Fuel delivery

Paulj65

Member
Hi
I suspect I now have a new problem
would anyone know what the delivery amount of fuel would be in litres per minute ?
 
It depends on what sort of pump you have.

Do I remember correctly that you have an electric pump fitted? If so, which one is it? Got a pic?

Richard
 
Hi you are correct,
it does have an electric pump, as yet unable to locate the thing
there must be an amount or fuel required to run the engine ?
it appears I’m now short of petrol,ie starts runs and stops repeat!
the tachometer wasn’t working so replaced, tacho now works fine,
the car was delivered, i had driven it fine, it then when parking poured petrol out,it turned out to be an after market pressure regulator which had failed, so removed and replaced with a short pipe
now it seems I’m short of petrol as I can see it dribbles into the fuel filter
I am suspecting a blocked return pipe, but at the moment can’t find detail on the fuel system, lots on carbs a bit on pumps ,but not much on the whole system
hence the post and many thanks for the reply.
regards pul
 
If it's a factory electric pump it will be underneath the tank at the back. it has a built in strainer on one end that needs cleaning occasionally. Its a bayonet fitting cap on one end and there is a fuel tap on the pumps inlet so you don't drown in fuel when youtake the end off and just jacking up the back only also helps to keep you dry. The tap is a push pull thing which has no position lock so check it is fully open. Also check the reserve switch isn't stuck halfway, on electric pump cars the tap is part of the pump plumbing and the switch cable is very long with lots of places to stick

If the engine idles fine but behaves badly with open throttle and reasonable revs then either carb float height or LOW backpressure in the return line can also be the culprit but check the fuel pump end first.
M
 
That’s a great help I will follow your advice and post with hopefully a good result
thanks again regards paul
 
Hello again
im back ! This fuel thing I found a dodgy fuse and a bad earth connection for the pump.
it pumps well enough but as soon as reconnected to the carbs it appears to struggle, also the petrol reserve switch is electric as is the valve.
I wondered if any of this is correct, and maybe if anyone knows its origins
pictures this time many thanks paul EBAF4169-5A8E-4EF5-83E6-37BC41CC2252.jpegBA0049C2-B795-49D9-B725-4E0A66F61BAB.jpeg
 
That all looks a little bit like a Heath Robinson contraption. It wouldn't have arrived at the dealership like that from the factory. I'm not entirely certain exactly what I'm looking at though! It would seem to have been fitted by or for a previous owner, and perhaps it now isn't working as well as it did when first cobbled together. Somebody more knowledgeable who can actually help you will doubtless chime in presently.
 
Hi again just to add the car was running until this pro flow thing decided to pour petrol everywhere.
I removed it and now don’t seem to get enough fuel
I thought this just regulated the fuel, I am Probably wrong wrong if anyone has any ideas please7A2A1285-F7F2-4B7E-9840-668A2C1BC18A.jpeg
Hi, I agree, they must have bought a job lot of hose clips.

Colin
i thought the same but what to do I’m thinking a facet and check the reserve solenoid valve works .
but I’m not keen on regulators having had one fail,
with the fuel circulating all the time anything that would be a weak link is not desirable.
and what pressure to go for a 1972 3500S, again too much could compromise the float valves and just cause another flood ☹️
any advice appreciated thanks
 
When I got my car it had no mechanical fuel pump, instead there was a Facet electric pump mounted vertically behind the near side headlamp. I moved it to the back of the car beneath the tank, like in your pix Paul. I also moved the reserve tap from the back of the engine bay to close to the tank outlet. I had to fit a longer reserve cable. The car didn't have a fuel pressure regulator when I got it, and I haven't needed to add one. The Facet pump provides the twin SU carbs with enough fuel to reach the manufacturers claimed top speed. The only time I've had overspill from the petrol overflow pipes that dump in front of the engine block was when the carb floats had sunk and needed replacing.
I think I'd be inclined to remove the fuel pressure regulator, also dump the electric reserve solenoid, revert to cable operation for the reserve tap, with a nice new Viton O ring, and fit a Facet fuel pump at the back there. They are a bit noisy on start-up but once the engine is running you don't hear it any more.
 
Brilliant just what I needed to hear
I’ll get a new pump ordered , the reserve petrol solenoid I’ll check it out if it functions I might keep it,
because the electrical pull switch might prove challenging to both source and fit
but thanks for the heads up on the pump regards paul
 
Which line was the Pro Flo thing on? If it was on the return line your problem isn't the pump. The return line reduces the pressure and flow to the carbs. The regulator has been put there to provide back pressure so the carbs can take in enough fuel. taking it out means the fuel bowls in the carbs can't flow enough fuel in. putting a restrictor in the fuel return will raise the pressure and fix the issue. though I'd first check your float heights are correct as they may well be too low.
 
