AC T type fuel pump problem

[Robin Oldfield]

I thought I would treat the AH to a new fuel pump from The Seven Workshop but could not get it to work.  Jamie very kindly sent me a replacement and told me to keep the first one for spares.  However, I can't get the second one to work either.  Whether I'm pumping air or dipping the inlet pipe in petrol I get no output at the exit pipe but air or petrol exits through a tiny hole in the pump body.  See attached photo.  Has anyone else experienced this?  I have an old original one which behaves as I would expect, so what am I doing wrong?

  t type pump.jpg (Size: 971.8 KB / Downloads: 579)

[Tony Betts]

hi robin,

ive had plenty of customers come to me with problems on these pumps.

but so far they are all saying there problem is to much fuel is being pumped. as if the return valve is set for a much higher pressure system.

its the first time ive heard they dont work.

the obvious thing is to test of the car, by putting your finger over the inlet then outlet. you should feel suction and pressure. 

if unsure as you have probably done put a tube from the inlet into fuel, and see if it pumps by hand.

if not, if the system has been sitting  for some time. and jamie does not need it back. fill the fuel chamber with fuel. to see if it will inisiate the system to work.

if it pumps the fuel go back to hand pumping.

always be careful when fitting, that the pump arm is on the correct side of the cam.

the other thing is on original fuel pumps, austin seamed to use two different part numbers on the arms. dont know why but the number ending 049, seems to work on all engines. the other number only seems to work on SOME? engines.

i dont know which number arm jamie used for his new pumps.

good luck tony

[Nick Lettington]

If petrol exits from that hole, which is beneath the diaphragm, it can surely only mean that the diaphragm has a hole in it.

[andrew34ruby]

If petrol exits from that hole, which is beneath the diaphragm, it can surely only mean that the diaphragm has a hole in it.

Or could it be a hole in the casting?

[Ian McGowan]

I incline to the same view as Nick, if fuel exits the hole below the diaphragm,  there has to be a hole in the diaphragm or, as has been said , in the casting.
Robin, I would stay with the original pump that appears to work and, if necessary, install a new ethanol proof diaphragm.
If it were mine, I would blank off the hole in the crankcase and use a SU electric pump ( as I actually do!!).

[David Stepney]

I had a replacement 'U' type pump from Jamie some months ago and that refused to pump fuel. Rather than cause a fuss, (and I needed a pump!) I replaced the valves and it worked fine, except for the 'dripping carb' syndrome which has been discussed on this forum in the past. To be fair, when i mentioned the matter to Jamie en passant (I had sorted it out by then) he was very good about it, said that i should have returned it to him and and knocked money off my subsequent order.

However, having found a 'T' type pump repair kit  whilst looking for something else in a box of bits I had had for years, I have since rebuilt my original pump and this is working fine.

There does seem to be a bit of an issue with the quality of these replacement pumps.

[Bob Kneale]

The cause of the dripping carb problem can possibly be traced to higher fuel pressure from the new pump.To a large extent, the fuel pressure depends on the strength  of the spring below the diaphragm. The needle valve in the float chamber is doing its best to regulate the fuel flow but is being forced to admit more petrol until the float has the extra buoyancy to force the needle shut.Probably the easiest way to solve the problem would be to replace the new spring with one from the original type 'T' pump. I've done this before and it has solved the problem, but I've only done it once and I may have been lucky..... The basic physics of the problem must be right however.

The number stamped on the pump arm is usually 4079, which works on my engines. The bottom half containing the diaphragm is the same for both type T and U pumps, but make sure the flange mounting is the same - I was caught out by this, and only found out when I came to fit the pump. The type U pump is a better device if you're not too bothered about absolute oriiginality because the one way valves are much more reliable.

Hope this advice/diatribe is of help.
Bob

[Robin Oldfield]

Thanks to everyone for their input.  I have dismantled both new pumps and the diaphragms seem intact. The old one that was on the car was not too reliable.  The other old one I had was the one that worked beautifully so I put that one on.  Duly tried to start the car and clunk - it locked up.  Removing the pump and hey presto the engine turned again.  It was then that I looked at the number on the arm and remembered a previous thread about this.  Hopefully no damage done.  So I am now putting a new diaphragm on the unreliable one which has the shorter actuating arm (ending in 5) and hoping for the best.  In the meantime looking for a genuine one that works.

[Jeff Taylor]

I saved this information from a previous thread on the old forum:

The correct arm number should be 856955.

though 1524079 does apparently work fine without problem.

I wish someone would commission a batch of new arms of the correct shape / spec as I've got a NOS Army Surplus AC pump from the 1940's in its original WD box - but the arm is different from those on a Seven.

[David Stepney]

The top of the 'U' type pimp will fit straight onto the bottom of a 'T' type pump. Just undo the six screws. The diaphragm comes out with a half turn after pushing it against the return spring, so, effectively, one can put the new pump onto the old bottom and (assuming the valves are ok) all should be well.