View Full Version : TR2/3/3A Vapor Lock TR3?

09-02-2008, 06:32 AM
Has anyone had an issue with vapor lock in a TR3? A few weeks ago my car sputtered to a stop 3-4 times before it finally quit and would not start. On side of road it would run at idle and higher REVs, but would sputter again after I pulled back onto the highway. It had been parked in hot 95 degree sun for five hours at a Central PA car show and air temp was still in upper nineties on drive home. Had to be transported home on flatbed truck.

Car started the next day and has run without problem since then (have not driven in similar hot weather). Everything in electrical system is new and checks out. I did put can of dry gas in tank during problem (did not help), but had nothing to cool gas line by engine. Am still running on same tank of gas. I am wondering if the addition of ethanol (with a different vapor pressure) to our gas has caused similar problems in other cars with mechanical fuel pumps? I am installing an electronic fuel pump which should correct for a vapor lock and or a bad mechanical fuel pump. Any feedback would be appreciated.

09-02-2008, 06:38 AM
I'd say you've already decided on the prudent path! An electruc pump should sort it. Be aware of the pressure issue, a "low pressure" Facet or Carter (#50604) would be correct.

<span style="font-style: italic">EDIT: I ~highly~ suspect a combo of ethanol and a "weak" pump as primary cause of the problem.</span>

09-02-2008, 06:40 AM
I certainly have problems with fuel vapourisation after I stop the car following a long run. Usually the car starts after a lot of cranking, but it runs fine once started. This only happened after leaded fuel was no longer available in Scotland.
We don't experience temperatures like yours though!

Don Elliott
09-02-2008, 07:26 AM
I still haven't proved it conclusively, but I had similar problems while I was driving my 1958 TR3A to VTR in Valley Forge in 2007. I mostly happened as you describe - when it was hot and I was in heavy stop and go traffic. I Canada, I had similar problems with Petro Can and Sunoco. But I never had any problems with Shell or with Esso, so I only buy my gas at these stations. I'm assuming that thase brands do not have any ethanol in the gas.

TRF sell a heat sheild made by Joe Alexander to try to prevent vapour lock.

09-02-2008, 09:00 AM
I think various degrees (no pun intended) of vapor lock are unavoidable in a TR3 over 85F. I've run mine in Arizona (up to an ambient temp of 115F) on leaded and unleaded, experiencing vaporization in slow traffic and/or after a a shut down. I've since moved to central Virginia (ambients up to the mid-nineties), have a heat shield (granted, over a s/s header, that throws more heat than the cast iron manifold), with fuel line run above vs below the carb, and while I don't vapor lock in traffic anymore, like Nick, will still have a sputtering start after a long, mid-summer heat sink. It evens out after 30 seconds as fresh fuel flows. I'm running a stock fuel pump.


09-02-2008, 10:02 AM
Have had the same problem this year. Installed a electric back at the tank. Since installing pump have let the it stumble and turn pump on it would pick up and go on. Also let stuble and quit then turn the pump on it would start right up and not have anyproblems. Have gotten in the habit of turning pump on after it sets on hot days for a little while before starting. Doing this have not had stumbling for vapor lock.


09-03-2008, 06:56 AM
Thanks to those who responded about my vapor lock problem. I have talked with others in PA who said they had never heard of a vapor lock problem in a TR3. Your comments support my hypothesis and think the electric fuel pump will resolve the problem.


09-03-2008, 07:26 AM
The manual pump gets very hot from engine heat soak, and thus heats up the incoming fuel, which then travels via a hot fuel line beside the engine. While idling at traffic lights, fuel passes slowly through the line, and it can actually boil. To overcome the resultant vaporisation in the old days, my father lagged his engine bay fuel line with steam pipe asbestos wrap. Obviously a big no-no now.

Bypassing the manual pump with an electric pump gets cooler fuel to the engine bay, and it's a constant supply. No fluctuations as engine revs rise and fall. That's not to say the manual pump is inadequate, it's just that electric is an improvement.

Where the fuel line passes around the front of the engine, the metal clip onto the thermostat housing needs insulating to avoid heat soak. Just widen out the clip and use a short piece of rubber fuel hose over the metal line as the insulator.

I have run the 3A on a 42C (106F) day in city traffic with the above two mods (and an electric fan) without any vaporisation. Driver melt down was another story !.


09-03-2008, 01:55 PM
Problems with fuel boiling in the bowls do seem to be getting much more common, likely due to changing gasoline formulations (ethanol). Joe's heat shield seems like the right solution to me (and might even yield just a bit more power, by keeping the carbs cooler).

09-04-2008, 11:18 AM
I've never had fuel problems of that severity.
We often have temps of 110 plus thru out the summer and the only issue I've noted is a few more revolutions for the starter after prolonged driving and then shut down/restaring. Evaporation in the bowls until they refill.
It might be evaporation and another issue causing that severe a supply problem.

09-04-2008, 11:47 AM
BTW, an electric pump does little or nothing for fuel boiling in the bowls or jets; which is technically different than vapor lock. Boiling in the jets leads to "percolation", which can carry liquid fuel into the intake manifold and cause flooding, etc. Usually only happens under very specific circumstances; where high ambient combines with high underhood and hot exhaust. For example, I've seen it when driving through the hills above Palm Springs, then parking for just a couple of minutes in the 115F heat. Honestly, it was a relief to have an excuse to go hang out in the cool store for 20 minutes or so!