Mechanical or electric fuel pump.

[tanglediver]

I have a basic question, in my carb'd '73 chevy, I only have an electric fuel pump. I have been having the engine cut out on me. That pump is about 3 years old and I was told by my regular go-to mechanic that I would be better off with a mechanical pump as the main pump. His opinion is that an electric does ok as an auxiliary, but he doesn't trust them to run constantly. Does anybody have a good take on fuel pumps? Maybe I should put a stock pump back in, the engine is fresh from a crate within the last two years.
Thanks!

[Oldiron2]

The newer fuel-injected cars use electric pumps at much higher pressure and with very few problems, so electric pumps aren't inherently worse. It just depends on the brand/quality of pump you use. I think that some are very good but can't recommend one. I have an auxiliary (bypass) pump in a truck to use when one tank runs dry and I'm switching to the other, and the main problem I have had is the diaphragm didn't last as long when California required MTBE in the fuel. I also have one NOS mechanical pump for the truck.
BTW, there used to be one fellow who's company rebuilt nearly all the old mechanical pumps for NAPA, CarQuest, PepBoys, etc but about a year ago, he quit supplying them while trying to sell his business and finally retire. Has anyone tried to find any old rebuilt fuel pumps lately?

[daddy]

Danny, My two cents is that either one is probably fine if it delivers the volume and pressure needed to make her go. My 79 chevy still runs a mechanical pump with no problems, but I remember years ago helping my dad with his 78 ford, where we went electric, and never looked back.
I would rig something up to check the pressure and go from there.

[lewray]

Danny, My two cents is that either one is probably fine if it delivers the volume and pressure needed to make her go. My 79 chevy still runs a mechanical pump with no problems, but I remember years ago helping my dad with his 78 ford, where we went electric, and never looked back.
I would rig something up to check the pressure and go from there.

My 79 toyota FJ uses a mechanical pump. Replaced it once 10 years ago and provides plenty of pressure; infact, I installed a fuel regulator...just my 2 cents

[tanglediver]

OK, thank you very much! It sounds straight forward enough. I found a Jegs pump online for $45.00, but I will check with my regular wrench first, because I value his service! :p


BTW, if you ever have to push your '73 Chevy when it goes on strike, get help, they're reeeeeally heavy those chevys. :rolleyes:

[farmersamm]

I've tried both on my old Dodge.

I was having the same problem as Oldiron2. When one tank ran dry, and you were'nt going at near highway speed, the mechanical pump wouldn't run long enough to draw from the fresh tank before the truck rolled to a stop. Then trying to draw with the mechanical pump would sometimes leave you with a dead battery because it just wouldn't do the trick at cranking RPM.

I switched to a solely electric pump. They seem to last only about a year or so, no matter who makes 'em. Square, and cannister type. They seem to last even less if the truck is operated at idle for longer periods. No pressure regulator, and the thing still tries to pump like mad.

Switched back to a mechanical pump this year, after about half a dozen of the electrics. I keep a can of starting fluid in the truck for when I run out of gas on one tank. It gives the engine enough run time to pull the gas.

Oldiron2's bypass sounds like a good alternative, but I don't know how long the diaphrams last with the Ethanol crud we have to buy nowdays.

[Oldiron2]

Farmersamm, I had driven that vehicle enough in the 'old days' that I could tell by the gauge, within about a mile, when I was going to run out; but just to make things easier, I put a small pressure switch in line between the pump and the carburetor. That way, a light comes on to tell when the fuel flow stops but the carb. is still full, so I can switch before the engine quits. The pressure switch was surplus electronic gear and uses a metal accordion-style diaphragm, so isn't bothered by any type of fuel. Wish that were true of the pumps.

[Rojodiablo]

One thing of note with an electric pump: If the pump is a submerged unit, in the gas tank, try to always keep at least 1/8-1/4 tank of fuel load. The pumps are cooled by the gas they are sitting in, and they will run hotter when fuel level is low. Also, running them dry is a real problem, as they overheat rapidly. And, unfortunately, an electrical pump will run the entire time the key is turned, so you can burn it up sitting there waiting with the ignition on, while out of gas.

[STwelder]

Any electric fuel pump should be as close to the gas tank as possible ( unless it's an in tank pump) which we are not talking about here. The further away from the tank the harder the pump has to work.
To far away and it will vapor lock ( create a vacuum and wont pump until pressure in tank equalizes).
So make sure it's as close to the tank as you can get it.

