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General Tech Carbs Flooding While Car Sits

CJD

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OK, this is what I am hearing...

When you look down the carbs after shutting the engine down the throats are dry, with no fuel bleeding out of the jet and down the intake manifold. To me that eliminates a float or float valve problem. What that alludes back to, however, is that you are getting vapor lock.

For vapor lock, I would wait for a cool morning and see if the problem goes away or gets better. That would confirm it. The next step would be to run that tank down near empty and fill up will premium from a name brand station...see if that helps. The next step would be to do anything you can to keep heat away from all fuel lines.
 

Sarastro

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Sorry, I wrote this yesterday but forgot to post it! Anyway, FWIW....

If you can't see raw fuel in the throats of the carbs, it's unlikely that you are flooding. I agree with John, it sounds like classical vapor lock.

As for the jet position--if you screwed them out 12 flats, they are two turns lower than where you started. That's a mechanical certainty. That "12 flats" recommendation is just a starting point, anyway. You still need to tune them. That should be done AFTER valve adjustment and ignition timing.
 

charleyf

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Interested in why the fuel filter should be only 1/2 full ?
I have two TR4's each with the fuel filter located between the thermostat housing and the first carb. I also run HS6 carbs on both of them. My fuel filter is always half or less full. It bothered me a lot at first but decided that it is due to the location being a high point in the line. The only problem it has caused is that only the lower half of the filter is getting used. So on one car it caused the car to starve for fuel at upper speeds. I rotated the filter and all is good again. I drive these cars in temperatures of 90 to 105 and have never had a vapor lock.
Maybe I am just lucky.
Charley
 

RJS

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Hi All,

Late to the party but, have a couple of thoughts which hopefully are beneficial:

1. Someone above mentioned winter fuel. This issue actually impacted me this May here in CT. I had a load of fuel in the car from December and it went into winter storage until April. One weekend early in May the temps hit 80*+ and as soon as car warmed up, it started stubbling really badly, had to keep goosing the throttle to keep it running at stop lights. And, once shut down, it needed 20-30 mins to cool before it would restart. After I topped her up with 10 gallons of Shell Ultimate - perfect! I did some research, and in colder parts of the country oil companies add butane to the fuel in the colder months to raise the vapor pressure (VP). I think party to improve emissions and also partly to provide better cold starts. The higher the VP, the easier the fuel percolates under high heat conditions

2. Further on vapor lock/bubbles, most modern cars with fuel injection run modern fuel pumps with relatively high pressure. The pressure alone mitigates/minimizes vapor lock/bubbling. We don't have that luxury

3. Many years ago, a recommended "British Car" mechanic adjusted my carbs. Turns out he made them ultra rich. It started great cold but, hot start was impossible. Burned through a battery, starter and nearly a full year before I diagnosed it. Effectively, it was like having full choke on all the time. Suggest you pull and read the spark plugs.

Good luck and keep us posted

Bob
 

CJD

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If the fuel filter is mounted sideways, it will have a bubble that may or may not eventually blow on through the system. The filter must be mounted vertically, like the OEM fuel bowl/filter to remove all the air. However, if you have a vertical filter and still see air in it...your fuel is boiling and you either have vapor lock or are approaching vapor lock conditions.
 
OP
KVH

KVH

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I seem to notice with the cooler weather (and some recent checking and reassembly) that if the car sits for 2 hours or more it starts almost instantaneously with the turn of the key. However, if the car sits for less than 45 minutes after it is turned off, it can take anywhere from 10 to 25 seconds to get it to start.

I just don’t get why I’d have a vapor lock issue.

It would require some effort new hose cuts to mount vertically, tho I’m sure I could do it. Would the pump have sufficient power to push the gas like that? Of course, there is a significant vertical rise that comes directly off the pump before the line is routed under the upper radiator hose.

