Is my fuel pump bad?

#1
Hi all, I've just gotten my car last week ('66 SC with a 2200 motor) and have driven it a few times. It runs absolutely fine when cold, but after the car has heated up for awhile it will start cutting out, especially under load.

I have now established that when this happens, I can see lots of bubbles in the fuel pump. Since the dome is on the inlet side, that points to the line upstream, between the pump and the fuel tank. I fitted a clear filter downstream from the pump, between the pump and the carb so that I could see what was going on. It turns out that in this condition, it is pumping a LOT of air. A lot more than I can see in the dome on the pump. Big bubbles coming up inside the clear filter. The car will usually idle, but if I watch that filter there are times when it is almost entirely filled with air/fuel vapor. It seems like too much for fuel vaporization.

Given that it seems to be sensitive to heat I can only guess that it's vaporization in the fuel line upstream from the fuel pump, or an air leak in the pump. Note that in order to fit the clear filter, I replaced all the hose and fittings between the carb and the pump and there is not an air leak there. The bubbles are clearly visible in the glass dome on the pump. This is a pretty good volume of air or vapor so my guess is it's air introduced by the pump? Is this a common failure mode?

Help appreciated!

Thanks
Karl
 
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#2
I wonder if your supply lines to the fuel pump are constricted with rust? I would suggest taking off the delivery to the carburetor and operate the pump by hand. It should spray fuel out, not dribble fuel out. Have you tried your other fuel line? Does your oil smell of petrol? If your diaphragm has a hole in it, then gas will leak into the oil.
 
#3
I wonder if your supply lines to the fuel pump are constricted with rust? I would suggest taking off the delivery to the carburetor and operate the pump by hand. It should spray fuel out, not dribble fuel out. Have you tried your other fuel line? Does your oil smell of petrol? If your diaphragm has a hole in it, then gas will leak into the oil.
Thanks for the response!

By other fuel line, do you mean switching the reserve valve? I haven't tried that, I will give it a shot. It takes some driving for this condition to happen because the car needs to get pretty warm.

I didn't realize it would leak fuel into the oil system if the diaphragm was leaking. I've now parked the car where it store it underground so I'll have to go back over tomorrow to see if I smell fuel in the oil. The oil was just changed so it may not have any evidence of odor yet.

I'll also work the pump by hand and see how it does. Thanks for the suggestion.

Cheers,
Karl
 

Chalky

Active Member
#4
Fuel vaporisation is very rare in a 4 pot. I would look at the coil. They often work when cold then fail when they get hot. Common fault.
 
#7
Depends on the environment. It was very common in 4-pots where I grew up.
If you route the fuel line above the upper radiator hose then starting when hot will be difficult. Also I had exhaust work done once, and the left the heat shield off afterwards. That made it run badly.
 
#8
Thanks for the response!

By other fuel line, do you mean switching the reserve valve? I haven't tried that, I will give it a shot. It takes some driving for this condition to happen because the car needs to get pretty warm.

I didn't realize it would leak fuel into the oil system if the diaphragm was leaking. I've now parked the car where it store it underground so I'll have to go back over tomorrow to see if I smell fuel in the oil. The oil was just changed so it may not have any evidence of odor yet.

I'll also work the pump by hand and see how it does. Thanks for the suggestion.

Cheers,
Karl

One of my cars runs better on the reserve fuel line, it starves on the main line after a while.
 
#9
Thanks everyone, I'll do some further investigation. It's definitely a fuel issue, not spark, as I can see the air in the pump and the clear filter sometimes is almost empty. Now that I understand things a little better I'll switch to the reserve intake as @j_radcliffe suggested and see if that solves it. Since it's a completely different line from the back of the car that would help rule out the fuel line from the tank if the behavior is the same. I'll also check for fuel smell in the oil. I'll report back.

Cheers,
Karl
 

cobraboy

Well-Known Member
#10
Without cutting any of your new pipes you could always fit a temporary clear filter up stream of the pump, then you will see if the air is in the fuel before it gets to the pump.
 

sdibbers

Well-Known Member
#11
My fuel pump started failing only when hot on my TC two years ago. I think it’s a combination of heat and ethanol in the fuel caused the rubber flaps to distort in the pump. I rebuilt it with new rubber parts and it’s been fine since.
 

Chalky

Active Member
#14
If you decide to get a new fuel pump look for one listed for a David brown 990 series tractor. The exact same pump and about a quarter of the price of one listed for p6. Around £30 up against £125.
 
#17
I'm missing something. Is that a Fawlty Towers joke? Anyway, my profile says where I live, so that's how @Chalky knew. I live in Dublin but I'm American.
yes a faulty towers comment, it just came to me when I read the reply, " hes in Dublin" and I immediately thought of basil saying He's from Barcelona , regarding Manuel, all in an instant. not intended to cause a ripple or imply....:)
Peter
 
#18
If you decide to get a new fuel pump look for one listed for a David brown 990 series tractor. The exact same pump and about a quarter of the price of one listed for p6. Around £30 up against £125.
Thank you! I had found the other thread about that as well. There is company in Ireland stocking them as well. Super good info.
 
#20
Well done for finding that pump Chalky is there a section on the forum for different replacement parts that work for a fraction of the cost? :p
If not I think we need to start one.

Relistan it sounds like there is an air leak you could try taking off the fuel line at the pump that connects to the carburettor float bowl I just took my float bowl lid off with the pipe in place and then blow down the end that connects on to the pump I did this and a load of dirt and fuel come out,
then reconnect the pipe to the pump then see how much fuel comes out of the float bowl lid if you hold the lid upside down it will cut the fuel off
However if there is air getting in at the pump or anywhere else this wont resolve your issue but at least you will know your getting fuel.

I don't wish to send you off into a wrong direction but I had a problem where the car will start and drive absolutely fine could even go for a drive ect but would then run rough and cut out and it was the mixture being to rich so the car would run perfect from cold as it had loads of fuel no need for choke lol :)
 
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