The Stovebolt Site Forums The Shop Area Engine Shop Mechanical/Electric Fuel Pump Question

I've been having some trouble with one of the old beasts... Yeah, I know, that's what I get for owning a Ford!

At any rate, the old flat-head has both a mechanical and electric (6 volt) fuel pump. The electric is in the fuel line between the mechanical pump and the tank. The mechanical pump is on the block and between the electric pump and the carb.

I believe my mechanical pump has been going south on me for a while, as previously, I could run the engine just fine on the electric, but it sporadically cut out on the mechanical pump, once it's warm.

Now the question... Running it set up like this, if the mechanical pump were to go completely out, would/could it prohibit fuel from getting from the electric pump, through the mechanical pump, and into the carb?

I'm just working on theory now and awaiting your responses. If this doesn't pan out, I guess I'm gonna have to check out the rest of the fuel and ignition system.

Thanks in advance for your opinions/help!

Jed,

Without analyzing the problem, my opinion would be to replace the mechanical pump and get rid of the electric unit. I can't imagine how a mechanical fuel pump could function sporadically unless there was something floating around in the tank blocking the suction. Maybe the existing dual pump setup worked through this blockage. Sheesh, looks like I tried to analyze it...I can't help myself!

Stuart

You could be pumping fuel directly into the crankcase if the diaphram ruptured if it's set up like a Chevy.

Stuart, Baldy,

Thanks for the input.

Stuart, when I said the mechanical pump was working sporadically, I meant I believe it's on it's way out. It works at times, but at other's it seems to leave the vehicle starving for fuel. In the past, I have been able to get around the engine cutting out, by starting up the electronic fuel pump and running on both.

On Sunday, I was doing the same, when it would just periodically quit running. If I sat by the side of the road for a minute, let the electronic pump build up some pressure, I was good to go down the road again (at least for a bit).

I haven't ruled out the possibility that something might be floating around in the tank. However, I've never had a problem with it before.

I've kinda gotten spoiled to the electric pump, so I hate to get rid of it. It makes it awful nice to prime the carb after she's been sitting for an extended period of time, or on those hot days when she seems to be exhibiting the signs of vapor lock.

I was just kinda wondering, based upon how these pumps are built, if it could be possible that a malfunctioning mechanical pump might block the flow of fuel from the line, even though it is being "pushed" by an electric pump.

Baldy, Didn't think about that. That should be an easy verification process. Check the oil, and see if it's got gas in it.

Thanks.

What about a partially clogged fuel filter?

Opinion, you asked! Azone sells a little inline fuel pressure gauge that would let you verify what the fuel pressure was to your absolutely beautiful 41! Personally, I would shelf the electric pump, add a new mechanical pump with a good filter between it and the tank.

As was pointed out, dumping gas into the crankcase from a ruptured mechanical diaphragm could pose a serious problem and IMHO would outweight a little extra cranking after extended periods of inoperation. I found that adding a regulator as well as the inline gauge allowed me to tune my line pressure to match what made my carbs happy!!! Just my $.03!

Dave

I wonder why you have both electrical and mechanical pumps. I would do an "eney meny miney mo" and pick one to dump.

The design of the mechanical pump should let you push right through it with a electric pump. It primes the system just fine doesn't it. When you say the eclectric will pressure up and run for a while, this is a sign of some other problem. If it was just the engine pump bad, the electric should get you around all day, that flat head won't use to much fuel or need much pressure.

Look for crap in the tank or filter. Don't try to suck through a filter, always push through, which means, don't install one at the tank!

Just more to think about, Joe.

You say it has a 6 volt electric pump in it. I didn't know there were ever any 6 volt fuel pumps made. Is it possible that it is a 12 volt pump? If so, it will probably work in a 6 volt system, but at less than half capacity.

I have to agree with others, though. I'd put a new mechanical pump on it, with a fuel filter between the fuel tank and the pump, and get rid of the electrical pump.

But than again, my father had a 1962 Jeep Wagoneer and the float bowl would not stay full if it was parked overnight. I never did find out why, but we added an electric pump to fill the bowl and shut it off when the engine started.

Jed, We are having the same problems with my boss's '41 Ferd. These old flatties appear to be designed to induce "vapor lock" and the "easy" solution most often used is to add a booster elec pump.

A lot is being asked of the ford diafram pump. It sits high at the back of the engine level with the carby and it has to pull fuel a long distance from low at the back of the car and the fuel line is heated quite a bit as it goes up over the engine.

By contrast, our old stovebolts gravity feed from a tank closer to the engine, high in the cab, to a pump low on the block, opposite the side where the main engine heat occurs.

It doesn't take much to to get to the point where the mech pump is trying to suck flmes. Sometime's it could be as simple as winter-formulated gas (vaporises easier) used during a warm spell.

There is lot's of info on this in the early v8 forum over at fordbarn.com including the argument that there ani't no such thing as vapor lock.

Stark, Joe H. FLA54:

Thanks for the input.

Stark, 6-volt electric pumps are pretty common in the flathead world, as they tend to have an issue with vapor lock. These can easily be purchased through JC Whitney.

From some of the posts I received on the Early Ford V-8 site, it sounds like there are typically two types. Those with a diaphram and a gear driven version. The diaphram type pumps are blieved to deteriorate with the use of Alcohol blended fuels, (which we have to run in Colorado). When this happens, the diaphram turns into black goo and begins to clog up the fuel system.

Another party responded with the theory that I should check the fuel pressure as FLA54 suggested. (I have an inline regulator, but have never checked the actual pressure.) This gentlemen suggested that the pressure needed to be below 3 psi on a flathead. Anything over that would be too much fuel for the car.

This coupled with the fact that I'm running blended gas, and the car was running hot, could be the problem.

So guess what I'll be doing this weekend?

Thanks again for the suggestions.

FLA54, thanks for the positive comments about the car.

Thanks for the info, Jed. I know zip about Ford flatheads except that my brother had a 51 4-door with one in it and I really liked that car.

I owned a highly-modified flathead in a 47 Mercury convertible for 13 years, so the suggestions I'm about to make are from lots of hands-on experience!

First, be sure you don't have any seep leaks in flex lines, fittings, etc. The pump sits about 16" or so above the tank, and that's a long way to lift gasoline. I had a flex line from the body to the pump with a pinhole leak that drove me nuts! It would suck air, but wouldn't leak gas. Look for any flattened spots in the metal line down the frame to the tank, or rusty spots that might let it lose vacuum theough a tiny pinhole. Be SURE the tank pickup is clear. They didn't put a strainer in the tank, just an open tube, and a 2" long grasshopper will fit very nicely into the pickup tube. Don't ask me how I know, but it has something to do with a missing gas cap, and getting parked in a grassy field behind the shop for a while!

Last, and most important- - - -Forget the Ford-manufactured fuel pump, or its clones. Get a Carter pump if you can find one! Lose the electric pump, buy a good Carter mechanical pump, and new flex line, etc. Your fuel-starvation problems will disappear.
Jerry

Hotrod,

I always appreciate your input. Particularly when you mix in a bit of your sense of humor.

You've never steered me wrong.

Sure would have liked to have seen that Convert.