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MG MGA - Petrol pump ticking

I got fed up with SU petrol pump failures. So I purchased and fitted a brand new Jaguar SU pump.

This also failed after a couple of years and required the gentle tap with a small hammer to encourage it to operate.

So I now have an SU style electronic pump which so far is behaving itself. The only problem is you can hear it ticking. If I leave the car for a few hours when I turn the ignition on the pump appears to tick for about 30 seconds while it fills the system and I can also hear it ticking when I'm driving

My question is why is the pump always trying to add pressure to the system? There don't appear to be any obvious leaks and there is no smell of petrol in the garage. Is it possible that the pump should be fitted with a non-return valve which is not working?

Regards...John Bray
J Bray

Mine does it as well, but I just concider it music to the ears! It's the cars way of telling me she is going to start today :)
WMR Bill

It should tick while driving - otherwise it isn't pumping - the rate of tick depends on how fast you are using fuel. I can only hear mine when I switch on - once the engine is going (with the top down of course) I can't hear anything else!!- cheers Cam
Cam Cunningham

John----Cam is right. Pump has to tick. When the fuel level in the carbs drop enough to open the float valve the pump responds by ticking.(working)
Just remember NO TICKEE NO DRIVEY.
Sorry I had to say that cause I couldn't resist.
Sandy
Sandy Sanders

I appreciate the pump has to tick whilst driving, and the rate of ticking is roughly proportional to throttle openings.

The question is the excessive ticking once left for a few hours? and in particular I'm trying to establish if there a one way valve designed to maintain pressure in the system which may be faulty.

I also quite like the idea that its the car talking to me, but its also a constant reminder of how much fuel I'm using.

Regards...John
J Bray

Sandy, is that comment related to the ne owners of MG? :>)

The "excessive pumping" could be related to junk in the input check valve inside the pump. If there is any dirt on the plastic disk, then you will leak back into the tank. Not a serious problem if you cqan sustain high speed under load. there are 2 check valves in the pump one on the input side and one on the output side. Based on your description, I suspect that the input check valve may need cleaning.

Chuck

C Schaefer

15 years ago I fitted a solid state Facit. It ticks all the time the ignition is on, even if the motor is not running. It is a smart little jigger, it ticks like mad at first, then when the fuel reaches correct pressure it slows down. It still ticks at this reduced rate because it has a "pressure regulated by-pass"!
Maybe your pump has as well!! Check it out.
Barry
BM Gannon

25 years ago I installed the Moss solid state pump, 377-420. Flawless ever since. The only time I really hear it is when the tank is almost empty. It is a much better gage than that thing on the dash that has never worked right AND it sounds an alarm!
Steve
Steve Meline

J, I understand your question. You’re wondering why you get the burst of ticks every time you turn the ignition on after sitting awhile. IMO, I don't think the system was designed to be like our hydraulic brake/clutch were constant pressure is needed. With the thinner liquid (Fuel) and the constant temp change (Expansion & Contraction),the fuel line is not designed to maintain a sealed constant pressure without the assistants of the fuel pump.
WMR Bill

John

The fuel just drains back into the lower part of the system whenever the engine is not running. I always have to let the system prime for a few seconds before starting the engine. The valve in the pump is just a simple disc that is operated by a spring. It's not fuel tight, so it always allows the fluid to seep back in he direction of the tank. The pump reacts to the fall in presssure with another pulse, so this is why you hear the pump clicking on a regular basis even when the engine s switched off.

The valve is a bit like modern heart replacement valve in the way it operates, so think of the tiks of the pum as th heartbeat of your car. If it's clicking nocely, then all is well
dominic clancy

Thank you everyone for your helpful comments, I now understand how the system works.

Regards...John
J Bray

This thread was discussed between 08/09/2007 and 10/09/2007

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