the above problem.
Does the tach moves when this happens?
Pull the Tach Filter any time you have problems w/ HEI system. That can cause weird problem too. But no filter = no tach for time being too. See my Cave, HE Ignition
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Originally posted by Rexgirl: My guess is that you have high resistance somewhere in your high voltage system. Have you looked at your plugs, cap/rotor, or sparkplug wires? You may have oil/fuel fouled plugs.
Could be... Even an Iffy coil.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Don't drive a car w/ problems like that. May have some no-start problems now turning into a big problem latter or even have a car fire when some E-part finally dies.
Old T-lights put extra load on High side of ignition. That can do odd thinks even "solving" the above problem.
Does the tach moves when this happens?
Pull the Tach Filter any time you have problems w/ HEI system. That can cause weird problem too. But no filter = no tach for time being too. See my Cave, HE Ignition
[QUOTE]Originally posted by Rexgirl: My guess is that you have high resistance somewhere in your high voltage system. Have you looked at your plugs, cap/rotor, or sparkplug wires? You may have oil/fuel fouled plugs.
Could be... Even an Iffy coil.
[/QUOTE]
Thanks. Next time it happens, I'll be sure to watch the tach. The cap and rotor are new, and the plugs are clean- less than 1K miles on them. I'm going to pick up a set of wires and put them on and see if that helps.
Update- no start again this afternoon but I saw that the tach worked while the engine was cranking- about 400-500 RPM. For the heck of it, I stuck the timing light on the #2 plug this time and it still didn't start. Stuck the light on the #1 plug and it started. Very strange.
Now Find tach filter and pull the plug and leave it. Is "bolted" on 1 of trans bell housing bolt head.
even if tach works filter can cause problems.
If still happens Buy new plugs, wires and cap/rotor set. New parts you have can "die." Before buying cap... check center part hits the rotor... that must have a spring and easy pops up when pushed in. If that doesn't help save the olders as spares.
What plugs do you have? Gimmick plugs claiming add HP etc and some others can fail. AC Champion Autolite & other "basic" plugs or their platinum tip are good and cheaper them some others and most shell made so won't rust.
If still happens buy a coil. Wells/WVE or Standard Blue Streak (Not Standard w/ T at end of part #.) Make sure is bolted to engine w/ OE coil bracket. "iron" core needs good grounding or that can cause weird problems even tho not connected to the windings. In fact If coil you have now is loose rusty, fit that before buying new coil.
Ok, now things are worse I disconnected the tach filter but after several trips, it quit and now she won't start at all- even with the timing light connected. So I replaced the plug wires and reconnected the tach filter and still no go. I'm going to order a new coil and ignition module and as those would appear to be the only two things left in the ignition system.
What is the condition/age of the distributor cap and rotor? I've been working on cars since they all had distributors with points, and in my experience, a worn cap/rotor combination can cause:
A V8 to run rough; A V6 to stutter and run very rough; An I4 to not run.
I've found this to be true whether the distributor has points or electronic pickup. I had kind of forgotten about this, with several cars in my family being distributorless, but my 2000 Blazer reminded me a couple of months ago. Assuming the cap/rotor are worn but not damaged, and have no carbon tracks or other problems, I know of no good way to visually inspect them for wear (maybe the carbon button, but not the electrodes). They just gradually degrade until they cause problems. They seem to last a little longer than standard spark plugs, but I like to change them at the same time.
If you replace these parts, choose carefully - there are a lot of crappy ones out there. I realize this may seem like throwing parts at the problem, but if you don't know/remember when they were last replaced, they probably need it.
Also, if you haven't already done so, check all connections in all wiring related to the ignition. I had a problem like this once, only with a V8 I had put into an '82 Grand Prix. I finally (after months of searching) found a bad connection in a ring lug. It was one of the self-soldering types that never made a solid connection (I will never use another). Finally found it with a wiggle test, but it took nearly forever. A bad crimp or a loose pin can cause real headaches.
A no-start is always is a fuel/air/spark thing. Are you sure the no-start is no spark?
Ok, I've made some limited progress. So far I've replaced the cap, rotor, wires, plugs and ignition control module without success. The timing light thing seems to have been just coincidence. Last night, just for the heck of it I shot some carb cleaner into the throttle body and cranked it over and she fired right up. Tried it again this morning, no start, but shot a tiny squirt of carb cleaner into the TB and she fired right up and ran fine. So maybe I've been chasing the wrong thing- the problem appears to be whatever tells the injectors to fire when cranking isn't happening, but once it starts, everything seems find.
EDIT: I should add that I can hear the fuel pump solenoid click and the pump run so that appears to be working fine.
[This message has been edited by Yorgle (edited 10-27-2021).]
