[danbaldwinbuilders]

no spark, no access to the manuals yet, when the helper needs help it's sad but I'm trying to reach out for any advice, new module and coil and battery, plugs. Should I get him to rework the wires. Where is the condenser on this thing?
Any engine diagrams would be helpful for this onan MS/2434C.

 

[Ray_McAvoy]

Welcome!

That wiring has obviously had some repair work done, but as long as it's feeding 12V to the positive coil terminal with the key in the run & crank positions, you can rule it out as the source of the no spark condition.

That engine will have points and a condenser located on top of the engine in a box right behind the carburetor. It will probably be the style where you have to remove a cover plate on the back side of the box to gain access to the points & condenser. I believe removing the battery will give you better access. Or if you're lucky it might have the type where you remove a single screw from the top and lift the cover off the points & condenser (that style gives you better access and is easier to adjust the points).

But with either style, you'll want to check the condition of the points, check the points gap (I think it's supposed to be 0.025" for the BF), and check the condition of the wire that connects them to the coil to make sure the insulation isn't damaged and shorting to ground where it passes out through the points box. Also, if you need to replace the condenser it doesn't necessarily have to be put back inside the box ... you can put it up near the coil and connect it to the negative terminal (just make sure it's securely mounted so it has a good ground).

 

[danbaldwinbuilders]

Welcome!

That wiring has obviously had some repair work done, but as long as it's feeding 12V to the positive coil terminal with the key in the run & crank positions, you can rule it out as the source of the no spark condition.

That engine will have points and a condenser located on top of the engine in a box right behind the carburetor. It will probably be the style where you have to remove a cover plate on the back side of the box to gain access to the points & condenser. I believe removing the battery will give you better access. Or if you're lucky it might have the type where you remove a single screw from the top and lift the cover off the points & condenser (that style gives you better access and is easier to adjust the points).

But with either style, you'll want to check the condition of the points, check the points gap (I think it's supposed to be 0.025" for the BF), and check the condition of the wire that connects them to the coil to make sure the insulation isn't damaged and shorting to ground where it passes out through the points box. Also, if you need to replace the condenser it doesn't necessarily have to be put back inside the box ... you can put it up near the coil and connect it to the negative terminal (just make sure it's securely mounted so it has a good ground).

I will start with your thankfully detailed instructions I have limited time to spend and will post the progress thanks so much

 

[danbaldwinbuilders]

Welcome!

That wiring has obviously had some repair work done, but as long as it's feeding 12V to the positive coil terminal with the key in the run & crank positions, you can rule it out as the source of the no spark condition.

That engine will have points and a condenser located on top of the engine in a box right behind the carburetor. It will probably be the style where you have to remove a cover plate on the back side of the box to gain access to the points & condenser. I believe removing the battery will give you better access. Or if you're lucky it might have the type where you remove a single screw from the top and lift the cover off the points & condenser (that style gives you better access and is easier to adjust the points).

But with either style, you'll want to check the condition of the points, check the points gap (I think it's supposed to be 0.025" for the BF), and check the condition of the wire that connects them to the coil to make sure the insulation isn't damaged and shorting to ground where it passes out through the points box. Also, if you need to replace the condenser it doesn't necessarily have to be put back inside the box ... you can put it up near the coil and connect it to the negative terminal (just make sure it's securely mounted so it has a good ground).

I just tested for 12v at the coil and the voltage drops to 8 then 2 does that mean it's the ignition or the wiring, can I jump it maybe from the battery?

 

[Ray_McAvoy]

Yes, with the voltage dropping that low, it would indicate a problem with the ignition switch, wiring, ammeter, or fuse / fuse holder. Something (bad switch, poor / corroded connection, etc) in the circuit is adding excess resistance and causing the voltage drop.

To narrow in on the problem area you can take voltage measurements at other points in the circuit. Say for example, you measure full battery voltage on the ignition switch "B" (battery) terminal, but get the low voltage reading on the "I" (ignition) terminal, that would indicate a problem with the switch itself. However, if you're also seeing the low voltage at the "B" terminal, that would indicate a problem somewhere between the switch & battery (such as the fuse / fuse holder, ammeter, or bad connection in the wiring).

And yes, you can temporarily bypass the ignition switch & tractor wiring by running a jumper wire from the positive coil terminal to the positive battery terminal.

 

[danbaldwinbuilders]

Thank you again I appreciate your guidance, I think I will rework the wiring since I don't know who made the connections, I did ohm out every one but some have more than one splice. I will go through the testing process again and see if I can get a spark with the jump. Do you know the spark plug gap setting? The owner put them in without checking the gap I think I should double check, Have a great weekend!!!

 

[Ray_McAvoy]

You're welcome! Yeah, re-wiring to get rid of any questionable splices is probably a good idea. The wiring in my old 446 was a mess too ... it had some wires that were just twisted together & taped, a few random left over wires from accessories someone had added then later removed, and other issues. So I took all that old mess out and put in all new wires. Fortunately, the wiring in these tractors is pretty basic, especially the earlier models, so replacing it all isn't that difficult.

If possible, try to match the wire colors up with what was used originally to make future troubleshooting easier. To help with that, you can find a wiring diagram in the operator's manual. And that can be downloaded from the Technical Library section of this site ... just use the model & PIN (serial number) of the tractor to get the correct manual. Note, the parts manuals also have wiring diagrams but those don't always show the wire colors like the diagrams in the operator's manuals.

According to the Onan BF/MS service manual, the spark plug gap should be 0.025" (which also happens to be the same as the recommended points gap on these engines).