Onan 6.5 MCCK Genset

Express 390

Well-Known Member
Sep 14, 2018
661
South Shore of Long Island NY
Boat Info
1986 SeaRay 390 EC
1993 SeaRay 290 DA single 7.4 /Bravo 2
1992 SeaRay 230 DA 4.3LX Alfa drive
Engines
Twin 454 Crusaders inboards 4 blades
The 6.5 two banger has never failed me, Till today! It just shut down after 10 minutes restarted then shut right down again. Now when it turns over it pops one of the three 12 volt fuses on the panel marked ignition. I have spark, and its getting fuel. What's popping the 5 amp fuse ?
 
It sounds like a wiring problem. Check the ignition wire if it is frayed and shorting to ground. Follow it from the coil/distributor back to the wire harness and look for anything where it might have worn off the wire insulation and is making intermittent contact with the block. Sometimes it is a connector or splice that has gone bad.

One way to check it is to tug on the harness and see if it starts running again. If it does... you know you have a possible short on that circuit.

Do you have a wiring diagram for it?
 
It sounds like a wiring problem. Check the ignition wire if it is frayed and shorting to ground. Follow it from the coil/distributor back to the wire harness and look for anything where it might have worn off the wire insulation and is making intermittent contact with the block. Sometimes it is a connector or splice that has gone bad.

One way to check it is to tug on the harness and see if it starts running again. If it does... you know you have a possible short on that circuit.

Do you have a wiring diagram for it?
No i don't I've been online looking but not having any success. Thanks for the help
 
I couldn't find one either. It seems Onan doesn't have them available or you have to order them.

One other thought is the control relays. Normally that circuit goes through a relay from the control board. If the relay is original.....it might be drawing more than 5 amps to stay closed. It is just a guess without the wiring diagram.
 
I couldn't find one either. It seems Onan doesn't have them available or you have to order them.

One other thought is the control relays. Normally that circuit goes through a relay from the control board. If the relay is original.....it might be drawing more than 5 amps to stay closed. It is just a guess without the wiring diagram.
Yes Thanks i was checking and theres a start , stop , anda rut!n relay one of them could be shorting out. Alsoi was thinking high Temp switch might have a short . Again thank you for your imput.
Les
 
Blowing the ignition fuse is almost always caused by a short in the ignition wires. The first thing I would check is to be sure the braided ignition wiring shield isn't shorting out on the terminal on the side of your points box. If it is I would add a boot to this terminal- most deteriorated and fell off long ago or were lost.

Your high temp sensor, and oil pressure sensor (if equipped), are all normally closed so they should fail open. You can bypass these, for testing only, by joining the wires together.

You didn't mention the spec ID of your MCCK so I made some assumptions above. If this doesn't work let us know and I'll post a link to the wiring diagram and other files that I have for the MCCK.

Ben in SC
 
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Blowing the ignition fuse is almost always caused by a short in the ignition wires. The first thing I would check is to be sure the braided ignition wiring shield isn't shorting out on the terminal on the side of your points box. If it is I would add a boot to this terminal- most deteriorated and fell off long ago or were lost.

Your high temp sensor, and oil pressure sensor (if equipped), are all normally closed so they should fail open. You can bypass these, for testing only, by joining the wires together.

You didn't mention the spec ID of your MCCK so I made some assumptions above. If this doesn't work let us know and I'll post a link to the wiring diagram and other files that I have for the MCCK.

Ben in SC
Knowledge is power, Thanks Ben I'll take all you got!

Think I found the problem with the stalling and blowing fuses. As i was pulling at the harness on the motor checking i came across a loose wire. The wire was the hot to the fuel pump. It appeared when it came off it must off shorted against something to blow the fuse and without the fuel pump could not start. The problem is i took the water pump out to rebuild it but the parts are on back order. I'll have to wait to confirm it!
 
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Knowledge is power, Thanks Ben I'll take all you got!

Think I found the problem with the stalling and blowing fuses. As i was pulling at the harness on the motor checking i came across a loose wire. The wire was the hot to the fuel pump. It appeared when it came off it must off shorted against something to blow the fuse and without the fuel pump could not start. The problem is i took the water pump out to rebuild it but the parts are on back order. I'll have to wait to confirm it!
 

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