in-line elec fuel pump not pushing through mechanical pump

[dbdevkc]

I have an in-line electric fuel pump that we installed to help fill the carb bowl after the flathead sits for a while. But when we turn on the electric pump (before attempting to start the engine), it fills the mechanical fuel pump glass bowl then immediately the gas starts squirting out of the top of the mechanical pump glass bowl. As if the fuel is not passing through the mechanical pump into the carb. We did remove the fuel line from the carb and verified that while cranking, the mechanical pump (alone - electric pump off) is pushing a bit of fuel through. We have not tried turning on the electric pump with the fuel line removed from the carb because we were a bit freaked out with the fuel coming out of the mechanical glass bowl and just assumed that the mechanical is not letting the fuel pass through for some reason.

Any ideas?

 

[69a]

The glass bowl gasket should not leak! Address this issue first.
Perhaps you have a high pressure electric pump. Too much pressure is not good for the glass bowl gasket, the needle and seat in the carburetor, and the mechanical fuel pump diaphragm.
The carburetor doesn't like pressure above around 2.5 PSI.

 

[69a]

I'm assuming it will operate on just the mechanical pump. If this is correct the only thing that can induce pressure into the line is when the needle and seat has closed, ie fuel bowl in carburetor is full.
There is a lot of information on this site on this setup.

 

[Flathead Fever]

The electric pump needs to be mounted back by the tank with a filter between it and the tank. Every electronic fuel pump needs to be mounted as close to the tank as possible with a filter between it and the tank. They make a fuel filter that looks like the canister on a 1960 FORD fuel pump but with an aluminum mounting bracket. It's a nice size so it should catch all the junk in your tank for years.

The pump needs to be a low pressure around 1 1/2 lbs. Then it also needs to be "open" when it's turned off so the stock pump can pull fuel through it. Very few electric pumps are made this way, they are closed when the pump is turned off. In the Airtex fuel pump catalog they have pages listing the electric pumps by pressure, volume and if they are open or closed when off. There are only a couple of them made that are 1 1/2 pounds and open when not in use. I used to bring the old catalogs home from work, so I'd have all the wonderful info in them. So, make sure your pump is not rated too high a pressure.
Turn the pump on and prime the system but then turn it off before you start the car or it might flood over with two pumps going. You can also remove the air cleaner and see if the accelerator pump is squirting to see if the carb is getting fuel before starting it.

 

[dbdevkc]

Thanks for the replies. The electric is a flow-through model, installed closer to the tank on the frame, it has a filter between it and the tank, and it has an adjustable regulator on it.

I am going to check the regulator on it - it might be set to 3-ish - because the Carter WCFB carb we have on there uses a lot of fuel when those 4bls open up. Maybe I'll turn down that pressure for now. But the idea was to use it only before starting to prime the system.

The mechanical fuel pump was one that we got from Charlie NY, but yeah the fuel squirting out the top of the glass bowl is a consern.

I think I'll pull the fuel line off the carb, then see what happens when we turn on the electric pump. That will at least show me fuel is flowing through the mechanical ... or not.

 

[Mart]

It's probably quite normal. The side of the fuel pump where the leak is is normally under suction rather than pressure. It has exposed a weak gasket in that area. If you do disconnect the pipe at the carb the chances are it will spurt out with the electric pump running.
The leaking happens to me when the cars have sat for a while. It stops after the gaskets are wetted a bit and swell. I've shown it in some of my videos.
Mart.

 

[Merc Cruzer]

Just a few pictures of the cork gasket, that needs to be replaced.

 

[petehoovie]

Just a few pictures of the cork gasket that needs to be replaced.

 

[dbdevkc]

Here's an update. We removed the fuel line at the carb and yes the electric pump pushes fuel all the way. But ... the regulator just after the electric fuel pump was set to 4. I am thinking that it is very possible that over quite a few "hard starting sessions", we may have blown out that cork gasket.

Since we only plan to use it as a way to prime the system/get fuel into the carb bowl and not use it while running the car, I turned the regulator down to 2. Might be able to turn it down even more.

