Understanding that each engine is different, let's start with the proper technique for one situation: Starting a high-horse powered diesel engine (300 hp or above) on level ground. You should be able to ease the clutch out slowly and get the rig moving without giving the engine any fuel with the foot throttle. If it stalls, you are experiencing one of the following problems:
- You are releasing the clutch too fast for the engine governor to pick up the load.
- You are not in the proper starting gear.
- Your truck is geared too high for normal highway running.
- Your brakes are not released completely.
Diesel Engines on a Hill - With or Without a Load
Too often, here's what happens on the road. A driver lets go of the foot brake and goes for the throttle. As he releases the clutch, the truck starts rolling backward. He gets excited, pops the clutch out and jumps on the throttle trying to catch it. Unless, he's lucky, there goes the truck's "U" joint, drive line, or axle.
To avoid this problem, begin by holding the truck with the service (foot) brake to keep it from rolling back. Then, as your left foot eases out the clutch gently to the contact point (while your right foot is still applying the brakes) get ready to apply the throttle to eliminate roll back.
HINT: Ease the clutch out very gently with your left foot until you sense the engine starting to pick up the load. (The clutch will be partially engaged). At this point, hold the clutch right where you have it with your right foot still on the brake pedal. As you feel the clutch starting to engage, move your right foot from the brake to the throttle. Then, very, very, gently start releasing the clutch pedal, applying just enough throttle to keep the engine from stalling. This is something you must develop a feel for. Use only the ball (or the toes) of your foot on the clutch. Try to keep your heel on the floor. This will help you achieve a much smoother movement. Don't put your instep on the clutch pedal. This places the entire weight of your leg on the clutch, giving you very little feeling for delicate pressure.
There are three alternatives to the above plan.
- Use the trailer handbrake valve to hold you until you're ready to move. The key to this approach is good timing. If you don't carefully coordinate the trailer brake release with your clutch/throttle movement, you can still roll back or wipe out a "U" joint.
- If you don't have a trailer hand valve, or if you can't seem to coordinate the trailer handbrake release with the clutch/throttle movement, you can use your Maxi brake. Set the Maxi brake on the tractor or trailer. Then, coordinate your clutch and throttle with the Maxi release. Here again, you may find the brake release slower than anticipated and you wind up stalling the engine or scorching the clutch. Either method takes practice.
- A third method of starting a diesel engine on a hill is simply to couple the method described in the HINT above with a low/low gear, one that you feel is sufficient for starting with the load you are hauling. If you have any doubts at all as to what gear would be best to start in, start in the lowest gear you have, low or low/low, and stay in it until you feel it is safe to grab another gear. It is not recommended trying to shift up a gear on any steep grade.
The least difficult startup operation that you will encounter as a driver is starting a loaded or empty gas rig on level ground. In this situation, the rig is not prone to rolling before you have control of it with the clutch and engine.
But let's go through the starting process anyway. Release the parking brake and place the unit in the proper starting gear while you hold the rig still with the service brake (foot brake). Start easing the clutch out slowly just as you would with a diesel-powered rig. As soon as you feel the clutch starting to engage, release the brake pedal and move your right foot over to the throttle (gas pedal). Now, very gently apply more throttle as you continue to slowly ease the clutch out until it is completely engaged. Continue to increase engine RPM until you have reached sufficient speed to shift to the next higher gear. The important thing here is to apply enough throttle so that the engine doesn't stall until you get the unit moving.
Because each truck will vary according to starting gear ratio, load, engine size, etc., it takes time to develop a feel for both the clutch and the throttle. It takes time to determine how much throttle is required to prevent stalling when the clutch makes the initial contact. The clutch requires a slow, steady release movement after initial engagement, but how slow? With practice, you'll be making all the right moves without even thinking about them. It'll come in time.
Gas Engines on a Hill - With or Without a Load
Starting a gasoline-powered truck on a hill is a little more difficult than starting one on level ground. Your biggest problem is holding the truck to keep it from rolling back. Many drivers release the service brake first, then dive for the throttle to keep the unit from rolling backward. This is one driving habit you don't want to develop as it usually results in stalling the engine, or worse, tearing out a drive line.
The clutch action described in the diesel HINT section above will also work on a hill with a gas-powered truck. It requires more throttle, however, because the gas engine does not have the torque of a diesel. The big difference is that the gas engine has no governor at the idle speed to bring the engine RPM up automatically under a starting load. Gas engines will stall unless you give them some throttle.
Begin by holding the rig with the brakes. If you're driving a gasoline- powered tractor-trailer unit, you have a choice of using the trailer brake, Maxi brake, or parking brake. If you're driving a small bobtail, you may use the mechanical hand brake or, if your truck is air-brake equipped, your Maxi brake operates the same as in a larger rig.
Place the truck in a good starting gear (usually low). Then use the clutch/ throttle movement that we described earlier, timing it with the release of either your trailer brake, Maxi brake, or mechanical hand brake (which- ever you have). Don't try to move the rig with the clutch while the parking, trailer, or Maxi brakes are still applied. Clutch abuse such as this will eventually result in clutch burnout.
