Do I have to prime mechanical fuel pump?

Displayman

Displayman

Senior Member
I took apart and cleaned my fuel pump because it was loaded with
a bunch of crud from an old gas tank. Put in new tank.
Now I am trying to start the car and there is no gas in the bowl.
Do I have to prime the fuel pump? I put some gas in carb to
get car running for a short while. no gas in bowl
If so, how do I do that.
I put it all together the way it was. CLean out the screen above bowl.
Sprayed carb cleaner in every opening. Let is set for a while, sprayed again. Lot of crap was in the screen and above bowl.
Appreciate any thoughts. Maybe it is time for a new fuel pump?
Mechanical or electric?

Thanks,
Bob- Hampshire, Illinois
 
why didn't you replace the diafram when you had it apart.if its the old style diaf. your gonna have to do it again when the corn gas eats it up. dosn't take long. and it well get in your carb also. ken ct. yea if theres not much gas in the tank [prime]
 
Ken,
This is my first flathead. Everything is new to me.
Didn't even think to change diaphram. I wouldn't know an old one
from a new one. How do you prime the pump? The gas tank is 3/4 full.
Do I just put gas in bowl? or do I have do do anything else?
Thanks,

Bob
 
Yeah, if I were you (and I was a couple weeks back) and had to do it again, make sure of the following:

1. Decent amount of gas in the tank.
2. No leaks at all in the lines or potential for leaks
3. Fuel in the line all the way up to the fuel pump or as close as you can get it
4. The fuel pump has no internal leaks that could prevent it from creating vacuum
5. Fuel in the pump itself
6. Put fuel in the carb bowl as well, to give yourself a head start

These old style pumps don't draw much vacuum at all, so if there is one of the above working against you, you'll be driving yourself nuts getting fuel into the pump and into the carb.

Mike
 
I installed a NEW fuel pump on my stock '38 V-8 engine a short time ago; it started fairly quickly. do everything Mike said and make sure the carburetor has fuel in the bowl.
Squirt a small amount of fuel in the carburetor with the air cleaner off; stand back, (possible backfires) and start the engine. If it's a good fuel pump it will keep the engine runnig with out problens. Been there done that, Mark
 
Yeah, a good pump will prime itself a lot faster on a running engine than at cranking speed. A weaker pump may well run the engine well enough but be unable to prime.
Any leakage at valves will greatly handicap things, as will wear at several points that can reduse stroke.
Ford said that most important fuel pump test was vacuum it could pull on inlet side... it is a lot harder for a pump to pull than to push. I think spec was 10 on the gauge... can't lookitup right now.
 
PS...don't prime engine with gas down carb throat...it is far better to fill bowl, which can be done through bowl vents. For Strombergs and prewar Ford carbs, vents are small and inconveniently placed, so just rig a pouring device that ends in a very small tube that can go in. Fill slowly til you just start some dribbling into throats.
 
A tip for assembling a fuel pump is to press the actuating lever fully up while doing up the screws that hold the diaphragm in. Otherwise the diaphragm is pushing against itself when operating. Hope this makes sense.
 
If I may add to all the great tips you have received; be sure that the glass bowl is seated tightly otherwise it will never prime itself.
 
some times you need to put a little air pressure in the fuel tank to force the fuel up to the pump, get an air nozzle with a long snout on it so you can put it in the filler pipe, then stuff rags around it to seal it, have some one put a little gas in the carb, them you squirt a little air in the tank while your buddy starts the engine, the air will push the gas to the pump and prime it, it doesnt take much air pressure to move the fuel to the pump, so be gentle
 
Many times when I was driving my '39 Coupe back in the 60's I have just blown into the filler neck to pressurize the fuel tank and push fuel to the pump if the car had not been started in a few days. Takes patience and strong lungs. I doubt that I could do this any more and besides, I now have an electric pump just for this to save the battery and starter.
 
I have primed the fuel pump by leaving the nuts off the fuel pump stand and everything else connected to the carb from the tank. With the cam lobe on the high spot I just push down on the pump until I have the bowl full or can get fuel to the carb. by looking down the throat and moving the acceleratorump linkage. Worked for me! Kerk
 
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