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TR4/4A Air Filter Soaked With Gasoline - TR4A

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fpstude

fpstude

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As you can see, I'm new to the forum. I've been lurking around and have learned many interesting things. I need to post a message about my history with our Triumph, as requested.

At this time I have a question about a fuel system problem. I've recently experienced a gasoline odor after driving. I could not find any leaking connections and finally found the bottom of the air filter on one of the Zenith-Stromberg carburetors very soaked with gasoline. The inside of the carburetor show no sign of gasoline. I'm not sure where to start in finding the cause of this problem. I would appreciate your thoughts on this issue.
 
Pull your oil level dipstick and smell the oil on it. If you smell gasoline in the oil, don't start the engine. Change the oil and filter. Some gas may have flowed in the opposite direction and drained into the engine diluting the oil.
The gas in the air filter had to come from the carb's float chamber. There is a needle valve that allows fresh gas to enter the float chamber as the engine uses it.
The needle valve can stick in the open position and if the fuel level in the gas tank is high enough, the gas can leak past the needle valve even when the engine is not running.
 
Perry - how long have you owned the TR? Has the gas been soaking the filter for a long time, or just in the last few days?

By the way, I *really* envy you those Studebakers. Wow.
Welcome to BCF!
Tom
 
I agree with Poolboy - and if you do start the car up look at that carb very carefully while the engine is running - if the needle valve in the float chamber is not working properly you will likely see gas dripping from the carburetor. Not a good thing if so, which means you should fix the needle before driving it again.
 
Thanks for the input.

Tom, we purchased the TR in September of 1966.

I started to notice the odor a few weeks ago and just narrowed down the source yesterday. Randy, would the dripping be from the bottom adjustment nut, or the air intake? I'll be checking the suggestions about the needle valve. In shame, the TR has been taken out of service. I'll be driving a Studebaker.
 
The bottom adjusting nut sometimes has minor leaking, that's pretty normal and fixed with new o-rings. If your needle valve isn't sealing though, the fuel pump will dump fuel into the carb beyond where it should - and you will see it come out the front port that is the vent to the float bowl. That would be my guess as to why your air filter is soaked. The needle valve itself could have a problem, or potentially the float inside is having trouble.
 
I have a gasket kit in the mail and will then check out the needle valve and float. No time like the present to learn how these things work. Thanks for the input.
 
Re: Air Filter Soaked With Gasoline - TR4A Update

I've taken the carburetor apart. Nothing obvious that I can see. The needle and seat assembly shuts off air flow when in the up position, so it appears to be working. The float is very close to the 0.73" dimension, as indicated in the manual.

What is the float material? The test I've used is to submerge a float in hot water and look for bubbles. This float has bubbles coming out in several places, but no indication of any fluid when shook. The float is not brass or plastic, so it is new to me.

I may just get a new needle and seat assembly. Moss offers two. One is a GROSE-JET (superior replacement), the other standard. I searched floats on this forum and saw some negative comments about the GROSE-JET. Any comments would be appreciated.

Is there anything I am missing?
 
You didn't mention changing the fuel pump, but JIC : the fuel pressure may be too high. SU carbs only want about 2-3 psi (2.5 is the spec) while many replacement pumps supply more than that. There needs to be some margin to cover all circumstances, so it may work with the carbs cool but overflow when they get hot (for example).

HS6 floats were originally plastic I believe, but apparently they were not resistant to ethanol in the fuel. Burlen (who now owns SU) is bragging about their "unsinkable" floats which are apparently similar to the old "Nitrophyl" floats (closed cell foam construction). So new floats is probably a good idea.

Personally, I feel that the Grose Jets are a non-solution to a non-problem, at least on a TR. They don't seem to be any better than the "standard" Viton-tipped replacements; and at least in my limited experience they are even more sensitive to fuel pressure than the stock valve. I've fixed several cars now by throwing the Grose Jets as hard as I could, and reinstalling the "old and inferior" needle valves. Last time it happened, I was driving someone else's car, in the rain, and noticed I was leaving a fuel slick on the road behind me!
 
Okay, I just installed a new needle valve (standard, not Grose Jets) and a new float. The replacement float look identical to the one removed. Both nitrophyl. I did a crude comparison of the float weights. The old one was 1 oz., the replacement was 1/2 oz. Anyway, the carburetor is back on the car and everything seems to check out, no leaks. Although it may take more than a 2-3 mile ride for a real test. No leaks.

Probably unrelated to this, but recently the car has had a hesitation upon moderate acceleration in first and second gear. That is not the case now. Most likely the carburetor adjustment I did along with the float / needle valve replacement helped this.

Thanks for the input from you folks on this. On to the next event in the 47 year adventure with this car.
 
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