300D engine problem

[mickey mouse]

My 79 300TD is starting hard, smoking excessively, and has no power at low engine RPM. I feel these symptoms point to some air in the fuel intake. I have tried three other lift pumps from other cars that start and run well. I temporarily eliminated the cars tank/line system by placing a 2 gallon can in the engine compartment. The valves are adjusted. The injuctor nozzles test good. No excessive blow-by with the oil filler cap off. A compression test shows an even 300 lbs. on all five cyls. Of all the things I've tried, the only thing that had any effect was one of the four lift pumps made more power and a little less smoke than the others. Do I need a valve job? Should I try an injuction pump? or a re-man lift pump? Any feedback would be a plus. Thankx

[mickey mouse]

I need to add, the filters have been changed. When starting the first time in the morning, I have surrendered to hooking the jumper cables from the other car and starting the nurse car for five min. to give the system a good hot start. The cranking speed is ok otherwise but the extra voltage from the jump is required to get the thing to fire off. Also, the preheet system is working.

Not sure how you determined the "preheet system" is working, they can be misleading. Make sure your glow plugs are getting 12 volts. If they are not getting any voltage, check the fuse strap inside the glow plug controller (black box about 4"x4"x2") normally located on the driver's side front fender well. Check your glow plug resistances, with an ohm meter, by removing a six pin rectangular plug under the cover of the glow plug controller. Find a good ground for one ohm meter lead and the other must contact the inside of the female pin connector. If any glow plugs are open or have a high resistance they must be replaced. Each of the 5 female pin connectors has a number indicating which cylinder it is linked to. One is empty.

Another trick is to turn the fuel ratio screw on top of the injection pump upward to increase fuel flow. It may be under a round cap (removable with sidecutting pliers) if sealed from the factory. Loosen the jam nut with a 10mm wrench and turn the screw upward (counterclockwise) a 1/2 turn at a time. Remember how many turns you have made. Usually 2 turns is extreme. My 79 300D was slow to start and way under powered. This made a tremendous difference. The down side is more fuel consumption and possibly more smoke. Don't go to far as this may decrease the life of your engine. Not sure about the legality of this in California.

If neither of these fix your problem, you may want to consider additional diagnosis before doing engine reconditioning.

1. Air filter -> If clogged can limit the air flow
2. Timing -> Crankshaft, camshaft, and injection pump must be timed within specifications. A stretched timing chain or bad tensioner may allow timing to become out of specifications.
3. Injection pump/governor problems-> Rare on Bosch in-line pumps, but possible.
4. Engine mounts -> If bad, may be keeping the throttle linkage from reaching full throttle, affecting power.
5. Turbocharged engines -> Boost pressure line may be plugged coming from intake manifold to injection pump through overboost controller. This limits the fuel flow.
6. Cylinder leakage test -> Where is the leakage? Valves, rings, or head gasket/cracked head or block. Determines what is worn out or damaged before rebuilding a head that may be good.

Good Luck,

JD