Fuel Pump Installation woes

[BigOrange78]

re: 1978F250 with 460/514 stroker. Previous mechanical pump was a realatively new one (summit high volume) I installed. It had issues losing prime so I decided to replace with a standard one that I got at local parts store. For the life of me I can't get it to work. I put it in then turn it over to see if it will pump fuel out into a bucket and no dice. I've had it out/in numerous times. I understand the arm on the pump is supposed to go under the cam which I assume I'm doing. Any tips for me ? this is ridiculous! thanks

 

[m78]

Exchange it for another.

 

[fatherdoug]

I guess there are three possibilities. The pump arm lever is not situated properly under the cam, bad diaphragm on a new pump right out of the box, or the pump is sucking air from somewhere upstream.

It wouldn't be the first time new parts have been defective. Do you feel pressure on the arm when the pump is installed? Not familiar with the 460, but on the 400, you have to press downward on the pump to get the bolt/nut in place. This indicates that the pump lever is in place under the cam.

 

[BigOrange78]

pressure on the arm-yes and with the downward pressure on the arm that raises the pump up to get the bolts to line up. I also tried to manually work the pump to test it but I assume that would take a lot of effort I gave up after a handful of pumps. Guess I'll try swapping it out.

 

[Fellro]

If you have or have access to a vacuum gauge, hook it up to the inlet side and crank it. You should be showing it pull vacuum if it is working. When you say the Summit pump was working, but now it keeps losing prime makes me very suspicious of a leak upstream, between the pump and tank. It only takes a pinhole, and you don't have to see fuel leak for it to be an issue. I have seen old rubber hoses do it, even had a case on my old man's 84 where the plastic fender had rubbed through the steel line just enough to make a pin hole. That one did leak fuel too though... Rust is another reason for issues and fuel lines.

 

[BigOrange78]

well that makes a lot of sense, I may as well check or replace the line that would be about the only thing left. I've replaced one of the two tanks, the fuel tank selector solenoid, both sending units but the main old hard line from the driver side front tire are back to the tanks has not been checked out or replaced. Ever since I had my engine build years ago it would occasionally surge and act like it was running out of gas--especially when you romped on it good. I'll check the lines and report back in a week or so. Thanks everyone for the tips

 

[fatherdoug]

If you have the plastic midship tank, there is a 6" piece of rubber hose connecting two steel lines that only be gotten at by dropping the midship tank.

 

[BigOrange78]

great--I just love dropping that tank yeehaw. And of course it is full of gas too. Regarding the fuel lines are the SS lines worth the $30 or so more than OEM? I assume not really...

 

[DNFXDLI]

SS won't rust....if the difference is $30, I'd be all over it.

 

[Mil1ion]

With the cranking the correct position you can install the pump without worrying about bolt line-up.
I had a problem on the highway one time thinking they gave me the wrong pump.

Which they did.
Another trip with a borrowed car later got the correct one.
The actuating arm should be long one in the shape of a dogs rear leg.

Try having the fuel source in a gas can and test pump.

If that works then an in-depth fuel line source test would be next.

Too bad rubber rots ..and causes air sucking thru it.

 

[BigOrange78]

I had not even thought of that simple trick to pump from a gas can--I'll do that! thank you. I have this sneaking suspicion now that my problem all along has been a line/hose issue.

 

[BigOrange78]

update:
sorry it took awhile flu bug hit here got derailed. Pump was fine when pumping from a gas can and ran the engine for a bit as well while pumping from the can.

Thus I figure it is tube/hose etc system and my suspicion is the fuel selector switch area. i replaced that switch in the summer so that area is my #1 guess. I disconnected the hoses in that area and put a new section of hose on the tubes to bypass the switch and the rear tank. i assume this will work as short term fix. Got it all connected up and will test it out tomorrow. Time for some football..

 

[DNFXDLI]

Thanks for the update.

 

[BigOrange78]

test was good this pm. Held 6psi on the fuel pressure gauge just fine and ran ok. Guess I'll order another fuel switch and replace it and the short associated hoses. I drive the truck very little and short trips only so don't particularly need the back tank albeit a new one I put in a few years ago so hate to just abandon the thing totally. At least I should be ok for now running on just the midship tank. Thanks all for the tips...

 

[Fellro]

The switch may not be the issue, it can be just as simple as the hoses were the problem after having been disturbed.

 

[BigOrange78]

Truck seems to be running good on the mid-ship tank and having the fuel selector switch bypassed/rear tank disconnected. Fuel pressure is noticeably higher on the gauge now at 7+ psi range it was not that high when the other items were connected

 

[fatherdoug]

Truck seems to be running good on the mid-ship tank and having the fuel selector switch bypassed/rear tank disconnected. Fuel pressure is noticeably higher on the gauge now at 7+ psi range it was not that high when the other items were connected

Good to hear. Thanks for the update. I think that the fuel selector will default to the midship tank when there is no power applied to the selector. That was my experience, anyway.

 

[Ozzie]

Since all is well when operating on the forward tank, it seems like the remaining problem should be either:
sucking air somewhere from the selector valve to the rear tank
a selector valve which will block flow from the rear tank
a congested filter/strainer in the rear tank (if there is one)