View Full Version : Need diagnosis 51 Commander

08-25-2018, 08:46 PM
I have been working on the 51 Commander for awhile and finally felt good about the running condition. However I ran into a problem. I took her to a cruise in tonight and on the way back she was not running smoothly. It was 98 degrees out and she was slightly above mid temp. When the accelerator was depressed she would not downshift and bog down. If she was floored she would not accelerate properly and bogged down. At first I thought maybe vapor lock. She does have trouble starting when warm. I insulated the fuel line above the intake manifold. If she sits a couple of days she has a real hard time starting(like starving for fuel) I have to use starter fluid. Once she is started she will start without the fluid. Fuel pump problem? Carb? Throttle/trans linkage problem? Thoughts. She idles fine. Right now I think the idle is a little slow.

08-25-2018, 09:06 PM
Have you changed all of the flexible fuel lines to modern ones to be compatible with today's fuel?
Have you checked for pinhole leaks/rust spots in the solid fuel lines? If you have a clear or translucent fuel filter, look for air bubbles when running.
Is your fuel filter fresh and clean?
Is the fuel pump putting out adequate pressure?

08-26-2018, 07:23 AM
98 degrees is pretty hot for today's gas in older carbureted engine, and the 51 232 has the fuel pump mounted up high, so I wouldn't be surprised if you don't have some vapor lock problems. Do you use gas without ethanol?
I try to only use the better gas without ethanol and I mix 4 ounces of Marvel Mystery Oil with each 10 gallons, and so far my 50 Land Cruiser has done fine.
Someone reported good results by adding a quart of diesel to each tank of gas, and I'll give that a try when I get stuck with crap gas.

08-26-2018, 12:47 PM
I have used mystery oil before. I will try it again.
Fuel pump has correct pressure.
Do not see visible air bubbles in glass dome.
Fuel filter looks good.

This happened half way on the way home. It was fine up until then. No acceleration. Would not down shift properly. Would not pop off the line.
98 was a cooler day for us.

08-26-2018, 01:33 PM
I had the same problem with my '51 commander. I added an electric flow through pump to pressurize the system before start up. The first time I tried it I found the sediment bowl seal was leaking. I replaced that and all the problems were gone.

08-26-2018, 01:36 PM
I thought of an electric pump backup. I will look into the seal.