AP Fuel pump

peterg · #1 (**permalink**) 27-03-14, 08:05 PM

Does anyone know if the Bristol AP fuel pump was fitted to any other (more common) cars?

The diaphragm 'bar' will no longer locate into the operating arm on mine. So it looks like I must source another.

GREG · #2 (**permalink**) 27-03-14, 08:40 PM

It's a UG pump that is identical to the G pump used on loads of Fords etc except the fuel goes the opposite direction

All the parts can be bought from Bristol or InRacing etc

GREG · #3 (**permalink**) 27-03-14, 08:42 PM

But don't by new old stock diaphragm as it can't stand up to modern fuel and ends up sending fuel to the engine oil ! New ones cure this issue

Geoff Dowdle · #4 (**permalink**) 27-03-14, 11:22 PM

Peter,
The Pump is a AC brand ( I don't believe there is any connection with AC Cars Ltd) , there are many variations of the same pump fitted to many British cars of the 40's , 50's & 60's
Bases vary in their bolt pattern to the block
The lever that operates the pump from the cam was made especially for Bristol .
Tops (above the diaphragm ) vary a lot also .
The operating rods on the diaphragms vary also

The closest I've found over the years are tops and bases from two different model Standard Vanguards of the 50's but you still need to use the original operating lever from the Bristol AC Pump .

Geoff

peterg · #5 (**permalink**) 28-03-14, 08:21 PM

No Geoff, but it is related to Champion and AC spark plugs.

Further checking today suggest that the pump is working but that I am sucking air into the system. Bubbles are clearly being drawn into the in line filter when the engine is at tick over.

I've checked all the joints and the only thing left is the fuel cock. It was very stiff but I have used it several times when removing the in line fuel filter and petrol pump.

Is this a known problem? It couldn't have been used for decades previously.

peterg · #6 (**permalink**) 29-03-14, 07:41 PM

By passed the fuel cock and I now seem to be drawing in petrol only. But the problem remains. What I thought was the pump working was probably only the vacuum from the carbs drawing in fuel.

Got half a mile up the road and it died again tonight.

Back to the fuel pump.

peterg · #7 (**permalink**) 30-03-14, 12:27 PM

Pump off yet again. It all seems to function. The one thing is that the rocker lifts about half an inch before it makes contact with the inner lever.

Is that correct or should it make contact much earlier? Could the locating spade on the diaphram be too long?

Geoff Dowdle · #8 (**permalink**) 30-03-14, 10:26 PM

Peterg,
what is the history of the pump ?
Have you ever had it running correctly on a Bristol engine before ?
or did you just purchase it and this is your first trial run?

I had a similar problem a few years ago , rebuilt a pump for a new engine in the 400 . After a few miles had fuel starvation problems .
I found for some reason the operating lever that runs on the camshaft was bent , this meant the lever was not giving the pump the full stroke and inturn not the correct pressure .
I checked the lever against another original one , straightened it , and it has run at correct pressure since.
These pumps are usually trouble free after fitting a rebuild kit .
Bristol 450's used them for Le Mans without a problem

Geoff

peterg · #9 (**permalink**) 05-04-14, 06:49 PM

I'm getting tired of this problem. Is there any reason why I should not put a low pressure pump in the line?

I know the AC pump works on suction supply which would be redundant but the outlet has a pressure control to stop excess flow to the carbs. The problem seems to be getting fuel to the pump. Even with a separate supply pipe it isn't being sucked through by the pump.

I've bought a new pump. A Standard Vanguard pump XP4602 which is almost identical on the bottom half except the rocker arm is slightly longer and I will transfer the top half if I cannot connect the inlet pipe (faces towards the engine block) up.

But in the mean time my daughter's wedding is now just weeks away and it's an immovable feast so my Bristol must be moveable in time!

