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MG MGB Technical - Fuel Pump Question

I have a 1971 mgb roadster and a 1974 MGBGT. The '71 is a driver in very good condition. I acquired the GT about six months ago and I am just now starting to work on it. On the '71, the fuel pump clicks three or four times and stops when the ignition switch is turned on. I understand that this is normal. On the GT, the pump does not turn off. It continues to run as long as the ignition switch is on. There are no visible leaks and the carbs are not flooding. I removed the gas line at the carb and inserted a pressure gage. The gage reads a steady four pounds and the pump continues to run. Again, no sign of leaks. I turned the ignition switch off; the pump stopped running, and the gage still read four pounds after about ten minutes. I do not know the brand of the pump, but I assume it is an aftermarket replacement. Are there aftermarket pumps that are designed to run continuously? Do I have a problem; and if so, How do I correct it?

Thanks,

Mack

A Sneed

Most of the aftermarket pumps run continuously. The most common units are a little square box in shape. They work very well and make noise continuously. It is normal.

As a side note, I believe there is an isolation type mounting system for those units if the noise bothers you. Any decent auto parts store should be able to find it in their catalog.
Jeff Schlemmer

Mack - The SU fuel pumps do normally stop clickiing once the float bowls are full and will only click about once every 15 seconds or so unless the car is running. Jeff is correct about the after market pumps. If you have the little square, run all the time, make a lot of noise, Facet pumps, they never shut off until the ignition is turned off and are rather anoying. That said, they are a good pump and should serve you well for quite a number of years before it fails. I am not sure that most auto parts houses will have a listing for the resiliant mounts available for the pumps, but they are available from Pegesus Racing at: http://www.pegasusautoracing.com/advcat.asp?CategoryID=AIRFUEL
Click on Fuel Pump Accessories and scroll down to Fuel pump mounting kit. This quit works very well. I installed a Facet fuel pump on the back of the battery box on the passenger side of our MGB, using these mounts and it is impossible to hear the pump except when the car is sitting still with the engine off. Cheers - Dave
David DuBois

If you have an SU pump, it looks like somthing designed by Captan Nemo. Lots of bolts holding it togeather. Generally It is located at the point of maximum inaccesabilit€y, behind the boot, behind the starboard rear wheel. Personally I hate the things, have been given a very bad time by these incarnations of evil on earth. Put in a japanese Subaru pump and forget about it, I say. But everyone has their own opinion.
Could be the points need adjustment. this is done by undoing all those screws areound the edge, carefully loosening the delicate diaphram, then winding it in a screw hole or two (rotating clockwise). If after you do this and bolt it all back together and it doesn't 'kickover' then you've gone too far and must unbolt all those screws and wind back a notch. If it still runs continiously, you've not gone far enough and you need to unbolt it all and wind in another screw hole or two. Don't forget to get yourself liberaly and generously covered in petrol when you do this. When it runs up your sleave and soaks your armpit, well, that's something extra special.
All this winding tensions up the delicate points spring. You may find at the end of all this that the solinoid winding has 'gone' and you need buy a new SU pump because unless you've got a 10 ton press you're not going to be able to dissemble it. In my case it appeared that the wretched thing would not work on the West Gate Bridge, in the rain. Anywhere else , just fine. Something to do with all that steel and induced current. My place of work lay on the other side of the West Gate Bridge.
FVI the west gate bridge is a 10 carriage way bridge located in the upper statisphere here in Melbourne. Traffic on it consists almost entirely of large numbers of very large trucks moveing in excess of 80 km/hr. And of course, all too frequently in the past, one broken down MGB. With the owner bashing at the petrol pump and dodging said trucks.
That was until I put a '82 SUBURU pump up in the engine compartment, and never ever again had a problem.
Peter

Thanks for the comments and advice. I don't have a little black box but I suspect that it is one of those "run-all-the-time" aftermarket pumps. It is a metal cylinder about three inches long and about one and one-half inches in diameter. I don't see a brand on it. It doesn't look anything like the pump on my roadster. It mounts with a rubber lined metal strap and you only hear it run when the ignition is on and the engine is not running. The car was a gift and right now, I am just trying to get it running long enough to figure out what I have. For the price of a new pump, I think I will live with this one for a while.

