Warm Start and Hand Throttle

jcwolff · 07-05-2006, 07:30 AM

I have a 73.5 T. I started flipping through the manual the other day, and I was surprised to see that it recommended pulling the hand throttle up on warm starts. I had never done that before. I was always told to push the gas pedal to the floor on warm starts. It also said that you should only push the pedal to the floor on very hot days when the engine is very warm. Can anyone shed some light on this? Thanks. - Jamie

Early_S_Man · 07-06-2006, 12:57 AM

I don't believe that the starting procedure in the owner's manual was altered for the 1973.5 engines ... sounds the same as previous MFI engines.

The factory recommended procedure was intended to counter prevalent habits that were based on decades of carburetor familiarity and usage ... in which an accelerator pump was actuated by the throttle, and pumped during startup. There is no such mechanism on fuel-injected engines, hence raising a hand-throttle to a higher setting accomplishes the same task as the stepped automatic choke on a carbureted engine!

Generally speaking, I don't believe there is any need to raise the hand throttle OR push the pedal to the floor during warm or hot restarts.

Jim Sims · 07-06-2006, 05:45 PM

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. Cheers, Jim

LakeCleElum · 07-06-2006, 06:26 PM

Thax Jim........I have had my '73.5 CIS for 15 years and just learned something new.....Previously I had only used the lever for cold starts. This explains why it has to crank awhile if left sitting for a 1/2 hour or so.....

jcwolff · 07-07-2006, 06:39 AM

Thanks Jim. Good stuff. I also received a great response from Souk:

If the system is adjusted properly you shouldn't have to push the pedal to the floor. A small crack of the throttle (w/ the hand lever) will introduce a little air into the combustion chamber when you are a little rich. Some CIS cars are usually running a little rich.

Keep in mind what you are doing by pulling the hand throttle or flooring the throttle pedal. You are allowing air into the engine while cranking. Some guys may have to floor the pedal because there CIS is adjusted to the very rich side, so they need to allow the engine to suck more air into the engine. Some just need a crack of the throttle. So there is no one correct way to do it. It just depends on your tuning. If your car will start with a small crack of the throttle, then do it that way. You are just trying to match the air to the fuel so you have a combustable mixture (no matter hot or cold).

Eventually you will develop your own routine and you'll be able to start your car cold or hot, because you will know your car.

I need to expand on the last e-mail.

The hand throttle and the foot throttle, both affect the flow of air into the engine (w/o opening the throttle, the air into the engine goes through the throttle bypass-ie, idle air). The flow affects the airplate (more flow more lift)....When the air plate lifts, it pushes the fuel plunger in the fuel distributor up. The higher up the plunger goes the more fuel.

So like I side before, you are trying to create a combustable mixture....learn how your engine likes to start...and adjsut the routine as temperatures change.

Jim Sims · 07-07-2006, 06:48 AM

What is missing for the '73.5 and '74 CIS cars in Souk's explanation is the fact that if you don't pull the lever all the way up, the CSV will not be activated while cranking. Without the enrichment of the CSV these cars are hard to start unless they're tuned (mis-tuned?) to run rich which of course wastes fuel and increases emissions.

Zeke · 07-07-2006, 06:54 AM

When did the CIS change to no have a hand throttle? My '77 didn't have one. On that, one just used the key, no throttle.

Jim Sims · 07-07-2006, 07:01 AM

I believe 1975 was the transition year; I know the hand throttle was gone (at least in the US) by 1976.

Sunroof · 07-07-2006, 07:08 AM

Life is good with a hand throttle!!!

You must pull the hand throttle up on start up!!!!!!!!!!!!!

You will get used to it like putting on a seat belt after awhile. You will start with a high idle (set the hand throttle so your at 2000-2500 rpm) and just drive. Watch the temp gauge because the thing will not come down on its own and once your around 170 degrees push it down and see if the idle stabilizes. Your then set.

On the hand throttle is a plastic claw that is attached to the throttle that is set with a set screw and will over time have to be replaced because it gets brittle and breaks. You can see the claw where the hand brake and throttle level are located. Take a good look at it. Its an inexpensive piece and not too difficult to replace.

The 73.5T is unique in only that its the first CIS model without the thermotime switch and your warm up its basically a manual maneuver, not unlike the old British cars with manual chokes.

Maintaining goor mixture settings in the summer and winter will make the warm up process easy. The CIS likes to run a bit rich. I hope your air-box is equipped with a "pop-off" valve.

Enjoy the ride

Bob
73.5T