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TR2/3/3A Running rich

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doc50

doc50

Jedi Trainee
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Hi all. My recent rebuild runs great but has a niggling issue.

When I start it recently, it smells very rich. Have not noticed black smoke. Mileage has been around 20 mpg, which to me, adds evidence toward being too rich.
I don't recall the 'super rich smell' before, though I only have about 1K on the rebuild. (...Big pistons, mild cam, balanced).
I have the big red OEM manual so from that, I'll find the number of flats to start start the needle valve adjustment. I also recall that raising the dash pot piston slightly will tell me if it is lean or rich (haven't done that either).

Any thoughts that may lead me in a direction?

Thanks.

Thom
1959 TR3 #TS34909L(O)
 
Certainly doing the "lift the piston" test would be the first step. You should be able to get the idle mixture right with that; if not then there is something else wrong (like a leaking float valve or a worn carb jet). (Don't forget to double-check that the jets are returning up against the mixture nut. They sometimes don't, which is like leaving the choke on.)

The cam and big bore kit may affect the mixture profile, meaning you'd need to change needles and/or piston springs to get the mixture correct under conditions other than idle. Generally, though, those kind of changes make the mixture go lean at the high end, so I doubt that is your problem here. Do the easy stuff first.

IIRC the book says 12 flats (2 full turns) for the initial adjustment, but I've seen that be off by quite a bit. It's just close enough to get the engine started, and you've already done that; so I wouldn't bother with repeating it.
 
Thanks for the prompt thoughts, Randall and Jedi. (BTW: I always thought 25-30 mpg was more 'normal' for this car....)

I'll pull the piston to make sure I didn't screw up the placement of the needle (pretty sure I didn't...) then will do the recommended 1/32" lift to see if it is rich or lean.....which I have always thought was impossible for mere mortals to gauge. (1/32"? REALLY???)

The piston drops freely with a clunk, so I guess that is OK.

Thom
1959 TR3
TS34909L(O)
 
25 mpg was normal for me. You'll need to check air flow through the carbs before and after any mixture adjustments. As the engine breaks in and becomes more efficient you'll need fewer carb adjustments.
 
I have never figured out how to lift the piston 1/32" of an inch on a running, vibrating old British motor. I read the plugs and also note starting and warm up on a cold day, if it starts without the choke (easily) it is probably running too rich. If it doesn't sputter or miss a little when Started on a cold day and given a little gas ( off choke) it is probably running rich.

I like Randall's suggestion that the choke or something is sticking on the carbs. Your post seems to imply that it was running fine for a while, then suddenly started running rich. The mixture adjusting nuts tend to stay put, so probably something else. Also make sure the floats/float valves are working right (fuel level should be just slightly under the top of the metering jet).
 
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The 1/32" given in the TR2 workshop manual was later revised to 1/8" (as documented in the Driver's Instruction book, Practical Hints and the TR4 workshop manual). The exact distance is not all that critical IMO, just move it some without going overboard. There is a lifting pin on the side of the carb that is a lot easier to use IMO.

FWIW, I average around 22-25 mpg in everyday driving (with overdrive), a mixture of freeway and surface streets; and I don't think my carbs are set too rich. Well, at least not after I leaned them out one flat the other day, since the warm weather has returned to SoCA :smile:

IIRC, one of the books suggests that 30 mpg is 'normal', but I believe that is Imperial gallons, no ethanol, and likely driving at a relatively modest, relatively constant speed (40-50 mph). Big bore kits and performance cams are likely to lower it even further.
 
Thanks, folks.
Glemon:, I'm not sure if it just started running rich, but I did just notice the rich smell recently.
Randall, I'll check for that lifting pin. I do recall that feature now.
Thom
1959 TR3 #TS34909L(O)
 
Just to add an update: I adjusted the carbs according to the 'lift the piston" instructions and found that one carb was actually too lean. I then sync-ed them with my "Uni-Syn" and found the same carb to be pulling way more than the other. (Methinks I was not clear on the concept earlier and perhaps did NOT isolate each carb when I first did it).

At any rate, it idles much better now (with less need to kick it down) and sounds just like it should.

I also started using a little Marvel Mystery Oil in the fuel after reading the "upper cylinder oiler" responses. I agree that it couldn't hurt!
 
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