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MG MGB Technical - Fuel Pump

I have a 79 Mgb and have had fuel pump problems for about 2 years. I removed the original SU pump, fuel sending unit, gas tank and fuel filter replaced with new items but still no luck. When I turn on the ignition, there is no clicking sounds that indicate the pump is active. Someone told me that the contacts on the pump may need adjusting. When I installed the new pump I never played with the contacts so could this be the problem or may they need replacing.
Hope someone can help me.
Duncan Armstrong

Hi Duncan.

I assume that the pump sometimes ticks merrily away ?.

It might be sticky contacts, try giving the body of the pump (not the plastic cap) a tap with a screwdriver handle with the ignition on. Don't get carried away !.
A little Servisol switch cleaner (which is intended for use on contacts like those in the pump) can help in my experience, but some ppl don't like it as they fear it will attract dust.

Is the supply to the pump reliable, and is the pump properly earthed ?.
Check with a test lamp that there are volts on the feed side and no volts on the earth side.
The wire that feeds the pump sometimes chafes and shorts to earth, it is a good idea to fit a fuse under the bonnet anyway.

Please let us know how you get on.

Don
Don

Duncan - I assume that you replaced the fuel pump with another SU fuel pump and would ask how often do you drive your car? If the car is not driven often, the points in the fuel pump are probably filming over from disuse. The film that develops is insulating and will keep the pump from starting up after long periods of inactivity. Look at my article on fuel delivery troubleshooting guide at:http://www.custompistols.com/cars/dave/ddFuelDeliveryTroubleshooting.htm
for other possible problems in line with the advice that Don gives above. It is not likely that the points in a new pump are misadjusted bad enough to kep the pump from running, but anything is possible and if you need instructions on the adjustments beyond what is in the shop manual for your car, e-mail me and I'll send you a write up on doing the adjustments. Good luck - Dave
David DuBois

Thanks gents for your great assistance. I will give your tips a shot in the next week and see how things work out. I will let you know how things shaped up. Again, thanks for your speedy help.
Duncan
Duncan Armstrong

No clicks at all sounds like a power problem.
-A new pump should work out of the box. Are you getting power to it?. You might have loose/broken wire. If you don't have a volt meter then make up or buy a cheap test light. Infact go buy a cheap multimeter, they range in price from $20 to Hundreds. Endless uses, you'll never regret it.
Once you've guaranteed you are getting power then go the next step.
Is it wired the right way around? you might have got an old positive earth style pump.
Is it a point problem(unlikly new out of the box)Switch on ignition and connect/disconect a wire. If it's a point adjustment problem you will get at least one click/ker-puck noise.

If at this point it still doesn't go then your new pump is a dud, back to the shop, or really get into it with Davids most exellent guide.

Of course (as David and others are aware!) I personally would bypass the awful thing with a short piece of fuel line and unstal a pump from a '80's subaru in some out of the way corner, up in the engine compartment. I wrapped mine in a bit of foam mat and pushed it into that corner at the back passengerside of the engine compartment.
Cheaper, better, more acessable, stronger, more reliable. It even makes the same noises!
I'm told a hond civic pump will also do, check the archives.
Peter

Peter - If you keep this up, people are going to get the idea that you don't like SU fuel pumps ;) Cheers - Dave
David DuBois

New SU pumps usually contain a slip of paper in the box saying that in the event of the pump not working the contacts should be cleaned before returning the unit as faulty, for precisely the reason that David says. The contacts oxydise over time, and need some mechanical abrasion through normal working to keep them clean. Once they are clean they should stay so for some time, I regularly leave mine for a month or more over winter and don't have a problem. Before fitting a new pump you should always jury-rig it to a 12v supply to make sure it *does* work before going to the effort of fitting it. It should chatter like billy-oh, which for the second or so it will take will do no harm, it will chatter for much longer than that when you empty the tank before the float chamber empties to stop the engine.

If two pumps are the same then it is more likely to be a power supply problem, and has already been suggested make sure you have 12v on the 'hot' spade and do not have any voltage on the ground spade.

SU pumps get an unwarranted bad-press usually caused by 30 years of no maintenance. If they start getting intermittent it is a warning to do to check/replace the points, and a quick thump usually gets you going again. Only if you ignore these warnings is it likely to become terminal. Which is more than can be said for the electronic type of SU pump, when these get a problem it is usually terminal straight away. After several bad experiences with one of these I went back to a points type and had no more trouble.
Paul Hunt 2


I'm still getting over the fact that the coil/magnetic windings in the pump would not work; ONLY, on the west gate bridge, ONLY about three quarters of the way to the top, ONLY in the rain! Everywhere else, just fine. Bizarre. I still suspect poltergeists were involved!

FVI-The West Gate Bridge is a HUGE 8 carriageway Bridge here in Melbourne located somewhere in the upper stratosphere, that has traffic made up mostly of trucks traveling in excess of 80 kilometers-per-hour. A lovely place to lounge around under your car bashing at the SU. I delt some pretty heartfelt blows I might add.


Peter

Pete - I remember that problem from some ago. Did you eventually give up and change the pump? Or diagnose the actual problem? I'm interested as it is a good example of how spooky apparently simple electrics can be, like the car that wouldn't restart after its owner bought chocolate ice-cream but did if he bought vanilla.
Paul Hunt 2

Adjusted points, cleaned then sandpapered then filed etc, Bought new points (was charged $50!), adjusted cleaned and rechecked at least half a dozen times. Checked resistances etc etc.
The diabolical thing was it would cut out just prior to the top of the bridge so usually (but not always!)I could just coast over the crest. It would kick in the moment I was off the main span. No change in angle or steepness. Eventually concluded that it was something to do with induced currents. In the mean time the one and only car was necessary to get to work (other side of bridge!) I put in my old Subaru pump and it didn't miss a beat, until I put in the Fuel injected V8.
Peter

Peter - It must be something about bridges. I lost all of the oil in our TD and hammered a couple of rod journals on the crank while on the Tacoma Narrows (Galloping Gerty) Only it was before hitting the crest. The State Patrol trooper that stopped to help and direct traffic around us said that she thinks there must be magnets under the bridge that cause car problems (as good a theory as any) as all the break downs within the ten mile streatch that the bridge is on, always happen on the bridge. Cheers - Dave
David DuBois

This thread was discussed between 11/03/2006 and 15/03/2006

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