Is there a handy photo of the correct fuel filter setup? And, is it settled that my floats aren’t the problem? I confirmed that my needle jets are the standard length and width, and using the “SU“ instructions to measure the gap between the floats and the lid when inverted, I seem to be on the mark there, too.
 

charleyf

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Is there a handy photo of the correct fuel filter setup? And, is it settled that my floats aren’t the problem? I confirmed that my needle jets are the standard length and width, and using the “SU“ instructions to measure the gap between the floats and the lid when inverted, I seem to be on the mark there, too.
There was never a "second" fuel filter on the TRs. You have the one on the fuel pump. That was it until we owners started adding a second one. Some prefer to put the second filter before the fuel pump and I believe most put it after the fuel pump just before the carbs.
If i were voting on what your problem is, i would say your engine is running to hot. This could be caused by either excess fuel (rich), to little (lean) fuel or improper timing.
Charley
 

CJD

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The bubble in the filter will not cause any problems. Here is why your car acts like that:

The design of this engine puts the fuel through a fuel filter and pump that are metal and hard mounted to the block. Thus, the fuel temp starts to climb. Then, the fuel goes through a steel line mounted high in the engine compartment, where all the heat accumulates, and runs around the entire top of the engine, including the bracket attached to the hottest point on the engine proper...the thermostat housing. Next, the carbs are located directly above the hottest parts in the entire car, the exhaust manifold.

While driving these parts heat up, but the airflow from motion keeps the fuel line cool enough that there are no problems. BUT...as soon as the engine stops, the airflow stops and the fuel lines start to bake from the rising heat in the engine bay. When the temp of the fuel reaches that particular fuel's boiling temp, the lines start to boil. The boiling causes bubbles, which then expand and displace the liquid fuel. Once the lines have boiled out, then the temp can sky rocket.

So, now you go to start the engine. While cranking, the fuel flow is minimal, and as it pumps it reaches the superheated lines, and immediately sizzles into a gas. The carb cannot deal with gas vapor. Peak heat is about 15 minutes after engine shutdown. At about 30 minutes the engine begins to cool, so fuel can start to flow again, and after about 45 minutes everything is cool again.

If you are getting vapor lock in the northern hemisphere in November, then you are most likely using bad fuel. Run that tank out and add premium from a name brand gas station. If that does not help, then you have to wrap the fuel lines with insulation. Other things that can contribute to vapor lock is anything that makes the engine run hotter. This includes lean mixture, retarded timing, fast speeds, and vacuum leaks.
 
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KVH

KVH

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I’ll check timing, but it sure runs spot on. Also, my gas line is insulated with that flex plastic stuff also used on electric lines. Maybe no good. I also have a carb heat shield. As for vacuum leak, my guess is I’ve got one. My distributor is old and the vacuum diaphragm probably broke during the Carter Administration. But all good leads and I really appreciate it. Happy Thanksgiving to everyone.
 

Madflyer

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normal filter location most all TR's this is a GT6 pic one note fuel line around head.pic two and three is TR6 in pic three if you expand pic check fuel line around head. I added a screen door spring over my fuel line to act as cooling fins. I think your cover is doing the opposite of what you want.
NOTE here is a tip I learned this year. With motor idle and at temp thermostat open feel your carb tops they should be not cold but cool and twin carbs should feel the same temp. Why?? our carbs work as a Venturia to pull fuel and then mix with air raw fuel does not go into cyl but air fuel mix is atomized or vapor. So your fuel is say cold and ready to burn but if to cold as in to rich poor burn rate less power fuel out the tail pipe. As in raw gas smell. That is the reason for the water tube through the intake manifold to raise fuel mix to a better burn rate. There is a system for every thing in our cars. Knowing how things work in a system and seeing and understanding the same makes for quick work when some part is not right.
 

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OP
KVH

KVH

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I just don’t know. I only use premium. Mostly Chevron. Sometime Quick Trip. Issue exists outside the ethanol period.
 

CJD

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Well, that does rule out the gas. And if you want to hold off on vapor lock, here are other problems with similar symptoms:

Bad ignition coil that dies when hot, although it will usually be associated with tailpipe back firing.

Excessively rich carb settings.

Weak fuel pump.

Weak battery, although this is normally accompanied with slow cranking.
 

RGK

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Have you checked the temp at your fuel filter and checked a spark plug for excess fuel when having the problem?
 
OP
KVH

KVH

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I will check both and report back. What about this— my current tank of gas set for 4 months. Would the gas go bad?
 

RGK

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I doubt it, mine has been in the tank since January, started this morning testing a cold start at 29F after my choke adjustment. Choke cable itself needs some help; ordered something the 2 wheeled crowd uses for their cables, should work :unsure:
 
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