TR6 tr6 poor idle

[rjc157]

looking to eliminate the carbon canister because i think i have a vacume problem ,no mater what i do i just can't get it to idle ,it revs up fine but when i release it it wants to stall .will change the points rotor and condencer today hope that works

 

[poolboy]

Not that it's a bad thing to change points, etc. but if it is a vacuum leak, how's that going to help ?
By looking at what you say in your "profile" you have an A-H 3000, so this won't apply unless you have a TR with an Anti Run-On Valve.


Look at all the nipples on the carb and manifold.
Check the nipple on the left side of the carbs, the ones closest to the air filter housing. Do Not cap or plug those, even if you do remove the hose that went from there to the carbon canister.

 

[cmacmillan]

On that note, does anyone have a good bird's eye pic of a set up with the emissions removed, or at least reduced (preferrably on a '75 TR6, but anything close would do).

...I think my PO put stops on the outlets poolboy's referring to.

 

[poolboy]

If those ports on the left side of the carb are plugged or capped, you will have trouble maintaining an idle.
Those nipples provide a dual role. Most important role is to provide ventillation for the float chamber when the engine is at idle.
Secondary is to provide a port for the manifold vacuum to prevent fuel from rising up the jet when you turn the key to "OFF". The anti run on valve under the carbon canister controls that function.
If you can live w/o the Anti Run-on feature, the Anti Run-on Valve and Carbon canister can be eliminated.
The EGR valve and the associated plumbing can be eliminated regardless.
Now it's not as simple as I've made it sound because certain nipples need to be plugged and others like the float chamber vents, not.
Then of course you have the air pump, diverter valve and exhaust manifold to deal with that I didn't with my 74.
Yeah maybe a picture would be better.

 

[rjc157]

now the car refuses to start have spark but it looks weak could it be the coil how do i check it

 

[cmacmillan]

Not to jump in and hijack the post, I'm just curious because I've been trying to figure this one out for a while! If the ports are capped, what's going to be the result? Is ti just uneven idle or are there going to be other outcomes?

...picture....anyone....Bueller?

 

[poolboy]

Not to jump in and hijack the post, I'm just curious because I've been trying to figure this one out for a while! If the ports are capped, what's going to be the result? Is ti just uneven idle or are there going to be other outcomes?

...picture....anyone....Bueller?

Let me see if I can explain. Starting in 1973 there are 2 vent ports for the carbs' float chambers. One is a 1/4" diameter hole, usually brass lined on the carbs air filter housing mounting flange. It is inbetween the top and left threaded holes that hold the air box (air filter housing). The other is the one I described earlier, the nipples.
On the left side of the carbs in about the middle, you'll see an "L" shaped pivoting lever. The vertical arm of the lever operates a brass plunger valve. The horizonal arm of the lever rest on the throttle stop lever.
When the engine is at idle, the "L" shaped lever pushes the brass plunger in and the nipple port is open. When above idle the throttle stop lever allows the "L" shaped lever to pivot and the spring loaded plunger moves out, closing the nipple port and opens the flange port.
Ok and now to answer your question.
As fuel is depleted in the float chamber, the level drops and pressure decreases above the fuel level. If there were not a vent, a vacuum would gradually develop making it hard for fuel to flow up the jet. Air must be let in to replace the used up fuel.
And therein lies the principle of the Anti Run-on valve. Instead of just having one vent (the one on the flange), the nipple vent both vents at idle and receives the manifold vacuum when the ARV opens to the manifold vacuum by activation of the ignition key turned to the "OFF" position.
The manifold vacuum just speeds up the process that would occur if the nipple vent were capped or plugged.
It's the same principle that would prevent gas from draining out of the fuel tank, if the tank did not have a vent hole to allow air to displace the gas asit is used up.
Plug the nipples up when the engine is idling, with your fingers if necessary, and see how long it takes for your engine to start to sputter. That's probably the best way to see the effect.

 

[poolboy]

now the car refuses to start have spark but it looks weak could it be the coil how do i check it

If you see a spark, I doubt that it's the coil. Maybe the rotor or the condensor. Are the points opening and closing with a spark as they do ?
Then again there are other things, like fuel supply to the carbs, a blocked or capped float chamber vent as described above. You kind of have to go thru a process of elimination one component at a time.

 

[poolboy]

macmillian, I don't know why I didn't think to include this above. The author makes a brief statement saying that "the Atmospheric pressure above the fuel level in the float chamber must be maintained" in his description, but the pictures are good if you look down close to the bottom of this page. https://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm

 

[rjc157]

eureka from nothing to victory it started don't ask me why but it did idle alittle rough but not too bad

 

[cmacmillan]

Poolboy - many thanks for the description/link...this has now jumped to the top of my to-do list - I believe it actually makes sense now!