CIS questions on a 73.

[dmcummins]

Ive been reading up on the CIS threads and I'm still confused. My car will start cold only if I turn the key and let the fuel pump run for 5-10 seconds. When I turn the key I can definatly here the fuel pump. Then the car will idle but takes awhile to warm up and seams cold natured. Also I assume I have vacumn leaks because I can cover the air snorkel and it runs the same.

The car runs ok when it is warmed up, and will start back up if turned off when warm. But I recently went golfing and I though it was going to leave me stranded. It would run breifly and die, it would pop and spit and would not keep running. I finally got it going and once I was on the highway and was able to open her up she ran fine.

I have had the car for several years but tore it apart when I got it home and just recently started driving it some. I would start it from time to time but that was it.

I would think that the first thing to do is to check for air leaks. Shouldn't at least the idle change if I put my hand over the air intake? Could the mixture have been adjusted to run with the air leaks and be causing the starting problems?

[Jim Sims]

First, are you following the below proper starting procedure? Cold Start Valve (CSV) operation on a 73.5T CIS is very important for easy starting.

The owners manual for a 1973.5 CIS states that the hand lever should be pulled fully up (so the micro-switch on the throttle body closes and sends power to the cold start valve) for all starts when the engine temperature is less than "very high". Very high is defined as an engine temperature of 212 to 250 F. Unless the engine is running hot and the stop is very brief (so the engine doesn't cool off) this in a practical sense means the lever is pulled up for every start. The manual further states that when the ambient air temperature is below -5F the lever should be fully pulled up and the gas pedal partially depressed; then when the engine starts, the lever is positioned for a 1200 RPM warm up speed. For "nominal cold starts" (air temp above -5F and engine oil temperature below 155F) the lever should be pulled fully up without gas pedal application and then once the engine starts the lever is lowered to set the engine RPM at 1200 for warm up. When the engine is warmed up (~155-160F oil temp) the lever is fully lowered. When starting a warm (as opposed to a "very high" temperature) engine the lever is pulled up for starting and immediately pushed back down after the engine starts. For the very high temperature case (212 to 250 F oil temperature) the hand lever is left down and the gas pedal is fully depressed during starting. It is important to note that the '73.5 and (also the 1974?) CIS cold start valve (CSV) circuits do not incorporate a thermal time switch so the driver has to control this function. Note though that as usual the CSV only operates while the starter is turning, it does nothing for cold running after that time.

[ossiblue]

Add to Jim's post:

You've got classic lean conditions which could be from air leaks, as you suspect. Also, the fuel accumulator or check valve in the fuel pump may be bad if you need to "prime" the system 5-10 seconds. Could be fuel system pressures too.

Start with pressure checks of the system to establish if the WUR is operating correctly and your cold, system, and controlled pressures are in specs. If good, track down air leaks. Covering the intake will not necessarily tell you if you have a leak as the auxilary air valve lets air bypass the intake during cold starts--that may be misbehaving too!

Don't get discouraged but I'd suggest starting with your pressures to get that out of the way.
Check out this link for an overview of how all these CIS components work:

http://members.rennlist.com/jimwms/CIS/CIShome.html

Use the search and read as much as you can and keep asking questions when you find out more specific symptoms or results of tests.

[HarryD]

Jims procedure is correct. Works every time for me.

When I first got my car, the electrical leads to the CSV were disconnected. The car was very hard to start and ran terribily until warm. Once I reconnected the CSV, starts were no longer dramatic. Check that your CSV is connected.

Also, when I first put my key in the run position, I hear the fuel pump run and after a few seconds the tone changes. I have been using this change to indicate that the fuel system is fully pressurized and the car is ready to start.

[boyt911sc]

Originally Posted by Jim Sims

First, are you following the below proper starting procedure? Cold Start Valve (CSV) operation on a 73.5T CIS is very important for easy starting.

The owners manual for a 1973.5 CIS states that the hand lever should be pulled fully up (so the micro-switch on the throttle body closes and sends power to the cold start valve) for all starts when the engine temperature is less than "very high". Very high is defined as an engine temperature of 212 to 250 F. Unless the engine is running hot and the stop is very brief (so the engine doesn't cool off) this in a practical sense means the lever is pulled up for every start. The manual further states that when the ambient air temperature is below -5F the lever should be fully pulled up and the gas pedal partially depressed; then when the engine starts, the lever is positioned for a 1200 RPM warm up speed. For "nominal cold starts" (air temp above -5F and engine oil temperature below 155F) the lever should be pulled fully up without gas pedal application and then once the engine starts the lever is lowered to set the engine RPM at 1200 for warm up. When the engine is warmed up (~155-160F oil temp) the lever is fully lowered. When starting a warm (as opposed to a "very high" temperature) engine the lever is pulled up for starting and immediately pushed back down after the engine starts. For the very high temperature case (212 to 250 F oil temperature) the hand lever is left down and the gas pedal is fully depressed during starting. It is important to note that the '73.5 and (also the 1974?) CIS cold start valve (CSV) circuits do not incorporate a thermal time switch so the driver has to control this function. Note though that as usual the CSV only operates while the starter is turning, it does nothing for cold running after that time.

Jim S.,

The '74 (911) has thermotime switch and all later (up to '83) CIS models. Please refer to wiring diagrams in factory manual.

Tony

[dmcummins]

Thanks guys, when I pull up on the lever I cant tell any difference. I'll check that today and see if its connected.

I'll have to buy a guage to check the pressure. Are there any kits out there already made up? I don't see one listed here.

[Sunroof]

Its all in the lever!

If you feel no difference with the lever up, then check the connections. Their will always be a slight resistance if the lever cable is connected properly. If its an effortless pull, then check under the lever where their is a small plastic fitting that often gets brittle over time and will break. This plastic "claw" fitting attaches the hand lever cable to the throttle cable under the handbrake/lever plate. If your not sure have someone pull up the lever while you look at the throttle linkage in the engine compartment for starters. With the lever up I get up to 3,000 rpm and adjust down.

One thing on start up I do as well is turn the key on to hear the fuel pump and listen for the injectors to fill before ignition. Its a sound like sucking a drink through a straw for a few moment then stops. With that, I'll wait a few seconds more and the bastard will spark right up!!!! If I ever had to make a fast getaway when cold with this car I'm screwed!!!! This is what I love about these older cars. Its like a multi step process to get 'em going.......

For the 1973.5T CIS model, life is so much better with a warm up throttle lever!!

Bob
1973.5T

[dmcummins]

I finally got around to checking the throttle lever and the plastic thing on the bottom of the lever is broke. I'll order one from our host and see if that helps.

Wouldn't holding down the gas pedal slightly do the same thing as the lever? What does the plastic thing hook up too?