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MG MGB Technical - MGB GT Fuel Pump not working

Hi

I have a MGB GT (1971) and it has been garaged for five years. Prior to this the MG did run.

I have a fuel pump (SU) problem with the car.

The original pump had stopped working, no ticking noise at all and no fuel getting to the carbs.

I replaced the original pump with a 2nd hand pump (bought from a reputable supplier), this ticks constantly and no fuel is getting to the carbs. I have disconnected the inlet pipe at the carbs and can hear & feel air coming from the inlet pipe. Is this a air leak issue?

I also in desperation took the original pump apart and cleaned the points.... I refitted the original pump and it worked. Car started but would not idle and backfired and the engine rocked quite a bit, that night I read into this and it would seem that i have put the ht leads back on in the wrong order.

The next day I went back to my car to change the order of the HT leads, turned the key and nothing the Original fuel pump has died.

Now not being a mechanic I am not quite sure how to fix this.

The original pump, even though i did get it to work for a while has completley died.

The 2nd hand repalcement appears to have an air leak and i am unsure how to fix this.

So my question is this should i just buy a new pump or can the 2nd pump be fixed? or is there another issue here?

What i dont want to do is pay out for a new pump, fit it and for it still not work due to something else.

I dont think the fuel pipes coming from the tank to the pump are damaged, faulty or blocked as after i got the original pump to work the car did start.

Oh, I replaced the O rings for both inlet and oulet pipes attached to the pump as the orginals had worn out.


Apologies for such a long thread.


Thanks any help in advance.

Rick73
R Parsfield

The original pump may be coaxed into life by tapping it with a hammer or even slamming the driver's door may jolt it into life - it is a well known issue with sticky points on these pumps.

In my experience, fitting a used pump or trying to fix an old pump is at best a temporary measure.

Get a new SU pump - don't be tempted to buy any of the cheaper plastic bodied pumps - the failure and leakage rate on these is high.

If you do buy a non SU pump, make sure it is NOT a high pressure unit, these will overfeed the carbs and cause problems unless a pressure regulator is also fitted.
Chris at Octarine Services

Check feed pipe from the tank to the pump. They often corrode and allow an air leak which may account for your air delivery but no fuel

Jim
jim soutar

Hi

Chris, I agree I think a new pump is required.I tried tapping the original pump but no luck.

Jim, I have checked the pipes and they all seem to be ok. I sort of ruled a dodgy pipe out as I got the orignal pump to work (albeit for only an afternoon)and the 2nd hand pump I purchased ticks away like mad but dont deliver fuel, so i think the problem is with the pump, but i could be wrong.

Thanks for both your comments its most appreciated.

Rick
R Parsfield

Check the second hand pump on the bench to rule out tank, pipework, pick up and electrical issues.Repair it, probably needs a new diaphragm, and put in the boot as a get you home spare. Get a new pump!
Allan Reeling

Does the 2nd hand pump need priming? Has it become dry inside and can't suck petrol? Try priming it. I only throw this in the pot as an idea because I know that other makes of pump (eg Facet) are not too happy if they are completely dry inside.
Mike Howlett

Hi

Allan, thanks for the advice, keeping and repairing the old one as a spare is a good idea.

Mike, priming? I know the 2nd hand pump is dry as there has been no fuel leakage after I removed it (unlike the original pump), not even a little. Due to my lack of knowledge I have no idea how to prime a fuel pump, could you explain further.

Thanks for the advice
Rick
R Parsfield

As I recall in my days in the auto elec bay we use to repair SU pumps, having cleaned the points refit them to the cap assy screw the diaphram assy and rod through the main body into the rocker assy holding the points 9 complete turns, push up on the diaphram assy till the rocker clicks the points open if it dose not unscrew the diaphram half a turn and repeat the operation, do this untill the rocker assy works the points open and then complete the assy of the pump,
Bench test with 12 v battery and listen for rapid clicking action of pump. If that's ok fit pump to vehicle.

