Home Forums Gear Hunting Trucks and Four-Wheel Drives Substituting electric for mechanical fuel pump on older pickup

Sooooo,

I came on here awhile back with questions about my '77 GMC 3/4 ton that I'm using to plow snow. The plow is working great. lol

However, I am experiencing issues with the motor not getting fuel. If I pour gas straight into the carb it'll fire up and usually after one try, almost always after 2 then it'll keep running after it burns up the gas I pour in. I'm loath to tear into the quadrajet as A: I'm not handy with carbs, and have had very little experience with gutting one, B: It's cold out and I don't have a heated shop to work on it in, and C: when it runs it runs great. Just seems like it's not getting fuel. I just bought the truck about a year ago and the guy I bought it from put a new pump and lines on. Honestly I'd rather keep the mechanical pump on and run it as is, but it was suggested to me to just bypass the mechanical pump and wire in a universal electric pump. My question mainly is, where the hell should I mount the pump? Inside the frame rail under the cab, or somewhere under the hood? Or is this even a good idea.

Any help from the board would be awesome.

Jason

Anywhere under the cab or bed works fine but keep it as far from the exhaust as possible. I've done it a couple times. It's an easy conversion. It's also a good fix for most vapor lock problems.
Since you'll be running new wires, if you wire in a hidden in-line switch under the seat or somewhere easy to get at, it's a good theft deterrent. A thief can't drive it far with no fuel pump.

I put one in the same place on a 85 Ford 460.It had a pump in each of the tanks and one of the engine. That truck would vapor lock just looking at a mountain pass. For some reason,the one in the tank would always fail first. With my luck, it was always when the tank was full.

After draining the tank a few times and taking it off to change the pump,I aid the hell with that and cut a hole in the bed and put a hinge door on it.

I also had a switch inside that I could turn it on/off

Keep them as close to the tank as you can. Electric pumps push fuel much better than they can pull it.

fwiw- if your engine mounted fuel pump
has a ruptured diaphragm, that means
you're pumping fuel into the engine oil
supply, and will be scoring the cylinders
and prematurely wearing out your engine.
if you do away with your mechanical pump,
remove it completely and buy or make a
plate to cover the mounting surface and
install it with a gasket to cover where
the pump would normally mount.
good luck

Find the actual problem and fix it. Instead of buying extra equipment to go wrong.

That might be true,but changing out a mechanical pump on my old Ford didn't help, nor did replacing the bad pumps in the tank.
A third electric pump and a racing ice bucket got me over the passes without vapor locking.

His truck was fine for 40 years. Now, suddenly, it must have an electric fuel pump? Bull!

Zackly.

Just like everything else.Technology has come a long ways and I'd bet an electric fuel pump of today will out perform a mechanical fulel pump of 40 year old technology

Don't know which engine you have but my old '77 Suburban with the 350 V8 had a small fuel filter right where the fuel line goes into the carb. Remove the fuel line at the carb, fish out the small filter and replace with same. Other than that, a new fuel pump once in awhile was all I ever did in terms of engine work.

I used to have a '77 Wagoneer with the 401cid. The fuel pump was electric but mounted near the alternator. I had constant vapor lock problems. My fuel pump went out in UT and I limped into a Jeep dealer. He put on the new pump mounted upside down so it was up above the engine where it got more cool air flow. It helped but didn't entirely fix the vapor lock on hot days. The engine compartment was so tight that on a hot day I could hear the gas boiling in the carb float bowl. There was no way to keep it cool.

Yep,that is why I put a racing type ice bucket on my old Ford. It was a coil of gas line in side a insulated container that fit under the hood.I would fill it up with ice before I started up a mountian pass

None of my cars or trucks ever required such devices just to gain elevation. And I've towed travel trailers over some of our highest ranges.

I've never heard of the ice bucket thing. Interesting. From here, to get to the mountains involves at least 70 miles of desert. In the summer, the desert is the problem. Once I get to the mountains, I have never had a problem. The problem with the Wagoneer was the tight engine compartment. There was almost no air flow at all in there.

Depends on how old your vehicles were and how big a load you were pulling. Fuel injection stopped all that.The 85 Fords were the last year with carburetors

. I was running about 17,000 pounds which was the truck and a loaded 20 ft goose neck.The fuel line ran up along side the block on the driver's side. I moved it ,but it still ran across the intake manifold which was hot.

That 460 took a lot of fuel.Completely loaded ,I got 3mpg pulling up mountains.Empty, on a good day, I got 8 mpg. It didn't take much to disrupt the fuel flow

I agree.

To the OP:

Try to verify it is a fuel delivery problem. Mechanical pumps either work or they don't. If they fail, they spray gas out the atmospheric vent hole side of the simple diaphragm body.

Fuel delivery issues with a mechanical pump that does not have a bad diaphragm, points to restriction/blockage upstream of the pump. (between pump and tank or tanks)

Often times there are inline filters between the tank and pump, if those become plugged then the pump will starve. Kinks in hard lines, old soft line pieces at the tank outlet, screen sock on the pickup tube inside the tank on the sending unit.

Guys...

Not going to argue with anybody but I want to point out that the OP's truck is carbureted. An elect fuel pump will require a fuel pressure regulator after the pump to knock the psi down in the 6-8 lb range so he doesn't unseat his float needle with high pressure and flood the hell out of his q-j.

It's just not the right answer for this truck.

The original "spurt-spurt-spurt" low psi delivery of a mechanical pump is what works best. Remember, it's feeding a small fuel reservoir (float bowl) that the carb meters from, via squirt, idle bleed and staged vacuum processes.

In my opinion, if you toss an elect pump in there, it will only be the beginning of a full circle journey that brings you back to a mechanical pump and a new piece of 3/8" rubber fuel line back by the tank, or something such.

lol.

Go back and read the OP original post.After the truck runs out the gas he poured down the throat, the truck continues to run and run good.Doesn't that negate and blockage question. Could the float or needle be gummed up and after a little flush out,it clears itself.Maybe the pump is not putting out enough pressure out to clear that.Maybe he needs to try a can of Seafoam

The OP just manually fueled the carb...............