Electrical fuel pumps? Which ONE???

[Daddio]

Hello again, I'll get right to the point:

Truck sits for a few days and the fuel drains from the carb all the way to the filter.

Mechanical fuel pump (new) isn't strong enough to overcome the air in the line.

Replacing fuel lines doesn't seem to help.

Any recommendations on an electrical fuel pump for a 1978 620 pickup? There are only a zillion different pumps out there to choose from.

It has a relatively new Weber carb, because the original was eaten up by ethanol. (had to replace the muffler when it exploded too 🧨😲)

Once it gets fuel it runs fine.

Your experience greatly appreciated.

Daddio

[datzenmike]

Once again, once fuel drops into the fuel bowl in the carburetor it can't magically climb up hill and go back into the fuel line and into the tank. Besides there are two one way valves in the fuel pump that would prevent this. If fuel is siphoning back, it's the fuel in the line, not what's in the carburetor. Check the rubber fuel lines on the suction side of the pump for any small cracks and the hose clamps are snug. Gas can't siphon back by gravity if the engine end of the fuel like is sealed properly like it should be... air must be getting in.

[Stoffregen Motorsports]

Fuel can drain back to the tank from the nipple up to the carb, and that is a sign that the fuel pump is failing, but as Mike said, once it is in the carb it will not siphon back. It can evaporate or boil out from a hot engine though, making cold start difficult. My 1980 Chevy K30 had a bad mechanical pump that would pump just fine, but the check valve was bad and it would crank and crank and crank before it would fill up the carb enough to fire the engine. So yes, Mike is right on that count, that fuel won't siphon back, but it can evaporate.

 

Factory-like fuel pumps are not hard to find. Nissan used a cylindrical pump that was common at the time, made by four or five different manufacturers. Facet is a brand that still makes those pumps. Pegasus racing sells them in a few different varieties with options like nipple thread size and output flow. They do sell one with no check valve, but I think the check valve is normal in 99% of new electric fuel pumps.

 

You can buy these lots of places, but I like the Pegasus site because they list them back to back so you can compare all the different options - https://www.pegasusautoracing.com/group.asp?GroupID=FACET12CYLIN

[Daddio]

Soon as it warms up enough to enjoy leaning over the grille, I'll check the hoses and prime the carb. Thanks for your help. I'll return here and let you know what happened. Many thanks. 

[Daddio]

Hello friends.

 

I'm very confused. Went out the truck to see if I could find gas lines that may have been letting air into the system, only to start the truck within 10 seconds of cranking the starter. Huh?  For two weeks, I couldn't get it started (yes, it has spark and gas). I could crank on it forever and not even get a faint smell of gas from the carb. I opened up one gas line and it was dry. Now, it starts like nothing ever happened.

 

I don't trust it. It's going to leave me stranded 30 miles in the back country with nothing more than half a bag of cheetos and a kiddie box of Yoohoo with no straw! 

 

Meanwhile, my quest to figure out what is going on continues. Question: could it be the electric choke is causing issues? It's a (relatively new) weber carb with an electric choke. How would I test this? 

 

Thanks for the insight. Daddio. 

[datzenmike]

While it's still cold take the top off the air filter. The choke flap should be slightly closed.  Pump the gas and the choke flap should snap fully closed. Once warmed up it should be fully open. That's about all you can do.

 

When you go to start your engine, you step on the gas once to set the choke on? Yes?? This is important on a carburetor vehicle. The choke is not and won't set to on without this. In addition the carburetor has an accelerator pump and this squirts raw fuel into the primary barrel which helps richen the starting mixture.

 

And again there should be residual fuel in the float chamber from the last time it was running. More than enough to start the engine the next time.

[Daddio]

I'll try that and see what happens. Usually set the choke. It's been warmer, so it fires right up. However, if I leave it for a week it gets fussy or refuses to participate. We shall see what it does. Thanks. 

[banzai510(hainz)]

a guy has this on hos later model 510. https://www.pegasusautoracing.com/productdetails.asp?RecID=9616

I dont know where made but is German Japan US then I say get it.

But what Stoffregen Motorsports posted i most likely the better ones maksure under 4 pounds pressure