I know someone who uses Permatex Ultra Gray or Ultra Black as a cork gasket dressing (not globbed on - just a thin smear) in other engine applications to make cork gaskets leak free. Ultra Black claims to hold up to gas and also remain flexible. Not sure if using that might help.

But we did get it started today and gave it a good highway run. When we got back the mechanical fuel pump had a slow but steady drip of fuel that took a few minutes to stop.

Conclusions:
- Spark is ok
- Fuel pumps work
- Carburetor works - might still need cleaning/adjustment, but at least it is not completely shot, or clogged.
- Need to fix the leak at the mechanical fuel bowl glass bowl

Next questions:
- Is it possible to determine visually if the carburetor bowl is empty/dry, or full? What we decided to do now is take the air cleaner off, give the accel pump a shot - if we don't see fuel squirt - we know there is no fuel in the bowl.

I think if we can get the mechanical pump leak fixed and the electric can be used to fill/add fuel to the carb bowl without leaking at the mechanical pump, then we may have at least a temporary solution at hand.

Thinking over the winter we'll take the carb off, fill the bowl and put it over a bucket overnight - then see where the fuel is the next morning.

 

[J Franklin]

You can get the gaskets off EPay like a half dozen for a few bucks. It is good to have some spares as they should be replaced anytime the bowl is cleaned out.

 

[Flathead Fever]

You can stick something down the carbs vent and into the bowl to see how much fuel is in there. The Holley 4V carbs have a screw that lets you see how much fuel is in the bowl. I have a tool for the Strombergs, it replaces one of the drain plugs, you replace the drain screw with the tool, then it fills up with fuel so you can actually see how much fuel is in the bowl, it's a pretty neat tool. If the accelerator pump is squirting that means, there is fuel in the bowl but maybe not the correct level. If it's an old carb it probably could use a rebuild anyway. Things like the accelerator pumps rubber was not compatible to the alcohol they put in new fuel. Supposedly, all the carb kits have been updated with compatible new parts.

If you pull the line off the carb, crank it and find the fuel supply is adequate, it might be time for a carb rebuild. Take a can of carb cleaner with the straw attachment and make sure every passage is clear. Carbs are very delicate so tighten all the screws up evenly and gently, so you don't strip them out, don't gorilla tighten anything on them. When carbs sit for around a year the gas turns to varnish, and the passages get clogged up.

My Shelby sat for much longer than that, the needle and seat got stuck closed. I tapped on it and got it to open up, drove it about a block and it ran out of gas. Got out, opened the hood tapped on the needle and seat and drove it back home. Got in the driveway and it ran out of gas again. Tapped on the needle and seat again and it fired right up so I put it in the garage and let it go back to sleep for another few years. I was a professional mechanic, but I've had a stroke and just don't have the energy to rebuild the carb right now. I could rebuild it but then it would just sit and turned to crap again so for now I'm letting it hibernate. Carburetors "have" to be driven every few months or they dry out, they may or may not survive sitting for months. When I was a mechanic in a fleet of 400 vehicles, carburetors were a big problem if they weren't driven often and even then, stuff went wrong with them. When Fuel injection came out it didn't seem to matter how long the cars sat, they fired right up. Greatest car invention ever. But they don't look as cool. I have rebuilt hundreds of carbs over my 30-year career during the carb era. When the vehicles were all fuel injected, we probably could have gotten rid of one mechanic at work, somebody was always rebuilding a carb in the shop before fuel injection replaced carbs. Especially the Holley carbs on the big trucks. They last about a year and need a rebuild, usually the power valves would blow out.

 

[TerryOH]

You may want to look at the fuel pump internal valves and how they function.

 

[dbdevkc]

You may want to look at the fuel pump internal valves and how they function.

I am not sure what you are trying to say - that I should verify that it is functioning correctly? Or that I should open it up to learn how it functions?

With our most recent run and test, I think I can verify that is functions correctly but we now have a small leak at the glass bowl cork gasket.

 

[Merc Cruzer]

I have a electric fuel pump in my system and don't use a fuel regulator.

