Moparts
Can I run a mechanical and electric fuel pump?
Posted By: VITC_GTX
Can I run a mechanical and electric fuel pump? - 06/16/08 04:30 AM
My GTX keeps vapor locking after I turn it off (fuel boiling out). I'm currently running a Holley mechanical pump, Eddy RPM Performer and Holley 750 DP. I have used an electric fuel pump before (Carter super pumper) and it was soooo loud, so I don't like it.
Can I put a "cheap" electric fuel pump in line with the mechanical pump so when I turn it off and the fuel boils out I can just flip a switch and turn the electric on to get it started? Will the mech pump let the electric pump through it?
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:31 AM
yup
Posted By: goldmember
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:44 AM
You can,BUT, if the diaphram in the mechanical pump were to rupture you'll have a mess.
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:48 AM
How much would the cheap electric fuel pump restrict fuel flow when using the mech pump?
Posted By: goldmember
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:53 AM
I'm not sure. I assume this is a big block car and you've tried the conventional approaches to the problem?
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:54 AM
440 car. No, I haven't tried anything else. I can't do a spacer (air grabber hood). What else would help?
Posted By: goldmember
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:00 AM
Insulating the fuel line(steel lines?) can be a big help. There used to be an aluminum heat deflector(thin) that the GM dealer sold for the 69 Z/28 (holley carb)that can possibly be a help. Jegs might have the same type piece. Jegs PN 510-108-70 is the same item.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:06 AM
I used to do this, but there are some issues. You of course should mount the electric near the tank. However, with the mechanical only, the restriction through the non-operating electric will cause a drop in the suction line, and could CAUSE vapor lock. You might be better off just running both all the time.
Your GTX is a '70? If so, you should already have the necessary vent lines to hook up a "vapor return" system like my six-pack had. I'm a HUGE believer in these. I don't remember the part no. but Wix (NAPA) should still make "universal" filters with a vapor return fitting. You simply mount the filter with the vapor return "up" and plumb the small line to a return line back to the tank.
If your car came with a tank carbon canister system, you should have a line already under there that you can "tap" into.
Also check for ANYTHING that can restrict the suction side, which will aggrevate the vapor lock condition.
Is the tank/ cap properly vented?
Are the suction hoses in good shape, and not collapsing?
Any chance the feedline is rusted, leaky?
How about the suction screen in the tank?
You should test the pump for proper suction (vacuum), pressure, and volume. Vacuum/ pressure test gauges just aren't all that expensive at any parts store.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:21 AM
he said to help with a vapor lock problem.. so yah it'll work. going down the 1/4 mile it'll work. continuous use,
it won't work.
Posted By: 440trk
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:30 AM
Quote:
he said to help with a vapor lock problem.. so yah it'll work. going down the 1/4 mile it'll work. continuous use,
it won't work.
Why would it not work for continuous use? 
Running an electric to feed the mechanical is an old trick...and they worked fine under continuous use. The only problems I'm aware of is the extra noise from the electric pump and (as mentioned) if the diaphram in the mechanical fails, the electric will pump fuel directly into the crankcase.
Posted By: goldmember
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:34 AM
Correct.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:40 AM
Quote:
...if the diaphram in the mechanical fails, the electric will pump fuel directly into the crankcase.
bingo
Posted By: AlexP
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:41 AM
I have a Carter 4601 HP electric pump on my car with a recirculating system. On a quiet day, I can barely hear the pump running with the engine off.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 06:19 AM
This scare nonsense about pumping gasoline into the pan if the mechanical pump fails is silly--because--
The mechanical pump is no more prone to fail whether you have an electric pump inline or not, and--
If the mechanical pump diaphragm ruptures, it will STILL pump gas into the pan, whether you have an electric pump or not!!! You are just as likely "not" to notice the problem, either way.
The body of my old '70, as well as my '64 Polara 426 had thousands of miles on them this way, and I never had a problem.
Posted By: Joshs68
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 06:44 AM
yup,
I run 2 pumps on my charger,
also ran 2 pumps on an f250 years ago,
works fine.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 01:05 PM
there is ZIP, ZERO, & NOTTA need to run a auxillary fuel pump during normal cruising. so why take the chance?
BUT hey.. do what you want.
Posted By: DaytonaTurbo
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 03:27 PM
I don't know what these pumps are you guys run that are so loud. I put a walbro 255 in my brother's rampage. It's it's the hi-pressure version of the walbro 255, and an external in-line unit. It's the highest overall flowing 255 series pump made by walbro. And with the little dinky 2.2 running, I can't even hear the pump running. Someone has got to make a good flowing, low psi pump for carb apps that isn't overly loud. Run it with a return-style regulator and it'll both keep your fuel cold and evacuate any vapors out of your line. And it'll fill your carb bowls right back up before you even turn the key. Seems like a no-brainer to me if you've having evaporation and or vapor lock issues and cannot solve them.
