MGB & GT Forum

Welcome! Sign In Register
Please Sign In or Register to Search

fuel pump questions

Posted by redundant 
Geoffrey Beale
Columbia, USA   usa

I have a '72 MGB which I finished rebuilding about 5 years ago, my first and only such project. It's never run very well, and I stopped driving it for that reason. Recently I decided to try to fix whatever the problem might be. The fuel pump runs continuously when the ignition is on, whether the engine is running or not. When the fuel line is disconnected at the carburetor, fuel flows rapidly out the end at fairly high pressure, such that I cannot stop it by holding my thumb over the end of the fuel line. I seem to remember that before when the ignition key was turned on, before the engine started, the pump would run a little then stop, then run intermittently to keep the float bowls full. So that seems to be wrong. I found the rear float half full of fuel and thought that was the problem, but replacing the float made no difference. The carbs (SU HIF4) were rebuilt previously. I've drained the fuel system and put in new fuel, checked for air bubbles in the fuel at the carb end and found none, disassembled the fuel pump and found it ok (it is stamped "Model 12V2401" and has a date on it 7-91.)
So, before I spend a lot on a new fuel pump I wonder if anyone can advise whether I have the wrong pump, or a defective pump, or what other tests I might do. I have balanced the carbs, adjusted the mixtures, and generally done whatever the books I have instruct.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
mac townsend Avatar
Fairfield, CA, USA   usa

you did not identify the pump by brand.

SUs are sensitive to fuel pressure. too much and they flood.

sounds like you may have a pump putting out more than the carbs can take. The initial solution is a pressure regularot, but most of the inexpensive ones I've found don't doo all theat well.

You should be able to find a replacement low pressure pumpo in teh $35 range. Or go for a genuine SU pump which will run about $100 +

once this is resolved, the carbs will need to be re-set. it would be best if you had spmeone familiar with SUs do this...most shops these days are ignorant about such things.

You should alter your profile to indicate where in heck "Columbia" is...Missouri, Oregon, where? because folks might have other suggestions based upon your location.



1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks: www.mgrescue.com
chris Avatar
Chris Roop
Pendleton, OR, USA   usa

Mac is on a good track. My bet is that you have a square Facet or Purolator style pump, hence the continuous running and excessive fuel delivery. They do make a low fuel delivery version, or again like Mac said, you might be able to find their regulator. Set it at 2.
Better choice would be a new SU pump.
HTH!

Member Services:
Not just for MG parts. Quality new parts at 15% off of list. No sales tax in Oregon Check out the Vendor Market page.
ingoldsb Avatar
Terry Ingoldsby
Calgary, Alberta, Canada   can
1971 MG MGB

It is almost impossible for an SU fuel pump to run continuously unless the reed valves are cracked (or something is leaking badly).




Terry Ingoldsby
terry.ingoldsby@DCExperts.com
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
Geoffrey Beale
Columbia, USA   usa

Thanks for the replies. The pump has no markings other than what I described in the original post, no brand name. It has a cylindrical body containing a solenoid and points and a filter/valve mechanism attatched to the top of the body. Much like an SU pump.
It runs continuously when the ignition switch is on, whether the engine is running or not and I'm sure it's not supposed to do that. But I couldn't see anything obviously wrong with it when I dismantled it. It pumps just fine. I guess the question is whether it should stop pumping when I plug the fuel line at the carb end. It had so much pressure I couldn't prevent the gas from squirting around my thumb. But I have no way of actually measuring the pressure. From reading other posts here, it seems it should have low pressure, though.
ingoldsb Avatar
Terry Ingoldsby
Calgary, Alberta, Canada   can
1971 MG MGB

The pump is definitely putting out too much pressure if you can't stop it with your finger. That also means it is not an SU pump - they are incapable of high pressure.

I'm sure you can get many hours of fun out of tinkering with this setup, but if it were me I would just get hold of a real SU pump and go back to the factory setup.



