V8 SU Fuel Pump - Winch Challenge

[Team Idris]

For a very long time I've run a Durite fuel pump http://www.durite-shop.co.uk/0-673-12-fuel-pump-electronic-12-volt-pressure-box-of-1-5802-p.asp (probably too long, maybe since 1998 - good value really)

Now I'm getting fuel starvation when the beast is really steep nose up. In one sense I am tempted to get another, but I also wonder about this type http://www.motorsport-tools.com/facet-red-top-fuel-cylindrical-pump-competition-works-spec-480532e-p-250608.html?zenid=b102f6e5b043de29573e8e3f3bc6ea82 which Darren at works runs on his midget sprint.

Any preference, or any other good options?

[RedLineMike]

i think it was a redtop i ran on my trialer

[FridgeFreezer]

Surely fuel starvation is down to the fuel pickup / tank design, not the pump?

[Bowie69]

Or float levels in the carbs... assuming that's what you are running

[Team Idris]

I might be wrong yet, but it is so very very much like low pressure.

We were backed up against a fence with the front up, sitting at say 40 degrees. Result was a proper 4 banger with no power!

We ran the top line out and winched it up with some 4 pot engine help. Once it got to 10 degrees we got full V8 back.

Driving showed you could do any hill climb as steep as you liked, as long it was completed before the carbs ran low.

Never had a problem when tail up.

Showed similar problem at Lea bridge weeks ago, but I had left the carb cooling fan off, so I assumed I had boiled the petrol (maybe I had?)

Showed similar problem marshalling at Baden hall on a steep climb, but the tank was nearly empty.

So it has maybe hinted at a weak pump for a bit?

I'm still to check the flow and pressure, but even if I found a problem it has to be time to get a 'new' pump. I'm asking it to do a metre of head and more regularly. But which one??? The red top does literally have a 'track record'

[Bowie69]

It could still be the floats, at that angle, the float needle could be shut, but not enough fuel in the chamber to reach the jet properly.

Looking at the pump, it's 0.3 bar, which depending in where you have it mounted means if you are getting to around 3 metres above the pump, it just won't be able to pump due to the weight (pressure) of the fuel trying to come back down the pipe. Could be a sign it is weakening as you surmise though

You probably don't want to up the pressure too much, but the Facet red top is 6.5-7.25psi, which is a smudge up on that durite one, and give you ~4.5m of head.

I don't know where your fuel tank is so that will have abearing on it.

[Team Idris]

"It could still be the floats, at that angle, the float needle could be shut, but not enough fuel in the chamber to reach the jet properly."

You'ld think so, but I havn't found that point yet. It achieves angles I can only assume the auto would be struggling for pressure, even with too much oil in it. And 'floats' is more of an 'every time' fault. It was nose up for at least ten minuets in the morning with loads of power? It does seem more like the windings breaking down when hot. When the S1 SU pump failed it ran for ever shorter time periods as the insulation got weaker.

I did wonder about replacing the tiny orifice in the return line with a regulator. But it worked okay before, so maybe best not complicate it. And its that restrictor combined with the flow that controls the pressure at the carbs float inlet. Maybe time for a gauge to see what is really going on if I up the flow with a stronger pump.

One concearn is that competing is the only way to create fault conditions that happen while competing

One fix I don't like and terry hates is a swirl pot resevoir in the engine bay with a second pump. I like the constant head, but not the really flamable fuel volume next to the hot engine...........

[Paul Woodward]

I've been hearing good things about Holley fuel pumps.

http://www.earls.co.uk/earls/fuelsystem/pumps/holley.html

Being a gear type pump they are noisier than the Facet type.

They do a regulator as well if required.

[Team Idris]

I like the look of the 12-801-1;

"Has externally accessible pressure relief valve (max 7 PSI)
Rotor/Vane pump design is more tolerant of contaminated fuels"

And

"Repair kits are readily available".

Sitting here with my engineering hat on, a motor driven pump sounds better for a changing head than a fixed spring rate? More head just means more current draw.

[Team Idris]

I'm a bit further on in research. We think the holley is too much for the job. Nice pump, but mad flow for the RV8 3.5 needs.
We think the solid state facet is too little, even with 2.
I liked the durite, but I think I will go facet red or blue top. Which means I'm agreeing with Mike
The blue-top is points-switch, and I have SU points pump on the old 1958 landy. They aren't inspiring, even if they are fixed with a rub of sand paper. It might have been recommended with good intention on the V8Forum, but I think I'll go 'modern'.

I am sure I like the Mocal fuel gauge. It is in white, so I can see it and is the right price range. I'll be able to see what is going on and adjust the leak-back to a viable average for the SU carbs.

So there you have it. But how can it have been so hard getting here? I thought I'd be inundated with answers and might even get a "have you tried the search"?

Maybe a horray for modern fuel pumps that you can chuck nearly anything on and it'll work fine

(If you're looking for an injection pump, then the 044 Bosch got a thumbs up from people).

[Team Idris]

Another option; http://www.roadcraftuk.co.uk/index.php?route=product/category&path=41_122 which is a Fedral-mogul rotary like the Holley, but without the 'bling' markup. FMP4070HP.

It's more flow than I need, but it does look a nice pump.

