Triumph Repair: Spitfire idles hight, fuel pressure gauge, float chamber

Question
QUESTION: Engine idles at about 2000 rpms when its warm.

At cold start, I start the car with full choke out and it starts up easily. I then
push choke in (almost all the way) while it warms up and pushed in all the
way once I feel it wont stall.

I can play with the idle screw and get it down but it idles too rough and
usually conks out soon after.

Once it stalls, i try to restart the car and if it starts it will usually just lose
power and stall again. So i restart it again and same thing will happen but on
the third attempt it will usually be ok and idle again at 2000 rpm.

Also, sometimes when i am running the car it just floods but I dont have the
choke out and when i open the bonnet,  i can see gas coming out of the carb.
Even though have the choke in. I also have a single SU carb.

Also, sometimes when I close the bonnet, the car stalls but if i have the
bonnet open, it idles great.

Any idea what it could be?



ANSWER: Hi Harold,
You first need to put a fuel pressure gauge on the fuel line at the carburetor and see that the pressure is not more than 1.5 to 3 PSI. Then you need to open the carburetor and check the float, float level and probably replace the float needle and seat and reset the float level. Also check the float chamber venting to see that it is not stopped up.
Howard

---------- FOLLOW-UP ----------

QUESTION: hey Howard,
I just checked the PSI and it's squeaking just above 4 psi.
how do i fix this? add a fuel regulator between the pump and the carb?

Answer
The high fuel pump pressure will not cause a high idle. The high fuel pump pressure can be caused by either an aftermarket pump or the wrong spacers between the pump and the block causing the pump to sit too close to the block thus increasing the throw of the pump arm which causes a higher pressure.

If your car were brought to me in a dealership I would need to start from scratch and first run a compression test. Set the timing and then remove the SU and open it up and adjust the float level, Preset the jet about 1/8 inch below the bridge and check to see that with the fast idle screw and the throttle stop screw backed off check that the throttle butterfly (throttle plate) seats good in the bore. Confirm that the float chamber vent is open. Check the metering needle in the piston to see that the shoulder of the needle is about flush with the bottom of the piston  and reassemble the carburetor testing that the piston when lifted to the top and dropped that it falls all the way down and hits bottom. Then add oil to the top pot so that when you remove the thumb screw on top and lift it up and push it down you must feel hydraulic resistance like a shock.

Leave the choke fast idle screw backed off and run the idle stop screw in until it just contacts the throttle and turn it in one and a half turns. (Be sure the throttle cable does not hold the throttle open at all and there must be a little free play between the cable and the linkage.

Than start the engine and worm it up and set the idle down or up to about 700 to 900 RPM and at idle give the throttle a quick blip open and watch the exhaust for a puff of black smoke but none at idle or at about 1500 RPM. If you can't get the idle down to the correct idle speed then you need to look for a vacuum leak. (no engine can run fast without an extra supply of air)

let me know what the compression readings were on each cylinder.

Howard