Regards Patrick
P.T. Tighe

Hi Patrick

I dismatled the orignal SU fuel pump as you described.I have refitted the original fuel pump, this worked for an afternoon before it siezed up again. Fuel was reaching the carbs.

The 2nd hand replacement pump clicks away like no tomorrow but no fuel is reaching the carbs indicating an air leak. As the original pump worked (albeit briefly)I am presuming that the 2nd hand replacement SU pump is at fualt rather than any other part of the car.

But you know what they say about presumptions....

thanks for you help.

Rick



R Parsfield

Rick - E-mail me at SUfuelpumps@donobi.net and I'll send you information on assembly and adjustment of the pumps. Cheers - Dave
David DuBois

Sorry to jump in. My MGA pump has been acting up lately by working then not working. I just took the old one apart and went at it with a nail file on the points cleaned up nice put it together. Its working fine but I would like to have any specs you have to set the points as Im sure I just got lucky.
Sorry to butt in Rick, Oh and goodluck.
Rick73

Dave I sent an email, Sorry to be so forward but I could use the advie if you have time.

Thanks.

Steve D
Steven Devine

The SU pump should be perfectly capable of priming a completely dry system (bar the tank!) just by itself. If you can feel air coming from the pipe at the carbs then it must be sucking air in somewhere, which could be a bad air leak on the tank side, or the pick-up pipe inside the tank rotted out, which on a 71 means a new tank. Remove the tank side from the pump and blow down it to see if you can hear bubbling. If not, some aperture in the pipe is above the fuel level. How much is in the tank?

The points on SU pumps oxidise if not used for some time, even new ones are shipped with a slip of paper saying to clean the points before returning a non-worker as faulty. You also need to check you have 12v at the two spade terminal on the pump on any pump that isn't clicking.

If cleaning points you really need to check the throw afterwards. Remove the screws around the diaphragm i.e. where the solenoid half joins the pump half. Screw the diaphragm spindle into the points until the points just fail to throw over, then unscrew until the just throw over, then a further quarter turn, then to the next alignment of the screw holes. Make sure the fixed contact is resting on the bar on its mounting plate when the points are open, and lifted off the bar when they are closed.
Paul Hunt

Hi Paul

Thanks for your comments and advice.

I dont think its the tank... I only say this as one pump delivers fuel when the pump is working, this is the origanal pump. This pump has had its points cleaned and works for a while then ceases up.

The 2nd hand repalcement pump clicks rapidly and no fuel gets to the carbs.

I think I have two duff pumps,,, the original has given up the ghost and the 2nd hand replacement has an air leak.

I think I will remove the 2nd hand repalcement pump (the one that dont deliver fuel to the carbs) and attempt to see if it works off the car. This way I will see if its the pump or not.

Many thanks Rick
R Parsfield

as posted on previous thread IMO the points type pump are just a PITA and I prefer the metal bodied electronic versions of the same, I'm not a fan of the noisy cube ones either

I'd fit and forget a more modern electronic equivalent and also avoid and forget the 'period charm' of slamming doors or grovelling around on the ground with a stick or hammer and spend that time driving your car instead

many years ago I once lost a day's work because of the 'charm' of having an original style points pump fitted so it was one of the first things I changed, even though it was working, when I got my present Midget, a car that wont start is really annoying to me, I don't understand why owners enjoy unexpected unreliability and fiddling with their classics when they can make them very reliable and able to drive them more, I think some owners have classics to fiddle with rather than drive and that's up to them but it doesn't usually provide for a reliable car if only for the lack of being driven
Nigel Atkins

Metal bodied electronic pumps are an equal PITA - they fail in exactly the same way!

I spent quite a lot of money on a Facet pump which lasted all of a few months before failing. Replaced that with an electronic SU and that needed constant adjusting of the damper arm to get the thing to run.

