Electric Fuel Pump Mounting Question

[desmondmonster]

Hi everyone,

 

I'm installing an electric fuel pump to act as an auxiliary to the mechanical pump on my '51 B3B to prime the system after spells of inactivity, etc.

 

I had planned to bolt it to the inside of the frame, but heightwise it's about midway up on my aftermarket fuel tank.  I've read that you want your electric pump to be at or below the fuel intake in order to have correct siphon pressure, so I'm concerned that the frame location is not low enough to prevent backflow from the pump.

 

Where have others mounted their electric fuel pumps?  Have people run into trouble when the auxiliary pump is not low enough?  

 

thanks

Desmond

Edited October 2, 2022 by desmondmonster

[Los_Control]

To be honest, not sure you have much choice. I know I would want to keep it along with fuel line protected by the frame.

 

I know when I removed my old tank, there were a few different areas with road rash & 1 patched hole. I would not want a fuel line that low.

I would also guess that as a auxiliary pump it will be just fine, just keep it as close to the tank as you can. Electric pumps are good at pushing not so much at pulling.

Either way your pickup tube still goes to the bottom of the tank And will need to be pumped up & over.

 

I can share my neighbor has a old Ford shoebox, the original tank does not sit as low as our trucks but still pretty low.

He has a later engine with fuel injection that requires a electric pump, it is mounted to the frame. Same story it needs to pull the fuel from the bottom of the tank up & out.

It works with no problems ..... I imagine it will not last as long as a oem installed in the tank but works.

[desmondmonster]

I think you're right that it's best to protect the pump and lines from the road by hiding them in the frame.  I can get the pump pretty close to the tank itself.  If the suboptimal height somehow shortens the pump life I will not lose sleep over it so long as it can do its job of priming my system.  These pumps are not expensive.

 

Thinking about it now, I may be able to put a check valve in line in front of the pump to prevent the fuel from siphoning backwards.  But that sounds like a "version 2" upgrade once I actually experience a problem.

 

Glad to hear your neighbor's setup is working fine.  

[Merle Coggins]

Depending on what type of fuel pump you are using it may already have a check valve built in. The 'clicker' types certainly do. 

I have mine mounted inside the frame just in front of the pump. It seems to work well when ever I need it. 

[bkahler]

 

I installed an electric pump on the cross member that is just in front of the gas tank.

 

 

[desmondmonster]

I'm not sure if the pump has a built in check valve.  online reviews say that the flow is restrictive enough that the mechanical pump can't generate full power and suggest adding a bypass line with its own check valve, so if I need to do that anyway I may as well add another check in front of the pump just to be safe.  what's one more valve?

 

thanks for the input

[bkahler]

I do know the Carter P4070 pump that I used does not have a check valve.  This same pump was used on Airstream motorhomes as a pusher pump used to assist the mechanical pumps on the 454 engines.  Many times the only way owners knew the electric pumps had failed was when they were climbing grades and needed the extra fuel flow provided by the electric pumps.  The engines would sputter their way up the hills.

 

[Los_Control]

4 hours ago, Merle Coggins said:

I have mine mounted inside the frame just in front of the pump. It seems to work well when ever I need it. 

I bet it works just fine, especially for the purpose you installed it.

Also would work for @desmondmonster

 

Reminds back in the late 70's as a kid I had a 1968 chevelle with a worn out 327 .... it had a cam that the lobe for the fuel pump was worn flat and no longer work a fuel pump.

I installed a electric pump right at the original mechanical location, because it was easy for a 17 year old kid with no tools to do.

I was always told later why it would not work, I know it was still working over 1 year later when I gave the car to my sister.

 

Just being used momentarily as a pusher pump to get some fuel into the system when needed .... Probably last for years no matter where you put it.

[desmondmonster]

@Los_Controlout of curiosity, why would a fuel pump fail in this situation?  or fail prematurely?  is it because it runs dry for a bit while it primes the system and that produces extra wear?  or because it doesn't like to "pull" and the extra strain of being above the fuel intake causes additional wear?

 

[Merle Coggins]

The general consensus is that electric pumps are better at pushing fuel than they are at pulling. So the rule of thumb is to always place an electric pump as close to the fuel tank as possible. 

[Los_Control]

Just my opinion, a mechanical fuel pump is good solid old school technology.

