Gregar

1984 4000 Q that I love is killing me! She sat garaged for many years and is now almost restored; EXCEPT still running rich and no warm start. She cold starts great, then just runs rich across full rpm, then will not warm start. Tried over priming and still no warm start, good spark and starting fluid into manifold won't even get a cough.

Rebuilt entire fuel system; tank, filters, pump, dizzy (took twice to get it right), injectors. Everything seems to check out; CSV and ISV operate properly, no smoke detected vacuum leaks (4' of hose replaced). Good spray pattern from new injectors, but did not measure volume or Pressure. New O2 sensor, Differential Pressure engine coolant temp sensor replaced and working (lower at top hose at head), Pressure regulator and potentiometer at dizzy both check out good. Pulling the ECU fuse kills the engine, as does disconnecting the temp sensor.
NEED HELP HERE!! SO close yet so far!! thanks to all
Greg

Sleeper8

I don't think you mentioned it, so just asking: DId you already back out the mixutre adjustment screw on the air meter housing? Referring to the screw in the hole between the fuel distributor and the boot that takes 3mm allen wrench.

Gregar

Thanks Sleeper8,
Bentley refers to that as the CO adjustment screw, that adjusts the contact gap of the pot plate (and also changes plunger). When I rebuilt the dizzy I set it at spec. But while chasing rich running condition I have adjusted it without any significant effect! Set it back to spec after another disappointment. But more air without more fuel is what it needs.
Have all the tech notes on dizzy rebuild, and did a careful job that seemed good. BUT am now suspecting it, and also reluctant to dive back in there! The potentiometer resistance is in spec.
ANY thoughts appreciated!

Gregar

When testing CSV, I pulled it, covered the hole and ran the engine. CSV sprayed a short nice cone into a jar. Then slowly uncovered it's hole letting air in, and engine ran better.
Is it possible that fuel pressure is too high and causing injectors to spray too mush fuel? I didn't think the injector nozzles would do that.

Gregar

Testing fuel dizzy pressure regulator, (again). First checked return line by undoing at dizzy and blowing through it while listening at tank filler hole. Fine.
Hooked up ammeter to test regulator, found it hunting around 20ma, about twice Huw's spec. Adjusted CO valve (3mm) and got it down to 10ma, and hunting. As if ECU responding to O2 sensor. Suddenly went to 0 ma and stayed there, which may indicate ECU not sending consistent (or any?) signal to pressure regulator. Or faulty regulator. Whole time exhaust is kind of black smokey, and not changing much. No warm start, so had to stop there.
Swamped in used Force 5 pressure regulator, and will try again tomorrow. May have a bad P regulator. Building fuel pressure gage to work on this dizzy.
Starting to seriously consider ECU. Anyone know of good working one, I might rent for a day.
My heading is really starting to hurt here! NEED HELP
NOTES: New O2, and temp sensors were recently installed.
ISV and CSV are operating to spec.
Also engine dies if 10A ECU fuse pulled, or if temp sensor unplugged, but I don't think either should do that.
ANY THOUGHTS OR SUGGESTIONS APPRECIATED
Greg

Emanjo

Hey man I don't know if I'm late to the party or not but I'm chasing the exact same issues on my CGT right now. You mentioned yours is an '84, not sure if it's CIS or CISE. I've got CISE and all leads point to the coolant temp sensor. But replacing, cleaning and checking connections didn't work... will report progress.

Gregar

CIS-E here, found it to not be any sensor. Bur after rebuilding dizzy and setting plunger to ~0.6 mm still too rich to start. Adjusted CO screw by iterations and got the mixture corrected. I believe the CO screw has more effect on plunger height than plate air flow. Chasing a ignition miss now!
What we did to test richness was unplug fuel pump while starting. As fuel was depleted it would start and run for about five seconds!

Emanjo

Oh interesting. I'll keep playing with my setup and see if I can get it half decent. At the moment it's running with the coolant temp sensor unplugged, and with the other areas of adjustment tweaked accordingly. Overall rich as a result, but it's the best I can do right now. Which direction do you turn the CO screw to richen or lean the mixture?

Emanjo

Something crazy happened. I turned the CO screw clockwise a full turn, and the car started with the coolant temp sensor plugged in for the first time since i've bought the car. My ecu is finally reading temps, good lord it's been long enough. Now time to fine tune and start driving