I agree that a bad connection SHOULD shut you down completely. But, two people have replaced the horseshoe connector due to connection problems, and in one case it fixed a problem like you are having. That I cannot explain, but I believe.

Anyway, I just checked Rusty and he shows 6.9v at the Bat terminal on the coil with the key on. So, if that's basically what you are getting then the resistor is working. And, if that is the case then I can't buy three bad coils in 5,000 miles - at least not due to too much voltage/current. And, there's nothing else the ignition module can do to the coil.

I'll ask again - have you checked the dark green/yellow wire? Might it have the insulation off at some point and it is shorting out?

 

Don't be ashamed of bias confirmation. In fact, you should embrace it. Life is much easier that way. It applies to many thing, not just troubleshooting. For example, please take my daughter's former boyfriend. (Literally, please take him...) I knew I didn't like him from the moment we met, and in due time he proved me correct. That reminds me, I should go out to the shed and check on him, and see if I can let him out any time soon.

All seriousness aside, back to those three coils. Were any of them from China? If so, that changes the equation. The underhood temps must be very high on a E-series motorhome, working hard in the mountains. The tight confines of the doghouse can really trap the heat. I've also learned the hard way to be very leery of Chinese electronics. Add lots of heat, and that could explain some of what you've experienced.

I once had a 20 year old OEM starter solenoid give up the ghost on another vehicle. The replacement, from China, lasted about 2 days. (I went with another OEM solenoid and it has lasted for years.) For giggles, I cut apart the original OEM and the failed Chinese version. The OEM version had much beefier windings, better insulation, you name it. I was shocked at the difference. It looked very amateurish inside. Of course not all Chinese parts are this bad, but with so many on the market, it's something to keep in mind if new parts seem to go bad.

 

I think Chris has posted pictures of a Chinese solenoid with steel or iron contacts made as part of the core.
Needless to say it was welded closed.

 

Gotta love Engineered Lifespans ...

-Enjoy
fh : )_~

 

Thanks Jim, it's comforting to think it's bad parts and not a lack of skill!

I disconnected the two wire plug at the duraspark ignition module and disconnected the horseshoe at the coil and obtained the following readings with my crappy ohm meter:

Red wire at plug to red wire at horseshoe 8 ohms.

White wire at plug to red wire at horseshoe 1.0 ohms

Battery voltage running 14.65, voltage at coil, Bat + terminal 11.43

I also tested the resistance of three coils:

1) Coil currently in.vehicle, lug to lug 1.1 ohms, and 9,520 ohms at center terminal.

2)Stock coil, lug to lug 1.0 ohms, and 8,680 ohms at center terminal.

3) Coil that worked for many years but was replaced because it leaked oil. 1.1 ohms lug to lug and 9,250 ohms at center terminal.

Key on, motor not running I also measured 12.11 volts at the coil with the battery reading 12.62, however this was with the horseshoe disconnected from the coil.

Gary, I looked at the tach wire and didn't find any chafes or possible shorts but I did find where somebody used one of those crappy clamp on connectors to attach the cheap aftermarket tack to the horseshoe ground wire. The way those things slice into the insulation (and wires!) can't be good.

KR98664, heat, yes. And without a doubt the lazy (built in China no doubt) fan clutch is not helping the situation one bit.

It gets plenty warm pulling the steep pass at 5,000 feet elevation doing 40 mph, in 2nd @2,700 rpm, pulling 3,000# (on top of the 9,200# the rig weighs already) and I've never heard this particular fan clutch stiffen up and pull in more air.

But even worse, imagine driving it on a 100* day and then parking it. With no air flow it stays hot in there for a long time and just bakes. The fact that each of these episodes occurred shortly after (like the next time out) after running in the heat really makes you wonder if that's simply it. IIRC I've read the coil temp @ 180* with an infrared thermometer.

At this point I should probably try another fan clutch and splice in a new horseshoe connector a) making sure to cut out the crappy tach connection and b) using longer leads that will permit brining the coil up out of its hiding place under the air cleaner behind the AC compressor and mounting it on the vacant smog pump bracket out in front of the motor, where it should get better air flow.