Uses a rubber diaphragm to pull the fuel from the tank. .... it still pushes the fuel to the carburetor  as it leaves the pump.

I think it can pull fuel further then it can push fuel.

 

Main thing to remember, a carburetor only wants 3-5 psi fuel pressure to operate properly .... too much pressure will cause problems.

 

A electric fuel pump is modern technology & operate differently using vibration. It simply pushes better then it pulls. .... both push & pull.

The thing about a electric pump is it provides far more fuel pressure then a mechanical pump.

My Dodge caravan only needs 35-40 psi fuel pressure to run .... some cars require 60-90 psi ..... A electric fuel pump can deliver these pressures.

 

So my opinion is, you could probably mount your electric fuel pump on the roof of your truck. Run your fuel lines to it with the other end going across the hood, through the grill directly to the carburetor & it would deliver the 4 psi pressure needed to run your carbureted  engine.

 

Same time if we tried the same experiment on my neighbors fuel injected 302 that needs 60 psi fuel pressure to run .... I doubt it would work enough to even start the engine.

If it did start the engine .... I imagine it could not last for long. Simply working too hard.

 

Moral of the story, there is a proper way to install a electric fuel pump ..... our trucks just do not care. .... I would spend more money on a fuel pressure regulator & simply bypass the mechanical pump if I had 12 volt system & a electric pump.

 

 

 

[Jeff Balazs]

Fwiw. I have been running a full time electric pump for more than 7 years and 30K miles. The arrangement I have is similar to what B Kahler has shown. It has worked flawlessly this whole time. I don't understand why anyone would want a "primer" type system. If the diaphragm in your mechanical pump fails you can wipe out a set of main bearings in a hurry.

Jeff

[desmondmonster]

@Jeff BalazsI've wrestled with the question of "if I'm going to put in an electric pump anyway, why bother keeping the mechanical pump?"  It is redundant and is an extra point of failure (although these things are pretty reliable these days).  In my case I just rebuilt the mechanical pump so I am not worried about the diaphragm leaking.  My electric pump delivers the correct 3-4.5 psi without a regulator.  And it's not clear how necessary a primer system is if I drive the car at least every two months.  So I could easily either keep the stock setup or go full-on transition.  But why do both?

 

For me the answer is emotional and aesthetic - I think it's cool.  Having the original mechanical pump looks sweet with the floating glass fuel bowl and the stone filter out in the open.  I don't want to lose that.  Including an auxiliary electric pump gives me another switch to toggle when I start the truck (awesome) and gives me the feeling that my system is overall slightly more reliable, whether it actually is or not.  If feels like an upgrade.  It is also Something To Do, which is essentially why I bought this truck in the first place.

 

From a logical point of view I can appreciate the strangeness of this endeavor.  If the setup gives me problems I'll probably go with a simpler approach.  For now I'm just chasing the feeling of "this will be fun."

 

 

[Los_Control]

Just another option that I plan to do with my fuel line.

The electric booster pump is often used to fix a vapor lock condition. Modern fuel heats up & turns to vapor.

When you are at a idle or driving slow, the float will close off the fuel to the carb & it sits in the line above the exhaust manifold & heats up.  So while you are driving around the parking lot looking for your parking spot, you park & shut off the engine .... The already hot fuel now gets heat soak from the engine and can turn to vapor.

No fuel in the system when you go to start it. .... The booster pump is a easy way to replace the fuel ... not really a "fix" though. .... You are not fixing anything.

 

Newer vehicles   started in the 1970's??? started running a return line to the fuel tank. This will allow the fuel to keep flowing & not sit & heat up.

I'm using nickel/copper for fuel lines, I have a glass filter right before the carb I will add a brass T between filter & carb. Then run a line back to the tank.

My new tank has a block off plate where I could easily add a fitting for the return line. ..... Key thing is to use a smaller return line to provide some resistance. So the carb will get priority fuel, the return just takes excess.

 

I got the idea from Tony of Uncle Tonys Garage where he showed a trick adding a fuel filter with 2 outlets, 1 being a return line & how the factory did it on some vehicles.

I think the engine would be happier getting cooler fuel, I feel like I'm fixing something by adding the line.

