TR2/3/3A TR3A Vapor Lock

[TRcheologist]

I recently had the fuel line running from the fuel pump to the front carb on my TR3A replaced, and have since developed a regular-as-clockwork vapor lock. After about 30 minutes of driving - less if I hit a few lights and heat-soak - its sputtering. It's hard to restart and pronounced when hillclimbing to altitude. The engine temperature is rock-steady at 185-195F, and the ambient has been 65-75F.

The new line was hand-fabricated, and appears to run exactly the way the original, pre-vapor locking, line ran. It occurs to me that it may be a difference in the new line's wall thickness or the heat-conductive property of the metal in the new line. All that said, I'm interested in the forums thoughts around solutions - insulate the line? install an auxiliary fuel pump (as shown in the Moss catalogue)? all of the above? I'd rather not reroute the line as I like the stock appearance.

Thanks for your feedback!

 

[NutmegCT]

Well, just my 2¢ worth ... but if the line was replaced, I'd check for free-flow in the line itself, plus any air gaps or bubbles along the route. Even check the float bowls and operation.

If you put a cold wet rag on the line, does that clear up the problem? That's an old timer's remedy for vapor lock in some cars.

What material is your hand-fabricated line made of?

Tom

 

[TRcheologist]

Thanks Tom.

Fuel delivery seems okay, at least until the under-hood temp rises. The new fuel line is steel. I'll try the wet-rag trick and see if that alleviates the problem, confirming that the root cause is, indeed, the line heating up.

 

[Deleted member 8987]

Or, good old-fashioned wooden clothespins on the line.

 

[MGTF1250Dave]

Aloha,

You didn't say if you have the "push on" or banjo bolt fuel line connections to the carburetors. If you have banjo bolt type, check the fuel strainers at the float bowl lids. Perhaps some debris in the new fuel line has fouled them. Also check to make sure the vents for the float bowl lids are not blocked, this applies to both types of lids. If they can't vent, it may block fuel flow in to the carburetor.

 

[Geo Hahn]

I, too, am suspicious of the vapor lock as a cause. I use the stock fuel line, original routing, stock pump, no heat shield and have never experienced vapor lock even driving in 110 degre heat or at 9000' with a very hot engine.

 

[TRcheologist]

Thanks All.

I'll try your suggestions and see if I can get a handle on this.

 

[toysrrus]

Hi There Folks,

I too am very interested in some answers and suggestions to solve the problem. I`m exp. the same symptoms on my 948cc Bugeye. I just can`t figure the dang thing out.

Thanx, Russ

 

[Geo Hahn]

Guesswork here -- but from the original description of the problem I'd think about trying a different coil. A spare coil is a good thing to have in the boot -- so perhaps the acquisition of a second coil is not a dead loss even it is not the problem.

Unlike vapor lock -- I have experienced coils which would falter or fail when hot.

 

[toysrrus]

Hi Geo Hahn,

Thats exactly what I`m going to try today. I had an XK140 where I changed everything to include to wiring harness (Except the Coil). Went out for my 1st. test drive & She died on me. Changed the coil later on & problem resolved.

Regards, Russ

 

[PeterK]

My 3A used to suffer from hard starting after a long run. I installed Thermotec Thermo-Flex tube over the gas line and the problem went away.

 

[RJS]

Hi

Just another angle on this. A few summers ago I struggled with what I thought was a vapor lock problem. Car started cold and ran fine but would not fire up again after a short run or would sometimes stall out at a stop light. I killed a starter and a battery with this problem. I replaced many ignition parts and also replaced and re-routed the fuel line from the fuel pump to the float bowls.

Ultimately, it came down to an under-qualified mechanic who adjusted my carb mixture overly rich. So, on cold start it acted as a natural choke. But, once the engine warmed up, it was too much.

I traced it down using a Gunson's Colortune (best tool I ever purchased). It was because of this experience and a few more that I have now taken on nearly all of my own maintenance on the car.

So, is it somehow possible you upset the carb mixture or float bowl levels when replacing the fuel line?