 

I am in the process of making a "two outlet" air cleaner snorkel, One goes to the stock air cleaner, and the other goes to a 12v fan and a thermal switch.
Once under hood temps reach 160 degrees the fan kicks on, and stays on until it gets under 160 degrees, (stays running even with KOEO)
This was done to eliminate my hot start problem, and seems to work......

 

The 12.61 at the coil is ... questionable. I checked Rusty the other day and where the engine was sitting the voltage to the coil was 6.9. Apparently the DS-II module does effectively work like points, meaning it keeps current flowing when the engine is sitting at a point where the points would have been closed. (I had assumed it wouldn't.) So, your engine must have stopped where the points would have been open as no current was flowing and there was no drop across the resistor. Or, your resistor isn't working.

I suggest testing the voltage after you've bumped the engine over to see if you find it down around 7 volts. Several times until you get the lower voltage or determine it isn't going to happen. You may be running full battery voltage to the coil, and that will burn it out.

 

Gary, I think you're on to something. He did say he had 11.43 at the coil with the engine running. Is it supposed to be down around 7 instead? I can check my truck tonight when I get home.

 

Thanks Gary and KR but I think the KOEO voltage test at the horseshoe was flawed since the horseshoe was completely disconnected from the coil.

With 0 current flowing the resistor wire voltage drop will not manifest and you should show full voltage. I will repeat the test with the coil connected and report the results.

Reamer, would love to see the details of your electric fan set-up! I've often thought an electric fan controlled by a thermal switch could be a solution to the problem of finding a good mechanical fan clutch and also address the heat soak after shut down issue.

Finally, if anything, the 8 ohms of resistance on the red wire at the duraspark module plug to the hot wire at the horseshoe (disconnected) seems high to me. From what I can gather the resistor wire should only be 1.5 ohms?

 

Quote... Key on, motor not running I also measured 12.11 volts at the coil with the battery reading 12.62, however this was with the horseshoe disconnected from the coil.

You are correct, the IGN system needs to be intact and working correctly to see the voltage drop across the resistor wire, you must have current flow to get the voltage drop.

Also the DS2 IGN module always has current flow when it is power on, engine not running.
If the DS2 IGN module has failed, meaning no current flow through it "Key ON" then no voltage drop.
Any break in the circuit means no voltage drop.

The OHM's check is a harder why to check the resistor wire as the numbers are low and quality of meter vary, I prefer to read the voltage drop.

Add me to the list of people that had to change the coil connector.

Try to cool the DS2 IGN module, maybe ram air or washers under the box to add air flow under it.

Jim

 

You could "glue" a massive heat sink to the module, I have seen modules "moved" to the front of the core support, but protected from the weather....

 

Didn't realize the voltage check was with the connector off. Absolutely right, no current flow means no voltage drop: E=IR. Multiply by zero and you usually get zero.

And, 8 ohms is too high. The EVTM shows the resistor as 1.1 ohm. Need to find out why you are reading 8 ohms. First, tough the leads of the DVM to each other and see if you get zero.

 

I'm officially confused. Sorry if I misread your reply and steered the conversation in the wrong direction.

From post #20:

Was the first voltage reading at the coil (11.43) measured with the horseshoe connected and the engine running? That was the reading that seemed high to me.

I fully agree with the others that the second reading (12.11) with horseshoe disconnected doesn't really mean anything as no current was flowing.

It's the first reading that has me scratching my head if that was measured with the engine running.

 

DVM's can't show the voltage on the coil with the truck running. That's because the voltage is all over the map, with some time spent at ~7v when the "points are closed", and some time spent at battery voltage when the "points are open". And, in between there's all sorts of ringing that takes place as the spark occurs. A DVM is set up to either read DC or AC, and this is neither or both so it can't give us a reasonable number. Further, depending on the chip set in the DVM you'll get a different reading.

 

Yes, this was the voltage at the coil with the motor running.

Took additional voltage readings this morning:

12.68 battery voltage, key off.
12.2 battery voltage, KOEO
6.7 at coil KOEO

If anything, 6.7 at the coil may be a little low?

Gary, the gross ohm reading was 9.5 less the 1 to 1.5 ohms I get with the leads touching. I will check the battery within the device to make sure it's good.