Imagine being in a local home town parade going 1 mph stop & go & hit with vapor lock ..... there is a reason why car manufacturers added a return line.

 

For me it just seems natural to add the line. When my truck gets out of paint jail & I install my tank & run the lines, I already have the line & T ... It is just 1 extra step.

 

As far as using a booster pump to start the truck after sitting a few months, I do not plan on letting it sit that long.  

[ggdad1951]

I've never had vapor lock, even on 95°F days.

 

[Los_Control]

Just now, ggdad1951 said:

I've never had vapor lock, even on 95°F days.

 

Excellent point. Yet some people seem to be plagued with it. .... My truck has never been out of the driveway so I wont know.

It seems to be a topic that comes up often enough & a electric booster pump on a toggle switch is a easy peasy cure.

It is not just this forum but other forums with older cars. Often enough youtube videos are made about it.

 

I wonder what conditions are needed to actually cause a problem.

We know heat causes the fuel to turn to vapor .... just physics, some engines will run hotter then others. Cylinder bores, headers, cams, radiators .... every engine is different.

 

Then there is ambient temperature, while 95 is very warm especially with heavy humidity. We had over 100 straight days this summer over 100°F typically 108-110.

But it is a dry heat  ???

 

I wonder if altitude also plays a roll?    

At sea level, water boils at 212 °F. With each 500-feet increase in elevation, the boiling point of water is lowered by just under 1 °F. At 7,500 feet, for example, water boils at about 198 °F.

I wonder at what temps fuel boils?

 

I just feel I'm not smart enough to solve the problem for everyone. I do not even know if I have a future problem .... I have simply convinced myself that a proper fuel system deserves a return line.

Like adding a 2 stage brake master cylinder ... it is a improvement on a older vehicle.

 

All ya all you do you .... Like buying a fire extinguisher I sure hope you never need it. Sure is a good feeling knowing you have one.

 

I think where @desmondmonsteris at and asking advice about his fuel line installation .... Just another option & real easy to do now ... more difficult later.

[Merle Coggins]

I've experienced it a couple of times after an extended run on the highway on a high 90's type day. It was fine as long as I had good air flow through the engine compartment. Once I got off the highway and was putting through town it would start to stumble and struggle to run. I recognized it as fuel starvation from high temps under the hood and switched on my "primer pump". The engine smoothed out and ran fine again. After a few minutes the temps under the hood stabilized and I was able to switch off the pump. 

[desmondmonster]

sometimes I wonder if "vapor lock" is just a catchall for "gremlins are preventing my truck from starting".  I've experienced the phenomenon on my motorcycle if I've been at highway speeds, suddenly pull off and stop the bike, wait 10 mins, then try to start again.  It does not want to start and I'll crank for ~30 seconds before it catches.  And that has an electric fuel pump (and carbs, FWIW).

 

back to the topic, the question remains of "if an electric pump will solve the vapor lock problem, then why keep a mechanical pump at all?".  For me it still comes down to "because it's original and cool."  Anyone got any other reason?

[Los_Control]

I like @keithb7opinion on the subject .... he really does explain well what is going on ..... I also would simply add a electric fuel pump if I had a running driving vehicle.

I really am lazy, I would not drop a fuel tank and rebuild a fuel system when I could just add a electric pump ... Call it a day and move on.

 

 

Since I do need to build the rear tank mount, make the lines .... I think to myself how can I make it the best job I can do .... I'm thinking that adding a return line will take another hour or two .... What if that actually fixes the problem so a booster pump is not needed?

 

This video sold me on the idea.

 

 

What I do not like in either of the video's is Keith shows the quick fix & mounts the booster pump on the firewall & proves it works .... you will be fine mounting yours near the tank.

 

Tony he shows how to avoid the problem period. .... He claims 95% of the time. Not 100%  ..... 2 totally different videos.

1 How to approach it after the problem occurs.  Other to show you how to prevent the problem from happening.

 

Neither video shows them as ascetically  correct. .... I have a kit I have to put together ..... "I BELIEVE"  I can create a period correct looking fuel system with a return line.

 

 

 

[Bobacuda]

I recently installed an inline pump (from Brock) on my B4B.  Wish I had done it when the cab and bed were off, but I got it in, no leaks, and it appears to be working.  The brown wire is the ground on our positive ground vehicles.  I ran the hot wire to a toggle switch and then to the amp post on the ignition switch.  It would have been easier to run it direct to the battery, but I wanted to make sure that the key switched it off.