Posted By: BobR
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 03:28 PM
I haven't used a mechanical pump since 1974. When you can afford to do it right get a good electric pump with a return style regulator. Throw the mechanical in the trash and drive anywhere you want. -Bob
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 03:32 PM
Good info guys, keep it coming.
I think my problem with noise was my gas lines, not the pump. Let me explain, I had the pump mount isolated with rubber and actually hung the pump by plastic wire ties from the mount and the noise did not change. I can really hear it coming from the left rocker area (where the fuel lines are). I put rubber hose around the metal lines along the length of the car but that did not help. I think it the volume of fuel flowing through the lines that's making the noise, not so much the vibration of the metal lines. Maybe I should try another type of electric pump.
I don't have a regulator but I do have a return line.
Posted By: beepilot
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 04:42 PM
Some electrics are noisy...the Holley Blue I had for one. That was a noisy brute. It was an older one , maybe the new ones aren't as bad. My new Mallory 110 is whisper quiet. I also have been running electric and mechanical for decades. Like someone mentioned, I go weeks sometimes without driving my car and I just let the electric fill the carb a few seconds and it fires up immediately. I also run the return line. No problems.
Posted By: 540challenger
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 05:30 PM
Quote:
I don't know what these pumps are you guys run that are so loud. I put a walbro 255 in my brother's rampage. It's it's the hi-pressure version of the walbro 255, and an external in-line unit. It's the highest overall flowing 255 series pump made by walbro. And with the little dinky 2.2 running, I can't even hear the pump running. Someone has got to make a good flowing, low psi pump for carb apps that isn't overly loud. Run it with a return-style regulator and it'll both keep your fuel cold and evacuate any vapors out of your line. And it'll fill your carb bowls right back up before you even turn the key. Seems like a no-brainer to me if you've having evaporation and or vapor lock issues and cannot solve them.
The loud pumps are those holleys, But once the car is running you usually don't hear them over the engine.
Posted By: blairboy3
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 06:00 PM
I've got the new Holley HP150 w/ the gearotor style pump. It's pretty dang quiet. Can't hear it over the engine, and just a bit of a hum when the engine is off.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 08:30 PM
rubber isolate the pump.. problem solved.
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 08:36 PM
Quote:
rubber isolate the pump.. problem solved.
Been there, done that, no help. See my post above. I even hung the pump from plastic wire ties (from the rubber isolated mount) to isolate it. I think most of the sound is coming from the metal fuel lines.
Posted By: Anonymous
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 08:43 PM
get out the drill/drill bits, goto home depot or whereever get some rubber isolated line holders (forgot the tech name for them),
install them to keep the lines off the frame. reroute if you have to. prob solved again.
Posted By: BSB67
Re: Can I run a mechanical and electric fuel pump? - 06/16/08 10:53 PM
Quote:
My GTX keeps vapor locking after I turn it off (fuel boiling out).
Can you restate exactly what the problem is or the symptom(s) and any evidence for your conclusion. This description sounds possibly like two completely different issues.
Posted By: RapidRobert
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 12:49 AM
Quote:
Quote:
My GTX keeps vapor locking after I turn it off (fuel boiling out).
Can you restate exactly what the problem is or the symptom(s) and any evidence for your conclusion. This description sounds possibly like two completely different issues.
ding ding ding we have a winner. You have too much heat in the intake/carb.yes properly setting up an electric to fill the bowls for the next days restart is good but it's about solving the real problem. heat riser? lower temp 'stat? blocking the crossover. cooling system mods? PS I think a carb spacer(wood not alum) would be a major help. Would it be possible for you to run one if you went to a lower height drop base aircleaner?
Posted By: blairboy3
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 01:17 AM
Changing from an Edelbrock (Fuel bowl sits on the manifold) to a Holley (fuel bowl up & away from he manifold) would solve the problem too! Plus, Holleys are better
Posted By: mkdart
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 01:27 AM
I run an 3 prong filter.One in/2 out,the 2nd outlet vents to the tank. Works for me.
Mike
Posted By: MoparforLife
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 01:28 AM
Quote:
If the mechanical pump diaphragm ruptures, it will STILL pump gas into the pan, whether you have an electric pump or not!!! You are just as likely "not" to notice the problem, either way.
I don't know what train of though that this comes from but --- 
-- If the diaphram ruptures in a mechanical plum there is no fuel going to be pumped to get into the oil pan,. The only way fuel will get int tthe pan is if the the vehicle gets parked in such a way as to have the tank at a level that is higher than the fuel pump location and the fuel can syphon out. This is entirely possible and I have seen it happen many times just taking the lines off to put on a new pump but to pump the fuel forward with a broken diaphram is obsurd. Pumping the fuel into the pan with an electric pusher is entirely possible and plausible.
Posted By: 340727dart
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 02:12 AM
I have such a setup on my '73 Dart Sport. I've got the Carter street mechanical pump and a Carter street electric pump with 3/8" fuel line.
Since I only drive the car about once a week, the fuel has evaporated out of the carburetor when I try to start it.
I turn on the electric pump for 15 to 20 seconds, pump the gas pedal once (no choke), and the engine fires right up.
