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MG MGB Technical - No fuel filter - will it cause problems?

My '73 BGT keeps getting a blocked fuel filter every 2-3 months and I've replaced it 3 times now. To get me home last night I just took it out and connected the fuel feed directly to the carbs.

I broke the filter apart to take a look at the debris it had collected and it's really fine (like dust) rust particles which must be from the tank. If I continue to run without a filter will it cause damage to the carbs/engine?

Thanks,
Matt
MattWilkinson

I would imagine you would end up blocking the valves in the float bowls or the jets in the carb. If the float valves stick, fuel overflows from the bowl and pours onto the hot exhaust manifold!

I think you're best off solving the problem by finding the source of the debris (e.g. rusty tank). Having said that, I have no filter on my car - perhaps ignorance is bliss!

Cheers,
Tim
T Jenner

I wouldn't run my car without a fuel filter - for the reasons Tim points out, but also, if those fine dust particles are able to get past the needles and into the intake, imagine what that might be doing to the cylinder bores. A simple (in relative terms) fuel tank change could turn into an engine rebore.
I suppose it could be a fuel line that is corroding and letting bits of debris flow to the filter, but I think it is more likely the tank. Also consider that if there is enough rust, the tank will be compromised and you could have vapours or liquid fuel creating a source of fireexplosion if someone happens by with a lit cigarette or if the Prince of Darkness creates a spark somewhere. I would urge you to bite the bullet ASAP.

Erick
Erick Vesterback

I replaced the tank in my car cause the top of it was rusted through. Its not a major job but if the captive nuts on the tank break free from their clips then it can become a bit of a headache, especially with the ones behind the rear valance. I wouldnt run without a fuel filter. That dirt has to go somewhere. The filters job is to collect this. The carbs are not designed to handle it. You wouldnt run without an air filter would you?
Ross Kelly

Gentlemen - Quite frankly, filters are treating the symptom. The suggestion to get to the bottom of the problem and solve it with a replacement fuel tank makes better sense than changing a filter every few months. Whatever you do, do not place a filter between the tank and the fuel pump (if you are using a SU fuel pump) A clogged filter on the inlet side of the pump will cause the pump to stall in a current on condition, resulting in damage to the pump if the ignition is left on, such as during troubleshooting. See the article, SU Fuel Pump Facts and Myths in the SU Fuel Pump Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

I agree with those above. If the filter's getting clogged by *ANYTHING*, then you probably don't want it getting into the carb to clog things up there instead.

Maybe you could put a larger fuel filter in place so it would last a bit longer between changes. But overall, I think your best bet is to address the issue (rusting tank or lines) before you end up with gas on the ground and stranded.
Jeff Grant

When I bought my B it had a rag for a fuel cap. When I was getting it running I installed 3 fuel filters - 1 post pump, one before the pressure regulator (non SU pump), and one after the pressure regulator. The one closest to the carb was always the first to clog up.

After replacing the tank I am now running one filter and it has been in service for 7 years now.

Fix the problem as soon as you can.
C Holm

When I bought my current 74.5 MGB in 1986 I had the gas tank lined. Now 2008, same tank and no problems. Perhaps your can be cleaned up and lined.
At any rate I would never run it without a filter. Rust is metal and small metal piece's do not belong in the cylinder under any circumstances.
Spend the 6-8 bucks and buy a filter and save your engine

Bruce Mills

Thanks for the replies everyone. I guess I already knew the answer but as the particles are so fine I thought it *might* be ok.

As Bruce says, rust is metal, and any metal that isn't supposed to be in the engine is bad news!
I'll be installing a filter today and keeping a spare for next time, that is until I manage to change/re-line the tank...

Cheers,
Matt
MattWilkinson

UK 73 cars didn't have a filter originally, mine hasn't and has not had a problem in 19 years. If yours has one, and it is clogging up as you say, then it seems that a PO fitted one in an attempt to cure a tank or pipe problem that was affecting the carb float valves. Fix the tank and/or fuel pipe problem and you will be fine.
Paul Hunt

Does the mesh 'sock' on the end of the pickup serve as an adaquate before-pump filter?
Joe Ullman

Yes, stops large bits being drawn into the pump and affecting the non-return valves, at least. If either of these stick open you will get insufficient fuel delivery.
Paul Hunt

I had a similar problem with a Toyota I once owned. Constant changing of fuel filters which contained rust particles. Checked the fuel tank and it was clean with no rust.

Lots of head scratching then I checked the metal pipe just inside the fuel filler cap, It was rusted and every time I put the petrol bowser hose spout in to fill up, a bit of the rust was scraped off and made its way to the fuel filter. Fixed the rust and the problem disappered.
tony

Quote: "f the float valves stick, fuel overflows from the bowl and pours onto the hot exhaust manifold!"

If this is the case, then I suspect your overflow tubes are missing. They direct any overflow to a safe spot underneath the car. If they are missing then you're driving a very unsafe car!
Steve Simmons

This thread was discussed between 03/07/2008 and 12/07/2008

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