why won't F 12 start with crank

bumblebee · Mar 9, 2015

I am the guy that has been on here a few times with questions about an F 12 that I am trying to bring back to life.

To make the story short, everything is as it should be, it runs great. It started once with the crank when I was going to double check the timing! It ran without the plug in the #1 cylinder. I double checked where I had the spark advance set before I shut it off. I haven't even been able to get it to fire while cranking.

I get the impression that the head may have been shaved at some time cause it has great compression.

Two of my tractor buddies that are smarter than I am are also stumped after looking everything over.

Is there something I may be missing?

Oldiron29 · Mar 9, 2015

Bee, if you disconect the fuel line at carb what kind of flow do you have when cranking? Most time I put a small lawn mower tank on the hood and conect to carb and start it that way to rule out a fuel line or pump issue. If you have spark it has to be fuel issue. oldiron29

Paul from MI · Mar 9, 2015

Is the impulse coupling on the magneto working right, do you hear a click when cranking. You need a good hot blue spark that will jump 1/4" to start reliably. Other items to check are fuel supply, especially the fuel pump.

John B. · Mar 9, 2015

My old F12 use to do that. I would end up taking the points out and cleaning them and then it would start right up. The points would get corroded from sitting for some reason.
Make sure your impulse coupling is working on the magneto. You should be able to hear it click 2 times for every 1 revolution of the engine when using the hand crank.

Loren in MN · Mar 9, 2015

The 1936 F-12 that I had was in great condition and would start on the first crank every time if it hadn't sat more than a day, but after that it needed to be pulled to start it. Otherwise I would find a way to prime the fuel pump. I was told that there is a priming inlet on some F-12s sticking out of the hood. It's been many years since I've had mine. Thinking you lost your fuel to the carb.

Nebraska Cowman · Mar 10, 2015

It is a common complaint with F12s.

John M · Mar 10, 2015

Whats your normal starting procedure?

Randy Shoe · Mar 10, 2015

Used to have the same problem with my 37 F12. Problem was fuel pump diaphram was weak. I made another one out of an empty purex jug. Works better than ever. A full tank of gas in tank seems to help with a weak pump also.

why won't F 12 start with crank

bumblebee

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Oldiron29

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Paul from MI

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John B.

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Loren in MN

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Nebraska Cowman

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John M

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Randy Shoe

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