Petrol Pump Puzzler

[jleyton]

A couple of months ago, I'd noticed that my fuel pump (SU - possibly original one) continued ticking with the ignition on, rather than the customary tick...tick.. (for a few seconds) then stop. First thoughts were sticking float valves but no fuel was getting dumped out of the overflow pipes. However, despite this, the car continued to run perfectly well , so I just carried on using it.

Anyway, for one reason or another, I didn't use the car for a few weeks, but when I tried to start it, it had a flat battery. I started it with a booster pack but it died after a few seconds and this happened on several further attempts at starting. Investigating further, I could still hear the pump clicking continuously and guessed that maybe something like the diaphragm was damaged and it wasn't pushing through enough fuel to keep it running. Still with me so far?

As luck would have it, I have a spare fuel pump that I got from Peter at LD (one of his electric ones). I fitted that but, much to my surprise, that continued clicking and I had the same start...run...die problem as before. Hmmm..two pumps, same symptoms

That then led me to think that it could be a leak somewhere on the inlet side between the tank and the pump so it was sucking in air. However, the plastic pipe looked good as did the banjo. I then tried disconnecting the pipe from the tank and putting it into a petrol can, to try to rule out any problem with the tank. Maybe it's not the pump or maybe they're not priming themselves properly I thought. Anyway, to cut a long story short, I did everything I could think of, including fitting new fibre washers, but to no avail.

Whilst my original pump was still fitted, I ran a separate 12v feed to it, just in case, but it made no difference. Finally, in desperation, I swapped over and fitted the new LD pump with the separate 12v feed and, guess what ? it kept ticking, but, lo and behold, the car started and continued running ok

So, my theory is that my original pump has a problem (quite what, is yet to be determined) but also my battery wasn't putting out enough to make the new pump operate correctly - so in fact it seems that I had dodgy old pump and a good pump with a dodgy battery - both giving the same symptoms

I’ve been running with the new electric LD pump for a few weeks now and all seems to run ok, however, the pump continues to click ALL the time – no click..click…stop

So, my question is, has anyone else experienced this ?

Cheers

Julian

[Arbman Al]

Nope.

[malc4d]

Yup, sometimes. And every time l start up again the filter needs topping up again....where does the bloody fuel go to....Also the electric pump seens to have a low pressure prob.

[Staggard]

I know sometimes that different problems can have the same symptoms. Just a thought, did you when you fitted the new pump and run a separate 12v feed did you try a separate fuel pick up from a can? I was only thinking that there could have more than one issue going on with the old pump that could have been transferred to the new one. Graham

[andy p]

I last started and used my car in September to go the monthly N&N, fuel light came on while driving home parked it in the garage and left it, went out to start it last week and the pump never stopped ticking, I am guessing and hoping it is very low on fuel, have got a can full to put in and find out but not got round to it yet

[jleyton]

Thanks Guys,

Andy, for once, I had plenty of fuel and yes Graham, I did try the new pump with a separate feed and a pipe into a spare can. Malcolm, I know what you mean, where DOES it go ??

And Al, thanks for your comprehensive, considered and detailed response

Cheers

Julian

[wilf]

My (new, SU) pump continues to click after the initial float bowl fill, about once every 30seconds.

[davidf]

I think you need to try the pump off the car, pumping out of and back into a spare can. See what happens when you completely block the outlet.

Maybe the non-return valves inside the pump are failing?

[V Mad]

If the pump keeps ticking (and its not faulty) then either it is not drawing fuel up (tank empty or air leak), or the carbs are flooding. If you cant see any fuel leaking out of the carbs' breather tubes it's probably going straight into the inlet manifold, and forming a nice puddle of fuel

[jleyton]

Thanks Guys for your comments and advice.

The odd thing is that the tank is 3/4 full and the engine is running as well as ever and I haven't noticed any increased fuel consumption having done a couple of hundred miles since fitting my ticking pump

I have heard of another case where this type of pump worked perfectly but continued to tick like mine does. I've emailed Peter at LD to see what he has to say however if my car continues to run as it is at the moment I'll be very happy

Cheers

Julian

[V Mad]

Could there be an air leak at the pickup tube on the tank?

[Stagsongas]

Julian,

I've read carefully through your post and it seems you've done everything I would do to isolate and identify the cause. Problem is with the conclusions, there seems to be nowhere to go, but it still ticks!

I'll keep thinking on it, but good luck. At least it's running well

Regards

Steve

PS - one thought - are all the pumps you have tried designed to deliver the same pressure, and do you have a fuel pressure regulator in line?

And another 'one thought' - Is it possible for there to be an air bubble in the fuel line, one that the pump is constantly trying to compress, but is then defeated by the carb.s taking fuel from the other side of that bubble, alowing it to expand once more?

[jleyton]

Thanks again Guys,

Chris - that was one of my thoughts which is why I carefully checked the plastic pipe from the tank and then put it directly into a can of petrol .. all with the same result

Steve - I haven't got a pressure regulator and this pump is supposed to replicate exactly what the original did (or so I believe). Peter (who I trust totally) has had one on his car for 100,000 miles without problem. The air bubble is an idea !

Just come back from doing about 10 miles in the car and whilst I'm not sure if it's my imagination or not she seems to be running better than ever !

Cheers

Julian

Ps The pump is electronic solid state and so, perhaps, the ticking is just an artificial 'add-on' to give the reassuring sound of the original ?? - It can't be the points opening and closing

[Stagsongas]

Julian,

I think the logic is pretty tight here - it probably isn't the pump(s).

Regards

Steve

[Mike Stevens]

Ps The pump is electronic solid state and so, perhaps, the ticking is just an artificial 'add-on' to give the reassuring sound of the original ?? - It can't be the points opening and closing

Hi Julian,

If the electronics is like the Burlen kit, then all it does is replace the points with a magnet and hall effect device. The 'tick, tick' noise is the punger and diaphragm moving back and forwards not the points themselves.

A compressible air bubble is a very interetsing idea, but doesn't the fuel fulter in the engine bay always have some air in it? That's a big air bubble!

Cheers,
Mike.