I have had the carbs off and back on four times, checking float levels, needle valves, etc; and the pump still ran. When I plugged the fuel line with a pressure gage and it still ran, I figured it was time to call in the experts.

Thanks again,

Mack
A Sneed

Mack,
had the same problem once and changed to another pump (Mitsumi). It did not cure the problem as it was the leaking welding of the fuel line on the fitting to the tank.
If air can be succed in at this pont, the punp will not stop and the delivery to the carbs is insufficient then. I checked the System with compressed air to locate the whole as no wet spots could be seen before. Maybe you should check this too.
Ralph
Ralph

Mack - The pump you describe is a Carter, also sold under various other names. While I have not had any experience with these pumps, but from what I have read, they should give you good service and last about as long as any other pump - 50,000 to 100,000 miles from new regardles of who makes them, be it SU, Carter, Facet, Mitsubitshi or whoever. All electro-mechanical devices have a finite life span. I have had Mitsubitshi pumps and Facet pumps as OE on Mazda pickups and of course SU pumps on MGs. When installed new, they have all lasted about the same amount of time - somewhere between 50,000 and 100,000 miles. The Facet pumps cannot be repaired or restored when they fail, but are cheap enough to be just tossed. The SU fuel pumps can be restored and be good for another 50,00 to 100,000 miles, and are expensive enough to make restoration worthwhile. The Mitsubitshi pumps, which are the same design as the SU pumps could probably be restored if a source of parts can be found. It all boils down to what you want to use on your car. Cheers - Dave
David DuBois

Peter, your pump is probably 30-40 years old and I'd say that Captain Nemo did a fair job at producing a device that was going to perform without maintenance and in a poor environment for this length of time. I somehow don't think that a replacement Facet or Suzuki pump can be expected to last that long.

Now I do admit that they are in an awkward position but can be removed in about ten minutes and dismantled on the bench for points replacement and setting the throwover mechanism. They can then be run continuously and flow tested so that you are sure that whenn you replace it it will perform reliably. I agree that the SU pump is not a thing of beauty but if you had removed it and given it a little bit of TLC then you would not have to fight with it on the West Gate Bridge. How you managed to adjust the throw over with the pump in situ I will never know. Lack of maintenance seems to be the source of most of our problems and I would have thought that at the first signs of trouble you should have removed the pump and serviced it. That way you might even have grown to like it.
Iain MacKintosh

Thanks again for the good information. I may, as Ralph suggested, pressure test the fuel lines; but from the foregoing, it appears that continuous running is normal for this pump. Otherwise, it seems to be working fine. So, I think I'll run it for a while and see what happens.

As i said, this car was a gift. The last license tag is 1996; but I understand that it was driven briefly about two years ago. Obviously without the benefit of current tags. When I got it, it would start but was flooding badly. I have that problem cured but it has some minor electrical problems to cure before it is drivable. I haven't done my own mechanic work in years and I am still trying to learn about these cars. I suspect that this won't be the last time that I will need to pick your collective brains.

Thanks a bunch,

Mack
A Sneed

Does anyone know if the New, Electronic SU fuel pump runs continuous or sporadic like the original one does??
Mike

If your's is actually an SU pump, and it is ticking
continuously, and there are no obvious fuel leaks
- then I would first suspect a cracked reed valve;
then I would also give the pump diaphragm
a good inspection.

All are inside the pump itself and are relatively
easy to replace.

Replacing the reed valves is pretty much a
straightforward swap.

The diaphragm needs a bit of care during
installation and I would recommend having
a workshop manual onhand in order to
get the number of turns required to correctly
align it with the points.
Daniel Wong

Mike - The SU all electronic pump operate exactly the same as the standard points style pumps, that is they run until float bowl is full and the needle valve closes, then stop. They run a bit faster than the points style pumps and are a bit quieter, but still shut off and then click periodically as the fuel is used fromthe float bowl and the needle valve opens. Cheers - Dave
David DuBois

Regarding a resiliant mount for the fuel pump, I recycled the old rubber mount from my transmission to isolate my Carter pump from the body. It works quite well and the pump can barely be heard when the key is turned on.
Phil O

This thread was discussed between 29/01/2006 and 01/02/2006

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