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.