[Team Idris]

I bought the Facet red-top kit from Merlin and a gauge. (having a sale). Pump is in and gauge is yet to do, as Darren was in work today, so I took the opportunity to stuff some ally structure into the back of the van where it is disintegrating. Anyhoo, I write to say that the facet doesn't stop like an SU does at full pressure. Instead it keeps pumping all the while, so I'll fit the gauge to see what is happening and if my return orifice is too big or maybe too small?

[Team Idris]

I didn't like my 'iron' 1/8" bsp fem-fem bend that I rooted out of the shed for the gauge, so I decided to go to the canal boat shop. There I found a selection of brass fittings (Their stock usually saves the day) including an "1/8" bsp female to 3/16 pipe" with a compression fitting. That will do nicely as 3/16 is cunifer brake pipe

Previous thread should say "I bought the Facet red-top kit from Merlin and a gauge. (having a sale). The pump is in, but gauge is yet to do. Instead of fitting it I took the opportunity to stuff some ally structure into the back of the van where it is disintegrating, because Darren was in work on a Saturday and they have a decent cut-off saw". It just does a way better job than the hacksaw

And then I went in with the mig welder on the rear spring mount. And next it wants waxoiling while it is dry weather!

'Tow motor' and 'race truck' is like chicken & egg when it comes to repairs

[Team Idris]

It does 6.5 psi with a 4mm bore return-line fitted, with no restrictors. It's higher than I would like, but I ran it a fair bit the weekend while Marshalling at S&S stone comp and it seemed happy enough.

I will re-check my mixtures as the choke didn't seem to be much of a necessity?

I didn't see if there were any pressure reading changes for nose up or nose down. But I did see the rear shock no longer has a round profile, explaining at least one clunking noise from the rear end!

[Tanuki]

I have always used some sort of pressure-regulator with these kind of electric fuel-pumps: the alloy-bowl "Filter King" with the built-in fuel filter being my favourite - it's adjustable and comes with an integral gauge so you can set the delivery pressure to whatever is specified for your particular carburettors.

http://www.fuelpumpsonline.co.uk/filter-king-fuel-pressure-regulator-v8-carburettor-models-1902-p.asp

Running a high-output pump without a pressure-regulator is going to overload the float-chamber needle-valves, which can cause overfuelling and is really not good for either economy or long-term engine life.

[Team Idris]

This is what I'm thinking, even thought it seemed fine over the weekend. So you've prompted me to ring Carburettor Exchange, where they were rebuilt, to find the right figure. He says 3-5 psi, so the proper fix is to replace the return line. But that might need the floor pulling up, so I'll try restricting the feed line first and look at the feed after this next event. As I do like the idea of maximum flow to reduce fuel entry temps.

[Team Idris]

A 2.5mm restrictor hole in the feed made no difference? Then I figured there must be a return problem/restriction!

And indeed there is, as the return carb connection has a restrictor machined into it, so I drilled it 2.5mm. Which maybe a bit much?

Next job is to re-lay the fuel lines up the chassis, with 6mm bore for feed and 4mm for return and then see how the pressure looks

[Team Idris]

All good, with the needle waving around 4psi.

I tried curing the 'waving' needle with a restrictor orifice, but I can't get the hole small enough. It'll be near enough for LRS6, as long as I havn't swapped rich mixture for weak? Only a work-out and plug check is going to show that though. And I can't see it being miles off.

Just for reference; As far as I can make out this early RRC had two restrictors, one at either end of the return pipe.

[smallfry]

Bit late on this I know, but harking back to my tuning days, you do NOT want any more than about 4 psi on ANY SU carb. it will just push the float valve off its seat.

The floats are small in comparison to any Holley/Weber/Rochester/Carter etc. and you cannot get the pressure on the valve like you can with a bigger float.

A bigger/higher flow pump is the way to go for sure, but with a constant flow return with not much line pressure.

Dont know about height or head though................no experience of that

[Team Idris]

That were odd? We got the same fuel starvation problem about 11:30am this morning at LRS6. Looked at the gauge and we had no fuel pressure, so Terry cable tied the rubber return pipe 'double' and we ran 7psi all afternoon. So I need to have another investigate to see if it does 3psi when it has sat overnight? Or if the system has changed in some way?

Also, we have run a bonnet fan for ages, as we got fuel boil in the carbs. But I forgot to switch them on at one point, and all was good? This suggests that the extra fuel flow of an un-restricted return line is really liked by the truck

[Bowie69]

Were you nose up again?

[Team Idris]

A little bit. This morning it is back to 3 psi?

Conclusion; petrol reduces in viscosity with temperature like any oil.

Fix; keep the fuel cool?

[elbekko]

Petrol can vapourise in the lines, so yes, keep the fuel cool. Don't run it near the exhaust etc.

[Team Idris]

Worse than that, the tank is by the exhaust and behind the rear rad. No reason to assume it doesn't gain more heat than it looses?

But I am confident we aren't getting to its vapour point in the return line. And it can't be a suction problem, as the problem was stopped by blocking the return. Unless it has a flow related cavitation issue before the pump? (blocking reduced flow to near zero).

As usual it is very hard to make any good tests in the middle of a forest, squirming around in clay as the rain falls

Lightly sprung return valve at the tank end of the return feels right. And a tap to adjust back pressure if I have that theory wrong.

Basically I'm getting a kicking by 'caring'. If I'd just thrown the pump on without a gauge, it would work fine and I'd be happy in ignorance

[Bowie69]

Do you actually need a return line? I have used SUs, but later HIFs, which just had an overflow, and not a return line, can't remember on the earlier stuff what the setup is.