Railguy

I came home from a long drive yesterday,when I opened the hood I noticed in the see through fuel filter it looked like the gas was boiling. Is this possible?Engine temp has always been an issue.
railguy

MDchanic

Sure. That's what causes vapor lock.

You may want to switch to a later model return-line fuel pump to reduce that.

- Eric

Railguy

Thanks I guess that would make the most sense,I do have a newer pump with out the return line.Is there any way to put a return line on the newer stile pump?
railguy

MDchanic

To set up a return line, you need a return-type fuel pump and a retrn-type fuel sender, with the extra fitting for the return line (you may already have one there), and, of course, you need to run the line.

- Eric

ah64pilot

I highly doubt that the gas is boiling in that see through filter. There is nothing to generate heat from the tank up to the carb except the engine itself, and the time it takes for fuel to get from the filter to the carb isn't long enough to boil the gas. It is more reasonable that the fuel pump diaphragm is letting fuel run back to the tank with the engine off OR that see through filter is not tight enough.

The see through filters are designed to come apart so that you can replace the plastic filter element. If you remove one side of the hose and tighten it up a bit sometimes it will keep fuel from draining back to the tank (which is what is giving you the bubbling symptom). If after tightening the filter up it still does that, throw a new fuel pump on it ($20) and your problem will go away.

MDchanic

I will admit that I took Railguy at his word about the fuel boiling.
If it is not boiling, and if the fuel filter is located AFTER the fuel pump (where it shouldn't be, because that would imply that you have rubber lines there), then bubbles could be caused by porous rubber lines BEFORE the fuel pump, allowing air to be sucked in along with the gasoline.

- Eric

ah64pilot

And after reading through again I realize you said you have a newer style pump...what do you have? If it's an aftermarket mechanical pump then I'm more inclined to see that glass "filter" as the culprit. I admit that they look decent but they are poorly made IMO. You probably need to tighten it a bit...but do so with one end of it disconnected from the fuel hose so the hose won't try to loosen it back up. That will probably solve your problem. I don't think the hose is where air is being introduced, I think it's that filter. It's happened to me.

DeltaPace77

I agree, as always run a return loop to keep fuel line temperatures down. My current set up has a Mallory electric rear pump, with front regulator. Make sure of using an orface fitting for the return, no matter the set up. I went electric, so I could prime the carb on start up, and stall it empty when parking.

Railguy

I agree, as always run a return loop to keep fuel line temperatures down. My current set up has a Mallory electric rear pump, with front regulator. Make sure of using an orface fitting for the return, no matter the set up.


The pump I'm useing now dose not have the fitting for the return line.Is there a fitting or valve to convert it?The return line is there.As for air being drawn in through the line,I did use a good quality hose.Also what is a orfase fitting?

DeltaPace77

It's really not an air thing, but rather keeping fuel flowing through the line on hot summer days idling in in traffic, help keeping it cool. You can maybe splice a tee connector in your pressure feed line to the carb for the return. An orifice(sorry for the spelling before), is just that. A small restriction fitting hole to the to the tank return line will loop some fuel, but you still need pressure to the carb. You can maybe just solder plug a tee fitting, and drill a small hole in it.

jpc647

If one doesn't have a fuel filter after the pump, cant small pieces from the pump wearing down be taken into the carb?

MDchanic

The carb has a built-in filter for these things.
There shouldn't be an aftermarket hose-clamp filter after the pump because if the rubber hose goes, your engine gets a gasoline bath, with often spectacular results.
A filter plumbed into steel lines would be fine.

- Eric

BlackGold

"Cool" is relative. I once used an IR thermometer to measure the bottom of my fuel tank after driving for about an hour on a 90-degree day. I can't remember the exact number, but it was something like 120 degrees, even though it had all that wind rushing past it just a minute earlier. It was all that radiant heat from the pavement being absorbed by the tank. And don't think it was just the tank that was hot. All that fuel inside makes a good heat sink. I guarantee it was close to 120 degrees, too.

Sure, the gas in the tank is cooler than that in the engine compartment. But don't fool yourself into thinking it's actually "cool."