Terry Ingoldsby
terry.ingoldsby@DCExperts.com
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
ddubois Avatar
Dave DuBois
Bremerton, WA, USA   usa

Geoffery - What you have is a Walbro bellows pump. The 2401 model puts out 4 - 6 psi, Which is too much pressure for the MG. The 2402 model is 2.5 - 4 psi, which would work much better on your car. Repair kits and/or peressure regulators specific to these pumps are available at: http://www.autoperformanceengineering.com/html/bel_pump.html
Cheers,



Dave DuBois
1953 MGTD
1966 MGB
http://homepages.donobi.net/sufuelpumps/

Member Services:
SU fuel pump restoration and conversion to solid state. Information and technical articles on SU fuel pumps.
danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

I read that the Walbro Bellows pump runs like an S.U., that they don't run continuously. In this case its different.



1971 MGB
1967 MGB GT
Geoffrey Beale
Columbia, USA   usa

I checked the picture on the autoperformance website and I do indeed have a Walbro pump. Many thanks to Dave. I'll probably get the lower pressure Walbro since it's much less expensive than a SU and I won't have to buy the banjo fittings and other stuff to hook it up. But maybe this will finally make the car driveable.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
ddubois Avatar
Dave DuBois
Bremerton, WA, USA   usa

Dan the Walbro is a points style pump like the SU, but my understanding is that they use a bypass valve to set the output pressure. If that is true, then it will run continuously like the Facte pumps do. I've not dealt with any of the Walbros, so I don't know first hand.
Cheers,



Dave DuBois
1953 MGTD
1966 MGB
http://homepages.donobi.net/sufuelpumps/

Member Services:
SU fuel pump restoration and conversion to solid state. Information and technical articles on SU fuel pumps.
DB Wood Avatar
Daniel Wood
Tumalo, OR, USA   usa
1969 MG MGB GT "Clyde"
1970 MG MGB GT

I went to NAPA today and bought a cylindrical pump for another application that is a quiet pump. It also comes in a low pressure unit. The Facets and Walbros are loud. I priced the low pressure one at $62. The guy at NAPA said they were much better pumps. I just looked on it and it was made by Carter.



Dan Wood
70BGT driver, OD, Pertronix, HS4's, Peco, .060 over, Elgin cam, Superlite wheels, poly bushings, panhard rod, rear tube shocks, 1" lowered front end, HD shock valves, etc, etc.
69BGT project (V-6?)
88 Saab SPG Turbo
86 Vanagon Westy (South African conversion engine 2.0 OHC 135HP)

Lucas= Loose
Unsoldered
Connections
And
Splices

Attachments:
IMGP0095.JPG (45.6 KB) –
IMGP0095.JPG

danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Daniel, what Carter part # is it. I'm glad I didn't buy the walbro. Have you hooked it up already and know first hand how quiet it is?



1971 MGB
1967 MGB GT
JerryB Avatar
Jerry B
Corner of Walk and Dont Walk, So. Cal., USA   usa

BUT...even with that pump you might get about 4 to 4.5 psi......in a situation where you need 2.5 to 3 psi max.

You should be using a regulator with ANY electric fuel pump except the o.e. type SU.

P74019 or P74029 is the number ...cant remember which is the 4ps and which is the 7.5 psi pump. That SAME pump in a private label is usually sold for about $35.


. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info

Reply to this topic or post your own questions!

Members Sign In if you've already registered, or

Register a New Account

Registration is free and takes less than a minute

Having trouble posting or changing forum settings?
Check the Forum Help File (FAQ) or contact the webmaster.


Join The Club

Sign in to ask questions, share photos, and access all website features

MGExp Menu

What's New

Membership

Forums ->

MGB & GT

MG Midget

Buy, Sell & Trade

Vendor Market

MG Engine Swaps

Original MG

MGA

MGC

MG Magnette

1100 & 1300

T-Series & Prewar

Modern MGs

MG Motorsports

Member Meetup

MG 2015 Event

Other Vehicles

Off Topic

Clubs

Forum Search

Random Topic

Latest Posts

Live Chat

Calendar

Journals

Tech Library

Car Registry

Cars For Sale

Model Info

Motorsport

Directory

Member Map

MGExp Store

Search Site

Advertising Info

Smartphone quick link
mgexp.mobi

Adjust Text Size

Larger Smaller
Reset Save