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Restart problems after engine has warmed up

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Olafthor

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My 73 TR6 will start cold, usually, on the first try. However, after driving it for 10-15 minutes...enough time for the engine to get heated up, it is very difficult to restart. I've noticed that the longer I wait to try to restart it, the more difficult it gets to start. The engine cranks fine...no electical issues. Its got to be something to do with the Air/Fuel ratio but I'm not sure.

I've installed one of those aftermarket heatshields intended to reduce the radiant heat from the manifolds to the bottom of the carbs, but this has had little, if any noticable effect.

...I'm sure the + 100 deg F. heat in California isn't helping too much either.

Any advice?
 
It could very well be an ignition issue. Check to see that you have spark.
 
It sounds more like a vapor lock problem. Also check to make sure the fuel filter is clear of debree. Does the car buck when it is at operating temperature at slow speeds? Double check the electrical but this does sound more like a heat related fuel issue.
 
Thanks for the advice. I verified that the electrical is working fine. Spark!

The engine runs find at temperature and at low speeds.

Many thanks,
 
Oil pressure switch is a possibility. Or the fuel pump could be going bad...........GL! Just went through the same thing with my TR8 ended up being the fuel pump.




Rod
 
Do you have an original fuel pump with a priming lever? If so you might be able to prove/disprove vapor lock. Also, did this just start with the heat or has it done it for a while. Does it do it when the ambient temps are in the 90's, 80's etc... Does the starter spin freely or does it seem to drag down when you try to start the car?
 
I'll have to check on the fuel pump. How would I address proving vapor lock?

Also, from what the previous owner had mentioned, this has always been a problem.

As for the starter, it is working great. I've made various voltage measurememts, too and all are ok.

Many thanks,
 
This is just a shot in the dark - have you checked your fuel supply? I had a similar problem with my 72 GT6. Started fine but at unpredictable times it would quit running, leaving me on the side of the road. I pulled the fuel hose off the output side of the fuel pump - it was dry. Same for the inlet side. I blew through the inlet hose until I heard bubbling in the fuel tank. After hooking it back up and cranking a bit, started and ran fine. On cars these old, there is a strong possibility of trash and sediment finding its way into the tank and stopping up the outlet.
 
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I'll have to check on the fuel pump. How would I address proving vapor lock?

Also, from what the previous owner had mentioned, this has always been a problem.

Many thanks,

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If you have the lever on the pump manually priming the carbs could push the vapor lock blocking the normal flow of gasoline out of the way. Much the same way that an electric pump can often defeat vapor lock. Mecahincal pumps put out the highest pressure on a running engine, not a cranking engine. If by priming the carbs the car starts and runs normally then it was most likely vapor lock. It doesn't take much pressure from the fuel pump to push the vapor out with the fuel, just usually more than a cranking engine can deliver.

If it been a problem for a while and not just heat related, I have seen it as a timing issue before but usally not when the car start so well from dead cold.

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No problem.

Just to clarify, this is just a re-start issue right?

Not a stall, sputter, die... then no re-start issue.


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Unless the temperature outside is really hot, vapor lock is really pretty rare.

I'd start on something much more basic and simple --- Is it possible that your choke is not fully returning? Check to ensure that when you push in the choke knob that the chokes are actually fully closing.

If the chokes are not returning, the car won't start when hot, especially if the carbs are tuned a bit rich.

You can also pull a couple of plugs to ensure that they aren't oily or covered in unburnt fuel.

Cheers,
Sam
 
Yes. This is a re-start issue. Once running, it runs great.

I'll check the choke, also tomorrow a.m.

You guys are great. Thanks for all of the ideas.
 
A quick check to find out if you have vapor lock in the fuel pump is pour cold water directly on your pump. I had that problem on a 61 Lincoln that I had when I was a teen. Rather than replace the pump I kept a jug of water in the trunk.
 
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