fuel pump

[andrew]

Hi folks,

I want to install an electric fuel pump on my 1970 SIIA 2.25. I'd like it to be on its own switch, so I can use it on startup only, and I plan to install it in parallel with the lift pump, which I'll leave as is. I'd install it close to the fuel tank, with a fuel filter preceding it. That's the plan anyway.

I think I need a low pressure pump (i.e., not for a fuel injected car), but I'm not sure how low is appropriate.

Local parts store guys' reaction: "Uh...what make, model, and year?" They are utterly useless, as always. I was able to extract from them that they do carry (oops, I mean can order; parts stores don't actually stock parts anymore) a simple ("universal" for all cars pre 1975 or so -- why, then, do they need make, model, year anyway?) pump rated at 5-10 psi.

My questions for anyone who may have done this, or who knows more than me: 1) how many psi should I be looking for? 2) do you have a pump in mind (model # or link, please, if you do) 3) are any of these things wired with their own switch, or will I just have to splice one in? 4) I thought of going the marine/boat route, thinking perhaps those might be low pressure, but they'd probably be 6 volts --other ideas?

Thanks in advance.

[siii8873]

Carter 4070 is what I see a lot of people using. I'm considering going with an electric pump also, but I would just eliminate the mechanical one.

[Opabob]

I am no expert, but just went through this. I checked to see what psi my particular carburetor liked and picked a pump that was rated to pretty much bracket that pressure in the middle. I think most low pressure pumps would fit the bill. I picked a carter because it paired well with Weber carburetors and got good reviews from the classic Porsche owners running Webers. I went to a marine supply and got an auxiliary fuse panel, and then got a relay at a local auto parts store. I will be running the pump all the time, but put in a switch because there are going to be times when I'll be wanting to have the ignition on while the truck is not running. In your case it looks like you will be wiring a switch up anyway, and if you use a relay, then you don't need to worry about the 5 amps or so the fuel pump will draw to be running through your switch. Just my two cents. I'm sure others will give you good advice.

[TedW]

Hi Andrew:

I put a Carter 4070 on my 1970 IIA a few years ago - works great with my Weber. I also installed the Carter oil pressure switch, so the pump only runs if there is oil pressure present: Great for added safety (the pump won't stay on if the engine stops after an accident), and also to allow for me to leave the ignition on (as Opabob describes above) to run lights / accessories without the pump running.

I don't understand why you want to leave the mechanical pump on the truck. Most folks seem happy to be rid of them. Can you explain why you want to run both? I'm a little slow on the uptake....

Just my $0.02 - Ted

[siii8873]

Ted,
how does the pressure switch work on startup? Does the starter build enough pressure to activate the switch to kick on pump? I guess the residual fuel in carb would get it going.

[TedW]

Ted,
how does the pressure switch work on startup? Does the starter build enough pressure to activate the switch to kick on pump.

Exactly. The switch goes on as soon as it detects oil pressure (only 3 psi, IIRC), and shuts off when the pressure goes away.

[andrew]

Hi Andrew:

I don't understand why you want to leave the mechanical pump on the truck. Most folks seem happy to be rid of them. Can you explain why you want to run both? I'm a little slow on the uptake....

Just my $0.02 - Ted

My plan is to use the electric pump to prime the carb on startup, which seems to be an issue in my case. Since I'm planning on installing a switch, I thought I'd just switch it off after the truck gets running. Since (a) I don't have the tools etc. to make an adequate blanking plate (maybe plates are available somewhere, though, I haven't looked) and (b) the truck runs fine once it's running, my thinking was to leave the lift pump in place and rely on it for driving, which is also safer in case of an accident. I also kind of like the redundancy if the electric pump fails. Seems simpler all around too. My understanding is that they can work in parallel like I'm planning, but if there's something I'm missing, please let me know.

Thanks for everyone's input so far.

[mearstrae]

I can see what you're trying to do, but if the mechanical pump diaphram fails the electric pump will be more than happy to fill your crank case with gasoline (not a good thing). Perhaps just by-pass the mechanical pump and run just the elec pump. I'm also running the Carter pump with a fuel regulator.

'95 R.R.C. Lwb
'76 Series III Hybrid 109
'70 Rover 3500S

[jac04]

Another option is to install an ignition system switch. This switch would cut power to the coil, so you can crank the engine for several seconds to get the fuel pump working, then turn the switch on. My Lightweight sits for extended periods, so I installed an ignition switch that allows me to crank the engine to build oil pressure (and also fuel pressure), before starting the engine.

[o2batsea]

So, what you are suggesting is that there is no fuel in the float bowl when you go to start the car, and you need an electric fuel pump to fill the bowl before attempting to start the engine?
I would be asking myself why the bowl is constantly going dry rather than try to bodge fix the problem with a second fuel pump.