[David R]

Both will work. Some of the 7 psi electric pumps pulse the fuel and can drive the float down when it shouldn't be. A 4 psi pump does the trick quite well.

I would go electric and keep a spare.

Mechanical ones are fine. I have seen a few where the drive on the camshaft wears down and the pump looses stroke so the volume goes down.

Cheby mechanical fuel pumps are a pain in the azz to change.

I wouldn't spray either into a hot engine. Its kinda rough on it. Plain ol gas works fine to get the pump to pick up the fuel.

David :)

[farmersamm]

Both will work. Some of the 7 psi electric pumps pulse the fuel and can drive the float down when it shouldn't be. A 4 psi pump does the trick quite well.

I would go electric and keep a spare.

Mechanical ones are fine. I have seen a few where the drive on the camshaft wears down and the pump looses stroke so the volume goes down.

Cheby mechanical fuel pumps are a pain in the azz to change.

I wouldn't spray either into a hot engine. Its kinda rough on it. Plain ol gas works fine to get the pump to pick up the fuel.

David :)

I did the gasoline thing once.

Here I am on the side of the highway, goin' nowhere fast, and I whip out the ol' gas can.

Put a few glugs down the carb, got back in, and hit the key.

Damn engine backfired up thru the carb, and it was all downhill from there:laugh:

I guess maybe I put a little too much gas in there. We're talkin' a real short mini fireball kinda like a little A Bomb. Then the thing settled down to burn nice and steady.

Dog's goin' Ape S###, and I'm just about doin' the same.

The fire was still confined to the carb, so I figured I'd real fast throw the air cleaner lid back on to kill it. Guess I was a little nervous, and half azzed missed, only got it halfway on. Now the lid's too hot to handle.

Long and short of it is...... My ex wife bought me this really nice Carhart lined jacket with a hood and all. It saved the day, but gave its life in the process. So now I not only don't have the wife anymore, I don't have the coat.

Thank God it wasn't Summer, or I'd of had to put my pants on the fire.:laugh::laugh:

[David R]

So farmersam, you lost your coat and wife. I lost my shirt....... :)

Gas in a pump oil can works great :)
OR I put a little in the plastic top of a spray can and pour it in. Never from anything bigger. You know why.

Then there was the guy working on a 64 cheby van with the motor inside between the seats. He put some gas in a coffee can, poured some in the carb and put the can between his legs. Fired up the van..... It backfired...and well.....

David :)

[farmersamm]

Experience is a great thing if it doesn't kill ya:laugh::laugh:

Own a truck for 30yrs., and you see it all:laugh: Puts me in mind of when the wiring under the dash caught fire near Limon, CO on I-70 at 2 in the morning. Another story for another day:rolleyes:

[boatbuoy]

One thing of note with an electric pump: If the pump is a submerged unit, in the gas tank, try to always keep at least 1/8-1/4 tank of fuel load. The pumps are cooled by the gas they are sitting in, and they will run hotter when fuel level is low. Also, running them dry is a real problem, as they overheat rapidly. And, unfortunately, an electrical pump will run the entire time the key is turned, so you can burn it up sitting there waiting with the ignition on, while out of gas.

the factory installed pumps only run for approx 8 seconds if the oil pressure sender does not see pressure. this is a safety feature to keep the pump from feeding a fire in case of accident. also,do you really believe that the auto companies would be stupid enough to put an overheating pump inside the gas tank? and then not recommend a minimum fuel level? if you run out of fuel and the engine quits so does the pump.

[Tractapac]

the auto companies ..... stupid enough

I can't see any links there!!

[MarkBall2]

If you have a carb on the truck, just a bit of gas in the vent tube will fill the fuel bowl enough to get er runnin.

If no carb, about a cap full of gas should do the trick. Cap off a WD-40 spray can that is.

Everybody keeps WD-40 in their vehicles don't they?

[Rojodiablo]

the factory installed pumps only run for approx 8 seconds if the oil pressure sender does not see pressure. this is a safety feature to keep the pump from feeding a fire in case of accident. also,do you really believe that the auto companies would be stupid enough to put an overheating pump inside the gas tank? and then not recommend a minimum fuel level? if you run out of fuel and the engine quits so does the pump.

It was what the diesel mechanic told me; he said if you run them dry, the seals get hot and damaged quickly, and the pumps will fail. I do know that the fuel pumps on my boats are the same way; we run them dry, and they are a pain to get going again. Run them dry several times, and they fail.

