CIS R&R on a 78SC

[Damomma]

I am just about to start the reassembly on my engine and tranny which I have rebuilt and was looking at the 25 year old parts on the CIS. The car ran fairly well before the teardown for broken headstuds (100k miles) but at constant throttle between 2500-3000 RPM the car would surge up a down within a narrow band like being unsteady on the gas pedal.

My question, while everything is out still is there some more extensive maintenance on the fuel system that I should perform? eg how long do injectors last ? can they be sent out for blueprinting and cleaning? Or do they just get replaced? The injection lines are very stiff but don't seem to be cracking. I see they are NLA on the PP Website.

I've done the basics like soft fuel lines and filter, air box pop off valve but haven't touched the accumulator.

Any good sources for CIS R&R out there?

Thanks Jim

[vash]

if it was me, i would just change the coldstartvalve. because that is the only part that is really hard to get to. at least test it....

and all the vacumn lines..

[RarlyL8]

I did this when rebuilding my CIS 930 engine.
Replace all your rubber hoses.
Check all components for proper function.
Clean/replace injectors (they can be cleaned).
Eliminate any component that is not needed (read smog crap).
Check/calibrate the air plate.
Remove the fuel head piston and clean everything with carb cleaner (be VERY careful).
New fuel filter.
Replace brittle electrical wires and clean connections.

Remember there are 3 components to the CIS, fuel air and electricity.
Check them all.

[Damomma]

Thanks unfixed and Rarlyl8, Can I use an ultrasonic cleaner for the injectors or just soak in carb cleaner or send them out someplace?

I'll have to do some research on the "fuel head piston" . Is that where all the injectors lines initiate from?

[oneblueyedog]

THe fuel distributor piston is the ultra precision machined piston that travels up and down via actuation of the sensor plate arm.

It's critical that it moves smoothly up and down its bore to meter fuel to all of the injector lines (fuel distributor).

Drop the piston and damage it and the whole assembly is junk.

I cleaned mine at one time and found my piston worn. It would slide up and down effortlessly only in one orientation with the bore. You could see polished wear marks on the piston, thus a little out of round.

Use Porsche gaskets on reassembly. Especially the foam pad perimeter gasket that the FI distributor and meter rests on. It's a cushion. I made the mistake of silicone sealing it back on. The vibration from the engine made it idle like crap. I reinstalled it with the correct gasket. Perfecto!

I bought all new injectors and tested the spray pattern. Some still streamed at a moderate sensor plate lift.

It's known that the fuel charge to the ports in these cars is not timed.
So, if a spray pattern is less than perfect, does it matter?

Lee 78 SC

[Jim Sims]

Replace all the rubber o-rings and injector seals plus the o-rings on the CSV fittings and the foam gasket that Lee describes above. I would also recomend replacing all the air hoses on the CIS system (such as the Y-hose on the AAR). I'd also replace as many of the rubber sections of the fuel lines as you can, all the way forward to the fuel tank. The rubber boots between the airbox and the intake rubber likely warrant replacing after 25 years. Plus check and repair/replace the engine wiring harness as required. The cost of these rubber and plastic parts can add up quickly but new ones can keep your car dependable and go a long ways towards avoiding fires. Cheers, Jim