Fuel issue when starting.

MtnClimber · 06-20-09, 08:12 PM

I have to start off by saying that my experience with carbureted fuel systems is quite limited.
My '73 40 has a hard time starting after sitting for any period of time and I believe it is due to a lack of fuel. I have a clear, in-line fuel filter that is on the line between the fuel pump and the carburetor (in front of the valve cover). If the engine is off, there is no fuel in the filter at all. I'll crank the engine a few times before it gets started and when it's running, the filter capsule is only a fifth filled with fuel. When the engine is shut off, the fuel slowly drains back and the fuel line is empty which makes it hard to fire up again. What should I do to remedy this?

73fj40lc · 06-20-09, 09:46 PM

Check your fuel line for cracks and all of your connections for any leaks. It sounds like air is being let into your fuel line when the motor is shut off and losing prime so the fuel runs back into the tank. Also check placement of your fuel pump. If you have an electric pump they are pushers and not really designed to pull fluids. They are the most effecient when placed close to the fuel tank. I had the same problem some years ago and finally replaced all of my rubber fuel hoses because the old ones were dry rotting, hard and cracking. This resolved the problem for me. Good luck.

k91 · 06-20-09, 10:43 PM

fuel pump diaphram.....

MtnClimber · 06-21-09, 08:57 AM

Well I double checked the lines and the tightness of the clamps and all seems good. The lines, clamps, filter and pump are all fairly new. Even though the pump is new, I guess there still is the possibility that the diaphragm could be bad. I really don't know how to check that.
Here's some pics of the lines and components.
Pump, lines, filter are all less than a year old supposedly.

This is the most amount of fuel that will be seen in the filter. About 1/5th full.

dargreg · 06-21-09, 09:07 AM

If the pump is pumping and you can start it after a fasion Iwould just install a check valve in the system ,at the tank preferrably.As it seams the pump is not hloding your residiual fuel.The fuel filter will only get 1/2 full at best when you are running dont be alarmed at that.

nailbender · 06-21-09, 09:13 AM

The float bowl on the carb has a site glass (little round window) The fuel level should be about 1/2 way up that window before you turn it over. Mine will drain down if it sets a few days so I think it needs a rebuild but too lazy. If it's not up to the window you need to adjust the float level. But like I said even with mine adjusted correctly it still drains down.

MtnClimber · 06-21-09, 09:18 AM

Huh, weird. I've seen clear filters have only a small bubble in them so I figured mine was supposed to be like that. So I could get a check valve at pep boys or something? I take it I just cut the line and install it with two clamps similar to how the filter is installed?

Degnol · 06-21-09, 09:19 AM

Quote:

Originally Posted by k91

fuel pump diaphram.....

That was the issue with mine. Especially if I parked it on a slight uphill.

dargreg · 06-21-09, 10:06 AM

Quote:

Originally Posted by MtnClimber

Huh, weird. I've seen clear filters have only a small bubble in them so I figured mine was supposed to be like that. So I could get a check valve at pep boys or something? I take it I just cut the line and install it with two clamps similar to how the filter is installed?

Thats right make sure the flow is going the right way ,And yes some filters will fill up however where yours is I wouldn,t be to worried.

Sea Knight · 06-21-09, 10:07 AM

Quote:

Originally Posted by nailbender

The float bowl on the carb has a site glass (little round window) The fuel level should be about 1/2 way up that window before you turn it over. Mine will drain down if it sets a few days so I think it needs a rebuild but too lazy. If it's not up to the window you need to adjust the float level. But like I said even with mine adjusted correctly it still drains down.

I have exactly the same issue, if it's an issue. New OEM fuel pump and filter, all new fuel lines, stock AISIN carb. If the truck sits without being started for 3 or more days, there's little or no fuel in the sight glass and I have to prime the carb in order to start. After priming, all is well until the truck sits for a few days, then I have to prime again. Between laziness and the fact that I don't know jack about carbs, I haven't been motivated to attempt any type of adjustment.

Degnol · 06-21-09, 10:14 AM

Quote:

Originally Posted by MtnClimber

Huh, weird. I've seen clear filters have only a small bubble in them so I figured mine was supposed to be like that. So I could get a check valve at pep boys or something? I take it I just cut the line and install it with two clamps similar to how the filter is installed?

Pull your dipstick and smell the oil and see if it smells like gas. If you do have a hole in the fuel pump diaphragm it may be draining into the crank case, not bavk into the tank. So, if you install a check valve between tank and pump you not only won't solve the problem, but gas may still be draining into the oil.

MtnClimber · 06-21-09, 10:18 AM

No sight glass. I have some sort of aftermarket American carb.

And as for adjusting carbs, I'm totally lost in that segment! I've always worked on FI systems before. I guess it's time to learn quick, eh? lol

MtnClimber · 06-21-09, 10:21 AM

Quote:

Originally Posted by Degnol

Pull your dipstick and smell the oil and see if it smells like gas. If you do have a hole in the fuel pump diaphragm it may be draining into the crank case, not bavk into the tank. So, if you install a check valve between tank and pump you not only won't solve the problem, but gas may still be draining into the oil.

You know, I did check the oil yesterday and it DID seem to smell like fuel and quite thin.

k91 · 06-21-09, 10:58 PM

once again.....fuel pump diaphram! I just had this issue. You can check by removing your fuel pump, take the top off and check the diaphram. It is made of rubber and check for cracking. If it is cracked, it is most likely the culprit. It really only takes maybe ten minutes to do this. You would save yourself $80.00 by checking for the cracks before running out and buying a new one.

MtnClimber · 07-05-09, 06:11 PM

I just opened up the top of the pump and looked at the rubber diaphragm and it looked mint. No damages or defects. I clocked the diaphragm one way and and installed the top another so the pressed indentation on the diaphragm would not line up the same as before. Any other reasons why I would have this problem?

MtnClimber · 07-11-09, 04:04 PM

If the diaphragm is okay, the pump shouldn't be leaking any other way, or would it?

Degnol · 07-11-09, 04:25 PM

Quote:

Originally Posted by MtnClimber

If the diaphragm is okay, the pump shouldn't be leaking any other way, or would it?

Well, there are two valves inside the fuel pump and I suppose if one is stuck open it could allow fuel to drain back. But the oil being thin and smelling of gas says it is the diaphragm. Sometimes you need to stretch and flex the diaphragm to see the breech. Gas in the oil = most likely the fuel pump

Could also be siphoning from the carb. Do you have a sight glass in the carb bowl? I don't know about R'Chesters.

GL

MtnClimber · 07-11-09, 06:21 PM

I didn't see any sight glass. Which part is the bowl anyway? This is the first time I've ever dealt with carbs.

When I had the top of the pump off, it was divided in half. One side was full of fuel and the other, very little. Is a diaphragm for one of these pumps available at any parts store?