In the end I fitted a standard points SU pump and it has run faultlessly for over 10 years...
Chris at Octarine Services

Chris - I have to disagree with your assessment of the all electronics SU fuel pumps. Once adjusted properly, they will run just about forever. I stuck one in our MGB to test it out after they first came out. It is still on the car and after at least ten years, it is still going strong. Unfortunately, a lot of the all electronic pumps were coming with the adjustment marginal right out of the box. I have lost count of the number of the all electronic pumps I have had to readjust for people. There are two adjustments that have to be done correctly - one is the throw of the diaphragm, which is adjusted with the magnet carrier and then locked down with an allen screw (I use a bit of green Loctite on that screw). Once that adjustment is made, the Hall mask (the fork shaped metal under the circuit card) has to be adjusted for optimum running of the pump. Not only do It make that adjustment, I further lock it down in the center of the range of the optimum operation so that nothing can drift off over time. I have never had one of those pumps that I have adjusted come back to me. Cheers - Dave
David DuBois

I havent yet been stranded by the old points type.

You always know when it time has come when they start acting up!

Mine is aboout 10 years old and just started acting up 2 weeks ago.

I would like to try the electronic one but Ill wait till one of my friends fails and offer a fair used price and fix one.

Thanks for the info Dave I was able to fix 2 of my old pumps. Cheers to you!

Oh ya there is nothin worse to have a car with an intermitant fuel pump out this way. They dont give you a break driving and everyone is an expert when you are stuck by the side of the road! Its a scary and humiliating situation!
Steven Devine

I fitted an electronic Q&H round metal body (no points) 6 years ago I don't even think about the pump and only hear it when I first switch on and when I run the tank far too low

I have absolutely no idea what is meant by adjustment these are not SU replicas, you fit them straight out of the box without adjustment, I am proof that an idiot can do it, SU are about twice the price and if you need to be an expert to set them up then also unecessarily complicated
Nigel Atkins

"I have absolutely no idea what is meant by adjustment these are not SU replicas, you fit them straight out of the box without adjustment..."

That is the way the all electronic SU pumps should be, but there are obviously some kind of quality issues with the pumps that Burlen Fuel Systems have been putting out. I have to wonder if that is not behind the current issue with inventory.

I have also heard recently, that the Q&H pumps are no longer going to be made. Does anyone know the story behind this? Cheers - Dave
David DuBois

Nigel,
You dont seem keen on getting the full MG experience. In order to become one with your vehicle a SU pump rebuild is manditory. Other wise you will always be looked upon as a Neophyte!

LOL!
Steven Devine

"In the end I fitted a standard points SU pump and it has run faultlessly for over 10 years..."

Ditto. Admittedly it was a plastic-bodied Moprod, but once it decided to start short-stroking there was nothing I could do until it decided to start working again. I was even able to get inside the electrics end while it was doing it (rubber bumper) one time but nothing I tweaked, pulled or poked made any difference. Put on a points pump and ... as I say, ditto.
Paul Hunt

Paul - For people like you and many others on this board (me included) who drive your MG on a regular (read daily) basis, the points style pump will give many years of faithful service. Unfortunately, there are a lot of people any more who only drive their MGs on dry sunny days and then only when there is light traffic. These are the people that the all electronic/solid state pump were developed for. Points style SU pumps that are left idle for long periods of time develop a film/oxidation on the contacts that is the whole crux of the problem with the points style SU pumps (I make the distinction because German points style pumps don't seem to have the problem of this film/oxidation - perhaps we should find out what alloy they are using for their contacts).

The issue of sloppy adjustments on the all electronic SU pumps should not be an issue if there was a better quality assurance program put into effect at BFS (my opinion) that would insure that the pumps are sent out properly adjusted and locked in position. As I stated in an earlier post, none of the pumps that I have adjusted for people have ever come back to me. As for the points style pump adjustments being easier and more reliable, may I forward the following - most of us, who drive MGs and have driven them since we were old enough to legally drive any automobile, have become very familiar with the adjustment of the points in the SU pumps and can nearly do it in our sleep. The all electronic SU pump adjustment is different and something we have to learn, just as we did on the points, before we can set the adjustments on them as a second nature, as we have with the points over the years (case in point, try adjusting the points on the German Harting/Hardi pumps using the method of adjusting the points in a SU pump).

