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MG MGB Technical - Electronic fuel pumps

This is a question for Dave D (or any one else in the know)

I note your comments on another thread about the position of the inlet and outlet ports on the S U pump, should they be the same with an electronic pump or doesn't it matter ?
I've just fitted a new electronic one and I am still having flow problems under pressure.For ease of fitting on a UK '75 I have the inlet on top.
Also, should these new ones constantly click with the ignition on or does this signify an air leak some where (I can't see a fuel leak anywhere)?

Thanks in advance

Dave G
Dave G

My electronic fuel pump clicks as soon as you turn on the ignition key, then while driving it's still clicking but not as noticeable. It seems to produce plenty of fuel pressure and the car runs great.
1977 MGB
randy olson

My electronic SU pump was marked with one port marked top...which I believe is the outlet port. Like you for plumbing reasons I initially installed the pump with the port marked top on the bottom. Big mistake! I would be driving along and the car would suddenly stall.....only to start up 10-15 minutes later....presumably after the air block that was created had resolved. When I turned the pump right side up....the problem went away. Hope this helps.

SU and Moprod solid-state versions of the original points-type pump operate in the same way i.e. they only click when they are pumping fuel ... or are faulty! A continually clicking SU/Moprod type indicates either a fuel leak including faulty float valve, or a leaky one-way valve (of which there are 2) in the pump.

Other after-market pumps may click continuously, whether they are points type or electronic.

Whatever pump you have it should be capable of delivering *at least* one Imperial pint per minute into a container at the carb-end of the plumbing, in a steady and consistent flow, and with negligible bubbles. An in practice it sould deliver nearer to two Imperial pints per minute.

I had a bad experience with a Moprod pump, cured by fitting a refurbished points type. I would certainly never use a Moprod again, and I'd have to be convinced to use an SU given that the points type are very long-lived anyway.
Paul Hunt 2

Dave G. - The electronic version of the SU fuel pump is identical to the points style pump except for the components under the end cover. They are both oriented the same, with the outlet fitting on the top. Mounting them upside down invites trouble due to the flow smoothing devices used in the AUF 300AZX 1300 series pumps used in the post 1964 MGBs. The constant running could be as simple as a fitting on the line between the tank and the pump not being tightened, but is more likely caused by an aie bubble trapped in the flow smootihing devices expanding and contracting as the pump is operating. Cheers - Dave
David DuBois

Thanks Guys
I've now turned the pump around 180 deg and the flow at the carb end is much improved.
Paul, I fitted an 'Ecco' pump from Mechspech in Yorkshire, I will test it with a pint glass and report back.
Kind rgds
Dave G
Dave G

I'm wondering if the differences between modern points-style SU pumps and solid-state SU pumps are more a matter of build-quality rather than design. I just had a two year-old points-style SU fail after less than 20,000 miles. That should not have happened. I replaced it with the solid-state replacement and in about 6,000 miles have had no problem yet, but the jury is still out.

Allen Bachelder


A pint in 45 seconds in a steady flow (after a few seconds), and the constant clicking stopped once reconnected .... seems OK.

Thanks again

Dave G
Dave G

Allen - I don't know what kind of driving you do in your MGB, but if it is put into hibernation each winter, that could be the cause of the early demise of your points style pump. The contacts used in the points style pump film over and depend on the current flow through the pump and a small amount of arcing to keep the film burned off. Fuel pumps in cars that are driven regularly have the best results with longevity of the pumps. Pumps in cars that are put in hibernation over the winer have the worst results. This is because a thick layer of film builds up during the lay up period, not thick enough to cause a problem right away, but too thick to be burened completely away. Due the wiping action of the contacts across each other when the points close, a lot of the film is pushed to the side and over the years that film that is pushed aside build up sufficiently to start causing problems. I found this out when I started getting a lot of pumps returned out of service back when I was just transistorizing the pumps and driving the transistor with the original points. I finally started examining the contacts under 20X magnification and would find a ridge of the waxy film pushed to one side of the contacts (it looked for all the world like snow hat had been pushed into a driveway by a passing snow plow). When the ridge go big enough, it would stop the contacts from making contct with each other. I have no proof of my suspicions, but I believe that the alloy of the contacts has been changed some time in the past 15 to 20 years, because the problem seems to be much worse now than it used to be years ago.

The only difference btween the modern points style pumps and the all electronic pumps sold by Burlen Fuel Systems is strictly the means of driving the pump. The points style pumps have a pedestal, points and now a TVS for arc suppression. The all electronic pumps have a Hall effect circuit controling a FET to drive the pump. Other than that, there is no difference between the two pumps. Cheers - Dave
David DuBois

"I will test it with a pint glass "

I can think of a much better use for a pint glass, in Yorkshire it would be Black Sheep :o)

And my local has just started stocking it as a guest ale :o) :o)
Paul Hunt 2

I'm with Paul.
David DuBois

Whilst at Uni. in both Leeds and Huddersfield I was known to partake in the local brew.
Unfortunately I'm now a 'stay at home dad' and my pint glasses don't get much/enough use....big sigh.....
Anyway Yorkshire ale doesn't travel well !
Enjoy :-)
Dave G


Thanks for your detailed explanation. Although my car is a daily driver most of the year, it does hibernate when snow and salt are upon the ground. This past year, that was just about three months: January-March. Perhaps this is the cause? Back in the mid '90s I replaced the pump on a '76 B that I had then with a points-style pump. That car too hibernated for 2-3 months a year. The pump was still fine when I sold the car 5-6 years later. Have the new pumps changed since then?

Regarding pint glasses. I'm a Newcastle Brown man myself. One of the few good ones that' available just about everywhere here in the Colonies. But I fill it in a lot less than 45 seconds. Actually, that's about the right amount of time to EMPTY it!

Allen Bachelder

The last two years my cars have seen very little winter use due to weather, but if I haven't been able to take them out for a month I do run the engine at a fast idle (throttle pedal wedged, not choke out) for 20 minutes or so. Not as good as driving I know (what is?) but I have never had any problems with the pump, fuel, battery or anything else. The other thing I do is give the wheels a 1/4-turn each month. One year I left them for a couple of months or more then the next time I drove it they had flat-spotted and I could feel the car bouncing up and down slightly. Fortunately a brisk 40 mile drive cured it.
Paul Hunt 2

Before I sold my business I imported 4 of the electronic pumps, 3 of them needed adjusting before I could sell them because they kept ticking - I always test new pumps before sale.
Garth Bagnall

This thread was discussed between 27/09/2007 and 07/10/2007

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