8v71 itt

Hello out there

I run a 8V71ITT engine with N90 injectors. I am having starting issues so am replacing the injectors with the same. I am having difficulty finding information on the settings required and would appreciate any help.

Thanks

Welcome to the forum.

I don't mean to insult you if you already know some of what I'm about to say but I don't know what your level of expertise is with the Detroit and there can definitely be a learning curve for someone just jumping in to straighten out a problem on one of these babies.

First I'll say that there are many checks that should be made before just throwing a set of injectors at an engine to alleviate "issues". Injectors are not always the "magic bullet". Probably not a bad idea anyway if they have a lot of hours on them but you might be disappointed if they don't do the trick and your repair turns into a very expensive, time consuming guessing exercise.

Ok, on to your question.

The N90 should calibrate out from between 87 to 93 ml of fuel delivered per 1000 strokes. Try to obtain a set that all have the same calibration number ie: 8-89's or 8-91's etc. I'll tell you now that it's not always easy to get all 8 the same as store personnel don't think the same as tech people and don't appreciate the finer points of a proper tune up.

If you find it just impossible to get a matched set easily, it's not the end of the world. There are plenty of engines out there happily doing their work with mis-matched calibration numbers. Just get them as close as possible so the engine will want to idle smoothly.

The N-90 timing setting is 1.460

Make sure you THOROUGHLY clean the carbon from inside the injector tube before installation. This is VERY important and should be done with great care and attention. There is a reamer tool for doing this but I've done it successfully many times with a screwdriver and a rag with a light coating of grease to keep the crap from falling into the cylinder. Just make sure to round off the edges of the screwdriver tip so as not to gouge the tube in any way. You want to remove carbon and dirt, not copper. When all is clean, wipe off excess grease with a clean rag soaked in carb spray so that the injector goes in "dry".

VERY, VERY important! Torque the injector hold down clamp to 20-25 lb.ft. Then, work the rack in and out to ensure it is butter smooth. Over tightening the hold down clamp can cause the rack to bind. The curved special washer is installed with the curved side toward the clamp.

Fill the fuel inlet of each injector with fuel before reconnecting the jumper lines so that they get a chance to lube on initial start up. Place a shop towel on the down slope of the head to prevent spillage from draining down into the crankcase.

I recommend using all new fuel jumper lines when doing a tune-up. These lines, being flared, have a tendency to crack and leak due to harmonic vibrations (which this engine make plenty of). They are the "usual suspects" in fuel oil dilution of the engine oil. If your Detroit starts "making oil" and the crankcase is over full, look there first. The proper torque for these lines is 12-15 lb. ft. and there is a special socket for getting it right. Here again, over tightening a flared fitting is not good and will cause them to leak.

Take care not to displace the valve bridges when re-torquing the rocker assemlies and double check them before cranking the engine or bad things will happen.

I hope all this verbiage is of some help to you and I wish you luck with your project.

Thank you for all of your advice it has clarifed a lot for me, it is very much appreciated and you are not insulting me at all. I could not get hold of any manuals on this engine here and experts in the field are scarce and contradicting each other so it is great to have good outside expertise.

Hello,the engine project is going very well, and the problems slowly getting straightened out, my engineer would like to ask if you would also have information on the injector settings for the 8v92iTT. Thank you for sharing your expertise on these engines.

Most likely his timing will be 1.484".
All of the Turbocharged 92 injectors are timed 1.484". (Kent-Moore tool J 1242)

The only exception would be the 9270 injector but I don't believe it is normally used with turbocharged engines.

Happy to help, and good luck.

Man thats alot of info. for a simple question, starting problem not the injs. good luck. Fuel shut off, fuel supply, air in fuel. Any other symtoms? Rack freedom?