Electric vs Mechanical fuel pump?

Discussion in 'Performance & Fuel' started by dsfloyd, Jun 12, 2013.

  1. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    For some people smarter than me. Now I know that this is technically on a 1960 Land Rover Series II 88, BUT the fuel pump is feeding a single barrel Holley for a 60's GM Truck inline 6, that and other parts have been GM'd in the restoration.

    So the engine is a 4 cylinder 2.25L petrol (its British) motor

    I am trying to get back around to restoring the rover, and an issue I have been having is with the fuel.

    It currently has an electric fuel pump (and has for many years) instead of the mechanical pump.

    A while back I had the rover running and the carb started over flowing. I thought it was an issue in the carb and eventually replaced it. Over the weekend I had the pump on (hadn't started it yet). Heard the pump shut off then it kicked back on and all of a sudden the carb started overflowing. I am thinking that the pump is putting more pressure than the float is able to stop.Not sure why this is a more recent issue and not sure if the electric pump has an internal regulator that isn't working. Its an old universal pump that is just on the frame and will have to check the ratings. My dad[​IMG] said at the time he did the conversion the electric was cheaper than the mechanical but doesn't seem to be any more. The mechanical is $45 and I can get some 4psi electrics for about the same but then get expensive after that. Question, is it just as easy (better) to go back to the mechanical pump or get another electric (I honestly don't even know what I should get as far as PSI ratings, but know it doesn't need to be high)?
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Do you have a return line set-up for the pump?
    I know older systems didnt use one/werent required to have one.
    New system run overflow into a charcoal cannister, back in the day it was popular to either run an overflow style tank, run a line back to the fuel tank, or run the overflow tank with a line back to the fuel tank.
    My experience with mechanical pumps has been due to the way they operate, pulling fuel from the tank, they tend to vapor lock often in hot climates.
    Im just not a fan of mechanical pumps after being stranded a few times by them.
    Most newer electrical pumps will shut off at a set pressure or set back pressure to prevent overflowing.
    My guess is this pump may be old enough it was mfgr before this requirement.
  3. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    the electric pump is a simple single line with no return (I'm not sure when the electric pump was put on, at least 14 years ago. That being said its probably only got a few hundred miles on it in that time). Same for the mechanical (by the looks of it). I couldn't see any psi readings on the pump. It had a bunch of numbers but nothing I could decipher other than 12 volt and flow direction (but there was one side of the pump I couldn't see without taking it off. I will be taking it off to see what other numbers it has (maybe something to cross reference) as I need to drain the fuel tank because the gas is really old. Is there a way to know what type of pressure is ideal with an electric pump? Ordering a clutch too so I can fix that this summer which is the main reason it's been sitting for long.

    Thank you

  4. marksoldtowne

    marksoldtowne Member 1 Year

    I like the idea of an electric pump,I beleive it should be set up with a relay and should be wired with an auto shut off, in case of an accident. I have seen pictures of the special oil presure swith that shuts off the pump if oil presure is lost. Another option might be to get one of those impact switches from a wrecked car, that shuts off the pump on impact. An electric pump would most likely require a presure regulator to get the presure down to 5.5 lbs.
    An advantange to the electric pump would be the fuel line could be run on the right side frame . You also have instant presure when the key is turned.
  5. steved

    steved Former Member

    Are you sure the pump is faulty, or has the carb float deteriorated to the point its no longer floating? I had this issue with a electric before, and it was a bad float in the carb...replaced the carb float and the electric pump worked fine. I want to remember most floats/needle valves will only take about 5 to 6 psi before they "leak"?

    Personally, if its installed like OE; a mechanical pump will perform as well as an electric...I have also found electrics have not had the same life expectancy as an mechanical (way too many failed electrical pumps).

    As for running the overflow into the charcoal canister...never seen that. I've seen charcoal canisters destroy because of it, but not purposely. They typically run the return back to the tank, the charcoal canister is really only for vapor coming off the tank (think of it as a filtered breather for the tank).
    1 person likes this.
  6. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    this is how it's currently set up. I found a 4 psi pump for about the same price as an OE style mechanical, but wasn't sure if that was enough psi, the next was 6 psi but almost double the cost.

    This is a brand new carb, as I thought it was the float the first time, but it just did it again which is why I'm wondering if the pump is faulty. Hopefully it didn't damage the new float.

  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Im presently in the proccess of rebuilding a 1954 Feathercraft Vagabond 16' boat that runs a 1954 Chevy 250/6 cyl with a Holley single barrel carb and mechanical fuel pump. The engine and fuel system were rebuilt to stock specs and have less than 5 hours on them, I mounted an inline fuel pressure gauge btwn the pump and carb this afternoon check the pressure, this is basicly the same system you have, at idle I get 3.5psi and at WOT it climbs to a touch under 4.0psi.
    This particular system runs a liquid/vapor charcoal cannister that allows liquid in the bottom and vapor/charcoal in the top. It also uses the vapor pressure to force any liquid back to the fuel tank.
  8. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    So after your guys help and after reading a good discussion on another forum I think I am going to go back to the mechanical pump. Weighing pros and cons of each I think its a little easier, plus I can order it with the clutch. I do like the fact that the electric pump I can prime by turning on the switch and letting it run for a few seconds as I know that can be a draw back to the mechanical. Looking at the stock one (as it is still on just not hooked up) it has a hand prime lever on it. Not sure if the new one will but that helps with the having to crank it for a little bit first to get some fuel pumping. I'll update with how it goes once installed (I am sure I will have to dial in the carb again) and not sure how soon it will be. I will do it in the same process with the clutch but hopefully I don't drag out the repairs too long. Ideally I want to get it all back up and running before the end of summer (before August). Thanks again for everyone's help.

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