VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Fuel pump

Can the fuel pump be producing the proper pressure but not be pumping a sufficient volume of fuel?

I don't know the answer but my gut feeling would be no.

Nice to hear from you Maxine...It sounds like a discussion we've had here many a time...And it usually means you have a "clog" in the pick-up tube in your gas tank...Usually because at one time or another some one put "tank liner" in the old tank and now pieces have come loose and are blocking said "pick-up" tube...Happened to me as well as countless others...One sure sign is it acts like it runs out of fuel on the highway or on hills...After a few minutes at idle, off you go again...'till that next long hill or extended highway speeds...Good luck, Kevin

I have seen the pressure to be ok but weak or restricted on the intake side. Have you checked the vacuum on the intake side, should see around 10 inches?

You can have enough pressure and not enough volume. As Kevin points out it usually comes down to a restriction in the tank and or line going to fuel pump. The best way to check things out is drop the gas tank and take the fuel sender out and have a look.

It should be noted that most times this happens it's because the installer didn't follow the manufacturer's instructions. I've used tank liner a number of times and have had 0 issues arise because of it. I lined my '38 with Redkote five years ago and have had no issues with the liner peeling.

THANKS TINY ........I CAN STOP SWEATING NOW ! I HAD MINE LINED .FRANK

The tests for a fuel pump include both pressure and volume. It can have one and not the other.
The prssure should be 3 pounds. With the fuel line disconnected and end of line held into a container the fuel should spurt of when the engine is turned over with the starter. While the line is off it is a good opertunity to blow out the line.
If in doubt I would be safe and replace the pump.

Thanks everyone, it would not surprise me a bit to find debris clogging the line in the tank. I will get to it and see what I come up with.

Kevin, you nailed it on the symptoms, but it also ran a little rough occasionally like it was missing once in a while. I went into the carb a couple times for the usual culprits and noticed the bowl was about a third full, which led to my question after I noticed it the second time. Thanks all, this was a big help, I am heading to the Houston car show this weekend and so will not be able to get to it right away, I will let you know the outcome.

Thanks for setting me straight. I can see how with a restricted suction line the pump could build pressure but it seems like if the volume would not meet the demands of the engine the needle valve in the carb would open and cause a drastic drop in the pressure? I have an in-line fuel pump pressure tester but have never had much occasion for using it.

Thanks for keeping us posted on your outcome. I'm going through some of this stuff right now (even with a new fuel system) and I'm anxious to see what you discover.

Unless your tank is hard to come by or your just plain...Let me think of the proper term...Anyway, don't waste your time with Redkote, etc. Unless you like the term "Good grief charlie Brown what were you thinking...?" You're tank has to be ABSOlUTETLY boiled clean first...Don't waste your time and energy just to do it again...GET A NEW TANK...It may cost $200 bucks but your worries are done...Ask Gene...I think he'll agree...

I'm telling you it's the pick-up tube...Wait 'till you see the inside of your tank...

BACK TO WORRYI'N . : ( FRANK

Depends one how long it'd been and how it well the job was done...Mine ( by a previous owner ) lasted years...Before I could figure it out...At least you have a clue as to when those symtimes start to occur....Unlike the rest of us...

That's good advise when they are available. There was no option for me at the time other than paying a fab shop a couple grand to make one from scratch. Now there are tanks available for my car although expensive. My experience has been that if a quality tank liner is used and the job is done right there will be no problems arise. Every liner related issue I've personally seen was caused by the installer cutting corners, not following the manufacturer's instructions.

Car show, mother's day, graduation week-end, it's like there is a conspiracy against a guy having a hobby. Anyway, picked the fuel system clean, front to back including the fuel pump; no improvement. I did the usual cylinder pressure checks and everything was pleasantly within specs. That left spark, which I know should have been the first thing to check, but I had just replaced the distributer cap, the rotor and condenser, set the timing and dwell, changed spark plugs and wires, in other words, the whole works.

Turned out, I had a bad plug. Lesson learned, "new" does not necessarily mean "working." It ran great after I updated the ignition and then suddenly developed the symptoms, but I still should have guessed.

FWIW

There is nothing wrong with a quality tank liner if it is done properly and can live with this ethanol crap. The FAA requires aircraft fuel tanks to be lined after a certain number of flight hours. I haven't done a tank in years but I got my liner at the airport (very reasonable price). Aircraft repair shops buy liner in 55 gallon drums. It has to be good stuff. Get new, clean cans & lids at a paint store and head to the airport.

'Glad you got 'er going!

Maxine
You like me learnt the hard way about spark plugs. Several years ago I bought a box of 10 plugs, within 3 weeks I had used them all on the 1 6 cylinder car (4 dud plugs in 1 box). Needless to say I was not happy.
Tony

I used gas tank liner 20 years ado and it still works without and adhesion loss. A friend of mine had his peel off and plug up the system.

Liner is great if you need to use it. If your tank is clean and free of pin holes etc., what is the purpose of using the liner?