516H - No spark when turning key to start

[TC10284 113]

I am having a bit of a perplexing problem. I got back on a 516H project I left sitting for about a year (sad, I know). I thought all it needed was a new fuel grommet and shut off. Well, now I am running into a no-start issue. 

 

At first when I tried to start it, it backfired twice. I hadn't added any fuel to the carb yet. When I tried again after letting it sit, it would run a bit on full choke and 75% choke until it died. Then a couple times after that, it only ran for a second. A couple times when I tried to start it, acted liked it fired and stopped the flywheel dead. That happened twice.

 

I changed plugs, tried swapping with another coil and condenser (both that I'm not entirely sure is good itself but I do not have a new one to try). Made sure the fuel pump was working by watching it and pulling off the hose and watching it spit out fuel. It did not fire even when putting fuel directly into the carb.

 

So the strangest thing I've found is that when I used the in-line spark detector, I didn't see much of a spark until I turned the key to Off (or On) and I got a strong spark then. 
So then I pulled the plugs out and looked for a spark when turning the key to Start. I saw no spark UNTIL I let the key go back to Run. Only THEN did I get a good spark. 

Another strange thing is that I was getting a bit of a shock when I turned the key to "start" and I was getting a slight shock through the key as the engine turned over. But I am attributing that to having the spark plug connected to the wire/coil and the plug laying on the metal exhaust cover.  

 

I am hoping it is not the ICM, because I know they are $150+ now, and it did run last year without having to dump fuel in the carb or anything else. 

Edited September 22, 2023 by TC10284

[squonk 43,770]

First thing I would do is check the key switch , safety switches and connections. The fact that you lose ignition in crank points to an issue right in the switch

 

[lynnmor 7,812]

Visit “My Wheel Horse doesn’t have spark” under the “Wheel Horse electrical” topic.

[953 nut 59,882]

19 hours ago, TC10284 said:

I am having a bit of a perplexing problem. I got back on a 516H project I left sitting for about a year   Did you remove the engine covers and remove any accumulated rodent nesting material?(sad, I know). I thought all it needed was a new fuel grommet and shut off. Well, now I am running into a no-start issue. 

 

At first when I tried to start it, it backfired twice. I hadn't added any fuel to the carb yet. When I tried again after letting it sit, it would run a bit on full choke and 75% choke until it died. Then a couple times after that, it only ran for a second. A couple times when I tried to start it, acted liked it fired and stopped the flywheel dead. That happened twice. Classic fuel starvation symptoms, rebuild the carburetor and this problem will go away.

 

I changed plugs, tried swapping with another coil and condenser  Why? you had spark before or it wouldn't have run. You can run an engine without the condenser for a short period, if ignition improves without it then it was bad. (both that I'm not entirely sure is good itself but I do not have a new one to try). Made sure the fuel pump was working by watching it and pulling off the hose and watching it spit out fuel. It did not fire even when putting fuel directly into the carb.

 

So the strangest thing I've found is that when I used the in-line spark detector, I didn't see much of a spark until I turned the key to Off (or On) and I got a strong spark then. Have you cleaned, inspected and tightened ALL electrical connections?  Could be some corrosion or mouse damage.
So then I pulled the plugs out and looked for a spark when turning the key to Start. I saw no spark UNTIL I let the key go back to Run. Only THEN did I get a good spark.    Is the ignition switch grounded to the frame ground?

Another strange thing is that I was getting a bit of a shock when I turned the key to "start" and I was getting a slight shock through the key as the engine turned over. But I am attributing that to having the spark plug connected to the wire/coil and the plug laying on the metal exhaust cover.  Is the ignition switch grounded to the frame ground?

 

I am hoping it is not the ICM, because I know they are $150+ now, and it did run last year without having to dump fuel in the carb or anything else. Do the simple free testing before jumping to the conclusion that you need to replace the most expensive component in the system.

 

[gwest_ca-(File Mod) 11,469]

So the strangest thing I've found is that when I used the in-line spark detector, I didn't see much of a spark until I turned the key to Off (or On) and I got a strong spark then

 

Each time the coil is turned off that creates one high voltage spark at the plug. This is accomplished by the trigger for an operating engine.

Turning the key to off is the same - one turn off = one spark.

[kpinnc 14,623]

As has already been said, I'd start with the key switch. My 520-H had similar issues: seemed to fire only as I released the starter. Turns out my key switch was worn out. 

 

Just make sure you research your part number and get the correct one.

[TC10284 113]

An update:

I tested the coil according to the manual, and none of the original spares I had were any good. The secondary winding was totally open on all of them. I compared to my new one. 

 

Afterward, it started up and ran, but kind of crappy. But it runs enough where I can get it to an air compressor. 

[TC10284 113]

I also checked the timing according to the manual, and it was good. 

 

Although, after I swapped the plugs with new plugs, it started doing the firing and stopping the flywheel dead. I finally got it started though. 

[RED-Z06 2,567]

My 416 does this sometimes...its a worn switch

[TC10284 113]

1 hour ago, RED-Z06 said:

My 416 does this sometimes...its a worn switch

I put in a new ignition switch earlier this week. Unless there is something wrong with the switch. It did not do this with the other spark plugs that were used. I didn't try starting it a lot though.

But the new NGK TR4's it did it. Although I have not experienced this issue on other Onans with TR4's. 

[RED-Z06 2,567]

21 minutes ago, TC10284 said:

I put in a new ignition switch earlier this week. Unless there is something wrong with the switch. It did not do this with the other spark plugs that were used. I didn't try starting it a lot though.

But the new NGK TR4's it did it. Although I have not experienced this issue on other Onans with TR4's. 

Mine might go weeks, dozens of starts without any problems, then suddenly crank crank..nothing, until i release the key.  I checked power at the coil and its very low when cranking when it does this.