I posted this in another forum but only got 1 view so that's why I'm posting here.

1994 Turbo IDI
The guy says its running rough and he thinks its injectors. He said it misses on a few cylinders but when he sprays diesel into the turbo it starts firing like it should. Is that an actual way of telling if its the injectors or could it just be anything in the injection system?

The whole spraying into turbo thing confuses me. SOMEONE HELP

 

All the turbo is doing is supplying more air. Remove the fuel filter, fill it with Seafoam, and a little ATF, run that threw, shut her down and let it sit over night with some atf in the fuel tank. I personally use 2-stroke oil but to each his own. Use half as many ounces to gallons. IE 10 gallons of diesel = 5 ounces of oil.

 

The only way I know of to check to see which injector is bad is while it's running crack an injector hose lose on top of the injector and listen for rpm's to drop, if rpm' drop that injector should be good. Tighten it and move to the next one. If you come to one and don't hear rpm's drop, then that one may not be firing. A diesel can have, and you'll notice this once you do this, 1-2 cylinders not firing and it won't be jumping like if you were to pull a spark plug off on a gas engine. As you do this, notice fuel coming from the top of the injector and that'll be a clue if your IP is squirting on that cylinder. Not a definite test, but it does give you a starting point.

 

Alright cool man I'll keep that in mind if I have any problems.

 

The real way is to pull all the injectors out, put them on a pop tester, and check for spray pattern, popping pressure to make sure they are all within +- 100 psi since they are likely worn in, and to make sure none of them stick open. Usually a good ultrasonic cleaning and shimming to rise popping pressure to about 2250 psi, and if the pattern is acceptable they can go back in.

 

Yes, dortiz, that's the right way, but my method gives you a starting point. It's a trick they taught us at UTI while doing tune ups.