 

There is damn little room to work with.  Buy about 3' of fuel line and good clamps.  I had to cut out about a 7" piece of the metal fuel line, and I installed a larger fuel filter.

The instructions say to put a "slight flare" on the ends of the metal lines - no kidding, make it slight unless you like filing metal flares until they are small enough to get inside the rubber fuel line.  it all fits inside the frame.

 

Anyhow, If I can get a photo to attach, I took one to show you.

 

[Jeff Balazs]

On 10/4/2022 at 10:06 AM, desmondmonster said:

@Jeff BalazsI've wrestled with the question of "if I'm going to put in an electric pump anyway, why bother keeping the mechanical pump?"  It is redundant and is an extra point of failure (although these things are pretty reliable these days).  In my case I just rebuilt the mechanical pump so I am not worried about the diaphragm leaking.  My electric pump delivers the correct 3-4.5 psi without a regulator.  And it's not clear how necessary a primer system is if I drive the car at least every two months.  So I could easily either keep the stock setup or go full-on transition.  But why do both?

 

For me the answer is emotional and aesthetic - I think it's cool.  Having the original mechanical pump looks sweet with the floating glass fuel bowl and the stone filter out in the open.  I don't want to lose that.  Including an auxiliary electric pump gives me another switch to toggle when I start the truck (awesome) and gives me the feeling that my system is overall slightly more reliable, whether it actually is or not.  If feels like an upgrade.  It is also Something To Do, which is essentially why I bought this truck in the first place.

 

From a logical point of view I can appreciate the strangeness of this endeavor.  If the setup gives me problems I'll probably go with a simpler approach.  For now I'm just chasing the feeling of "this will be fun."

 

 

Well if I were totally convinced that the original fuel pump was a reliable solution I certainly would not have bothered modifying my truck.

The thing is that they were probably fine back in the day but fuel formulations are radically different these days. I know of several people who have found out the hard way what can happen when their rebuilt pump has a catastrophic failure. Just so you know it has happened to folks on this forum not to mention guy's I know that have other sorts of vehicles. When that diaphragm fails the path is open straight into the oil sump. 

 

If you do a bit of searching you will find other issues with these pumps as well. I won't go into a lot of detail but several L6 owners have had the arm come off. And then there are the very common over heated fuel / hard starting issues that many folks have experienced.

 

Personally I think this should be enough for owners to "re think" the fuel delivery system on these engines. I suppose if I only used my truck once in a while and on lightly used secondary roads I might be able to look past all this. But quite frankly it would be just asking for problems here in the very heavy traffic I am regularly in.

 

I do get why one might want to retain the original look of the components. I think if I were at all concerned about this I could come up with a fix that looked right but did not actually function as the old system does. Falsies if you will. 

 

I am sure I will probably take some flak for this. That is ok.....I get it. But I think stuff like glass bowl fuel filters belong in a museum and not out on the road.

 

Jeff

 

 

 

[Bobacuda]

I installed the elec fuel pump upstream of the mechanical fuel pump for 3 reasons:

1.  A new Airtex pump made it about 2000 miles before the pin fell out of the arm. Fortunately, that was at my house. 
2.  The replacement Carter fuel pump made it about 500 miles before that same damn pin worked loose. I was about 75 miles from home, I tapped it back in and it mostly held up till I got home. I tapped the pin all the way back in, smeared epoxy over the ends of the pin, then cut some metal tabs that fit under the mounting bolts that I hope cover the ends of that damn pin good enough to keep it in,  but everyone in the family worries about getting stranded on a road trip. 
3.  Drive it for awhile, get it hot,  then forget about it starting until it cools down, and even then you have to crank it quite a while to move gas through the system.  Prior to the electric pump, It has left me stranded for hours among the inconvenient laughs from my friends. 
 

So, the electric pump is there in the event of another mechanical failure. I have to road trip it and try starting it hot, but it is definitely starting better cold. 
 

And before anyone wonders, I am only running non-alcohol gas in it. I used the standard corn piss when I first rebuilt everything, and the gas would evaporate from the carb and leave a sticky residual. The non-alcohol gas fixed that.