I'll let the electric pump run for a few more seconds after the engine is running then shut it off before I start driving.
Posted By: MoPar Jamie
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 03:27 AM
I'm running a Mr. Gasket HP pump (4-7 PSI I think) in my '86 D-150 along with a mechanical pump. Reason being that the cam lobe is worn out on the 400 so it wouldnt pump fuel. I left the vent line and the return line open and ran a conventional filter. Worked fine for me. BTW I mounted the pump on the frame under the bed, halfway between the tank and mech. pump. Had two holes already punched there and they worked great for mounting.
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 03:27 AM
Quote:
Changing from an Edelbrock (Fuel bowl sits on the manifold) to a Holley (fuel bowl up & away from he manifold) would solve the problem too! Plus, Holleys are better
I have a Holley 750 double pumper on the car now.
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 03:28 AM
Quote:
I run an 3 prong filter.One in/2 out,the 2nd outlet vents to the tank. Works for me.
Mike
I have the return line on the filter also (3/8" in and out with a 1/4" return to tank).
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 03:34 AM
Quote:
Quote:
Quote:
My GTX keeps vapor locking after I turn it off (fuel boiling out).
Can you restate exactly what the problem is or the symptom(s) and any evidence for your conclusion. This description sounds possibly like two completely different issues.
ding ding ding we have a winner. You have too much heat in the intake/carb.yes properly setting up an electric to fill the bowls for the next days restart is good but it's about solving the real problem. heat riser? lower temp 'stat? blocking the crossover. cooling system mods? PS I think a carb spacer(wood not alum) would be a major help. Would it be possible for you to run one if you went to a lower height drop base aircleaner?
Boy do I have a heat problem under the hood. I can not even touch the air cleaner within the first 30 minutes or it will blister my fingers.
I have no heat riser and I can not change the air cleaner (I have an Air Grabber hood), this means no spacer.
I haven't tried changing the stat or redoing the cooling system. I have a stock rad/clutch/fan/shroud. Keeps me under 210 on the road (including stop and go traffic). The under the hood temp is amazingly high, been that way since I've owned it.
Not sure what to do, I want to keep the stock look if possible but don't know how to bring the temp down under the hood.
Posted By: RapidRobert
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 06:50 AM
Van I was wondering if your bathtub intake gasket has open crossover passages & if your timing is in the ballpark?
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 02:54 PM
I don't know if the cross over is there or not. I have an Eddy 440 Performer manifold ( I need to check and see if it even has a cross over).
My timing is setup by Don at FBO. I believe it's 18 intitial, 36 total (close to that).
I wonder if replacing the fan with a fan that does not have a clutch would help keep the under hood heat down
Posted By: RapidRobert
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 03:02 PM
your timing is good. I'd be willing to bet my last $ that changing the bathtub gasket to a closed one would solve alot of this & a wood carb spacer would be nice but no way around that at this point in time.
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 04:20 PM
Thanks for the help.
I will add "Install new valley pan" to my to-do list.
Posted By: GTXKen
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 06:36 PM
My GTX runs hot as well but I didn't use my airgrabber hood and run a 2" spacer.
I am waiting for my new distributer from Don at FBO and I hope that helps. Don thiought it would but obviously it didn't help you.
I just installed a high flow thermastat and that helped a lot. I also moved my fuel line from the stock route to a braided line from the feed to the fender and down to get it away from the block.
I think adding another fuel pump is just masking the problem, a new thermastat is like 10
Posted By: VITC_GTX
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 07:38 PM
What thermostat are you running now, 160?
Posted By: GTXKen
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 07:58 PM
I'm still running a 180, its just a high flow rather than the $2 parts store crap. I don't want to lower the opperating temp for those cold days, don't want to make sludge.
Posted By: blairboy3
Re: Can I run a mechanical and electric fuel pump? - 06/17/08 08:18 PM
Quote:
Quote:
Changing from an Edelbrock (Fuel bowl sits on the manifold) to a Holley (fuel bowl up & away from he manifold) would solve the problem too! Plus, Holleys are better
I have a Holley 750 double pumper on the car now.
I'll read the WHOLE post next time!
Posted By: GTXKen
Re: Can I run a mechanical and electric fuel pump? - 06/19/08 03:44 PM
Quote:
My GTX runs hot as well but I didn't use my airgrabber hood and run a 2" spacer.
I am waiting for my new distributer from Don at FBO and I hope that helps. Don thiought it would but obviously it didn't help you.
I just installed a high flow thermastat and that helped a lot. I also moved my fuel line from the stock route to a braided line from the feed to the fender and down to get it away from the block.
I think adding another fuel pump is just masking the problem, a new thermastat is like 10
I'm quoting myself 
For the record I got my distributer from Don at FBO 16 initial 35 total, set the timing and then sit the idle mixture and my car now runs at 180 even while running in the garage at 3200 RPM to check full advance, went for a drive and pulled back in the garage and its running at 180. I'm returning the radiator I bought.
I'd take a hard look at your timing. Are you running vaccum advance to help it idle?