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You are here: Experts > Home/Garden > Auto Repair > Triumph Repair > TR6 spitting lean
Expert: Howard M. Fitzcharles III - 11/6/2009
Question
QUESTION: Dear Howard,
Thanks for help so far. I have sealed the bipass valve and achieved slow idle but both carbs test lean and spit back although I have the needles fully withdrawn. (One carb is worse than the other)I can detect no leaks. The pistons are free. The car has been unused for 3 years and now using PULP plus a recommended additive. there have been no changes made to the carbs, float settings unchanged.
I am lost for new ideas!
Regards
Peter
ANSWER: Peter, Is "PULP" the gas additive? Do you mean you are using the old gas?
Also, Which direction are you turning the 3mm Allen screw adjustment?
Howard
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QUESTION: Howard
By PULP I mean premium unleade petrol (a local name I guess).
The additive is marketed for use with unleaded petrol in the older engines. Do you have a product recommendation for this application?
There may have been about 5 L of the original fuel in the tank when I added 10L of fresh unleaded plus additive.
Do you suppose it may be old fuel to cause this effect?
I had a similar effect years ago when I filled two vehicles with contaminated fuel from the local pump. The fuel smelt like thinners.
Today I will bipass the tank and try running 100% fresh fuel and report back. Thanks for your patience, mine is waning.
Regards
Peter
ANSWER: Hi Peter,
Yes, it doesn't take much stale gas to contaminate good gas so your bypass is a good idea.
You didn't tell me which way you turned the adjustment screw for the needle.
Howard
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QUESTION: Hi Howard,
I have confirmed it was the old fuel even though it was a small percentage it was enough to cause the lean running symptoms.!!
Re fuel additives do you have any advice for use with unleaded petrol
Thanks for your help.
I have a solution for a clutch problem which I will address under separate topic.
Answer
You are welcome and I am glad you found the problem.
I have not found it necessary to put any additives in our fuel here unless an engine has been modified by raising the compression ratio too high.
If you get the rattling (pinging) sound on hard acceleration with the correct ignition timing and the highest octane fuel available then you may need a additive octane booster. But not if you don't get the noise.
Howard
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