The oil pressure relay sounds correct in function to me, so I can understand that part perfectly. Thanks for the info on that.

[farmersamm]

It was what the diesel mechanic told me; he said if you run them dry, the seals get hot and damaged quickly, and the pumps will fail. I do know that the fuel pumps on my boats are the same way; we run them dry, and they are a pain to get going again. Run them dry several times, and they fail.

The oil pressure relay sounds correct in function to me, so I can understand that part perfectly. Thanks for the info on that.

The owners manual that came with my 94 F-150 said, in big letters DO NOT LET GAS GET BELOW 1/4 TANK, or something to that effect. They build 'em, and we have to live with 'em:laugh:

Who on God's Green Earth doesn't let the tank go low? And it does mess up the in tank pumps!! Got $300 anyone?:mad:

BTW-- Hope you, and yours, aren't near the fires:waving:

[tanglediver]

Well that electric pump is done. I'll get another one installed first and then see about a reconfiguration with an OEM style mechanical pump in parallel. That will leave the electric pump as a back up. :blob3:

Man, something stinks like gas around here! :confused: :realmad:

Edit:- Oh, the smoke was thick saturday morning when one or another of them blazes started just south from here. It is a bad situation.

[Oldiron2]

Any poison oak where the fires are? If that gets into the smoke, and people breath it, you'll see sick people throughout the whole valley.

[tanglediver]

Maybe, that smoke is all bad if you ask me.

[Magnetic Mechanic]

I did the gasoline thing once.

Here I am on the side of the highway, goin' nowhere fast, and I whip out the ol' gas can.

Put a few glugs down the carb, got back in, and hit the key.

Damn engine backfired up thru the carb, and it was all downhill from there:laugh:

I guess maybe I put a little too much gas in there. We're talkin' a real short mini fireball kinda like a little A Bomb. Then the thing settled down to burn nice and steady.

Dog's goin' Ape S###, and I'm just about doin' the same.

The fire was still confined to the carb, so I figured I'd real fast throw the air cleaner lid back on to kill it. Guess I was a little nervous, and half azzed missed, only got it halfway on. Now the lid's too hot to handle.

Long and short of it is...... My ex wife bought me this really nice Carhart lined jacket with a hood and all. It saved the day, but gave its life in the process. So now I not only don't have the wife anymore, I don't have the coat.

Thank God it wasn't Summer, or I'd of had to put my pants on the fire.:laugh::laugh:

If you ran out of gas as often as I do - you would know to use a few drops of gas and when it blows crank the hell out of it. Sucks the flames into the manifold and saves the paint.

[Tractapac]

I had a '73 Subaru with an electric pump that ran for well over 100,000 miles, out lasted the engine. Parted the car out eventually and if I scratched around in the garage and found it, I'd be confident of it going still. It was mounted at the front as a "puller". I've an '83 Golf GTi injected and it's done 150,000 miles and nothing's ever been done to the pump. Replaced the relay that controls it but not the pump. Holley Blue Top pump on a 350 chevy in a jet boat, seems ok but doesn't do a lot of work in comparison to a vehicle. I've used the solenoid type, small squarish pumps in vehicles I've modified (usually as "pushers") and not had any problems except with a locally made copy of a Lucas pump.. When modifying, the electric pump has replaced the standard pump in order to feed twin Dellorto carbs.

When fault finding, the electric pumps give more hints as to whether they're picking up or have picked up fuel. The tick tick or clatter of a solenoid or the whirring of a rotary and the change of sound as they fill the carb and fight the needle valve. On the other hand I've had and seen lots of engines with mechanical pumps that have gone the distance too. On the 350 in the boat, I doubt the original pump was designed to feed a four barrel Holley, so that and an HEI dizzy and I know when I'm a little way offshore that I can hear if I've got fuel at the carb and with the HEI, there's a better chance of a spark than there was with the original dizzy that would occasionally close up the points. Turn the key on, listen for the carb to fill, hit the start button and wait for the rumble.

I find it amazing if auto manufacturer's have tanks and pumps that can't be run dry, without a safeguard for the life of the pump. Maybe it's questionable whether they should be bailed out currently?

[quietlikeachurch]

Mechanical fuel pump all the way...'62 Chevy Corvair Coupe...keep a spare in the trunk, you know, in the front...if the installed pump fails, just loosen three bolts (look out for the gas spillage), remove, and stick the new one in! It's right next to the generator (NOT alternator yet)!

-Ian

...and keep a bunch of starter fluid handy!