Which line was the Pro Flo thing on? If it was on the return line your problem isn't the pump. The return line reduces the pressure and flow to the carbs. The regulator has been put there to provide back pressure so the carbs can take in enough fuel. taking it out means the fuel bowls in the carbs can't flow enough fuel in. putting a restrictor in the fuel return will raise the pressure and fix the issue. though I'd first check your float heights are correct as they may well be too low.

Thanks Mike,
I have no clue as to which is the in and the out.
with the pump running and the hose at the flow restrictor off it appeared to pump fuel fine.
reconnected the fuel filter wont take the fuel,
im guessing this implies a blockage in the return feed, which at the moment I’m finding difficult to work out which one it is.
then again there’s a lot on here about the reserve valve giving the problem I have,
thanks very much for the input it does help and helps to make sense of this fuel system.
 
Hi, The two fuel connections on the sender unit are main and reserve, the return line 'T's into one of the pipes that connect to them. I can't remember which one it is but would guess the reserve, but it doesn't really make much difference because the excess will end up in the tank anyway to go round again.

Colin
 
Just to make the process of fuel delivery clear for you: the Carb float bowls require two things from the delivery; 1. Pressure to overcome the float pressure on the needle valve in the float chamber and 2. A certain level of flow so the float bowl doesn't empty out before the fuel rail can fill it.

It looks like your car has been converted to an electric pump, the original setup had two long tubes from the rear from the reserve and main fittings under the tank. these joined in a manual two position, three port tap located at the engine end of the transmission tunnel and operated by a short cable from the centre console. one pipe then went across th engine and along the sump endge to the front mounted , cam drive, mechanical pump. Then it went up to the fuel filter and across to one side of the carbs. Finally it went across to the second carb then continued (in a smaller pipe) back to the rear and joined the reserve line where it comes out of the tank.

Your setup has replaced the three port valve with a solonoid valve and moved it way back next to the tank outlets. ALL three pipes from it should still be on the suction side of the pump and there should be a filter between the solonoid valve and the pump (but I can't see one). From my memory of forty plus years of working on P6s yours is the first I've seen with a solonoid valve. It is a very elegant solution though it does raise a control issue as they normally remain on in one position which may mean there is no control with the car turned off and may possibly overheat and burn out if left on for too long. It would also need to have a valve assembly rated for petrol, not water or something else.

The pump design naturally makes aclicking noise when pumping. Normally the faster the clicking the more fuel is flowing. The clicking reduces as the pressure builds and the flow decreases as a result. With the V8 the overflow pipe means there is always an amount of ticking as the fuel does a circuit around the car. There is one significant performance difference between your setup and the mechanical pump setup. The mechanical pump gives one pump per two revolutions so it is a big pump AND as the revs increase the flow and pressure increases. The electric pump regulates the flow according to line pressure, not the engine speed; so full flow means no line pressure which doesn't work to well when there is a return line competing with the two float bowls. hence restricting flow in the return line is often necessary when switching from mechanical pump to electric, particulalry in the higher rev range.

finally, to get you started shopping you can find replacement parts for your current set up from holden.co.uk under fuel pumps.
Michael
 
PS.
That black wire bolted to the foot of the pump isn't doing anything as the threaded part doesn't go through the rubber bobbin...Might be good to make a decent earth terminal for it.
 
Thanks Mike
todays efforts haven’t worked☹️ I read your post several times
the reserve tap on my car is missing, also the return pipe is not there.
so I decided to fit a new pump by pass the reserve electric solenoid that had been fitted
I now have two fuel lines joined and feeding the in connection on the pump,and the outlet goes to the carbs with a fuel filter in line.
the pump runs fine the filter fills, but as before the car starts and won’t continue to run, if I remove the fuel line at the carb fuel comes out at an alarming rate, so it appears delivery is ok,any ideas gratefully received.
thanks to all who are giving advice
 
Having thought about this , is it possible both needle valves are stuck closed
seems unlikely, but when you have illimitated everything else, then it has to be what’s left
 
Okay all sorted
the problem was in actual fact a replacement rev counter ,
I had inadvertently connected wrongly.
thanks for all the help to one and all
 
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