DIY Network

Diesel Tuneup A student gets a lesson on tuning up a diesel engine. From "Trade School" episode DTRS-401

Diesel Engine

With the help of instructor Darrell Wayne DeBoer, diesel-repair student Chris Barnes performs a tuneup on one of Wyotech's training engines.

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Materials:

safety glasses
socket wrenches
torque wrench
dial type torque wrench
feeler gauges
T-handle Phillips screwdriver
large ratchet
start cart
impact wrench
dial indicator
ball peen hammer
transmission jack
clutch jack

Safety Note: When working on engines, always wear protective eyewear.

Each of the engine's six cylinders has an intake valve, an exhaust valve and a fuel injector, which are opened and closed by levers called rocker arms, driven by camshafts. A tuneup ensures that, according to manufacturers specifications, each valve opens and closes at the proper time, in relation to the position of the pistons in the cylinders. The result of a well-done tuneup is an engine that runs at its maximum performance.

	Figure A
	Figure B
	Figure C
	Figure D
	Figure E
	Figure F

Steps:

1. First, Chris removes the valve cover, giving him access to the valves and injectors inside the engine.

2. Before Chris can adjust the valves of the first cylinder, the piston needs to be at the top of its stroke, or "top dead center." He accomplishes this by "barring over" the engine, which means manually turning the crankshaft to move the cylinders through their cycles. He attaches a large ratchet to a socket on the end of the crankshaft, and starts cranking (figure A).

3. Alignment marks on the crankcase (figure B) tell Chris when the cylinders are in the proper position. Each cylinder has a companion cylinder that moves in unison with it, and each alignment mark refers to one pair of companion cylinders. Mark "A" indicates that cylinders 1 and 6 are in tuneup position, "B" indicates cylinders 2 and 5, and "C" refers to 3 and 4.

4. Once the first alignment marks line up, Chris double checks the cylinders by wiggling the rocker arms on the valves. They are loose, confirming that the cylinder is in the right position for the tuneup.

5. Each valve has an adjustment screw, which is secured with a lock nut. Using a socket wrench, Chris loosens the lock nuts. Then he makes the first adjustment, using a dial type torque wrench (figure C) to set the fuel injector to 70 foot-pounds.

6. To tune the intake valve, Chris uses a set of feeler gauges (figure D). These are flat metal blades, each of a precise thickness. Inserting the feeler gauge into the gap between the rocker arm and the valve bridge, he tightens the adjusting screw until he gets a firm drag. This means the gauge fits snugly into the gap, but can still be pulled out by hand.

7. Once the valve is properly adjusted, Chris has to tighten the lock nut. Holding the adjustment screw in place with one hand, he uses a torque wrench (figure E) to tighten the nuts to exactly 33 foot-pounds.

8. Chris repeats this process for the other valves, and then moves on to the other cylinders, barring the engine over as needed to bring the cylinders into position. With all the valves and injectors properly tuned, it’s time to test start the engine.

9. Using an external battery mounted on a rolling platform called a start cart (figure F), he fires up the engine and listens carefully. If the engine is out of tune, the valves will make a telltale clicking noise. Chris has done his job well, and the engine is running smooth.

10. After Chris disconnects the start cart, all that's left is cleaning up the excess oil and replacing the valve cover.

RESOURCES :

Wyotech
Website: www.wyotech.com