Mechanical fuel pump vs Electric?

[davla]

I'm thinking of fitting an electric fuel pump. A mate has an old Comma camper and he recons it's transformed starting as fuel is available immediately but are there any disadvantages? Assuming it's a good idea; where is the best place to locate an electric pump and any recommendations for which pump to buy? Thanks in advance

 

[ozziedog]

I’m still mechanical fuel pump wise, but before you waste any money on a new fuel pump and pressure regulator, why not test the one you have? If it’s in good shape then you will gain nothing at all by adding an electric one, however if it’s not up to the job any more then I’ll buy it off you if it’s an original. If it’s a repop then there is every chance that it is shagged bagged and bob tailed. To test, just take fuel pipe off of carb and fit into a one or one and a half litre water bottle, let it go into the bottle about an inch, now lay the bottle on its side. Make sure the motor don’t start by removing the rotor and putting the cap back on. Get a glamorous assistant or a handsome helper to crank it over for a few seconds while you watch what’s happening. After a few revs, the fuel on vinegar stroke should be ejaculating to hit somewhere between half way down the bottle to smacking against the end if it’s a newish pump. If it’s doing this then the issue of fuel supply (if it is one) is after the pump, if it comes out less invigorated, it might be the pump, or it might be something else restricting the fuel supply to the pump, like a blocked filter or a tank full of crud or a collapsing old pipe etc etc. At least you’ll know which way you’re going. Test should take about two minutes. :mrgreen:

Ozziedog,,,,,at least track it down, then you’re in with a shout :mrgreen:

 

[72baywesty]

Were on mechanical aswell, took off a facet pump that our specialist???(being polite) had fitted as they're a little noisy...

 

[starbiscuit]

There's nothing wrong with mechanical pump on a stock bus.
OK, it takes a few seconds longer to start if the bus has stood a long time and the fuel evaporated or leaked out of the carburettor float bowl, but has benefits, to my view. If it has stood long enough to need a good crank, it will build better oil pressure before firing, for example.

I removed a rotary electric pump when I got my bus and went back to mechanical. First the generator style, then alternator style (due to my lack of forward planning)

The electric pump was a bit noisy, but my bigger issue was that I was concerned about it running on in the event of being rear-ended or a fuel pipe coming loose or any other unlimited pumping scenario.

I may be paranoid, but a friend of mine ended up upside down in a ditch in an MGB with electric fuel pump rattling away, the keys having fallen out of the ignition switch. Fortunately no fire, but petrol everywhere.

I got an eBay re-settable cutout switch from a Land Rover, which goes open circuit when you thump it, intending to fit near the left-hand rear light, but decided that because I couldn't really test it in-situ without damage or with any certainty, it wouldn't really set my mind at rest.

And it still wouldn't stop it pumping if one of the pipes split or came adrift.

 

[cunning plan]

There's nothing wrong with mechanical pump on a stock bus.
OK, it takes a few seconds longer to start if the bus has stood a long time and the fuel evaporated or leaked out of the carburettor float bowl, but has benefits, to my view. If it has stood long enough to need a good crank, it will build better oil pressure before firing, for example.

I removed a rotary electric pump when I got my bus and went back to mechanical. First the generator style, then alternator style (due to my lack of forward planning)

The electric pump was a bit noisy, but my bigger issue was that I was concerned about it running on in the event of being rear-ended or a fuel pipe coming loose or any other unlimited pumping scenario.

I may be paranoid, but a friend of mine ended up upside down in a ditch in an MGB with electric fuel pump rattling away, the keys having fallen out of the ignition switch. Fortunately no fire, but petrol everywhere.

I got an eBay re-settable cutout switch from a Land Rover, which goes open circuit when you thump it, intending to fit near the left-hand rear light, but decided that because I couldn't really test it in-situ without damage or with any certainty, it wouldn't really set my mind at rest.

And it still wouldn't stop it pumping if one of the pipes split or came adrift.

All good points and also issues I would be concerned about too. :?

Although I have not done the conversion yet, but when I upgrade to an electric fuel pump, I was thinking of running one of the PS64 Oil Pressure Switches from Standard Motor Parts (SMP).

https://www.ebay.co.uk/itm/352514054775?ul_noapp=true

^ Image I found on the net showing the connections.

The idea being, the fuel pump relay is switched on by this switch, which in turn is switched on by oil pressure.

If you drop oil pressure, the oil pressure switch (AP64) will cut out and will in-turn turn off the fuel pump. You would assume / hope that if something happened, the engine would stall, making the oil pressure drop, which would in-turn make the PS64 turn off the fuel pump.

Also in the scenario you describe where a fuel hose has come loose, the engine would stall, oil pressure would drop, the PS64 would switch off the fuel pump relay and no more fuel would be pumped.

There is also a connection on the PS64 switch to the starter, so it can sense when you are trying to start the engine, where there would not be adequate oil pressure, and switch the pump on while cranking.

 

[starbiscuit]

I guess you could do something similar with a relay operated by the generator charge light with a "cranking" override to get it started.

But on my bus both the charge light and oil pressure light come on when stopping at traffic lights after a long run. Probably not long enough for the carb to run dry.

Crash switches are supposed to stop the engine; you could wire the coil and carb anti-run-on plunger through it to make sure, rather than rely on engine stopping in the event of a crash. Depends what you want to achieve.

Either way, both mechanical and electric pumps will keep delivering into a leaky pipe if the engine keeps running.

Perhaps there isn't a simple solution for that.

 

[Dci_Carter]

Hi I've opted for the faucet pump route with a malpassi filter king, I've also bought a relay that connects to the engine and cuts out if engine stops, I've seen a few fires with mechanical pumps wearing as well, I guess it's a case of always check before a journey

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[cunning plan]

Either way, both mechanical and electric pumps will keep delivering into a leaky pipe if the engine keeps running.

Perhaps there isn't a simple solution for that.

Agreed, I think sniffing the engine bay / prodding the fuel pipes before a long journey might be the only option. :|

 

[K@rlos]

If the engine is stock use a stock mechanical fuel pump. If you have twin carbs use an electronic fuel pump either a self regulating pump or in conjunction with a separate regulator. You will gone nothing using an electric pump on a standard motor.

 

[jonboylaw]

I run a Durite rotary pump, (suck version) with 2 1/2 psi out put. I have an inertia cutout switch from an MG rover in series with the pump.


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