Community Forums

HOTRDD · 08-20-2021, 08:19 AM

Wondering if someone can help here. Bought a new "old" ignition module for my Onan Marquis 5000 generator. Unit was running good in the fall and then no spark this spring. I can manually trigger spark at the coil so I know its good, but can't get the ignition module to trigger spark. I tested ignition module with 12v and I get 0.5mv for half a revolution and 8.35v for the other half. BUT if I test it with a 12v test light there isn't enough juice in the 8.35v to even turn the light on a little.

First of all why would I only see 8.35v coming out of the ignition module when I have 12-13.5 going in?

Is this a bad ignition module? The test is a little vague as it says the ignition module should alter between 1-1.5v and close to battery voltage. Is 8.35v close to 12.5?

MrMark52 · 08-20-2021, 08:28 AM

If you let it sit for several months without exercising the genset, I would look at the slip rings and make sure they’re polished first before doing anything else.

And, what lead you to it being a spark issue? Are the plugs wet after several attempts?

To answer your question - I went through all this on ours before I sold it but can’t remember what voltage I saw. But if I remember correctly, it was closer to 12vdc.
It turned out on ours, for the initial reason it wouldn’t run was gas had been allowed to dry out in the carb by the PO. Then dirty slip rings that looked clean, then finally having to replace both control boards - all over a period of the next 9 - 12 months..
Never had an ignition problem with the ignition.

HOTRDD · 08-23-2021, 11:17 AM

I pulled the spark plugs and verified no spark, I then pulled the generator and verified it was getting fuel but no spark. In the end I think I found the "issues". For one the Ignition Control Module was reading 8.36V but is BAD.

I plan to pull together some more information and to document what I have discovered. If I get a chance I’ll do some diagrams or a video.

But here are the basics so far. After a bunch of investigation I found that the main 12V+ feed had been modified for the new fuel pump but wasn’t reattached to the coil. Therefore the coil didn’t have 12v+ power, additionally the tech that was working on the generator wired up the coil wrong. For some reason they put the condenser/capacitor on the + side of the coil when it should be on the Neg. side, also they added a permanent ground wire to the Neg. terminal of the coil. I have no idea what they were doing. AND finally the ignition control module “ICM” was bad. I can tell you now that the manual says that for ½ the rotation of the engine the voltage must be close to battery voltage. My generator showed 8.36V which apparently isn’t “close” to battery voltage. So the ICM was bad.

HERE is the wiring that works

To the Coil + Terminal
- K4-B7 wire sends 12v+ to coil and fuel pump after a few seconds, when cranking.
Power comes from the bridge rectifier.
- T1+ wire to coil Positive
- ICM red wire to coil Positive

To the Coil – Terminal
- J3-1 T1 wire to coil Neg
- Condenser/Capacitor gets wired to coil Neg.
- ICM black wire to coil Neg.

MrMark52 · 08-24-2021, 07:25 AM

Quote:

Originally Posted by HOTRDD

I pulled the spark plugs and verified no spark, I then pulled the generator and verified it was getting fuel but no spark. In the end I think I found the "issues". For one the Ignition Control Module was reading 8.36V but is BAD.

I plan to pull together some more information and to document what I have discovered. If I get a chance I’ll do some diagrams or a video.

But here are the basics so far. After a bunch of investigation I found that the main 12V+ feed had been modified for the new fuel pump but wasn’t reattached to the coil. Therefore the coil didn’t have 12v+ power, additionally the tech that was working on the generator wired up the coil wrong. For some reason they put the condenser/capacitor on the + side of the coil when it should be on the Neg. side, also they added a permanent ground wire to the Neg. terminal of the coil. I have no idea what they were doing. AND finally the ignition control module “ICM” was bad. I can tell you now that the manual says that for ½ the rotation of the engine the voltage must be close to battery voltage. My generator showed 8.36V which apparently isn’t “close” to battery voltage. So the ICM was bad.

HERE is the wiring that works

To the Coil + Terminal
- K4-B7 wire sends 12v+ to coil and fuel pump after a few seconds, when cranking.
Power comes from the bridge rectifier.
- T1+ wire to coil Positive
- ICM red wire to coil Positive

To the Coil – Terminal
- J3-1 T1 wire to coil Neg
- Condenser/Capacitor gets wired to coil Neg.
- ICM black wire to coil Neg.

Great write up and explanation! Good you found it!

Sometimes people just need someone to bounce ideas off of - and in the case of using this venue as a means of discussion where the responder can’t see what the presenter is looking at - taking the initiative to find that the whole setup has been modified over what the responder can see and would have impact on their responses.