TR2/3/3A My 3B is thirsty!!

Hi everyone!
this is my first thread in this forum, and my TR3B is also my first !
You guys got to excuse my English, being a Norwegian living i France...

My 3B has done approx 90000 miles, and to my ear runs kinda smooth. Nice sound and ride,
but after two fill-ups and calculations I find that my car uses 4,3 ltr/10km(Norwegian standard), or to my Conversion approx 6 miles to the gallon.

I can see no leakage (no smell, nothing on the garage floor)
the motor runs smooth, at 1100 rpm
the motor responses fairly fast, very little smoke when pedal2metal
no backfiring
no petrol out of exhaust

I have not been driving a lot (just short trips in South of France countryside), and are some surprised of two tanks already.. Therefore I dont suspect the fault is in the speedometer, but it is a possibility..

I would like from one of you experts a simple list, in priority, where to start looking/testing.

Do you have a locking gas cap. Maybe someone is siphoning gas when you are not around.

If the spark plugs are really black, I would suspect that the jets are not returning to the full "up" position when the choke is not be used. The jet fork should be against the bottom of the adjustment nut. Also, the carbs could be grossly out of adjustment or the float needle valve sticking. The float could also be leaking.
Another possibility would be a hole in the fuel pump diaphragm, which could leak fuel into the crankcase-try pulling the dipstick and check for the smell of gas.
It is hard to believe that any of the above would result in fuel consumption of 6 mpg, either US or imperial gal.
Berry

I can't think of any one thing that would cause such gas consumption, except a leak which sounds like you have eliminated. You may not see a small gasoline leak on the garage floor but you should surely smell it.
In addition to the above faults, a stuck distributor advance would account for a considerable drop in gas mileage. It should be quite sluggish and perhaps run hot too. Tom

I ran the conversion to make sure...you are correct. There is no way it's burning that much without making a mess out of the plugs. I'd check those to see if it's going in the engine or out of the engine. Maybe a leak on the pressure side of the fuel pump that doesn't show when the car is sitting...or worse, from the pump diaphram into the crank case.

Thank you guys for quick response!

After my first tank fillup my thoughts were also siphoning..
but the two measurements were excactly the same.
and now I never park the car without having eyesight control.

if there is a leakage to the crankcase, the 3B would by the dipstick, "produce oil"..?
the oil looks and smells normal, so perhaps that option is out, hopefully..

If the distributor advance is stuck, that would gravely set back the accelaration?
I haven't measured it (don't know how), but to me it accelarates nicely with a fantastic sound!

The suggestions are all good, I will run them through and be back

Hermund

Hermund,
Please don't think I'm off the wall here, but I had the exact same problem with both my TR3's. I don't drive them often and when I did the gas seemed to have disappear. I took the tank out, checked all the lines; nothing, no leaks. And the cars run great. Finally, I put a square sheet of cut up plastic sandwich bag over the gas cap port (with the cap open) then closed the cap on the sheet to 'seal' the lid. Now gas isn't mysteriously disappearing and I'm getting 25 mpg (US gal). BTW, both cars are full ground up restorations with new Moss gas caps.

Just a thought. Good luck. Pat

PKPoole said:

Hermund,
Please don't think I'm off the wall here, but I had the exact same problem with both my TR3's. I don't drive them often and when I did the gas seemed to have disappear. I took the tank out, checked all the lines; nothing, no leaks. And the cars run great. Finally, I put a square sheet of cut up plastic sandwich bag over the gas cap port (with the cap open) then closed the cap on the sheet to 'seal' the lid. Now gas isn't mysteriously disappearing and I'm getting 25 mpg (US gal). BTW, both cars are full ground up restorations with new Moss gas caps.

Just a thought. Good luck. Pat

Click to expand...

Thanks Pat!
this is simple, and I will try it in Connection With the rest.
as soon I figure out what excactly a "plastic sandwich bag" is..
Rather thin plastic, I expect.



Hermund

I suspect that the previous opinions are on the mark. But here are a couple of ideas. The first is to take the car out and fill it up then take a ride of maybe about 50 60 miles on open roads and then refill the tank and see what that calculates out to be on a per liter basis. The other is if you were loosing gas as you were driving you could start the car and let it sit running for 5 to 10 minutes and see if you get any fuel dumped on the ground below it. I suspect that if you are dumping gas you would be smelling it inside the car. But a sticking valve in the fuel bowl can dump gas very easily. Our cars have a very convenient over flow tube to allow that gas to dump all over the engine compartment. But some folks have gone one better and put in tubing that drains that fuel down underneath the car and away from the exhaust. In a case like that you could possibly miss smelling the fuel.
Charley

Yes Charley, I took her for a ride.. 49,1 km.
That ride came out with 6,7 liters consumption, or approx 1,4 ltr/10km.
Conversion is difficult, but that might be approx 29 mpg? Nice figures!

But I also learned that I have a overflow tube at the tank. First fill-up (before the ride) I was kinda fast, so I didnt see the fuel pouring out, but I did the second time.. wow!
Guess I lost one liter fuel, but that estimate is not included in my calculations .

The makes the motor good then, so the fuel must be leaving through the gas cap! (or the overflow?)
I'll find a plastic bag and try to seal the cap!

Thanks guys!

Hermund