73.5 CIS air flow sensor plate adjustment

[rockreid]

OK, I can get my 73.5 CIS running by manually holding up the air flow sensor plate at just the right amount while the wife starts the car. I pulled an injector and there is no fuel spray with Key On- normal I think for my 73.5. However, the sensor plate has to be moved a good distance by hand before fuel is sprayed. Is this normal?

I never touched the adjustment screw while rebuilding this engine, and it seems the adjustment may be severely too lean at this point. Not even close. The air filter cover and air filter not being installed shouldn't throw off the sensor plate reading should it?

Also as a side note, I noticed a great deal of blue smoke out of the tailpipe. I hope I don't have a cracked piston ring already. The engine sounds great when running. No weird noises or clunking. Perhaps it just needs a proper break-in after this total rebuild.

[T77911S]

so this is a fresh rebuild that is just getting started?
with the key an the senor plate down (FP running), there should not be any fiel coming out of the injectors. i do believe the preliminary setting for the mixture is turn it CW until fuel comes out then back CCW until it stops.

usually the system is adjusted richer to compensate for air leaks, or it can be adjusted leaner for bad control pressures.

start with fuel pressures. check cold and warm pressures.
check your intake bolts and other places for air leaks.

if you need to adjust the mixture CW to make it run if you need to keep it running. (only because it is a new build at this point).

have you checked injectors?
what is the history on the FD? the WUR?

[boyt911sc]

Originally Posted by rockreid

OK, I can get my 73.5 CIS running by manually holding up the air flow sensor plate at just the right amount while the wife starts the car. I pulled an injector and there is no fuel spray with Key On- normal I think for my 73.5. However, the sensor plate has to be moved a good distance by hand before fuel is sprayed. Is this normal?

I never touched the adjustment screw while rebuilding this engine, and it seems the adjustment may be severely too lean at this point. Not even close. The air filter cover and air filter not being installed shouldn't throw off the sensor plate reading should it?

Also as a side note, I noticed a great deal of blue smoke out of the tailpipe. I hope I don't have a cracked piston ring already. The engine sounds great when running. No weird noises or clunking. Perhaps it just needs a proper break-in after this total rebuild.

Rock,

Don't touch the mixture setting at this point. Why would you adjust it? Simply because you can not start the engine? The fuel mixture setting won't even change if you had a head on collision or fell off into a 100-feet cliff. That's the last thing you want to disturb. Focus on the fuel pressures and absence of unmetered air going into the system.

If you still have the original WUR-001 with a TPR (throttle pressure regulator), checking the control fuel measure is not straight forward like those for the later '74 - '83 CIS. The presence of the TPR in tandem with the WUR contributes to the over all control fuel pressures. This particular model year ('73.5) is a peculiar CIS model.

Tony

[rockreid]

I did have the FD rebuilt so the plunger piston may be a bit different. All I know is that the air plate sensor is at the rest point in its bore where it is supposed to be. The spring under it is intact and fuel does not flow as it is supposed to upon start unless I lift up the lever plate myself. I can feel the pressure from the fuel in the FD acting down upon the plunger while I do this and I hear the squeal of fuel. I think I have this licked now.

Tomorrow I will button everything up and see if I can dial in the correct adjustment screw to get this car at least running enough to get to a local shop with a proper gas analyzer.

[rockreid]

Update- Ran the engine and drove car up and down street today- first time this car has moved on its own power since 1988. Engine sounded strong and ran up to 4-5k several times. The smoke died down a great deal after awhile so hopefully my initial panic over a possible cracked piston ring was not justified.

Still need to adjust ignition timing and perhaps dial in the FD sensor plate a bit richer. Seems to be running out of gas at high rpm but won't know for sure until I adjust ignition timing tomorrow. Anyway, feels good to bring this old 73.5 beast back to life after all this time.

Still lots of body trim work to do as well as replace a leaking brake line. But it seems like a 4 year project is finally bearing fruit.

[T77911S]

you should not spray fuel with the engine off and fuel pump on.

it is not the sensor plate height that is adjusted when adjusting the mixture. it is basically the plunger height inside the FD.

at say 1000rpm, the sensor plate may be open 3mm. bedcause the amount of air coming in does not change and the CP pushing down on the plunger does not change, when you adjust the mixture there is another arm in there that pushes the plunger up to let in more fuel. very basic explanation.