Geoff Dowdle · #10 (**permalink**) 07-04-14, 10:51 PM

Peterg,
You never advised the history of your pump .
Has it ever run correctly on your Bristol ??(it might not be a original Bristol pump)
What model Bristol do you have ?
Please advise the casting number on the lever that runs on the cam ?
I'll check it against an original one .
Have you fitted the diaphragm to the rocking lever correctly by pushing it against the blade spring and turning it through 90 degrees.
Is it the correct diaphragm /kit??
The rubber diaphragm must be set correctly before the fixing screws are tightened.
I doubt that the Standard Vanguard lever will be correct for the Bristol.
I don't believe there is a pressure control device within the pump , the correct stroke of the lever produces the correct pressure, from memory 2.5 - 3 lbs/sq in . Some owners fit a thinner or thicker gasket between the pump body and block to adjust the pressure , but I doubt this will make much difference to the pressure.
My experience with a pump fitted with bent lever only produced about 1 - 1.5 lbs , it was straightened only about 0.040 at the lever and the pressure increased to 3 lbs
Have you got the two valves seated correctly on the gasket and in the correct
position

These pumps are usually trouble free for up to 20 years , eventually the diaphragm rubber hardens .
How do you know that the pump is not producing the pressure ?
Have you put a pressure gauge in the line to check the pressure at about 3000 rpm for about 2 minutes.

If you need to take the car to your daughters wedding you can always fit up a temporary electric pump that produces no more than 3 lbs/sq in

Keep at it, you will fix it , they are a simple pump that work well.

Geoff

Geoff Dowdle · #11 (**permalink**) 07-04-14, 10:55 PM

Peterg,
here is a link to a AC pump used in a Riley , the principle is the same as the Bristol pump .

http://www.rileywa.org.au/RM_Manual/...section_BB.pdf

Good Luck
Geoff

peterg · #12 (**permalink**) 08-04-14, 03:42 PM

Thanks for your reply Geoff
The pump came with the car & I have no reason to doubt that it is not the correct one. It is stamped 4516xx. I did have a note of the lever but have mislaid it for the moment.
Once upon a time it worked OK!

I believe the (new) diaphragm is fitted correctly and I have put in new valves which give a good blow & weaker suck.
It is the correct diaphragm kit. Checked it against the new Standard pump. The primer works immediately and the lever lifts about half an inch before operating the diaphragm which is the same for the Standard pump.

I don't know if the pump is producing the correct pressure but petrol is sucked through when it is manually primed, it does pump when running (disconnected the outlet pipe) and I can blow petrol through the disconnected pipe from the tank.

The line has two clear full flow paper filters, one at the tank and the other below the pump because of fuel problems. Previously it worked OK with a clear filter at the front and a large VW filter at the rear.

The pump I have ordered gives 2.5 to 4.5 psi.

Regards, Peter

flyinghorse1 · #13 (**permalink**) 08-04-14, 04:09 PM

Peter,
I once had a brand new AC pump and found that the diaphragm was cut at one of the screw holes. (the small screws that go round the outside -about 6 of them.(Lotus elan)

I have also built the Bristol 400 pump I have on my car and the diaphragm rod is hard to relocate in the actuiating lever (like geoff describes).

You say one key thing for me--the manual primer works,suggesting poor mechanical engagement somewhere---note the pump when fitted rides on top of the camshaft. On the lotus you could put it on underneath if you were not careful and get no pressure--I recall this when fittinmg to my 400 as well. I would turn the engine over on the start handle so the cam lobe is at a low point.

I am assuming your diaphragm rubber is nice and shiny and not destroyed to just cloth by methanol in the fuel.

I also test the pump on the bench before fitting to ensure flow direction is ok & all works.

If you are fitting a electric pump a lot of people use Facet red or silvertops with a filter king filter & pressure regulator.
(made by Purolator Products Company, Elmira, New York. The UK agent/distributor can be contacted on 01784 493555 )
I would fit it out of sight at the rear of the car underneath.

