Electric fuel pump question

[Tinster]

I am pondering connecting my hard wired electric
fuel pump. When I test run it- it seems to operate
at one speed.

How does the electric fuel pump compensate for
different demands from different engine rpms?

thanks,

d

 

[NutmegCT]

I am pondering connecting my hard wired electric
fuel pump. When I test run it- it seems to operate
at one speed.

How does the electric fuel pump compensate for
different demands from different engine rpms?

thanks,

d

Dale - the carbs do the compensating.

Bless those wonderful SU's on my TR3!

T.

 

[Tinster]

<span style="color: #990000">Tom,

Another stupid Tinster question. If the electric pump runs
at a constant speed, why do the carbs not overflow like
they did with my defective made in India mechanical pump
that put out too much fuel pressure?

This on-going fuel delivery problem is a bugger, I'll tell ya.
The electric fuel pump will be pump No. 6 installed in 1,600
miles of TR6 car use.

thanks,

d</span>

 

[DrEntropy]

It runs at a ~relatively~ constant low pressure. As Tom says, the carbs do the "regulating" as far as volume is concerned.

Quitcherbitchin' and WIRE THAT PUPPY UP!! :laugh:

 

[kodanja]

Why do people pefer to go to an electric fuel pump over a mechanical one?

I've never had any problems with my mechanical ones over the years.

 

[PeterK]

High pressure electric pumps (as used in fuel injected engines) have a return line back to the tank.

 

[DrEntropy]

and regulators, and injectors needing 28PSI... The pump in question is ~supposed~ to be a low pressure unit for supplying Zed-S Strommies... not much need for bypass/recirculation there.

 

[Tinster]

Why do people pefer to go to an electric fuel pump over a mechanical one?

I've never had any problems with my mechanical ones over the years.

<span style="color: #CC0000">Bill, I've had 5 mechanical pumps fail on me in
1600 miles of use. Yes, I have another spare mechanical pump
but I think I'll try an electric for a bit and see what happens.

wish me luck!!

d </span>

 

[TR3driver]

It's the pump's responsibility to limit the fuel pressure it produces. How that happens depends on the pump you have. It is allowed to vary somewhat with flow, but for ZS carbs, it should be no more than about 4 psi and no less than about 1 psi (measured at the carb inlet).

With the pressure limited, the float valve in the carb is what sets the flow rate, to match requirements.

Dale, I'm really surprised you have so much trouble with fuel pumps. Normally they are very reliable, with a service life measured in decades. I've never had one of the little rectangular Facet pumps fail; although the old SU electric pumps do tend to wear out the electrical contacts after 10 or 20 years. I did have an AC electric pump fail after about 20 years of service, but that was because it's diaphragm was not compatible with MTBE/Ethanol.

I'm guessing that in your case, it has a whole lot to do with the water and crud you drained from the tank ...

 

[Tinster]

Thanks Randall,

Mechanical pump No5 was installed AFTER I removed and
cleaned the fuel tank, installed new fuel lines and a
new fuel filter BEFORE the new pump. This latest mechanical
pump has only tasted high quality, pre-filtered, high
test fuel.

I'll connect the electric pump and see what happens.
If it also provides only a trickle of fuel, that must
mean something is clogging my outflow at the fuel
tank bottom.

PS: No fuel additives were used- straight gasoline.

I'll report back with results.

d

 

[kodanja]

Thanx for the info!

what is the main cause for a mechanical pump to fail?

I have a Webber Dgv setup on mine, the pressure from the mech. pump seems sufficiant.

 

[Guest]

Dale,
Have you already blown through Paul's pump too? If so, could I possibly buy it off you?


.

 

[Tinster]

Dale,
Have you already blown through Paul's pump too? If so, could I possibly buy it off you?


.

<span style="color: #CC0000">Sure Stirkle - when gasoline sells for $0.50/gal
I'll sell it to YOU
d</span>

 

[Andrew Mace]

Dale, just what has happened to all those pumps? I'm curious....

 

[DrEntropy]

I sense sharks...

 

[TR3driver]

PS: No fuel additives were used- straight gasoline.

Things may be different in PR, but here in the mainland there is no such thing. 'Gasoline' has always been a mixture of many different chemicals; and the mix changes not only with grade and brand; but with season and area the fuel is sold in.

At the time, local fuel was required to have either MTBE or ethanol added to it. The oil companies chose MTBE as it's cheaper here. But MTBE was subsequently outlawed; and now there is a federal mandate to add at least 10% ethanol to all gasoline sold in the US.

Not all the retailers have the notice on their pumps yet, but on a recent trip across some 15 different states, all the fuel I bought smelled of it.

 

[NutmegCT]

Tinster: <span style="font-style: italic">PS: No fuel additives were used- straight gasoline.</span>

I think Dale means he didn't pour any bottles of additive into his fuel.

T.

 

[TR3driver]

I think Dale means he didn't pour any bottles of additive into his fuel.

And I was just trying to clarify that neither did I. Still didn't keep the AC electric diaphragm from turning to Jello; or the AC mechanical diaphragm to cheesecloth.

 

[TR3driver]

High pressure electric pumps (as used in fuel injected engines) have a return line back to the tank.

The main reason for that is because the motor-driven pumps heat the fuel so much it would boil in the pump without a constant flow. In many cases, the flow of fuel also cools the motor.

But as Doc notes, hopefully that's not what Dale is looking at.

 

[NutmegCT]

it might help if Dale would tell us what actually happened to each of those fuel pumps to cause them to need replacing. Somehow I doubt it was all due to fuel.

T.