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MG MGB Technical - Fuel Pump Failure

The fuel pump on my '77 B seems to be going. Recently on trips around town it will quit, usually on uphills, then start up again and get me back to the garage. Today it quit about 3 times on a 12 mile trip, again on the uphills under heavy acceleration. I have taken it apart and sandpapered the points, and that got me home this afternoon without a hitch (after tapping it a few times when I first started and the engine stopped), although I carefully avoided crowded highways with uphills and only applied the throttle as if saving gas. Now I need to decide if I should buy a new pump or simply replace the points. Is there a recommended replacement for the Lucas pump? Opinions and recommendations welcome.
Randy Olson
1977 MGB
randy olson

You can get a solid state SU pump from Moss, VB, ect.. It looks like the original, and even has the SU tick, but it is solid, state, so no more annoying points.
J Arthurs

Couple of issues with the points-type SU pump.

Some like them, since you get get worn ones ticking again by banging them with a hammer. One solid state goes thats it.

See Barney Gaylords MGA site at http://www.ntsource.com/~barneymg. He is the man as far as MGA's go. He has several non-SU solid state pumps that he has found to be very dependable. Moss also sells a non-SU solid state pump that seems to work forever.

As to SU, they work pretty long as well (e.g., 20+ years). You can get a complete rebuild kit electricals as well as seals/valves from Victoria British. Not that hard to install (cleaner, screw driver, tooth brush etc.) Cheaper than new SU pump electronic and points types, cheaper that non-SU electronic fuel pump.

Besides you still get to wack the pump if it starts acting up in another twenty years after the rebuild.

John D. Long
J Long

John - The problem with most of the non SU solid state pumps is that they run continously (i.e. they don't shut off when the float chamber is filled and they make a lot of noise (I refer to them as little square, run all the time, make a lot of noise pumps). As to their working almost forever - they really don't last much longer than an SU pump. The Mazada pickup trucks use this kind of fuel pump and mine died on me after a few years (bought the truck used). The SU pumps can be rebuilt, but getting them adjusted and running correctly can be a bit tricky and rather hit and miss without a test stand to run them on. After refurbishment, modification to solid state (I use a magnetic reed switch and magnet vice the Hall effect circuit that Burlen uses) and adjustment, I run the pumps for 24 hours before I send them back. It is really amaising how many quit running after 12 hours or so and have to be re-tweeked. Only after a 24 hour continous run do I consider them reliable. Dave
David DuBois

Does anyone just replace the points in the stock fuel pump?
I picked up a pump at NAPA today that is 2-4 pounds of pressure...the small square solid state generic pump. Does anyone have any suggestions for mounting it? I was told to install a filter between the gas tank and the pump. Other than that I'm not sure if there are any issues. I believe I read in the Archives that it was possible to install a generic pump in line with the original Lucas pump, so when it fails the generic pump kicks in...not sure about that one.
Comments and suggestions are welcome.
Randy Olson
1977 MGB
randy olson

Just recently replaced the SU fuel pump on my 79. No problems in 400 miles since. Repairing/rebuilding one is much more complicated than replacing the points in many cases. They have a diaphragm inside the unit that cracks.
Sam C

I junked my solid-state SU-type pump because it got so unreliable and went back to a points type. At least with them you have a chance of doing a roadside repair, with the solid-state you are totally stuffed. Are you sure it is the pump and not a partially blocked tank vent pipe causing a vacuum and fuel starvation under load?
Paul Hunt

Yep. I installed a NAPA generic pump last night and today started the car up. It ran great for the lap around the 3-mile block. But...lot's of noise from the pump. It chatters like a scared chipmunk upon startup then makes a dull, but very audible chattering whenever the car slows to an idle. Not good aesthetically, but IT RUNS! I'll see if I can stand the noise and report back later.
Randy Olson
1977 MGB with twin SU's (and a new fuel pump to feed them)
randy olson

Randy. David DuBois, here in the US (and who posts here) is quite well known for the quality of his SU pump rebuilds. A note posted to him will get a response. My daughter's car has an aftermarket, Faucet fuel pump which, like yours, is noisy. Especially with a factory hard top. The only thing you need to do is to go out and purchase a "vacuum gauge/fuel pressure gauge". These are available for about $20 at all of the discount stores/parts stores. Check the pressure of the new pumps output. With SU carbs, about 1.75 psi is the max acceptable. (The Weber will use up to 3.5 psi, but runs well with the 1.75 of the later model SU pumps.) If you are above 1.75 psi, you will need to either install an SU pump or a "fuel pressure regulator" in the line to drop the pressure to 1.75 psi. Excessive pump pressures can cause problems with the SUs. Les
Les Bengtson

Les,
Dave DuBois and I have been corresponding and he has a wealth of information on fuel pumps in general and noise reduction options for the aftermarket chatter-box pump I just installed. I'll investigate vibration/sound isolators first to see if there's any improvement.
I wasn't aware of the 1.75 psi issue with the SU carbs. I need to drive the car a little more to see if it's running right, but after the quick run last night it seems fine. Will the new pump, which produces 2-4 psi provide more fuel than the carbs can handle? Or, will the pump merely supply the amount the carbs call for?
Thanks for the input.
Randy
1977 MGB
randy olson

This thread was discussed between 14/07/2002 and 16/07/2002

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