Be careful with polarity of your car & the pump (ie positive or negative earth) and you will need to make a small blank plate for the mechanical pump or just disable it and allow the electric pump to push fuel through it for a period look.

Graham

Geoff Dowdle · #14 (**permalink**) 08-04-14, 10:49 PM

Peter & Graham ,
further comments
1. you need one paper filter between the pump & the rear carb ,not two on the suction side , this could be a part of the problem with the pump having to suck through two filters that could be partially blocked.
2. An Electric pump at the rear will push the fuel through the original AC pump , my AC Ace Bristol was set up like that .
2. I agree Graham a pressure regulator might be needed at 4.5 psi or the needle & seat could flood the carbs .
More Problems ,Polarity another problem .

3.I'd buy a low pressure SU pump as a temporary fix (even a used one )which will give 2 - 3psi for the wedding then fix the AC Pump , as I have mentioned before they are a very simple forgiving design .
Geoff

peterg · #15 (**permalink**) 09-04-14, 01:35 PM

I am loath to put a filter between the pump and carb as it is the original solid copper pipe.

The casting number on the lever is 822N3 (or the N could be 8).

Incidentally both filters are new. Location of the cam is an interesting issue that I haven't considered before. The polarity isn't an issue as it has been rewired negative earth.

Geoff Dowdle · #16 (**permalink**) 09-04-14, 10:07 PM

Peter,
you might have the wrong pump lever fitted.
The two original pumps I have are fitted with levers of casting number "1524280"

The Standard Vanguard pump I have uses 1524043 which is quite different .

I've attached a photo of the pump lever and sketch which shows the angle between the working surface on the cam and the machined surface between the locating tit of the spring and the pivot point hole of the lever is approx. 60 degrees .

http://www.bristolcars.info/forums/a...1&d=1397080785

If you have the wrong lever I doubt that it will work except at idle .

Geoff

flyinghorse1 · #17 (**permalink**) 10-04-14, 10:19 PM

This is the fuel pump from the Bristol manual (400) its a UG as previously indicated. I assume you have both springs.

flyinghorse1 · #18 (**permalink**) 02-05-14, 08:06 PM

Peter-Did you all get to the church on time?

Graham

peterg · #19 (**permalink**) 03-05-14, 03:46 PM

Thanks Graham,

Yes, I got us to the church OK. It was the first time my daughter had seen it in that condition and she was very impressed.

However it disgraced itself afterwards. Bride and groom were loaded for the trip down to the reception and people were taking photos of them. A nephew asked me to open the driver's window to take some pictures. It got halfway down when the window dropped into the door and snagged the lock cables causing the door to open and not shut.

Eventually they went by another car and I limped home with a friend holding the door shut.

At least I got her there and apart from that it was a very good day. One to remember for the right reasons (mostly)!

Unmentioned problem was the fuel tank leaking most of a tank of fuel while it was being retrimmed. Solution was to fit two BSA four gallon tanks to a cut down pallet tray and put them in the boot. Worked a treat.

Then the day before taking the car away the door strike plate fell apart and I got the last one from Bristol's at a price. If I had the time I could have got one cast for less than that!

The only issues now are getting the grub screws for the door locks and a replacement door winder as mine has cracked inside the 'square' section, and working out how to get the other one off the winder mechanism. Oh yes and the locking mechanism on the other door opens rather than locks the door!

flyinghorse1 · #20 (**permalink**) 06-05-14, 12:47 PM

Peter,
Thats good news that you finally got the car running to be able to get to the church.

Did you use the original mechanical fuel pump or the 6v electrical solution?

I dont know much about the door lock grub screws and lucklily the 400 has sliding windows. A decent fastener specialist should be able to help. I have a business card with one on that I will drop details at weekend(first opportunity to get card).

I assume the winder mechanism is held on the square section by a small grub screw that needs persuading out. May be lucky if its a brass grub screw and can be drilled out if it wont come out on its own. Some pictures would help.

Graham