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TR6 TR6/ Dies after idle

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TRdynamo

TRdynamo

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Hello to all, I haven't been on this forum in a very long time. But I really need your help.

I have a 1975 Triumph TR-6, it was running great until about 1 month ago. Right now it'll start fine, but once the choke is pushed all the way in once it reaches full temperature it'll hold a fairly normal idle. But once I give it some gas and rev it, it won't hold the idle and it will just die. I can keep my foot on the gas and it'll hold that no matter the RPM, it purrs, but as soon as I let off the gas RPM's just drop and it dies almost immediately, hardly even making an attempt to hold its normal idle speed. And often times it won't restart after it dies out. A few times I've been able to pull the choke and start it, but even with the choke out it tries to die out after I rev it, sometimes staying alive, sometimes dying again. I would appreciate any help you forum members could give me in this matter!

-TRdynamo
 
That's a strange one ! Have you checked that both of the valves for the float bowl vents are opening, and are not blocked by dirt or possibly the wrong gasket ?

Or possibly the carbon canister is clogged ? (Sorry, don't recall offhand if a 75 would have the serviceable canister, but I think not.)

Having a dry damper or a leak in a diaphragm are possibilities, but I think they would cause other symptoms besides the ones you've reported.
 
Well I read something about pulling the hose from the carbon canister that attaches to the Carbs. I Pulled it off and started it, but I revved it and it died once again. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif
 
Was there anything done to the car around that time?
Some things to check as good routine maintenance.
Pull the carb dashpots. Check the diaphragms for cracks or holes. Replace if necessary making sure to line the little nub on the bottom of the diaphragm to the indent on the carb body. When putting things back together, make certain that the pistons move freely and are not binding. Fill with oil.
Make sure that nothing is hanging up in the throttle and choke linkages.
Make sure you have no vaccuum leaks. The rubber elbows tend to go bad especially if they are in contact with gasoline.
Check your spark plugs. They will probably be black from running on choke. Clean them with a wire brush or replace if excessively corroded.
When was the last time the engine had a tune up? How old are the plug wires?
Good luck and keep us posted on what you find.
 
I'm not too savvy with the Z-S carbs. But i'll give your suggestions a try. The spark plug wires are only a few years old and they're the $$$ performance kind, very nice. The plugs are just as old. Has electronic ignition also. And about 4 months ago I changed out the fuel filter and changed the oil. The car ran real nice till about a month ago. I wouldn't be in a rush to fix it, but trying to sell it. Can't really sell it if it isn't even driveable.
 
Hmm, I'm not that familiar with a 75 ... but aren't there two sets of hoses between carbon canister and carbs ? The larger ones grab vacuum behind the venturi (but before the throttle plate); while the smaller ones are the idle bowl vents. Pulling the larger ones off would likely cause it to die at idle unless you plug the exposed ports; while the smaller ones would be the ones I was talking about before.

Some other things to check would be valve lash, and point gap (dwell).
 
I'd also like to mention that the carbs were completely rebuilt just 2 years ago, I'd hate to think they're shot already.
 
Unfortunately, defective or inferior "new" parts have become all too common these days. So I would never assume that something is good, just because it was recently replaced. Rubber parts (like carb diaphragms) are a particular problem, because the original parts would not stand up to our "reformulated" gasoline and there is no good way to tell by looking at a part whether it's made of nitrile rubber or not.

Not that I think that is your problem, I'm just saying ...
 
This just keeps getting more weird. So I pulled the dashpots, and looked at the rubber diaphragm on both carbs, and both looked to be in proper shape, no tears or breaks that I could see. I didn't even fully pull the dashpots out because the air filter housing prevented me from doing so. After that I just buttoned everything up and tried to start it. Started up fine, ran fine like but I revved it and guess what, it actually dropped back down to its normal idle range when I let off the gas. I didn't even have to choke it. Thought it was a fluke so I turned off the car, and it started almost immediately, and than I revved it again and it held its idle once more. After trying it several times again, I've come to the conclusion that maybe it isn't a fluke. Man am I happy. Any idea what the problem could have been? Or if you think it will come back?
 
Do you have any oil in the carb pistons? You must have moved something that was stuck when you took the dashpots off.

Check the diagram below:
 
I noticed the left carb had almost no oil in it, so I added some, added alittle to right as well. Tried to run it after that and it still ran bad, so I decided to pull the dashpots.

Is it possible the needle was stuck?
 
I equate the carbon canister to a wart on the end of my nose, certainly obvious but of dubious importance. It is supposed to capture the vent fumes from the gas tank and if the anti-run on valve is not working it can contribute to dieseling after the ignition is turned off.
Like pulling the tag off my mattress I removed mine. I then recited some secret incantations and have been happily driving ever since. /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif

I would do the maintainance suggestions that have been offered and check for vacuum leaks or a torn diaphragm to start with.

Or check out the fuel pump. This is easy to do and might be worth doing first. Also check the fuel volume delivery at the carbs.
 
Here's a wild thought, as the symptom is exactly what I experienced with my TR3.

The gas pedal (throttle) linkage was binding at the firewall. Rev the warm engine, foot off the gas, idle slowly deteriorated and engine died.

Freed up the linkage (accidentally! - while cleaning up firewall) - problem gone.

Just my 2¢.
Tom
 
Originally Posted By: TRdynamo
Can't really sell it if it isn't even driveable.

It all depends who's buying it....
 
What you might have done is "repositioned"so to speak, the diaphram from a concave position to the natural convex position.
Some times, if the carbs are dry of fuel, the suction of the intake valves will draw the diaphrams into an un-natural position, more or less concave when viewed from the top. If they sit too long in that position they may assume that position until they pop back up.
But if it all is working now, place the ad.
 
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