No re-start when hot.

Took it out for a short trip yesterday to make sure it would restart after warm-up. No problems there, but for some reason I now have no reverse! It's got to just be a linkage adjustment, so I'm not too concerned, just shaking my head, though... :wall:
 
And so it continues

I thought I had the hot re-start thing licked, but apparently not. The reverse issue was what I thought, a loose lollipop, which was easily remedied, but the starting issue continues.

I am not getting spark when the engine is hot. I tried plugging in a cold second ICM, won't start. I put in a spare coil, got the engine hot, won't start, no spark. Give it 30 minutes to cool down, there's spark and it starts. What else could be causing thermal failure?
 
AFM gets pissed after shut down and commencing heat sink? Maybe solder break that shows up after such heat sink but is okay after cool down (and normal running) WAG. Open your engine lid after a run for now?
 
This is a 1300 carbed motor, so no AFM. The weirdest part is, it doesn't seem to matter how far I drive, it runs fine as long as it's not shut off. As soon as the key is turned off, it won't restart.
 
Jeff, is it really a lack of spark?

Or is it something else?
You shouldn't be getting "no spark" in any case.
Have you checked to see if the spark IS there, and maybe something else?
I can't prove it here, but the chances that this new ignition box you rebuilt acts like the old one would be astronomical.

Suggestion: Bring a spark plug with a long plug wire, long enough to set atop the perch mount while plugged into the coil.
You should see spark under all conditions.
If not, I would suspect an electrical issue, but I really don't think it's that either.

I suspect a fuel / vapor lock issue. :2c:
 
I'm checking spark by taking off a plug wire and plugging in a long enough wire that I can ground it while turning the key. No spark as soon as it's shut off. I have a second ICM that I've checked as well when it won't start. No change.

What voltage should I get at the coil, and is it measured at the "+" terminal?
 
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oh duh, sorry carb, not FI so....
vapor lock? but it's a spark thing so I'll just sit back and listen
 
You can test with a 12v test lamp, with the key on, both sides of the coil ( terminals 1 and 15 ) will show as having power. If it does, cranking the engine over will show a pulsing at (1) and steady-ish power at (15).

It would be about 9v at coil terminal (15) in a late model with the resistor.
 
The thing that just doesn't make any sense is that I can drive it for as long as I want and it runs perfectly, then no spark or restart as soon as I shut it off until it cools off.
 
I'm showing 6.3 volts on the + terminal with the key on, 7.2 when it starts. I'm only showing 0.8 on the - terminal. These readings are with the positive lead on the terminal and the negative lead grounded.
 
That sounds close enough... is your coil stock? Does it have the resistor between power and the coil?

See if you have power there when it doesn't start.
 
Unfortunately it won't be until tomorrow at this point, since I have to go drive it around in order to get it hot. It does have the external resister.
 
Those readings sound correct.

I'm showing 6.3 volts on the + terminal with the key on, 7.2 when it starts. I'm only showing 0.8 on the - terminal. These readings are with the positive lead on the terminal and the negative lead grounded.

But you'd need an oscilloscope to see what's going on at the - (minus) terminal of the coil, as it's likely pulsing. (sharply) Or near ground potential. (engine not running)

If you have 7.2V at the coil's + terminal, you should be OK. You should also have 7.2 volts at one side of the resistor, and near 12 volts at the other side of the resistor. (FYI, 7.2 VDC is as much voltage drop as you should see, as I would have expected a little higher on that. (more like 8 V.)
You might want to consider changing out the resistor at some point but doing so does not address the reported lack of spark.

Your spark (Ignition) Control Module manages the - (minus) terminal signal to the coil. (pulses)

Attach a plug wire on the output of the coil and put a spark plug on the other end. Ground the plug casing somewhere to the chassis. (I use one of the 10mm strut housing nuts to ground the case of the Spark plug) Have someone crank the engine for ya and there should be a strong visible spark, regardless if the engine is hot or cold. If not, I'd be very surprised.
 
Here are my measurements at the coil terminals.

Cold
Motor off (+) 6.8v (-) 0.95v Motor running (+) 8.3v (-)3.7v

Hot
(+)7.1v (-)0.9v

Batter voltage is 12.5v at the battery and 10.5v before the resistor.

