1951 Ford - Not vapor lock- but something going on

[tjc1965]

Thanks in advance. I've had a '65 Mustang for 30 years now, this is my first older car experience so I'm still learning as we go. I've been lurking here a while, I sure would appreciate some experienced input!

My Dad and I have a 1951 Ford Tudor we bought a couple years ago, mostly restored to original, but a few little things needed, something he can putter on and take to cruise nights.

Always starts and runs good, but I think have messed something up this weekend. Previous owner installed a Mr. Gasket inline fuel pump many years ago. Pump mounted to the frame rail, basically under the drivers door. The pump is wired to only get power when the starter is cranking- hot wire right on the outlet from the solenoid. So I figure the pump is used to get the fuel flowing at start-up, and then the mechanical pump takes over.

Today I replaced the pump and filter, since the old pump had a slow leak. Bought a Carter electric, similar size as the old one, low pressure type. Wired it same as the old one - runs only when on the starter.

After installing, went for a ride. After about a mile, she stalls. Coast to the side, wait less than a minute, starts right up. Drive another half mile, does it again. So, we turn around head for home does it again a couple times.

Once home, decide to see if it's "vapor lock" due to heat. Let it idle in the driveway, hood closed for 20 minutes or so figuring it might make enough heat to boil the carb fuel. No dice.

However, with my foot on the pedal and holding it at 2000-2500 rpm, in about a minute she sputters and shuts off. 30 seconds, starts right up.

So, my theory now is the new pump is more of a restriction in the fuel line than the old one, causing the mechanical pump to lose prime when it's trying to suck thru the non-running electric pump. Any one have any thoughts on that?

For a solution, I think if I just run the new pump off the ignition hot wire, so it's running whenever the key is on, that should solve the problem. Only question now, do I need a regulator before the mechanical pump to not over-pressurize it, or not to worry?

Thanks for the help!

Tom C

[51 MERC-CT]

If you are using a Carter pump like that in my link there should not be any pressure issues. Could be restriction or Gas cap not venting.
Also if running the electric pump full time you may want to consider an impact fuel pump shut off.

http://www.macsautoparts.com/ford_me...FUYGhgodlQoNlw

[drolston]

I use a Mr Gasket pump and only use it to prime the carbs when the car has been sitting a while. The Mr Gasket fuel pump offers no resistance to fuel being pulled through it by the mechanical pump, even when the electric pump is not powered. I suspect that your Carter pump restricts or blocks flow when off.

[Ken/Alabama]

Why not just run a good mechanical pump?

[Ford Freak]

Originally Posted by drolston

i use a mr gasket pump and only use it to prime the carbs when the car has been sitting a while. The mr gasket fuel pump offers no resistance to fuel being pulled through it by the mechanical pump, even when the electric pump is not powered. I suspect that your carter pump restricts or blocks flow when off.

bingo !!:d

[paul2748]

Sponsored Links (Register now to hide all advertisements)

Can you check it if it's a flow through by putting air to the inlet when its not operating?

[drolston]

If you are 12 volt negative ground, Mr Gasket 42S will do the trick.

[Frank Miller]

Replace the pump with a piece of hose. If the problem goes away you have a restriction in the electric fuel pump. If not then you have a faulty mechanical pump or a clogged line.

[tjc1965]

Thanks all for the suggestions, appreciate the help.

Since it ran fine before the new pump, with the mechanical pump drawing thru the non-energized Mr. Gasket pump, I'm thinking the mechanical one works fine, and the Mr. Gasket was only added for the start-up after sitting.

I think I'll take the Carter out, run with out it to confirm, and then put another Mr. Gasket one in again, so we can get back on the road without worry.

[mustang8]

Why run both? Wouldn't it make more sense to just let the electric pump run while whenever the key is on? I removed my mechanical pump and put in a low pressure K&N fuel pump and it seems to run just fine. Just my two pennies worth.

[tjc1965]

Originally Posted by mustang8

Why run both? Wouldn't it make more sense to just let the electric pump run while whenever the key is on? I removed my mechanical pump and put in a low pressure K&N fuel pump and it seems to run just fine. Just my two pennies worth.

I'd do that, but I'm concerned about damaging the existing working mechanical pump by feeding it 4-5 psi all the time. Or worse, causing an issue at the carb by making the feed pressure downstream of the mechanical pump higher ( electric pump + mechanical pump = 8-9 psi?) Or maybe I'm overthinking it?

[JSeery]

You need an electric pump with the lower output or a pressure regulator.

[Drbrown]

Have Airtex at tank and active mechanical. Use Airtex only to prime carb. Either pump puts out 3 PSI which I understand is the maximum desirable.

Have problem like yours sometimes. Installed OE vented gas cap .... didn't make a difference. Suspect vapor lock between mechanical pump and carb due to ethenal gas.

Have recent rebuilt carb, crab, condenser and new coil.

[Dick Webber]

On my 49 Mercury I run a 6 volt electric pump just forward of the tank for priming the carburetor. Car takes extended cranking after sitting a week without the pump. It is on a toggle switch that I turn on for 20 seconds or so before using starter. Then I switch it off. Has worked great for 15 years. It has also helped a few times when I thought it was going to vapor lock

[mustang8]

Originally Posted by tjc1965

I'd do that, but I'm concerned about damaging the existing working mechanical pump by feeding it 4-5 psi all the time. Or worse, causing an issue at the carb by making the feed pressure downstream of the mechanical pump higher ( electric pump + mechanical pump = 8-9 psi?) Or maybe I'm overthinking it?

Just remove the mechanical pump. They make a nice little aluminum cover that closes off the opening on top of the engine. As long as it is a low pressure pump like 2-3 psi area you should be fine.

[Ford Freak]

Originally Posted by mustang8

just remove the mechanical pump. They make a nice little aluminum cover that closes off the opening on top of the engine. As long as it is a low pressure pump like 2-3 psi area you should be fine.

x2 !!

[ford38v8]

Originally Posted by tjc1965

I'd do that, but I'm concerned about damaging the existing working mechanical pump by feeding it 4-5 psi all the time. Or worse, causing an issue at the carb by making the feed pressure downstream of the mechanical pump higher ( electric pump + mechanical pump = 8-9 psi?) Or maybe I'm overthinking it?

Your pressure would be the highest of the two, not the sum of the two.

I have an additional idea as to why the new pump seems to cause stalling: Your plumbing to and from the new pump may be sucking air. If you are using the supplied spring clamps that come with many pumps, ditch them and use warm gear clamps.

I would mount whichever electric pump you wind up with closer to the fuel tank, wire it the same as it is now, but with an additional normally off toggle that you can pull when you feel it is about to stall, which may happen occasionally due to vapor lock at a stop light.

[tjc1965]

+1 on the hose clamps, tossed the wire ones and replaced them with SS worm gear ones before doing anything.

Just to close this loop, I replaced the Carter with a Mr. Gasket electric pump, and wired it to a toggle switch. When the car's been sitting more than a day or two, run the pump 5-10 seconds, then crank her over and she starts right up. No need to run the pump any longer.

Fixed it this past week, went for a long ride with no issues.

Thanks for the help and suggestions!