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MG MGB Technical - Leaks - fuel pump and carbie

After way too long I'm almost finished restoring the beast. Need to find another hobby. Anyhow, 1972 BGT with new or rebuilt everything. After finishing the engine run-in, noticed two fuel leaks: fuel pump and front carbie. New SU fuel-pump leaks are at the inlet and outlet which uses fiber washer and rubber O-ring. The fittings are fairly tight and I'm hesitant to torque them much tighter. The leak is a very small one -- not a gusher.

The front carbie is sending raw fuel to the carbon cannister. Have never worked on HIF carbies so their operation is new to me. Have a feeling that's going to change soon!

Any advice appreciated.

Tom
Tom Custer

If it's an SU it should be metal-bodied so you should be able to tighten the unions without risk of damage. I *think* late SUs only had the O-ring on one of the unions, but can't remember which one. Plastic-bodied Moprod repros can be damaged much more easily, but as these seal as well either you aren't tightening enough or there is something wrong with the seals and/or seats.

The problem with the HIF is almost certainly a leaking float valve. Try disconnecting power to the pump and running the carbs dry, then reconnecting power. If it's an odd bit of debris that may well clear it (out of the valve anyway) but if it continues to leak you will have to take that carb off and remove the bottom cover to replace the valve, which will almost certainly require a new O-ring for the bottom cover. Remove the hoses from the vent pipes going to the canister so you are immediately aware of any leak instead of waiting for it to come out of the canister. Replace before normal running, of course.
Paul Hunt 2010

Tom - You don't have a fiber washer and an 'O' ring on the pump body side of the banjo fitting do you? If so, remove the fiber washer. Also check the recess for the 'O' ring for any deformities. The 'O' ring has to fit exactly in the recess. If the 'O' ring will not sit in the recess while you fit the banjo fitting and bolt in place, put the bolt through the banjo fitting and slide the 'O' ring down around the bolt. offer the assembly up to the pump body and start the bolt, running it in one or two threads, then slide the banjo fitting and 'O' ring up against the pump body, insuring that the 'O' ring seats properly in the recess. Tighten the bolt until the banjo fitting is flush against the pump body. This should stop the leaks. Cheers - Dave
David DuBois

Paul and David, thanks for your advice. David, I don't have the fiber washers on the pump side -- only the O-rings. Now that you mention it, I did not have complete confidence that the O-rings were seating properly so that may be the problem. Thanks for the tip!

Tom
Tom Custer

Tom - If you find that the 'O' is damaged, you can get the proper one from NAPA under the part number 0-017. Cheers - Dave
David DuBois

David, had to go to Napa today for something else. I asked about that part number but they said it wasn't a valid number. Moss has them but it would be nice to know if one could get them locally.

Thanks,
Tom
Tom Custer

Tom - 0-017 is a Parker 'O' ring number and is a valid number, but probably not a NAPA number. Ask them to try just the 017 number. I am fortunate in that our local NAPA stores have been taken over by a local chain that has trained their people how to cross reference P/Ns. I'll get the measurements of the 'O' rings for you and you can try that way. Cheers - Dave
David DuBois

I couldn't stop the float overflow problem on my HIF4 carbs until I replaced the float needle with the neoprene tipped variety.

BH
BH Davis

Tom - "0-017 is a Parker 'O' ring number and is a valid number" That will teach me to quote numbers off the top of my head - the correct number is 2-017 The size of the 'O' ring is 0.070" cross section by 0.680" ID (also often sold as 1/16" by 11/16". If you are still unable to locate them locally, e-mail me at SUfuelpumps@donobi.net Cheers - Dave
David DuBois

Well, looks like I have the leaks stopped. Paul's and David's recommendations were spot on. Must have had some debris in the front carbie. And I don't think the rubber O rings were seated correctly in the fuel pump. David I measured one of the Moss O rings and the specs are the same as you have stated. BTW, stopped by Napa again and they tried to cross-reference 2-017 but it comes up as a muffler clamp. Maybe the local Napa here doesn't have both oars in the water. But they do give a discount to the Brit car club!!

Tom
Tom Custer

Tom - I keep forgetting that NAPA varies considerably from store to store. I am lucky, the NAPA here was taken over by the best auto parts store in the county. Often times the 'O' rings are carried by the last three digits of the Parker number (tell them to look it up in the manufacturers book, it is not a NAPA number) or by the dimensions. Cheers - Dave
David DuBois

This thread was discussed between 03/05/2010 and 12/05/2010

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