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TR4/4A Stumped Again on Carbs Fouling Plugs

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KVH

KVH

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Frequently, once every 10 times, when I choke the car, plugs 1 and 2 get fouled. Tonight they were soaking with black fuel soot mixture and then I went limping around on 3 plugs for a half-mile.

Any good advice here. Do I have a bad jet or needle? I just had the head done 3 months ago, so it's unlikely valves.

Could it be the floats?

Oh, I should add. I am seeing one of my two exhaust pipes very sooty, and friends say they can "smell" that my mixture is too rich. I had a friend driving behind me and he said it was clear I'm not burning fuel correctly.

Does that help with hints as to what I need to do? thx
 
If they are ZS carbs... Sure sounds like a float/needle valve issue. If you haven't had them apart it may be worth your while to have a look. I drove for many years living what with what the PO had done in there - but the engine ran much better (was too rich) when I correctly adjusted the floats. I also replaced them with new (nitrophyl) floats. Did not replace the valves but made quite sure they were clean and operated freely every time.
 
If they are ZS carbs and if the needle valves have been replaced with Grose jets, go back to the original type needle valves.
I'll hold off on any other suggestions until we know if they are ZS carb or not.
 
A couple of possibilities- Make sure the jet tube is against the adjusting nut when the choke is fully "home". Also, check that the metering needle is centered in the jet. Raising&dropping the piston should produce an audible click.
Berry
 
It just won't start without an initial choke at times. Coincident with my installation of a Pertronix ignition, but probably only that--a coincidence.
 
KVH said:
Sorry, they are HS6 SU Carbs, not ZS.
Click to expand...
Still could be an issue with Grose jets, if you have them. Certainly fits the signs of a needle and seat problem. There are also at least two other types of fuel inlet valves (needle and seat), one with a viton tip, the other, as original, all brass. Any of these could leak and cause the problem. These are not expensive and fairly easy t change. Check the float height if you do. Tom
 
You mentioned the Pertronix installation...this is not exactly related to the fouled plugs, but when installed in the TR6 distributor, the precise location of the Pertronix pick-up is a few degrees different from contact points relationship to the lobes of the distributor cam. You have to bring the relationship back by slight rotation of the distributor...in other words reset the timing.
Did you do that with your TR4 distributor ?
 
You sound too rich on your basic adjustment. I've read your posts before and can't remember if you are running an aftermarket fuel pump ( which could overpressure the Grose Jets or needle valves and cause too rich a mixture) , either way you need to get to a good mixture at idle.
 
KVH,
I as well run two TR4's with HS6 carbs. My suggestion is that you remove the air cleaners so that you can see the bottom of the jet. This is the lowest part on the underside of the carbs. It will have plastic that is about 1/4" diameter and about 1/2" long and metal parts coming out of it. The verticle one is the actual jet and the tube coming in from the side is the fuel line. The choke on these carbs work by pulling the jet down. If the jet does not return back up against the nut above it then your choke is essentially still ON, at least for that carb. This will make those two cylinders run rich. If this is the problem there are a number of possible fixes.

So remove the air cleaner ( best to remove them both so you can see the difference in how they are operating) and then watch the jet and see if it goes down when the choke is pulled on and then backup when the choke is released via the cable. You can push up on the bottom of the jet with your finger to make sure it is all the way up.
Charley
 
+1 on watching the jet movement.

When you pull the choke knob, the jets lower. Push in the knob and the jets should return to "normal" position. I'm betting that one of your jets never returns to normal.

On my ol' TR3, one jet was actually slightly bent and wouldn't return to normal position. Straightened it, rubbed it smooth with 1000 grit sandpaper, replaced and lubed the seals - and all was well.

Tom M.
 
My float valves are viton tipped, so I guess not gross jets. The bowl for the fouled plugs (cyl 1 & 2) had a little dirt in the bottom but otherwise looked clean. The float was not cracked or leaking, but nor is it adjustable. It's the non-adjustable type and the gap is about 3/16 when pushed all the way up. The jet does not stick open when the choke is pulled. Sounds like I need to see if the mixture nut is working the jet the way it should. I can't think of any other problem.
 
KVH said:
My float valves are viton tipped, so I guess not gross jets. The bowl for the fouled plugs (cyl 1 & 2) had a little dirt in the bottom but otherwise looked clean. The float was not cracked or leaking, but nor is it adjustable. It's the non-adjustable type and the gap is about 3/16 when pushed all the way up. The jet does not stick open when the choke is pulled. Sounds like I need to see if the mixture nut is working the jet the way it should. I can't think of any other problem.
Click to expand...

I think the measurements given for float setting are a start,but I sight the level in the jet to get the final setting,just below the jet end.If its at the top its to high or leaking by.
Tom
 
UPDATE! My carb that isn't fouling the plugs has a much smaller float gap than my bad one. It's incredibly different. My good one is about 1/8 maybe less, and I re-measured the bad one and it's over 1/4, actually more than double the other. That does seem backward, however. Shouldn't a bowl causing fouled plugs be too full, not too empty? In other words allowing too much fuel into the bowl?
 
Though the float gaps should be really close, once you start adjusting the jets with the bottom nut you then would be adjusting each carb individually. So you likely nullify much of the difference. That is if you have in fact adjusted each carb according to the manual. If you have not then that should be a starting point at least on the one carb that goes with the fouled plugs.
Charley
 
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