It is easy to remove the glass fuel bowl and inspect the cork gasket. Just put a towel or rag under the glass bowl and loosen it, and carefully remove it from the pump. Then carefully remove the the cork gasket. It may come out in pieces and if so then just replace it, because no matter what you do it will continue to leak.

There is no way to see how full the float bowl of the cab is unless you take the top off the carburetor. You are correct is saying that if the carburetor squirts gas when you pump it, then there is gas in the float bowel.

As to inspecting the fuel valves in the pump, as an FYI, I have attached a few pictures of the 53' Mercury dual action pump. I recently (in the last two weeks) rebuilt two fuel pumps for my car. One to serve as a back up.

 

[petehoovie]

I have a electric fuel pump in my system and don't use a fuel regulator.

It is easy to remove the glass fuel bowl and inspect the cork gasket. Just put a towel or rag under the glass bowl and loosen it, and carefully remove it from the pump. Then carefully remove the the cork gasket. It may come out in pieces and if so then just replace it, because no matter what you do it will continue to leak.

There is no way to see how full the float bowl of the cab is unless you take the top off the carburetor. You are correct is saying that if the carburetor squirts gas when you pump it, then there is gas in the float bowel.

As to inspecting the fuel valves in the pump, as an FYI, I have attached a few pictures of the 53' Mercury dual action pump. I recently (in the last two weeks) rebuilt two fuel pumps for my car. One to serve as a back up.

 

[dbdevkc]

Thanks all for replies and comments. The mechanical fuel pump we have was a rebuilt one from Charlie NY that had been built to push 3psi to supply the needs of the Carter WCFB. We will be replacing the cork gasket to at least get that to be leak free.

I guess the last question remaining is how to set the regulator that is in front of the electric fuel pump.

My initial thoughts were since we would only use it to prime the system we don't need to to be set very high at all. But then if we set it lower side (say 2psi), would that limit how much the mechanical pump could pull to just 2psi and so possible slowly starve the carb when under high demand.

I could set it to 3 to match the mech. pump Charlie built for us and call it a day, I just don't want the electric to over-pressure the pump and blow out the gasket again.

 

[69a]

2 PSI is more than enough to prime the system (motor off). This will pressurize the the glass bowl, the fuel pump and fill the carb. Switch the electric pump off and start the engine, you will now have the mechanical pump pressure (yours is set to 3PSI) between the mechanical pump and the needle valve on the carb. and negative pressure on the glass bowl. If it is sucking air at the bowl gasket it is difficult to detect.This is why it is important to have a good seal on the glass bowl.
If you have both pumps running you could have 5 PSI at the carb. I'm not 100% sure about that.

 

[dbdevkc]

2 PSI is more than enough to prime the system (motor off). This will pressurize the the glass bowl, the fuel pump and fill the carb. Switch the electric pump off and start the engine, you will now have the mechanical pump pressure (yours is set to 3PSI) between the mechanical pump and the needle valve on the carb. and negative pressure on the glass bowl. If it is sucking air at the bowl gasket it is difficult to detect.This is why it is important to have a good seal on the glass bowl.
If you have both pumps running you could have 5 PSI at the carb. I'm not 100% sure about that.

I understand what you are saying. And do not plan to run the electric while running. But would having the regulator set to 2 while the mechanical is delivering 3 to the carb - would the regulator constrain the mechanical pump's ability to suck enough fuel to continue delivering 3 to the carb? In other words, might the regulator set to 2 be a bottleneck?

 

[JayChicago]

With electric pump off, mechanical pump sucking, there will be negative pressure at the pressure regulator. So I would think the regulator will not restrict.

 

[Flathead Fever]

I had a '66 Mini Cooper S with an external adjustable fuel regulator. This was 30-years ago but they look exactly the same today. Every once in a while, the regulator would just shut the fuel off. I have to get out, reset the regulator and then I'd be good for maybe a month, and it would happen again. So, I bought a new one and then anther different brand regulator, and it did exactly the same thing. I think they are designed more of a 5-6 lb. system, because at around 3 lb. they seem to have issues. No manufacturer uses an external fuel regulator. They design a pump with the correct pressure required by the carburetor. If you're just priming the system, then use a low-pressure electric pump that is open in the off position.