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Ask Hank F. Your Own Question
Hank F.
Hank F., RV tech - emphasis on gensets
Category: RV
Satisfied Customers: 15183
Experience:  RV tech since the beginning of the millenium.
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Can you help me with this diag? : Im test ignition module. I

Customer Question

Can you help me with this diag?
JA: Sometimes things that you think will be really complicated end up being easy to fix with RV. The RV Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: Im test ignition module. I unhooked both wires and put 12v to red wire. When i turn shaft I get 9v down to 0v. Should it be 12v?
JA: How many miles are on the car? Do you happen to have the wiring diagram?
Customer: This is a generator
JA: Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: is this computer generated answers?
JA: Is there anything else the RV Mechanic should be aware of about your RV?
Customer: I need a real person
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the RV Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: RV
Expert:  Chris (aka-Moose) replied 1 year ago.

Welcome, I'm Chris (aka Moose).

Can I get the year, make, model, engine?

Customer: replied 1 year ago.
It is a Onan Marquis 7000 7NHMFA26105D
Expert:  Chris (aka-Moose) replied 1 year ago.

Sorry I do not work on RV generators, I will opt out.

Customer: replied 1 year ago.
Is there someone who does?
Expert:  Randall replied 1 year ago.

We have a good Onan tech who is very busy, but should be checking in between now and in the morning. I would wait for him. Thanks!

Customer: replied 1 year ago.
Ok ,thank you?
Expert:  Hank F. replied 1 year ago.

Hello, my name is ***** ***** I am going to assist you with this.

I have been an Onan tech for 15 years.

What is the problem you are having with this unit?

Customer: replied 1 year ago.
no spark. It started out with no crank and I replaced the control board and all set. Now won't start. I have 4 ohms on coil terminals and 21000 at towers. The ignition module goes from 9v to 0v. When turning by hand.
Expert:  Hank F. replied 1 year ago.

If you have 12V connected to the ignition module, you should have 12V coming out.

But 9V should be enough to fire the coil.

What procedure are you using to check for spark, and have you checked both cylinders, or only 1?

Customer: replied 1 year ago.
both cylinders. Pulled plugs and grounded body and turned over. nothing
Customer: replied 1 year ago.
i have unit out of coach
Expert:  Hank F. replied 1 year ago.

Have you ohmed out the plug wires?

Try this.

Jump 12V directly from the battery to the positive terminal of the coil.

See if you get spark like that.

If not, check the ignition rotor.

You have definitely got a glitch in the ignition system. There are 2 main parts to the system – the ignition module and the ignition rotor. You will not need to split the generator from the engine to remove the module or test the rotor, but you will need to split the generator if the rotor is bad and needs to be replaced. I can help you with that if we need to go that far.
First, remove the (2) 5/16” screws that secure the ignition module to the top of the generator housing, being very careful not to drop the screws inside. If they fall in, the generator MUST be pulled to remove them. They will do a lot of damage if the set is started with them inside.
There is a trick to getting the module out. The flywheel has fins on it to move cooling air across the generator. One of these fins is shorter than the others. The engine must be rotated so this shorter fin is at the top of the flywheel. Depending on how your set is mounted, it can be very difficult to see down in there, and I often have to use a small flashlight and inspection mirror.
Once this short fin is at the top of the flywheel, the module can be removed. It is a very tight fit, but it will come out. Pay strict attention to how the wires are routed in relation to the module. If the wires are not reinstalled EXACTLY as they are, either the module will not fit when putting it back in, or the wires will be hanging in the way of the flywheel and will get cut.
Once the module is out, simply disconnect the 2 wires from the coil.
After the module is out, we need to inspect the ignition rotor for damage. The rotor is a long piece of plastic that snaps onto the crankshaft, and has a magnet at each end. The magnets are what open and close the contacts in the module.
Looking down into the hole, turn the engine so one of the ‘arms’ of the module is straight up. Stick your finger down into the hole, and press sideways (rotational) with about the same amount of pressure you would need to slide an empty coffee cup across a table. Turn the engine 180 degrees and test the other arm in the same manner.
The arms should not move. If they do, the rotor is cracked and must be replaced.
If the rotor is OK, you may have to change the ignition module change the ignition module.

.

Customer: replied 1 year ago.
i have not ohmed the plug wires. What should be the resistence? I checked the rotor. It is good. I have the ignition module out already. I can try applying 12v to coil in the morning.
Expert:  Hank F. replied 1 year ago.

Resistance of the plug wires should be anywhere between 3,000 ohms and 15,000 ohms.

Customer: replied 1 year ago.
i'll let you know what I find tomorrow. Thank you.
Expert:  Hank F. replied 1 year ago.

Ok.

Customer: replied 1 year ago.
12v to the coil got me nothing. So i assume that means it is bad even though it ohmed out ok?
Expert:  Hank F. replied 1 year ago.

No. It means that something else is not allowing the pulse to go to the coil.

You did put the ignition module back in, correct?

That leaves only the ignition module. Even though 9V should be enough to create a spark, apparently on your unit it is not.

At this point, I have to suggest replacing the ignition module.

Customer: replied 1 year ago.
I already ordered one today. I did s pulse test at the coil and no pulse. So that is how I'm going. I'll know tomorrow.
Expert:  Hank F. replied 1 year ago.

Sounds like a plan.

Customer: replied 1 year ago.
Ok, this thing is baffling me. Got the new module and got spark. put it back together and hooked up a gas can to the fuel pump and a jump box to the cables and it fired right up on the bench. Ran for 5 minutes and i shut it down. restarted 2 or 3 times with no problem. Put it back in the coach and hooked everything up and as soon as i tried to start it, it cranked a few times and blew the fuse on the control board. Checked everything over and everything seemed fine. Put new fuse in and pushed the start button and it got hot almost immediately , blew the fuse and continued to engage the starter and melted the board. I had to unplug the board to stop it. This is a brand new control board. Or was. What the heck happened? It still will run if I unplug the board and put a hot wire to the coil and fuel pump and jump the soleniod. Have to work the throttle by hand though. Any ideas?
Expert:  Hank F. replied 1 year ago.

If the starter continued cranking without the fuse in the board, you have something miswired in there.

You need to check every wire on that unit against the schematic to make sure everything is wired properly.

Customer: replied 1 year ago.
Thing is , that it worked completely proper on the bench. Why the problem after install. Bad ground? When it was in the coach and I would push the control panel start button, it seemed to turn slow, kind of lagged then popped the fuse. If i jumped the solenoid it would spin fast as it should. Its like something is stealing power at the board.
Expert:  Hank F. replied 1 year ago.

a bad ground should not cause a board to melt down, but you still need to check it.

Low voltage getting to the genset would be more likely to be a problem. Low voltage means high amperage.

But all it takes in there is for the wrong 2 wires to be crossed.

Without being there and being able to see it, it is hard to say what happened.

Customer: replied 1 year ago.
I hear ya. Where can I get a wiring diagram for this, so I can trace down everything.
Expert:  Hank F. replied 1 year ago.

I have uploaded a wiring diagram and schematic for you.

Click here to download it.

Customer: replied 1 year ago.
Thank you
Expert:  Hank F. replied 1 year ago.

Not a problem.

Expert:  Hank F. replied 1 year ago.

Did you get the wiring diagram?

Customer: replied 1 year ago.
I did. Everything was correct. Bought a new control board and still having the same issue. Took it to a generator shop.
Expert:  Hank F. replied 1 year ago.

That sure is weird. I'd kind of like to know what they find.

Thanks for giving Just Answer a try, though, and please remember to leave me a rating for my performance.