There is a spark from the coil that is somewhat weak that sparks at a rate of 2-3 per second. There is no spark at the plug. This time, however, it restarted after only about 10 minutes. Granted though that I only let it get hot in the garage and didn't take it out on the road.

The second time, I let it get even hotter and this time there was no spark at the coil, but the same readings from the coil terminals. After cool down, spark from the coil again.

The coil is warm, but not hot. It's the second coil I've tried, so I'm not sure how two coils could fail. I'm not sure what Bosch coil the second one is, but the first is a Bosch #0221122012.
 
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SOME answers ...

My answers in BLUE

Here are my measurements at the coil terminals.

Cold
Motor off (+) 6.8v (-) 0.95v Motor running (+) 8.3v (-)3.7v <-- I expect to see this with the engine running.

Hot
(+)7.1v (-)0.9v <-- I expect to see this when the engine is NOT running. Very close to above values. ("not running" values) NORMAL.

Battery voltage is 12.5v at the battery and 10.5v before the resistor. TYPICAL. (although we'd like to see as close to 12V as possible)

There is a spark from the coil that is somewhat weak that sparks at a rate of 2-3 per second. NORMAL There is no spark at the plug. NOT NORMAL. Check wire from coil to Distributor. Check center conductor to the Rotor. Cannot be loose against the top of the rotor or frozen in place. Should spring in & out. (this is suspect!) I checked the resistor when it was hot and oddly it was showing 0 ohms. Not normally possible, the resistor should increase it's value with heat, but only by a little. (like .1 ohms max) This time, however, it restarted after only about 10 minutes. Granted though that I only let it get hot in the garage and didn't take it out on the road.

The second time, I let it get even hotter and this time there was no spark at the coil, but the same readings from the coil terminals. After cool down, spark from the coil again. How about the voltage at resistor? What happens if you quickly swap the Bosch module? (if you have a spare) No change when swapped? If no, not the module.

The coil is warm, but not hot. NORMAL It's the second coil I've tried, so I'm not sure how two coils could fail. I'm not sure what Bosch coil the second one is, but the first is a Bosch #0221122012.
Not the coil.

Suggestion: Change out Cap & rotor & change resistor. Use 0.8 ohms in your case. Coil will get slightly hotter, but since you have 10.5V, that would be a best choice for you.

Let us know results.
If you want, I can send you a complete (tested) setup.
 
The ohm measurement isn't accurate. I couldn't find my better VOM, so I'm using a cheapo, which won't calibrate to 0 that in the lowest range. However, from what it does show, the resistor is probably OK.

The inside of the distributor cap and the rotor looked OK, just slightly crusty on the contact surfaces, so I cleaned them all up with some fine grit sandpaper. The center conductor moved freely on the spring.

I took it out and it started running crappy, like it's got some crud in the carb. :wall: Aaand, no hot restart.
 
Jeff... I got dizzy reading through all this... but...

probably NOT as dizzy as you must be... So sorry for all this trouble.

I have these TWO remote possibilities with some simple tests to try... at least it will get these TWO possibilities out of the way for good.

1. Run the engine until hot and cause the no-start failure. Then with a good length of wire from the battery + post to the + terminal on the coil. Try to re-start it immediately. If this works, I suspect a bad ignition switch or the 4/5 wire connector.

(I just recently found a HOT DAY no-start issue with mine and it was caused by a loose connection to my ignition switch that was replaced by "pros" in 1986 or so... I surmise the high resistance and the HEAT generated PLUS the heat of the day caused this problem.)

If this proves NOT to be the case, then try this:

2. If you have not run a second ground strap up top, do so AFTER you prove the problem. Run the engine until hot again with a no-start failure. Add a second wire between the cam cover and the chassis somewhere and try and start it again.

That's all I got... But I do know that all the voltage and resistance measurements I took when I had a ground strap issue 15 years ago appeared correct, but the bottom line was... even though the voltage appeared correct, there was too much resistance for it to start. (With the engine off, I measured 12.5 at block from the alternator and 12.15 to the chassis. I was using an analog meter and didn't SEE the difference until I used a cheap HF digital meter...)

HTH...
 
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