Except for the distances used, most people using my optical trigger, solid state modification on the SU pumps will be much more comfortable trying to adjust them since I use the original toggle from the SU points to carry the interrupter vane. The only returns I have had with this modification was the result of transistor failure (I've never have had one come back due to and adjustment problem). I have correct the transistor failure by using a more robust transistor and paying more attention to controlling electrostatic discharge issues. Cheers - Dave

Note: I am not writing this in an attempt to convert everyone to the all electronic SU pumps (or to my optical trigger solid state modification). I am only trying to bring to light my observations of the issues with the all electronic pump issues that seem to be plaguing Burlen Fuel Systems and why people tend to want a pump without points.
David DuBois

I installed an all electronic SU fuel pump ten years ago when I also purchased a Moss supercharger system. It's behaved flawlessly under all the various driving conditions that I've put it through. RAY
rjm RAY

Steve,
I've had enough classic car experiences to last three lifetimes I don't need or want any more than I can't avoid now

as I keep putting I only enjoy driving my car nothing else, I leave that macho stuff to chaps like yourself :)


David,
I'm not sure about Q&H (or whatever the European parent company is called, can't remember now) I just looked at there website the last month and it was down and then someone put they were in receivership? / gone bust/ / out of business? / taken over? - sorry again I can't remember

the Q&H I fitted was about half the price of a SU electronic personally I don't looking for 'labels' on anything and certainly not under a car where it's be dirty, for a fuel pump I want out of sight and mind

and I didn't have to fiddle with it (me I mean not you) to get it working properly
Nigel Atkins

Nigel

What? At the tender young age of fifty two! You declare this.....

"I've had enough classic car experiences to last three lifetimes I don't need or want any more than I can't avoid now"

My response is......Impossible, you could live ten more lifetimes and never gain enough car experiences good or bad! Strap a set of nuts on my friend!
How about the ones from your trunion experiment....

LOL! :-)

"I leave that macho stuff to chaps like yourself :)"

HHHMMMM.... I never thought sitting at my bench with a bunch of jewlers tools squinting hunched over tiny components scattered in front of me made for a macho picture! If it were I guess I would be up for an award though! LOL! :-)


Steven Devine

Steven,
the macho stuff is your oxy-somethingorother torches, most car owners don't have those sorts of things, "you only need a few basic tools to run a classic"

some of us don't have workshops or garages or sheds full of obscure tools or lathes to make tools and components, even if we knew how, some of us don't even have a garage for the car so have to rely on the weather to do work outside in the elements and being Britain it's either too windy, too wet or even too hot to work on the car - and when the weather is just right to work outside on the car that's exactly the time you should be driving it not working on it !

and let's have this sorted once and for all











. . . I put I was nearly 35, so I'm 53 (not 52) ;-)
Nigel Atkins

Yes Nigel its good to be resourceful. Ive done plenty of time working out side with a minimum of tools.

If you like old cars and naturally like to see how they tick, eventually the tools of the trade find there way in to your tool box.

I didnt have the big bucks for a restored beauty, but I did have time to learn.

You can do a lot with a little when thats all you have to work with. Believe me I know I couldnt afford to have my car worked on, I had to do it myself in order to have it.

Nothing special about having a set of torches... Excellent for cutting things up you know. I was once able to cut up an mgb so small the whole car fit in to a rubbish can.

I do realize the weather can be tricky everywhere.

I do live an a part of the USA called NEW ENGLAND
perhaps you recognize the spelling as something familiar to you! LOL! :-) Im pretty sure the weather patterns would be close to what you experience in your home town.

Happy birthday..... I guess since Im not sure when yours was I must have missed you moving forward one peg!

Cheers!
Steven Devine

This thread was discussed between 15/07/2013 and 18/07/2013

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