Bob

 

[Tr4dude]

One other thing to try is get it warm at night and look at the plug wires with a load on the motor in the dark and see if you have any fireworks. They may have disturbed a ground wire or if they pulled the wires they could be leaking.

 

[poolboy]

If it happens again, open your gas cap and see if things improve. There may be a problem with the gas tank vent..

 

[Deleted member 8987]

Not TR's, but my LBC ended up having the wrong carbs.
Last shop (supposedly experts) rebuilt the carbs, told the PO that it worked best with no choke.
Except, it took 15 minutes of futzing to keep it idling.

I found the correct used carbs, rebuilt and lapped the surfaces, then played with the jets.
Its starts right up, idles and runs good, no "nibbling" on part throttle.

You deal with specialty cars, I personally feel you as the owner need to be up on maintenance and repairs, doing all you can yourself, to avoid the "expert mechanic" syndrome.

 

[toysrrus]

Howdy Folks,

Here`s an up-date on my Bugeye. I put in a "Good Used Coil" yesterday & "No Hick-Ups" so far. I`ll be driving her all day today for cont. testing. If proves positive; "New" coil will be installed on Sat. along with a good cleaning of both carbs & possibly the "Insulated" feul line wrap. I`ll post later in the day how she ran "All Day Today".

Regards, Russ

 

[toysrrus]

Good Morn`n Folks,

Yesterday; I drove my Bugeye around for about 1hr with the "New/Old" coil in her. She "Hick-Up`d" a couple of times but a little feathering of the gas pedal & off She went. Then, Later in the day another driving test & She stalled out on me after reaching normal oper. temps (170-175). I let her sit there for awhile & let the temps climb down a bit & She started up & ran; Well, She ran OK but not to my liking. So; In my case Its "NOT" the coil.

Today; Float Bowls, Jets etc will be cleaned out. Re-Check the timing etc. Probably wrap the feul lines with the Heat Shield wrapping & see what happens.

I sure do hope this solves the problem!!

Regards, Russ

 

[prb51]

Russ, what was the ambient temp? Sounds strange to me at that temp...I drive my TR3 in 110 degree Az summers and the temp at speed will get to 190 without any starvation....it will need to turn over 2/3 times to refill float bowls after sitting hot for awhile (evap) but starts up and drives/idles no issue. I've no insulation anywhere and stock fuel delivery.
Sticking bowls or jets? Carb leaks at the bowl lower gaskets?

 

[toysrrus]

Good Morn`n Folks,

Yesterday; My Brit Guru Mech & I took a spin. The "Good News" here is; That my B/E stalled when reaching normal oper. temps. ("PRB"; The outside temps were approx. 73deg & crystal clear). We took the float bowls off & "No Gas" in either one!?!?!? We let her cool down a bit & off we went again.

Back at the Garage; We took everything appart. The float adjustment for "H1" carbs is supposed to be 7/16". We were somewhere near 1/2". Cleaned the bowls, carbs, everything (Overall looked pretty good). We wrapped the "Feul Line" with some "Racing" cover stuff (Orange in color) at the area from the "Feul Pump" (Mechanical) to the Carbs. That portion of the "Feul Line" sits pretty darn close to the "Exhaust Header" & runs "Behind" the "Heat Shield" nearest to the block. We tried to "Re-Locate" it but could`nt without possibly pinching a line. So; We wrapped it. Got to dark to go out & play.

If this does`nt solve the problem than It has to be the "Pump" itself.

To be cont. later today. I have my fingers & toes crossed that I don`t have to replace or rebuild the Pump. Just in case; Who out there would have one?

Regards, Russ

 

[Geo Hahn]

...To be cont. later today. I have my fingers & toes crossed that I don`t have to replace or rebuild the Pump. Just in case; Who out there would have one?...

If this is for a Bugeye then perhaps your question is better asked over there -- but FWIW I have always prefered to rebuild an original pump over using a repro. A simple enough job on a TR, no idea what pump &/or rebuild kits apply for a Sprite.