Fuel line issue

[Brinken]

Hi guys, Sweden calling.
My 1961 M38A1, which have done service in Saudi Arabia once upon a time, have had problems with the fuel distribution since I got it in my possesion 6 years ago.
When it have been sitting for more then 24 hours it have great difficulties to get fuel up to the carburrator. Therefore I have an electric fuel pump as a booster before start. I have also installed a fuel filter with pressure regulator to get the correct fuel pressure to the Solex carburrator. I have now also installed a check valve to ensure the fuel from falling back to the tank.

But nothing helps, after sitting the electric pump have to work for a couple of minutes before it have sucked up enough fuel for cranking and start. When the engine have started, Iturn off the electric pump and the ordinary dual fuel pump deliver the fuel.

My questions are:
- Shouldn't the glass cap on the fuel filter be full with fuel? I can just see some small amout of fuel at the bottom. As soon as the engine starts, it runs without complains, getting enough fuel.
- Is the fuel filter located to high up on the inside of left side fender?
- Is the height between the bottom fuel line from the tank and the carburrator on top too heigh for the fuel to stay a longer time in the fuel line?
- Could that bee the reason for the fuel to fall back to the tank in spite of the check valve?
- The electric pump, nor the ordinary dual fuel pump are made for sucking air, but they are good at suckung, and blowing fuel.

Do any of you guys have some tips or trick to help me out here.

[Xamon]

You could have a hairline crack or a bad gasket in the carb that is letting the fuel out of the carb.

[4x4M38]

I don’t see much of anything that is factory or stock.

As far as the replacement fuel pump with glass bowl - they do not run with the glass bowl full.

[RonD2]

Hi Jan-Olof,
I hate to say it, but Rube Goldberg comes to mind.

I'm pretty sure the fuel filter on a stock M38A1 is inside the fuel tank. Does yours have one there?

[Brinken]

First: Thanks to your comments, they start me thinking.
Second: Below are my comments to your answers.

Xamon: I had the carburrator referbished last year, with new gaskets and nozzles. There is no difference after the referbishment.

4x4M38: You are correct there, the only factory part is the ordinary dual vacuum/fuel pump driven by the engine. Everything else is modern stuff, but I can't see anything wrong with that. The replacement with the glass bowl is the filter, not the pump. But still, your comment about the unfilled glass bowl is important for me to know.

RonD2: I am pretty sure there is a filter inside the tank on the sucking line. After a long thread with Wes Nettle in this forum some years ago regarding fuel pressure and Solex carburrator I installed the fuel filter with the pressure regulator just to make it safe for the carburrator.

[OKCM38CDN]

Check your inverted flare connections, the M-38A1 uses 5/16" fuel lines and you may have a fuel line that is leaking. I rebuilt my M-38A1 and redid all of the fuel lines myself using very good flaring tools and being quite patient in their manufacture. I had two that would not seal properly and this leaked fuel. I found that brass on brass connections (Brass nuts on brass fittings) was the problem. I changed the nuts on the fuel lines to steel and was able to get more torque on the nuts and thus a better seal. I would check all lines above the level of the tank, as those below the tank will leak fuel. You are getting air into the line allowing them to drain. This is my opinion and hope it helps...

[Brinken]

Thank you all for your advise. I will do a thorough investigation and replace the parts on the fuel line that looks suspicious.