Could this be vapor lock?

On the way home @ Lunch Nixon died on me. Sort of SFSF (Started, Farted, Stumbled and Fell).

I pulled over and almost automatically diagnosed it as the electric fuel pump again.

I pulled the line off first at the carb, then at the filter and then at the electric pump. No fuel was coming out with the pump running.

So, I took the pump off and went and bought another one. Hooked it up and turned the pump on and still no fuel coming through.

I disconnected the line @ the tank and sucked on the line and was able to pull fuel back through it.

Then I disconnected it at the upstream end of the pump and at the tank and blew through the line from the tank end and cleared out all the fuel from the line and reconnected it.

This time when I turned the pump on it pumped fine and the engine fired right up.

Normally I'd have expected a blockage in the line but I really don't think there was. It would have had to be big enough to completely block it and although I wasn't able to look at the other end of the line when I blew it out, I really don't expect it was trash.

Could this have been vapor lock? ( I really don't know what vapor lock is)

If it was I'm wondering if maybe this is exactly what was happening the first two times my fuel pump went out and I replaced it.

FWIW the pump seemed to be running fine it just wasn't pumping any fuel.

 

It almost sounds like an in-tank screen that is clogged --which you don't have (shouldn't at least).

Please tell me you didn't have cigarette after all that diagnosis R)

 

Was it particularly hot today?

 

No it wasn't hot at all. In fact it had just come a small shower so things were kinda cool.

This same exact thing happened two times prior to this and both times I replaced the fuel pump except the two times prior the pump solved the problem.

Now that I think about it I'm leaning towards an obstruction of sorts in the line. I remember sucking on the fuel line from the engine bay and I couldn't get anything to come through.

When I sucked on it from the tank end I got a mouth full of gas so I'm thinking that I must have broke the obstruction free.

 

Where is your electric pump located? They like to push a lot better than they like to pull. Vapor lock occours when the fuel evaporates somewhere in the fuel system, (usually in the engine compartment near or in the carb) and makes a bubble.

 

Baby John: Sounds like "Crud" in the tank. If you blew into the line from the pump "into" the tank, and that cleared it up and it pumped fuel, you just about isolated the problem--it's in the tank outlet at the fuel pickup line.

Might want to remove your tank and take it to a radiator shop to be cleaned out or buy a new one.

OR, depending on how one reads your description of the "FIX" It may be a pump that "lost prime".

To make shure what you have, if it happens again, disconnect the line from the tank to the pump first. If it's a bottom feed, gas should flow out and your tank line is OK (usually).

FLAPS elect. pumps can and do go out, as opposed to the $$$ ones.

 

My pump is mounted on the firewall behind and to the left of my air breather and it's pulling fuel from the tank. I'd think I'd have to have a pump inside the tank in order to push the fuel to the carb.

 

The two pumps I was running were Autozone $20.00 cheapos. The one I replaced it with was from Napa and cost $53.00.

The Autozone pumps had an in line filter upstream of the pump (between the tank and pump). The Napa pump doesn't have this but recommends it.

I have an in-line filter downstream of the pump.

Do you think I could simply move this in-line filter upstream of the pump and be OK?

Or should I have two filters? One up and one down of the pump?

 

John: Just mount it on the inside of the frame rail, or on the tub behind the tank, and it only has to "pull" about a foot or so, and pushes it the rest of the way.

 

I'd mount it as low and as close to the tank as possible. Those little pumps aren't very good at sucking.

 

OK I didn't know that. It was mounted to the firewall when I got it and I've just been swapping them out each time.

I'm seriously considering switching back to the manual pump. I can get a new one for about $35.00.

Only problem is I don't know why the PO switched to the electric pump. Seems like it'd've been easier to replace the manual pump it it went bad as opposed to installing and wiring up an electric.

 

John: Too many filters just restrict flow. If you're not sure of the condition of your tank, put the filter between the tank and the pump. No "crud" can enter after that if your lines are OK. This will also protect the pump.

If your tank is good, just put one before the carb, and make sure you don't have the little "sintered bronze" one in your carb inlet as this will eventlly plug up and restrict your flow. And, it's always the last thing you check!!!

 

People do it all the time for no good reason. IMHO, a cheap inline electric fuel pump isn't as reliable as a halfway decent mechanical one on a carbed engine. It probably was an availability issue. They wanted to get going right away, and the FLAPS (I like that acronym!) didn't have a mechanical unit in stock, but they did have a universal piece.

 

Baby John: That's the way I would go. DO YOU HAVE the return line to your tank? That will eliminate "vapor lock"!!!! If you don't have it, put one in--not hard--just get the 3 port mech. pump and run a line back to the tank.

 

I almost always co back to the mechanical pump if its available. I've had the electric let me down too many times.

 

Note only is the man correct, he has great avatars!!!!!

 

John what type fuel line are you running? If you stick with the elec it needs to be in push mode as stated. In the pull mode if your running alot of rubber hose it may be collapsing the hose also.
With the elec you really need a pressure regulator, and a return line.

 

John, I had a hard time with electrics also - I'd say go mechanical. I did, and haven't had a problem since.