[andrew]

So, what you are suggesting is that there is no fuel in the float bowl when you go to start the car, and you need an electric fuel pump to fill the bowl before attempting to start the engine?
I would be asking myself why the bowl is constantly going dry rather than try to bodge fix the problem with a second fuel pump.

Fair question and, yes, I'm guessing that the fuel is low/empty after sitting for a few days (but I've not verified this), after which starting is much harder than if I'm back to the truck within a day or so; also, very rough warmups when cold, with rhythmic rev/want to quit cycles, suggesting the fuel is chugging in from the lift pump. I've cleaned the jets, rebuilt the carb, etc....I've replaced the lift pump and filter, blown out the lines, etc... So, maybe this is an unnecessary step but it's my current thinking on the matter. I'm happy to be wrong, though, if you know what I'm missing.

[o2batsea]

If it were me, I'd check that the needle valve in the float bowl is not sticking. Very common problem with vehicles that sit. Zero dollar fix.
And what do you mean by "rebuilding" the carb? Which carb?
Why do you suspect feuling as the problem? Have you ruled out the ignition system completely? When did you last put in cap rotor points condensor wires plugs?
Oh and you did eiminate all possible vacuum leaks of course.

[andrew]

If it were me, I'd check that the needle valve in the float bowl is not sticking. Very common problem with vehicles that sit. Zero dollar fix.
And what do you mean by "rebuilding" the carb? Which carb?
Why do you suspect feuling as the problem? Have you ruled out the ignition system completely? When did you last put in cap rotor points condensor wires plugs?
Oh and you did eiminate all possible vacuum leaks of course.

Rochester carb; new gaskets, jet needle, springs, clean, etc. It's not the ignition system: I just replaced points, condenser, plugs, ignition switch, plug wires, battery and starter grounds, & solenoid. I also, of course, timed and adjusted valves. No vacuum leaks I can find.

[ArlowCT]

What brand of pump did you use when you replaced the mechanical pump? I have seen bad ones right out of the box, same with points and condensers. I have learned just because they are new doesn't mean they are good.

[andrew]

What brand of pump did you use when you replaced the mechanical pump? I have seen bad ones right out of the box, same with points and condensers. I have learned just because they are new doesn't mean they are good.

The pump is from our hosts. I do believe this pump is good, since it was replaced to chase a problem but there was no difference before/after (meaning I have a perfectly good spare now).

I learned the same lesson with the starter some time ago, which was "rebuilt" (by our hosts) but no good (worth noting they were good about it), which led to a wild goose chase of the problem (since it couldn't have been the new starter! ha).

Truck runs perfectly when warm, by the way; it's just cold start that's a PITA.

[stomper]

If it were me, I would use the mechanical lever on the fuel pump to fill the fuel bowl in the carb for a few mornings, to see if that is indeed your problem. That way you will know for certain that your pump hypothesis is correct.

[o2batsea]

Truck runs perfectly when warm, by the way; it's just cold start that's a PITA.
There it is. So it's not the fuel pump. I suspect it's your "rebuilt" carb. The choke is working properly? All I can say is that I have always found that a new out of the box carb trumps a rebuilt one every time.

[TeriAnn]

I will be running the pump all the time, but put in a switch because there are going to be times when I'll be wanting to have the ignition on while the truck is not running.

You are aware if you leave the ignition switch on with the engine not running and the ignition points are closed you will be getting a continuous current flow through the coil and points. Over time this can damage your ignition system . Have you considered a switch just to run things you want to run with the ignition off and not have the ignition system powered up?

About fuel pumps. Carbs used on Series trucks like low pressure & high volume. You only want about 3 lbs pressure. Most electric pumps pump more like 7 -14 lbs pressure and can cause fuel to force its way past the carb's float valve. If you do not locate a low pressure pump you need a fuel regulator to lower the pressure of a higher pressure pump.

Electric pumps are good at pushing fuel but poor at sucking fuel so should be mounted no higher than the frame.

If you have a rear fuel tank you should mount the pump and filter on the outside of the frame. The inside gets engine, gearbox and exhaust heat and on hot days the temperatures can heat up the pump & filter enough to vapor lock. The best routing I have found is along the top of the frame rail beside the brake line to the fuel pump. The best place I have found to mount the fuel pump is on the outside of the frame just in front of the outrigger that mounts the front of the rear spring. The outrigger protects the pump from things slung by the rear tyre or parts of a disintegrating rear tyre.

