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MG MGB Technical - Ongoing no start / fuel starvation

Well I seem to have an ongoing problem I can't solve.
Here's the problem, hopefully not too long of a description.
Can't get the MGB to start right now, it briefly runs and cuts out and when it does start, it idles but will quit after driving a mile or so.
Now here's the history.
We've checked both fuel filters we have and both are clicking away. We checked flow on both straight from the tank to the pump and got 2 pints of gas as required. then through the filter and just a few ounces less. Then from the pumps to the carb and got 25 ounces, just short of 2 pints.
Have also assured we have the right gas cap, no whoosh when it comes off, have also checked the float in the carb, a ZS 175, and it seems fine. Also replaced the needle valve seating and still no start at this time, even after assuring any air was out of the lines. Have made sure we have spark and compression, valve clearances are fine and no clacking anymmore.
A manual choke has also been installed which helped initially.
Any other suggestions on this.
Carb rebuild, adjustments???



Elizabeth



Elizabeth

Elizabeth. Junk the Z-S and contact Bob Ford at Brit-Tek about a Weber DGV carb with manual choke. This conversion will make your life much, much easier. Les
Les Bengtson

Due to being laid off, purchasing a new carb at the moment has to wait so I have to fight with this one.
But yes, in the end, if I can't get this one going.
Or off to the selling block it goes.
Elizabeth

Try removing the breather line from the carbon
cannister to the carburetor (Connects right above
the fuel line.) If a vacuum has
built up due to clogs in the evaporative loss
control system (clogged cannister or lines),
it will cause fuel starvation symptoms.

If the car runs again after removing the breather
line then you've isolated the problem to the ELC.
Ronald

Elizabeth. Ronald, due to living in California, is one of the few people still using the Z-S carb. He is one of the few people who may be able to help you trouble shoot this problem. Most of us have switched to the Weber DGV because it offers so many less trouble shooting opportunities. John Twist used to have a tech article on the Z-S on his University Motors Ltd website. Do not know if it is still there or not. Les
Les Bengtson

Thanks for the John Twist site, I checked it out and am finding it very informative. He continually points to the cannister in most of his replies on fuel starvation. We did find the line clogged and it started right up but are still stalling out. A call to him may be in place.


Elizabeth





Elizabeth

Why does it quit (and why start a second thread)? Are you sure you still have sparks to each plug at the right time when it has? Is your pump the continually clacking type? Is it still going when the engine dies? How long does it take before you can start and run again, albeit only for another mile? This is where the SU type is better which only clacks when it is delivering fuel. When switching on again if an SU clacks for severals seconds you know the float chambers were empty which is probably why it stopped. In which case either the pump is bad or the electrical supply to it. If the pump only clicks a couple of times you know the carbs are full, so the engine died either because of ignition failure or a carb problem.
Paul Hunt

Just noticed the reference to the canister. Take the pipe to the canister off the float chamber as a test. If this is blocked it could stop the float chamber filling properly, or if there are blockages elsewhere in the emissions plumbing it can cause a vacuum to develop and suck the fuel out of the jet so stopping the engine - just like the anti-runon valve.
Paul Hunt

We did clear the line to the canister and had the same stalling problem. We then checked the gas flow directly from the tank. We found that the sending unit in the tank (which doesn't get much attention in the manuals) had a clogged filter at the end of the tube. We removed it and had a successful test drive and it was running great. So that seems to be the problem at this time. We'll have to adjust the mixture as the smell is also quite smelly.
Concern: The filter had an orange coating which did not appear to be rust of any sort. it was sticky.
Could this be from a coating in the tank that the previous owner had done or something else?
I've also heard cleaning a tank can be almosty as costly as buying a new one.


EA Martin

Check the air filter to see if the inside is black. if it is the gasket is leaking at the manifold/converter and needs to be replaced. The outside of the filter could look brand new but be plugged solid with exhaust.
Jim

Air filter looks fine.
Can the orange film on the filter inside of the gas tank be from a coating added to protect the tank?
And how big is the hassle in cleaning the tank?
I've read that it could be a real heartache.

Elizabeth

Elizabeth. Very sorry, but the sticky, orange residue is typical of a tank that has been left for years with fuel in it. As the fuel evaporates, it forms a shellac or varnish inside the tank which is disolved by new gasoline (especially these mixed fuels). The residue will then get on things like the fuel pick up tube filter and the fuel bowl(s) in carbs.

I have had good results with having the fuel tanks cleaned, using the hot tank method, at a local radiator shop. They do, however, need to be sealed internally after being cleaned. As I remember it, the cost of the hot tank and external painting was about $50 last time I had it done. The gas tank internal cleaning and sealing kit from Moss costs about $60 (from memory), but Eastwood may have a similar product for a lower price. If money is tight, Mike Brown has mentioned using a can of Rustoleum Rusty Metal Primer, mixed 50-50 with paint thinner, as a sloshing/sealing compound for the inner side of the gas tank. I have not tried this myself, by you may wish to. New tanks were about $200 last time I purchase one. Cleaning and using a professional clean and seal is about one half the cost of a new tank. Cleaning and using the rustoleum about one third. Les
Les Bengtson

Thanks much for the confirmation on the residue.
Will the build up eventually desolve away to nothing with the new gas or is a tank cleaning mandatory?


And One other question - What is the purpose and how does the oil separator/flame trap work?
I can't find a detailed description in the Bentley or Haynes manuals.

One thing just seems to lead to another!!
: -)



Elizabeth


Elizabeth

The oil seperator/flame trap is part of the positive crankcase ventilation system. It stops backfires through the inlet manifold from igniting any fumes in the crankcase, it is just a metal gauze filter. As Davy discovered in 1816 when he built his miner's lamp a flame cannot pass though gauze even though gas can - http://www.wikipedia.org/wiki/Davy_lampa

However I was under the impression that it was a case of a flame not being able to pass through a hole of less than a certain size.

The gauze also causes oil vapour or spray to condense into droplets on the filter which should drop back into the sump.
Paul Hunt

Thanks Paul!!

Elizabeth

Elizabeth.

I used an old trick when I had to clean crud out of a gas tank that had been setting up for a couple of years.
Find a steel chain and just bang it around in the tank, (after removing the tank from the car of course) This should knock off most of the crud from inside the tank. It worked for me.
J W Hopkins

This thread was discussed between 02/07/2003 and 15/07/2003

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