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Tinster
06-12-2008, 06:39 AM
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
06-12-2008, 07:16 AM
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
06-12-2008, 07:25 AM
[quote=NutmegCT
Dale - the carbs do the compensating.

Bless those wonderful SU's on my TR3!

T.

[/quote]

<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
06-12-2008, 07:36 AM
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
06-12-2008, 07:38 AM
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
06-12-2008, 07:40 AM
High pressure electric pumps (as used in fuel injected engines) have a return line back to the tank.

DrEntropy
06-12-2008, 07:46 AM
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
06-12-2008, 07:48 AM
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
06-12-2008, 07:53 AM
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
06-12-2008, 08:03 AM
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
06-12-2008, 08:06 AM
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.

https://i90.photobucket.com/albums/k270/KODANJA7/jakes9-0715.jpg

06-12-2008, 08:07 AM
Dale,
Have you already blown through Paul's pump too? If so, could I possibly buy it off you?


.

Tinster
06-12-2008, 08:18 AM
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
06-12-2008, 08:26 AM
Dale, just what has happened to all those pumps? I'm curious....

DrEntropy
06-12-2008, 08:35 AM
I sense sharks... :jester:

TR3driver
06-12-2008, 08:43 AM
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
06-12-2008, 08:47 AM
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
06-12-2008, 08:53 AM
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
06-12-2008, 08:57 AM
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
06-12-2008, 08:58 AM
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.

Tinster
06-12-2008, 09:19 AM
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.



<span style="color: #990000">Exactly Tom!
Everything is new, tank cleaned spic and span with
10 gallons of pre-filtered, high test gasoline right
from the pump at a new station with new underground
tanks. I added no bottles of anything.

&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt; &lt;

Takin' a coffee break:

I am half way completed connecting the electric fuel
pump to the carbs and fuel tank. The pump runs like a champ.

I'll report back later.

PS:

Pump No1- Pedro's Spitfire pump- filled w/ sand; stopped pumping
Pump No2- 3rd world pump- defective,quit pumping- no idead why- I trashed it
Pump No3- Used OEM gift from BCF member- quit pumping- old age I reckon.
Pump No4- 3rd world pump- defective, about 16 psi, flooded my engine compartment
Pump No5. 3rd world pump- functional when removed to replace entire fuel delivery system last month.
Pump No6- OEM Rego rebuild- unknown; still in diagnostic phase.

d</span>

NutmegCT
06-12-2008, 10:30 AM
Dale - before you crank 'er up again, have you removed that soft (foam?) insulation you added under the carbs? Some of us thought it was an accident waiting to happen, as it seemed very likely to absorb any gas that dropped down on it.

Edit: insulation/ heat shield material (https://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/showflat/Number/445570/Searchpage/1/Main/445405)

Tom

Tinster
06-12-2008, 11:23 AM
Dale - before you crank 'er up again, have you removed that soft (foam?) insulation you added under the carbs? Some of us thought it was an accident waiting to happen, as it seemed very likely to absorb any gas that dropped down on it.

Tom



Thanks Tom,

Not foam- some insulation material
that does not burn. But yeah, it could
fuel and ignite. But without it, I seem
to get vapor lock from hot carb bowls.

d

NutmegCT
06-12-2008, 11:24 AM
whew - glad you remembered the danger. There are several hearts beating a bit slower now :banana:

T.

Got_All_4
06-12-2008, 08:00 PM
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.

The clincher for me was when my car sat for a couple of months and it was hard to start like it had jumped out of time. I discovered there was 4 1/2 gallons of oil and gas mix in the crank case. Apparently gas had seeped past the seal on the mechanical pump and into the crankcase. This is very common.

DrEntropy
06-13-2008, 05:39 AM
Especially maddening now with ethanol as a mandated additive! Some of those pumps are running original diaphragms, some "kits" are older and still susceptible to ethanol meltdown. Either way, the crankcase gets fuel-filled.
Some results from this condition can be dramatic. :eeek:

Electric pump also supplies fuel to carbs after the car has sat a while, no "extra cranking" to fill bowls. Kill switches can be installed on 'em, THAT'S hard to do with a mechanical pump.

hondo402000
06-13-2008, 06:59 AM
on a side note. I bought a carter electric pump, the only problem is it ran all the time with the key in the on position, so I bought a brass "T" fitting and screwed it in at the oil pressure switch outlet on the block, then purchased another oil pressure switch at napa Echlin # OP6092, Closes at 5 psi. ran the hot wire thru the new switch so the pump comes on only when I have oil pressure greater than 5 psi. I have never had a problem starting the car since the pump will not kick on till the engine starts and the oil pressure comes up

Hondo

foxtrapper
06-13-2008, 07:29 AM
How does the electric fuel pump compensate for
different demands from different engine rpms?

Electric fuel pumps like you've purchased work the same as a mechanical one. The difference is instead of a camshaft lobe pulsing the diaphram, it's done electronically via a solenoid. There are a set of "make or break" contacts connected to the diaphram.

When the system is empty or low in pressure, the contacts touch and the solenoid kicks. The spring pushes the diaphram back. This repeats until fuel like pressure pushes back against the spring, keeping the contacts from touching. This is why the pump clicks rapidly when you first turn the ignition key on, and then stops.

Cheap ones burn their contacts. Just be aware of that.

A decent example of how a mechanical fuel pump works can be seen here: https://www.secondchancegarage.com/public/535.cfm An electronic pump works the same way.

TR3driver
06-13-2008, 09:05 AM
The Facet pumps have no diaphragm to fail, and no contacts to burn. And at $30, hardly worth looking for anything cheaper.
https://www.aircraftspruce.com/catalog/eppages/facetpumps.php

TR3driver
06-13-2008, 09:19 AM
the only problem is it ran all the time with the key in the on position, Good point, Hondo, though most people just live with that. Was also the original arrangement on my Stags ... I managed to hydrolock the motor once by leaving the key on while working on something ! One of the float valves leaked a bit, and the fuel ran into the manifold ...

Come to think of it, that may have had something to do with the blown headgasket a few weeks later. The starter coming up against that slug of fuel might have disturbed the head/gasket just enough ... that's when it started running hotter than before though the leak had to get worse before I was sure it was there.