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TR6 Issue of the day......restart and idle after shut down

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edkap2002

edkap2002

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Hello,

My recently purchased 72 TR6 has offered few surprises and disappointments....however one issue remains and Im not sure of the cause.

On cold start, full choke, starts right up but it takes a little while to get to high RPMs.....then it does and warms up fine. When warm....perfect idle 750 rpm.....I go out for a twenty minute drive and the car drives strong and great but i i shut it down, even for 5 minutes....I have to do some real cranking of the starter to get it running......and when it starts it no longer wants to hold that 750 rpm idle...more like 400 - 500.....my guess is the fuel is heading back towards the tank when not running......is this a fuel pump issue or a leak in the line symptom? any help would be appreciated.....Ed K
 
Each carb stores a small amount of fuel in the float bowl, with what amounts to an air break between it and the fuel pump. Only way to lose that is to have a big leak, and even then it would be the same cold as hot.

So most likely you're having trouble with it going rich instead. To confirm, have someone watch the tailpipe during a hot start; they'll probably see black smoke.

One of the most common causes of that is heat from the exhaust manifold causing fuel to boil in the carbs. Here's a thread with some solutions https://www.britishcarforum.com/bcf/showthread.php?63423-Do-heat-shields-really-work

(Joe's web site seems to be down at the moment; he told me some time ago that it was being refurbished. But I'm fairly certain he's still in business; or you can buy his heat shield at a slightly higher price from most other TR6 vendors.)
 
Hi, thanks for responding...I agree with the rich theory...no black smoke whatsoever...there is a faint smell of gasoline where I store the car....does that add to the mystery?.....Ed
 
Thank you for asking....outside temp was around 60ish ....but it doesnt seem to be temp related....Ed
 
Is it any better when the tank is full over when it is low? What about behavior going uphill vs down hill? I have seen similar behavior due to a still working but not really up to the task fuel pump. If it behaves better when the tank is full or when going down hill (especially if there is any significant grade and length to the hill), it's likely fuel pump time.
 
I am thinking you are right about the fuel pump...it looks to be original. I will order one and get back after installation and thanks.
 
...Or just rebuild yours, if it’s an original pump.
 
The latest I got from TRF did not, if you are referring to the priming lever under the pump.
 
No..that's not part of the kit..any DIY kit that I've ever seen.
But FWIW, it probably does not need replacing.
There's a picture in the TRF catalog of the parts included in their kit.
https://trf.zeni.net/wc/specials13.15/26.php


Those symptoms do sound like fuel percolation, however the 60 degree temp doesn't.
I never experienced percolation until the contributing factor of the ambient temperature was about 90*F and then only when the engine got good and hot.
At only 20 minutes, your oil was just getting to normal operating temperature.
 
I will be interested in your resolution here, as I have the same issue with my 74 TR6. I have installed the heat shield from TRF, and my fuel pump is fairly new. My car starts fine, idles fine, and runs fine from a cold start. Also operating temperature is normal. However, after driving the car for a while, if I turn off the engine and try to restart within 15 or 20 minutes, temp gauge is it 3/4, car is hard to start, and runs rough, or cuts out. All goes back to normal, temperature, and engine performance, after driving for a few minutes.
 
That sounds like fuel percolation. The heat shield alone didn't do much to cure the problem...but when I lined the floor of the heat shield (top and bottom) with a couple of layers of "heat insulation" that cured it.
https://www.jegs.com/i/Thermo-Tec/893/13575/10002/-1
TR6heatShield.jpg
 
wingler said:
I will be interested in your resolution here, as I have the same issue with my 74 TR6. I have installed the heat shield from TRF, and my fuel pump is fairly new. My car starts fine, idles fine, and runs fine from a cold start. Also operating temperature is normal. However, after driving the car for a while, if I turn off the engine and try to restart within 15 or 20 minutes, temp gauge is it 3/4, car is hard to start, and runs rough, or cuts out. All goes back to normal, temperature, and engine performance, after driving for a few minutes.
Click to expand...

I will let you know for certain when I get is resolved...Im thinking about replacing the fuel lines all the way to the tank
 
Starting good cold, but not well hot could be a rich condition. Have you tried starting it cold with no choke? If it does start well cold with no choke, then you are running very rich for some reason. The first step then would be to lean out the idle mixture.

If it does not start well cold with no choke, then percolation would be the cause of the rich when sitting hot. The solution then would be to slightly lower the fuel float levels to keep the fuel in the bowls instead of running down the manifolds and accumulating in the intake.
 
CJD said:
Starting good cold, but not well hot could be a rich condition. Have you tried starting it cold with no choke? If it does start well cold with no choke, then you are running very rich for some reason. The first step then would be to lean out the idle mixture.

If it does not start well cold with no choke, then percolation would be the cause of the rich when sitting hot. The solution then would be to slightly lower the fuel float levels to keep the fuel in the bowls instead of running down the manifolds and accumulating in the intake.
Click to expand...

John...sounds like great advice and I try the cold choke-less start as soon as I return home...thanks much....Ed
 
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