The Stovebolt Site Forums The Shop Area Engine Shop 50 Chevy 235 fuel pump vs electric fuel pump

Through the years I've experience vapor lock on my 235, not a pleasant situation when you sit there unable to start the engine for 30 minutes or so leaving my battery near dead. Also many times after not running for a month or so the fuel evaporates at the carb and I have to crank the engine to the point the battery gets weak so that fuel can reach carburetor and start the motor.

It was suggested to me by others the install inline an electric 6v fuel pump prior to the mechanical fuel pump and to turn it on only when I came across those two situations. I would then turn it off once the engine started.

What is your take on this, could this damage the mechanical pump by forcing fuel through it at a higher PSI?

Would it not increase the possibility of flooding the carb?

DJ

I did something like that to the 637ci GMC when the mechanical fuel pump went out on it.
I could not get another one because they quit making them years ago. It mounted to the top of the engine, in front of the intake manifold and the lever arm was over a foot long to reach the cam.
Made a plate to cover the hole and installed a inline electric pump next to the frame mounted fuel tank.

It has worked good since.

Don

I, too, had the same problem with my 216. Vapor lock is not fun. I installed a 6v fuel pump between the gas tank and the mechanical fuel pump. Installed the electrical switch under the dash. I use the electrical pump to fill the carburetor if it has been a while since starting the 216, then turn the electrical pump off before starting the engine. When the 216 starts to stumble because of vapor lock, I turn the 6v pump on. It has worked for me. I've tried other remedies to prevent the vapor lock, to no avail.

Rick

It will work just fine, no worries. It will not over pressure the original pump.

The small electric pumps only put out 3-7 psi depending on which one you purchase. You will have no problems using one. I would use a momentary push button so there is no chance of you leaving it on.
Joe

I fixed mine old school way
By putting on cloths pins on gas line
It took care of my vaper lock
Used this 35 years ago on my Chevy tow truck
And it took care of problem

I was waiting for someone to mention the clothe pins idea, use those as a conversation starter at car shows. Now I've see clip on heat sinks, sort of high tech clothe pins.

For something a little less redneck-looking than clothes pins, try wrapping the steel fuel line with the same type of woven insulating material used to wrap motorcycle exhaust pipes.
Jerry

Hey, how about twisting tin foil from cigarette packs around the fuel line?!!

Ya gotta make these old trucks look authentic from back in the day!

Matt

Vapor lock on a 216/235/261 with properly routed fuel lines?

Maybe so, or maybe your solutions solved another problem/problems?

Here is an interesting article from fellow 'bolter Deve on this topic--

http://devestechnet.com/Home/FuelSystem

Matt

I replaced the fuel tank and put the new one under the bed of the truck. I'm not sure if its a vapor lock or over heating problem am having. My truck will start and run, but after about fifteen minutes if driving if starts to bog down, my fuel bowl on the mechanical pump is still full. Any thoughts?

Is your new tank vented? That’s important and exactly describes your symptoms.
When it dies open the cap and listen for a vacuum.

Fix:
1. Drive truck and don’t turn it off
2. Have you put cow magnets on your fuel line close to the carb (old myth)

Ok, all joking aside. I wrapped mine like HRL stattd and that seemed to help me. Cost about $10. I don’t understand why anyone would put 2 inline pumps (mech and electric). If you use the electric, won’t that cause issues with the mechanical and vice versa.

Is your fuel filter plugged up? (Just a thought)

Chris

I started using an electric fuel pump years ago and it works great. Just be certain to get a low pressure pump (2 to 4 pounds is all you need for an inline 6). I recently bought a spare and leave it under the seat in its box. Startup is quick. The one I bought was sold under the name of AutoBest and the part number was 4027. It puts out about 2.5 pounds pressure. Bought it over 10 years ago on eBay and it just ticks along. Why'd I get another? I couldn't remember if the original one was ok for ethanol, but the new ones claim to be. Amazon sells them for $17. These are vibrator pumps and should be mounted as close to the gas tank as possible...they push much better than they pull and the bottom connecting tanks in the AD trucks are a natural for these pumps. Be certain you know what pressure you're buying and don't get a high pressure pump. Let me repeat that...Avoid any pump made to be used with a fuel injection system. These are definitely not what you want.

Electric fuel pumps must have their uses.
I prefer mechanical, they have been more reliable in my experience, and certianly simpler.

The only time I get a chugging type of vapor lock is on a hot day sitting at a stop light. That's due to the real flat fan on an ill-positioned water pump (too low) on my 261 for the '48's radiator. Could it be a water pump problem? I gotta get pre-68's fix.