I get 12psi fuel pressure and the car now reliably starts with a shot of carb cleaner or ether into the TB immediately before cranking. Here's a question, with the engine running, should both the blue and red wires from the injector be a steady +12V? My service manual is confusing and seems to suggest that I should see a pulsing voltage on the red wire, but it is unclear what I should see on the blue wire. No pulsing would seem to suggest that my ECM isn't doing its job.
The red wire should be a solid 12V when ignition is on. The blue wire is the actual ECM signal which is active "low" meaning it pulls to virtual ground in the ECM when pulsing the injector. When the blue wire is "low" (near ground) current flows through the injector coil because of the 12V differential across the two wires which causes it to open (spray). When the ECM needs to turn off the injector, the ECM places the blue wire in the default state of "high" which is 12V. With 12V on both wires there is no current flow through the injector because the differential is now 0V which keeps it closed. I don't remember the exact number of pulses at warm idle but you can easily see that it isn't a constant spray.
You should be able to see the fuel spraying if the engine is running by removing the lid of the air cleaner. Also, if it won't start then have someone else crank it while you watch and see if it sprays while cranking. If it doesn't then you may have a problem between the ignition module and the ECM. I would expect you to see a code ( 42 IIRC) but who knows. The module produces a "cranking signal" to the ECM which tells it to spray fuel to get it to start. Once it starts the module signal is a higher frequency which tells the ECM to assert the "bypass" signal so that the ECM takes over the spark advance timing (EST) for the system. Maybe the cranking signal is low or flaky causing this. I seem to recall the cranking signal is equivalent to 400 RPM, or around 14 Hz IIRC. Could possibly be the module, the pickup coil or poor wiring between the distributor and ECM. Just my two cents since I haven't worked on the distributor-based system in a long time.
Some of what you said makes sense that this is the problem. The ECM controls the spark once the engine starts, thereby taking away the control from the ignition module. If that "hand off" works then that explains why it runs when you "snort start it" with carb spray. The ECM detects the increase in speed from the module and takes over. If the signal from the module isn't quite up to the 400 RPM (again, IIRC) then the ECM may not spray enough (or at all) because it doesn't realize the engine is cranking.
I know you changed the module so maybe it is a wiring issue? Maybe at the ECM end?
For posterity, I thought I'd update this thread as I finally found the source of my no-start issue. Turns out that for the past year I was wrongly assuming the problem to be that the injector wasn't firing, when in fact, it was the TPS- damn thing periodically go it into its mind to send a steady 4.5v the ECM for no apparent reason, causing the Duke to hopelessly flood itself. I figured it out only after hooking a digital multimeter to the TPS signal wire inside the car so I could see what was going on while driving. Sure enough, after a few days of trouble free driving, enjoying watching the TPS voltage vary with the gas pedal, it suddenly jumped to 4.5, the engine light immediately came on. I stopped and shut the car off, let it sit for a while and then tried to restart. Sure enough, it wouldn't start. Pulled the plug off the TPS and it started right up. Reconnected the TPS and it still read 4.5 with the ignition on (engine not running). Manually moved the lever on the TPS a few times and it dropped back down to .9v. Car then started perfectly. The lever on the TPS wasn't actually sticking, but there must be some sort of short inside that every now and then causes the wiper to contact the 5v feed. Anyway, I hope this info helps someone down the road.
The lever on the TPS wasn't actually sticking, but there must be some sort of short inside that every now and then causes the wiper to contact the 5v feed. Anyway, I hope this info helps someone down the road.
Good you have this solved, but these shady 80s electronics always seem to benefit from extra grounding. I would definitely consider running at least one extra ground wire direct from battery to the block or heads. If there is any resistance dropping voltages at the sensor or ECM, especially when the cars been sitting a bit and the batt is a little low, then the electronics go wild. Once running and the alt is upping the power it may be less of an issue or masking the issue.
I highly recommend this, you may find the car runs significantly smoother. I did this with my 2.8 and it was extremely noticeable.
I did have an issue with my 2.5 where one of the pins on the ECM was getting intermittent current, it had 12V at the ECM pin, but checking with a test light only lit it up dimly. I ran a new power line to it and my stalling and no start problems were solved. It is worth going through the harness at some point and ensuring that you can illuminate a test light at all the power pins going to the ECM, and ensuring your ground pins are low resistance.
A good quality ICM is also a must if you ever find it needs to be replaced. Try to find NOS so you can get a US made Delco one vs the Mexican made ones of today.
I am going standalone ECU for my new swap, and a big reason for this is to get a brand new wiring harness and much higher quality electronics. I love my Fiero but it has given me all the electrical issues in the time I have owned it.
[This message has been edited by zkhennings (edited 01-26-2023).]
I disconnected the tach filter but after several trips, it quit and now she won't start at all- even with the timing light connected. So I replaced the plug wires and reconnected the tach filter and still no go. I'm going to order a new coil and ignition module and as those would appear to be the only two things left in the ignition system.
