Hi guys,
I am starting this as a new thread although it may be related to my previous issue that I thought had been resolved (ignition problem-no spark after replacing )

two days ago I went to haul a load of firewood to the house. truck started fine and ran ok until I started up a hill with full load of wood. Truck than started missing and finally stalled just as I reached my shop Could not get it restarted, but it was firing at that time, just would not continue running. Yesterday it would not fire at all!
This is the Duraspark II with fender mounted ICM (new installed last week)
I have good spark at coil but none at number one spark plug.

Pulled distributor cap - contacts inside do have carbon build up and some erosion. Rotor looks ok, but with some carbon on contact (less than is on the 8 contacts to the plugs).

I checked resistance at ground wire - zero
and purple to orange wires - 460 ohms
also checked ac volts with rotor spinning various readings at 1 to 2 volts.

Where do I go from here?
Is it possible for the new ICM to be bad and still put out good spark at coil?
Should I replace the cap and rotor? Doesn't seem like the carbon buildup would suddenly stop all spark, but I could be wrong!

any and all help would be appreciated!

Thanks in advance,

Chuck M.

 

Remind me, what year, model and engine do you have?

I would recommend you check for fuel too. If you remove the air cleaner and look down the carb venturi, when you move the throttle to WOT do you see a stream of fuel squirt from the accelerator pump discharge nozzle(s)?

You say you get a spark from the coil but not from the #1 plug wire. What about from the #2 or other plug wires?

I assume you have someone cranking the engine while you hold the plug wire near a good ground (usually you stick a screwdriver or such in the plug boot to touch the metal plug connector and then you hold the screw driver by its insulated handle and keep the metal part of the screw driver about 1/16" to 1/32" from an engine ground.

 

what is your plug gap set at.

 

Country and Rebel,
Thanks for your quick replys!
1985 ford f250 4x4 auto 351W carburated

Plenty of gas at carb with WOT.
My plug tester is a just an autolite ap25 from this truck gapped at .044"

I used the same plug to test at coil and number one plug by holding in a gloved hand against a good ground to engine.

I did not test other plugs thinking if they were getting spark, I would be getting at least some firing in the engine.

Thinking of taking the ICM's (old and new) to Oriellys for testing this afternoon - Any other suggestions?

Again - thanks for your help!

Chuck M.

 

There is a "pickup" assembly inside the distributor. They go bad. How old is yours?

See Duraspark_distributor_recurve_instructions_index for a picture of this.

 

Quick additional.
I'm working this alone, so I'm using a remote starter and turning the ignition key on when testing for spark.

 

Country,
As far as I know it may be original to truck. Anyway to tell- date code,etc.?
The ac voltage test I did was supposed to verify if the magnetic pick up was ok.

This was from the www.fordmuscleforum a while back.

The spec was supposed to be 1 volt ac and I was getting 1 to 2 volts ac - not sure if 2 volts is good or bad but I think they meant it needed to be a minimum of 1 volt ac. How else can you test to see if the pick up is bad? And is that an easy (and cheap) replacement?

 

I think the 1 VAC is a just a starting point, more is better and not all meters will read this the same.

Testing the IGN module seems to be a good starting point.
Are you using a stock coil with the correct primary resistance?

 

Status update - Still no joy - need help!
Took both ICM's to parts store (Orielly's) and they both passed on their tester.
Bought and installed new distributor cap and rotor. No change is results - good spark at coil but nothing at plugs. I did not check all the plugs, but neither plugs 1 or 2 show any spark at all!
The coil is only 6 months old and meets the resistance tests specs.
The magnetic pickup passes the only test I know about reading 1-2 volts ac when rotated.

I'm wondering if there is a disconnect (wiring issue) between the ICM and the distributor? If that were the case, any idea which wire and how best to test it?
Would a continuity check tell me anything meaningful?

I'm open to suggestions!

Thanks,

Chuck M.

 

Your pickup in the distributor is reading good at 460 Ohms.
The Duraspark module only triggers the coil.
That seems fine.

You have spark at the coil and none coming from the distributor, yet you've replaced the cap and rotor...
You need to see why the coil to distributor wire is not getting power to the rotor.

 

I went back and reread this thread for some new ideas....

Put a test light on the coil negative and watch for smooth even flashes. I have tried different sized bulbs on this, some show up better than others.

Check and clean the single GRD screw and clamp under the Dist cap. This is where the 3 wires goes to 2 wires. This is the sole GRD for DS2 module and the coil Neg

With Key ON test the voltage on both sides of the coil.

If you are getting even flashes on the test light, then that means the Dist pickup, module and wiring are all good in theory.

That only leaves "weak spark" or low secondary coil output. Which means the spark might jump a .030 gap but not anything more than say .035.

You might have to make up a testing system like clamping all 6 plugs to a metal ruler (which is grounded well) and watching the plugs after dark to see if all 6 are working.

Back in the old days they had spark plug testers that used compress shop air, you would test the plug for spark then increase the PSI to 100 or so and see if it still sparked.

Sorry I don't have a quick and simple answer.

Good luck, JIm

 

Is your spark plug tester "in line" to the plug?

 

He mentions his "tester" is just one of the Autolite 25's from his engine gapped to the correct .044".

I'm thinking it has to be secondary wires, because there is nothing else between the coil and the distributor cap that hasn't been replaced. (recent coil, cap & rotor)

We know the reluctor is turning or there wouldn't be any spark.
Would be good to know if it is a bright blue spark or some dim orange glow.

 

I did Google the tester but I didn't find it. Mines is just an cheap inline Neon Glow Lamp style and I am not sure what it would do in a weak spark condition. The bulb is 65 VAC. GE p/n NE51H (B2A)

If you unplug the coil wire from the cap and hold it close to a good ground while cranking the engine over you should see a good strong spark jumping a large gap. I usually get my wife to hold the coil wire as I know better

 

I prefer the spark testers with the clamps. That way you can be sure you have a good ground and it stays in position so you can see it. I mentioned using a screw driver in my first post. To me that would be my preferred method if I didn't have a clamp-on tester. I don't like the idea of using a "real" spark plug to test with because you would be laying it on the engine and assuming you have a ground.