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MG MGB Technical - Fuel Pump Ticking.

Hello,
I have just had all the rear end restored,new valance, paint, new fuel tank, fuel lines etc. I have no leaks (what i can find)in the fuel system. With the ignition on and the engine not running the fuel pump clicks about every 5 seconds or so. Is this normal or does it indicate a leak somewhere in the system. I cant say with any accuracy if it clicked before the work was done. Any advice welcomed. Thanks, Chris.
Chris82

You could have a leak on the inlet side of the pump Chris, that would allow the pump to tick without a leak being apparent. With the ignition switched on and the engine not running the pump should tick approximstely every thirty seconds just to maintain fuel pressure. If you can't see a leak check to ensure that the float chambers are not overflowing due to leaky needle valves.
Iain MacKintosh

That is too often, it should click no more than once every 30 secs as the lower limit, in practice the time between clicks should be longer than that. Either a float valve in a carb is leaking, which should show itself as fuel coming out of the vent pipe from on top of a float chamber, or there is a faulty non-return valve inside the pump, possibly due to dirt, possibly due to work on the car, although there are filters inside the pump as well. A leak on the inlet side of the pump *external* to the pump wouldn't cause this.

If it's not a float valve then check the fuel delivery rate by removing a pipe from a carb and directing it into a container. It should deliver *at least* one Imperial pint per minute, steadily and consistently, with negligible bubbles, but in practice it should be more like two pints. If it delivers at least one pint you should be OK, but keep an eye on it and if it gets any worse, or if it is less than one pint, you may have to think about removing and dismantling the pump to clean out any debris, as you may get fuel starvation at large throttle openings. Hopefully it will be a one off, but if not you would then need to think about removing the tank and swilling that out. If it is dirt from the tank and you don't have a fuel filter in the engine compartment then it may also have contaminated the carbs, and indeed be a cause of a float valve sticking open.
Paul Hunt 2

Paul, Ian,
The fuel tank and rubber fuel pipes are all new as is the fuel to. The carbs are reconditioned units i bought last year.There is a filter in the engine compartment that i replaced about 3,000 miles ago and 'looks' clean. When i got the car back the clicking was apparent but more intermitent and i found a leak on the lower banjo which would not stop after nipping it up a touch. I bought new banjo's and copper washers and also the banjo bolts as the old ones looked a bit corroded where the copper washer seated. When i replaced these the top banjo was weeping but after nipping it up all appears o.k. There does'nt seem to be any fuel coming from the carbs. Thinking back to before the car was done i.m almost certain now that it never clicked after it had primed the carbs on start up. I'll check the banjo's again before i look at anything else. Thanks for your replys. Chris.
Chris82

Chris - Check that the fitting is tight for the fuel line at the side of the tank, that is a common place for an air leak. Beyond that, how old is your pump? It is possible on an older pump that the valves are worn a bit and need to be removed. It is also possible that a bit of debris from all the work on the back of the car has been trapped under one of the valve reeds. Try disconnecting the fuel line to the carburetors and directing it into a can of some sorts, then turn on the ignition and let the pump run full on for a minute or so (a good time to check the delivery rate - as Paul stated 2 pints per minute is the specified rate for the pumps). This should flush out anything that is trapped under one of the valve reeds.

Regarding the leaking banjo bolts - I have found that the fiber washers work the best of any other material in stopping leaks at the banjos. There may be another issue here - the newer pumps are set up for an 'O' ring between the banjo fitting and the inlet/outlet ports of the pump. If you have one of these newer pumps, no flat washer in that spot will stop the leak. If you will e mail me, I'll send you and article that show the assembly with the 'O' rings and has part numbers and dimensions for the 'O' ring. Cheers - Dave
David DuBois

Chris,

If I had your problem, I would disconnect the fuel line under the hood and plug it. This would tell if the carbs are the problem or not.

Charley
C R Huff

Dave, Charley, Ian, Paul.
Thanks for all your replies, i'm hoping to have another go tomorrow. I will try all your suggestions one at a time. Thinking on, i may have omitted an important detail when explaining my currant dilemma. This may be totally irrelavant 'but' my B is a 74 1/2 rubbernose with an NRP2 tank.The new fuel tank i had fitted is the later NRP1174. Is it possible that i need a vented or unvented fuel cap. Would the different tanks use different caps?