Also with an electric pump you might consider adding an impact switch that shuts down your fuel pump in the event of an accident. I have one in my truck and so far it hasn't gone off while driving off road. But just in case I have it mounted within easy reach from the driver seat.

mechanical fuel pumps are often more dependable than electric fuel pumps. When mechanical pumps fail they usually keep working and pump enough fuel for you to limp along. When an electric pump stops working you are walking unless you carry a spare pump and tools.


Electric fuel pumps usually allow fuel to pass though when they are not on. Some people put them in series with a mechanical pump and leave them off unless needed as a backup.

Anyway that's just some miscellaneous thoughts about electric fuel pumps.

[bugeye88]

As usual, I agree with Terriann. I am of the camp to use a electric low pressure pump in series with the mechanical pump with an on/off switch in cab to: 1. Prime the carb by filling the float bowl of the carb prior to starting. 2 .To use in case the mechanical one fails. I place the pump after the mechanical so it will not pump gas past a failed diaphragm of the mechanical pump, in the crankcase. Also o2batsea is right on about the carb needle valve and other other jets of a carb being obstructed/clogged in some way. Especially newly "Rebuilt" ones.

Cheers,
Rob
68 2a Bugeye

[Opabob]

All good info, thanks. I am convinced to put in an inertia switch :)

[TedW]

About fuel pumps. Carbs used on Series trucks like low pressure & high volume. You only want about 3 lbs pressure. Most electric pumps pump more like 7 -14 lbs pressure and can cause fuel to force its way past the carb's float valve. If you do not locate a low pressure pump you need a fuel regulator to lower the pressure of a higher pressure pump.

The Carter 4070 is rated at 6psi max - It comes highly recommended at various sites that specialize in Weber carbs - that's what swayed me towards the 4070.

I understand Teriann's point about running at 3psi or so, but my truck has run great (winter and summer) for the past 3 -4 years I've been running this pump as is. I've considered adding a low pressure regulator but haven't gotten around to it because things have been working well.

If you are going to run an electric pump I would reiterate the importance of adding (for safety purposes) the oil pressure switch I described earlier. Only $18 or so.

Ted

[printjunky]

I would dispute Terriann's contention that mechanical pumps are more reliable, but she is correct that a mechanical pump can partially work, and in most cases an electrical cannot. That being said, that quality may be offset by things like a breakable bowl (ask me how I know), and diagnosis difficulties and the easy, cheap availability of the electric pump I have. After chasing fuel issues for about six months a couple of years ago, I am currently very happy with it.

In my case, after first, recurring annoyances with the mechanical pump (and it's replacement (and also two carb rebuilds, a couple of rewiring/regroundings, replumbing, etc., etc.) and then running through a few cheap (though not cheap) Mr. Gasket universal pumps, I did a bunch of reading on pump reliability rates and reputations and such. And anecdotally it appears that solenoid pumps are considered to have low failure rates and are widely used in OEM applications. By far the biggest complaint I found was the "ticking" kind of noise they make (and that's true, but no more annoying than most fuels pumps would be mounted that close to an uninsulated cabin (standard SII fuel tank setup). So I tried a pump like this.

http://i.ebayimg.com/00/s/NDkwWDEwMDA=/$%28KGrHqFHJCsE+,+L!vmuBQOi3Squ5g~~60_12.JPG

It seems the most well known brand of solenoid pump (OEM and aftermarket) is Airtex. Mine (from O'Reilly's, I think, but I can't remember and their site is being wonky) was not Airtex brand, but upon further examination the small print on the pump or paperwork said "manufactured by Airtex." it cost less $20, and I put it on a relay (which was actually part of a previous diagnosis attempt on another brand new, but bad-out-of-the-box inline vane-type pump, and in contrast to Terriann's contention, this was an example of an electronic pump that worked just enough to make me sure for awhile that something else was up (and so I tried EVERYTHING!) and I have it on a switch - primarily for the purposes of phone charging and such - and yes I know that puts my pertronix unit in a possible overheat situation, but anecdotal evidence is that it takes significantly longer than I would leave the key on, anyway (and has worked fine for about 2 years). Oh, and I have a Rochester. The pump is rated at 2.5-4 psi, so potentially a little high for the Rochester, but what I found doing research is that almost NO fuel pump actually pumps at it's highest rating. The tests I saw always had actual, real-world pumping pressure at or below the halfway point between the min. and max. The Airtex seems to work fine for me, though I did do some float adjusting after the pump got installed (and probably need to fine tune it at spring tuneup time).

Oh, also, I eventually just bypassed the mechanical pump and left it in. My original intention was to get a new mechanical pump installed, and leave it as a backup. But so far, a better plan seems to be to stock a backup solenoid pump (again, under $20) in my spares.