Accelerator switch and throttle solnoid

[subwar2001]

Can anybody tell me what these two items are used for. And if anybody can tell me how to set up the Cold Start device to insure it is advancing properly on an 1987 SD25 for Canada it would be greatly appreciated.

[plenzen]

I assume that the "Accelerator Switch" that you are referring to is the one that controls the throttle chamber butterfly. There are two positions for that particular device and as the FSM describes it as "Half Open" and “Full open". The FSM states that:

“Throttle chamber is adopted on intake manifold to reduce suction noise while engine speed is low."

There are a number of devices within this system that have to be checked if not working but the easiest way is to first remove the air cleaner lid and look down the throttle body. The butterfly should be fully open when engine is stopped. Start the engine and it should partially close or "1/2 open". Then, operate the throttle and at approx 1500 RPM the butterfly will open fully. You will hear the difference with the lid off the air cleaner. If it does not open then there are a number of checks to perform in regards to the vacuum pump, a solenoid located near the vacuum pump, fuse, the actual vacuum diaphragm etc etc. On my truck I have changed the air intake system and removed the chamber that the air is drawn through on the inner fender and put what is basically a 4" pipe off the snorkel and down behind the rad support. I have the butterfly adjusted to remain in the “1/2” open position at idle up to approx 1000 +/- 100 rpm and then to open fully. I did this to reduce the amount of cold air in winter rushing into and past the air heater that I have installed under that device to aid in cold starting. The noise is not a factor as once that box on the inner fender well was removed you cannot really hear the difference once the butterfly is open. The switch on the fuel pump is adjustable through some screws that loosen the switch on some slots. Follow the vacuum lines from the diaphragm to the switch/solenoid on the front rad support and you will find the solenoid. If all is working then no need to mess with it. The correct clearance for "1/2" open is 10.7 mm ( 0.421in) between the butterfly and the throttle body.

The CSD is located on the side of the fuel pump at/near the bottom. Other than the clearance of the bottom set screw where it touches the plunger that comes out of the temp block there is really no adjustment for it. It works internally and I believe is adjusted by a fuel pump service tech. Easiest way to check to see if it is working is to disable it on a cold start. The colder the better really. On the side of the device there are two holes in the lever that comes from the side of it. The FSM says to disable it place a screwdriver shaft through the two holes (they show a phillips driver shaft) and rotate that device "clockwise" but, the arrow on the picture shows counter clockwise(shrug ). I have done it and I believe that it is counter clockwise or to the rear of the vehicle. There is considerable spring tension on it so be prepared for a bit of a twist. Watch your fingers as it will want to snap back into position, so, once rotated until it stops, block the driver from snapping back. ( there are many sharp things there that will remove skin from knuckles INSTANTLY !) Better yet, get an assistant to start the truck. As stated, first start of the day and the colder the better. When the engine starts, and the idle has smoothed out, then "re-engage" the CSD to the operating position. The engine idle should increase. It may only be 50 - 200 RPM as it (CSD) is temperature sensitive as to how much it advances the timing and actually moves the fuel control. If it (RPM) increases then it is working. The only adjustment that the FSM gives you is the clearance between what they refer to as "the block" (the plunger out of the bottom of the CSD) and the small set screw at the bottom of the lever that you rotated. It is a bit hard to see but it is down there. At the "disabled" position ( rotated to the rear) "The block length should be about 15mm ( 0.59in) between the CSD and the linkage"

Hope I have not confused you

Paul

[subwar2001]

Actually you didn't confuse me. When I bought this truck the CSD was not hooked up so I had to buy hoses for it to make it work but I was wondering about the setting for it on the pluger. As for the accelerator switch, that was me not reading my manual close enough and paying attention to detail. Right now I am pondering removing the injectors to test them as I have a fuel dilution problem and suspect a leaking injector as they are easier to look at, then the alternative.