Thanks again,
Chris.
Chris82

Chris - I am not familiar with the different tanks part numbers, but the tanks for North American cars have a vent connection that is routed to the charcoal canister. the tanks for the earlier cars are vented through the caps and use a different filler tube at the rear bulkhead of the boot to use a vented cap. That said, a tank that is not vented will not cause the fuel pump to run on after the float bowls are full. On the contrary, a tank that is not vented will eventually cause the pump to stall when the level of the fuel in the tank drops sufficiently to pull a vacuum. Cheers - Dave
David DuBois

NRP1174
Paul Hunt 2

NRP1174 is the UK 77 and on (after the first couple of thousand cars) tank with the integral sender and delivery pipe. This should have a *vented* fuel filler cap, as should all UK cars regardless of tank. If you use a non-vented cap paradoxically it will *stop* the pump clicking when it should do, and you will get fuel starvation. US cars from 1970 had a series of different tanks with a special vent that was plumbed to the charcoal canister to prevent fumes going to atmosphere, it is these tanks that should have a *non*-vented filler cap.
Paul Hunt 2

Chris,

you can install your old filler neck and cap to your new tank for a test.
If this does not change anything, new valves inside the pump would be on my list first, as the inlet valve of the pump might leak back.

Ralph
Ralph

chris
dont use the copper washers on the banjos as there not good at sealing uneven surfaces, get some fibre ones which take up the imperfections better
could make sure the sender unit is seated and sealed properly

ralph
unfortunatly he cant put on his old filler neck as the nrp2 tank up to 77 had a angled spout out of the top of the tank and the later nrp1174 from77 is straight

ste
Ste Brown

The filler neck and cap are irrelevant to the pump ticking too frequently, as is a leak external to the pump on the tank side. A leak on the carb side would cause it, but to make it tick every 5 secs instead of 30 secs or less it would have to be a considerable leak.
Paul Hunt 2

Gents,
I have looked again and cannot find any visible leaks. I checked the delivery rate as Paul suggested and the pump delivered just over 2 pints in exactly one minute. The overflow tube on the front carb(overflow pipes disconected)at one point got damp only. I plugged the feed pipe at the carb end as suggested earlier and the 'ticking was still present.
It may sound silly but the 'ticking' isnt as loud now as before the work was done. Although the tank is only 1/4 full, the seal on the sender unit appears o.k. Should i now concentrate on the pump or is there anything else i've missed. Thanks for all your suggestions so far, i really would be stumped without you guys. Chris.
Chris82

If it's delivering OK - and yours is fine - I'd leave it. The other thing is to check the ticking rate *after* the engine has been running for at least a couple of minutes i.e. turn the ignition off then back on again as soon as the engine has stopped, and then time it.
Paul Hunt 2

Chris,

This may not be good advice, but if it were my car, and if I were absolutely sure that it had no fuel leaks, I would drive it a while and see if it fixed itself. With all the work you had done, it sounds like it may have been sitting a while, and maybe it just needs some exercise.

Charley
C R Huff

Hi,
I've just had another few hours trying to sort this problem. As i said before there is definatly no leaks what so ever. I pumped some fuel out of the carb end again but this time held the pipe in the petrol and there was no bubbles to speak of. The ticking rate was the same before and after the engine was run.At the rate it ticks i would surely see fuel leaking somewhere (about every three seconds)would'nt i? As i said in my last reply the 'ticking' is not as pronounced as it used to be, its more of a muffled tick and when i put my ear to the pump in the boot it sounds as though somethings rattling as it ticks. Is there an non return valve in the pump? if so could this be the fault. Would it be wise to buy a new pump and then try and refurbish this one for a spare. Thanks again. Chris.
Chris82

I'm guessing it's the reed valves inside the pump.

Fortunately it sounds like your problem isn't too
serious and the valves in the SU pump are
user-replaceable and relatively inexpensive.
Daniel Wong

Chris,

Take a look in the MGB tech archives (from just earlier this month) under the subject "SU Fuel Pump life expectancy".

In there you will see a note from David DuBois, who also answered in your current post. That thread (about the 11th one down) contains a link to see his info on adding a second non-SU pump to your car. If you go to that link and scroll down, you will also see a link that has some info on the SU pump, and a description of David’s SU pump rebuilding services.

I was glad I had seen the info in that thread when my pump failed in California a few days ago. I added the NAPA pump to my BGT, and the price was up to about $48, at least in Petaluma, CA. That makes David’s rebuild pricing look pretty attractive. You might consider putting the NAPA (or other) pump on your B, and then send the SU to Dave. When it comes back, you can use his instructions for running the backup two-pump system.

I suspect that David didn’t mention his service because he did not want to push his services on the forum, but since I’m not David, and have never met him, I guess it’s okay for me to mention it. If I understand the structure correctly, David’s info is piggybacked on Les Bengston’s MG website.

I hope I have not broken any rules of etiquette here, and if I have, please accept my apologies.

