81 Rabbit injection timing trouble...

[joshuare]

I have been having a hell of a time getting the ignition timing perfected on my rabbit. I just can't seem to find the right spot for it. The manual suggests between .8 and 1.3 I think, and I've tried it all over that range, but it still runs with a lot of smoke, and can barely make it up a hill. Any suggestions would be most appretiated.

[zagrot]

i'm assuming that you have a diesel. is the smoke black or white? does it smoke all of the time or just under load?

[joshuare]

yes, it is a diesel. the smoke is always pretty whitish whenever the car is running. It doesn't seem to matter whether the engine is working hard or not.

[zagrot]

has the car recently been put back into service after sitting for a long period of time? is there anything that may have lead to the existing condition (something like "it was running fine, but after x srevice it is doing strange stuff")?

white smoke is usually due to to a cold engine (not enough heat to fully sustain combustion), low cylinder pressure (really any mechanical defect that lets air escape the cylinder on compression), and bad fuel. white smoke can also be attributed to various pump and injector problems.

cold engine:
that does not seem to apply, but any white smoke should clear up after a few minutes of running.

bad fuel:
if the car has been sitting for a long time try replacing the fuel in the tank or mixing in a substantial ammount of fresh fuel, maybe a splash of cetane additive/ injector cleaner would help in this case.

loss of compress on one or more cylinders:
not trying to scare you, but it happens. if you see oil in the water then the problem is almost certianly the head gasket. watch for this: if the engine cranks unevenly then there is probably something wrong with the engine itself. maybe worn/ broken rings, a burnt valve, a sticking valve, scorn cylinder wall, ect... many possibilities here. if you turn the engine over by hand twice you should get a good ammount of resistance and hear hissing on every 1/2 turn of the crank. if on one of those half turns the resistance drops apprecaibly there is a strong likelyhood that the engine needs a good beating. i'll leave it at that for now.

cloged injectors and faulty pump:
i can't add much to this. injectors *can* be disasembled and cleaned with solvent. should you decide to do this pay close attention to how the parts fit togather. to crack the threads put the injector in a vise so the jaws grip the two flats, not the big hex. gripping the big hex with the vise jaws will collapse it on the smaller part and make it unduly difficult to unscrew. once the threads are broken lay the injector on a large flat surface and arrange the parts like an exploded view diagram so assembly order is not forgotten. i think reasembly torque is something like 50- 70 ft. lbs, but i can't really remember. anyway, it is not a huge ammount; likewise to install injectors in the head the torque setting is surprising low, 55 ft.lbs i think. overtorque that and the head casting may crack, it is good practice to replace the heat shields when reinstalling injectors.

the insides of the pump are relatively new teritory for me so i can't help a whole lot on this one other than to say the pump itself may be at fault. if you have a spare pump and nothing else seems to be amiss you may want to swap the spare inplace of the current pump. oh, and look for leaks between the pump and the injector. since the injectors are pressure actuated, fuel leakage, on the order of drops of fuel, could cause impropper firing.

and one note on timing. i noticed that you gave the metric specification for injection pump piston lift. it is unusual to find metric dial indicators in the states so make sure you are using the correct units for the measuring tools you are using. if you are using an inch indicator the lift should be between 0.034"- 0.040" for the n/a diesel. don't forget establish a starting point for the measurement by tdc'ing the engine and turning it CCW untill the dial quits moving and then setting the indicator face to zero.