Charley
C R Huff

As I mentioned originally, if it is ticking frequently with no leaks the inlet valve is almost certainly leaking back. If driving it hasn't cleared it then you will need to remove the pump and get into the pump chamber. This is done by removing all the screws round the edge of the diaphragm and carefully parting the chamber from the solenoid body so you don't rip the diaphragm. There are two non-return valves inside the pump, side-by-side under two peforated valve caps, secured by a single clamping plate and screw. Take careful note of the position and orientation of each of the components under the valve caps, the inlet valve has a filter between it and the pump body, and a sealing washer either side of it. The outlet only has the valve and a single sealing washer to the pump body.
Paul Hunt 2

PS. Mark the position of the solenoid relative to the pump body before dismantling to ensure you get the same points 'throw' as before at least. Strictly speaking you should reset the throw in case it isn't correct currently. Screw the diaphragm in until the points fail to throw over. With the pump held horizontally slowly unscrew the diaphragm until the points just throw over, then unscrew the diaphragm a further 1/4 turn (the book actually says '1/4 turn or four holes', but 4 holes is half a turn).
Paul Hunt 2

Charley - Thanks for the good words, yes, I do restore SU fuel pumps and yes, I avoid pushing that on any of the BBS or other forums, but I do refer people to my articles from time to time. That said, I doubt that it would be cost effective for Chris to send his pump from the UK to Washington state for rework (although I recently restored four Rolls Royce 25/30 pumps for a gentleman in Wales).

Chris - Is the pump in your car a new, all electronic pump (if it is, there should be an aluminum tag on the flange at the bottom of the coil housing that says "electronic")? If you have an all electronic pump, then the 5 second throw over is normal. Unlike the points style pumps that depends on the throw over of the lower contact toggle to establish the triggering of the pump, the all electronic units have a designed in time delay that is set somewhat lower than what we have come to consider normal. The "muffled ticking" is also normal for the all electronic pumps.

In regard to Paul's instruction on getting to the valves, I would add the following. When removing the coil housing/diaphragm, don't move the diaphragm in relation to the coil housing. This is normally not a problem in that the diaphragm is usually stuck quite solidly to the coil housing. It is particularly important not to move the diaphragm on the all electronic pumps as it does nothing to change the speed or efficiency of pumping, rather it will move the magnet that triggers the Hall effect device and stop the pump from working entirely (if thing move inadvertently, e-mail me and I will send you adjustment procedures. Valves are available from Burlen Fuel Systems as are the three gaskets for the valves (the gaskets will probably distort from being soaked in fuel when removed.

Correction - "(the book actually says '1/4 turn or four holes', but 4 holes is half a turn)." Four holes is two thirds of a complete turn and is the correct amount of adjustment of the diaphragm for a points style pump.
Cheers - Dave
David DuBois

Almost 2o yrs ago, the fuel pump in my first B started to tick more often to the point that it seemed like there was no fuel in the tank even though there was. Basically my symtoms matched yours almost exactly, except that I let it go till it got real bad (although the car seemed to run fine). I took the fuel pump apart and found one of the valves was cracked. If I remember right it was a piece of clear or translucent plastic shaped like a fat plus sign. I found a plastic sandwich container waiting to be tossed, so I cut a new valve out of it and stuck that in. Worked perfectly. Since I had some gas in a jar from unhooking the fuel lines, I threw a piece of the plastic into the jar and let it sit for awhile. I was curious if the cheap plastic might be dissolved by the gasoline, so I watched the piece in the jar for a couple of weeks. It showed no deterioration, so I didn't bother doing anything further to the fuel pump. It was still working when I sold the car 7 yrs later. Super cheap fuel pump repair! FWIW.

Erick
Erick Vesterback

Ah yes, right you are, David. I forgot to look at Chris' location. Shipping would get in the way of that plan.

Charley
C R Huff

Dave,
I'm not sure if the pump is points style or electronic, i will look at it first thing in the morning. The pump ticks with the ignition on every 2 seconds (timed) and with the engine running at idle, every 3 seconds. If this is normal and it is an electronic pump, the problem (if i ever had one!)is solved. If its points style then i will buy a new one and refurbish this pump and possibly fit it in tandem as a back up. I shall print this thread for guidance when doing so. Thanks again everyone for sharing your knowledge. Chris.
Chris82

Chris - If the pump is a points style unit, you don't want to use it as a back up. Points style pumps don't like being idle for long periods of time and their revenge for not using them is that they won't work when you need them (the points film over and depend on the current through them to keep the film burned off. If not used for long periods of time, the film builds up sufficiently to keep the points from conducting). For information on a permanently installed back up pump, see my article at: http://www.mgexperience.net/article/backup-fuel-pump.html
Cheers - Dave
David DuBois

Gents,
Finally cured. I looked at the pump this morning and there was no tag saying it was electronic. I removed the pump and replaced it with a new electronic one and bingo, working as it should. When time permits i will try and refurbish the faulty pump and then put it in tandem with the new one. I will, after reading replies on this forum have the 'points' pump as the main pump and the electronic one as the back up. Can i thank everyone again for there valuable input that has helped me so much with this problem. Chris.
Chris82

This thread was discussed between 26/01/2008 and 01/02/2008

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