Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Detroit Diesel 671 injection

Detroit Diesel 671 injection

Detroit Diesel 671 injection

I need specifications/manuals about how to tune injection in DDs JT671T1.
A client is having problems: fitted new rings and serviced injectors and now engines smoke white and don't give full power.
I was asked to diagnose and (eventually)fix the problem. Thanks in advance for your help.

RE: Detroit Diesel 671 injection

I think the 'JT' prefix means the engines were customized by Johnson & Towers, so DDC specs may not be appropriate.


Call and ask for the oldest guy in the place...


Mike Halloran
Pembroke Pines, FL, USA

RE: Detroit Diesel 671 injection

In any case, this is an engineer's forum and most of us have an entirely different type of day job.  I doubt that many of my engineering colleagues are skilled enough as engine technicians to try to tune a Detroit.  Maybe a few, but precious few.  I'd tackle a Cummins any day and have actually done a few, but I wouldn't touch a Detroit and I have many more hours working on other aspects of Detroits than I ever did with the Cummins' that I once owned.  I also have the manuals on those Detroits (V-8's not six cyliners) and I still wouldn't tackle actually doing what the manual states in words.  Detroits are just too ticklish.

White smoke generally indicates unburned fuel and your loss of power suggests something very wrong with the injector timing as well as a good possibility on the fuel flow.  If you can find out the plunger lash you could check that, but setting the rack is another whole thing.

The first thing I would check is to see that the injectors were set correctly for the engine that they are operating in.  Did the shop that did them know the engine specs?


RE: Detroit Diesel 671 injection

Thanks Mike Halloran for your suggestion. I am waiting now for J&T's reply.
Thanks rmw for your advise.I will be traveling soon to see the engines. For what you say, tuning a Detroit is out of the limits of my competence. I know Cummins B and C series and they are lovely and friendly engines, simple and effective. I'd be happy with myself if I could 1.Check the injectors specs to find if they are the right ones; 2. Check/Adjust the distance between cam and injectors (Is this the plunger lash?). This adjustment value is something I must also find.
Thanks again to all and to this excellent forum.

All the best

Helder Ferreira
Ayamonte, Spain

RE: Detroit Diesel 671 injection

The lash would be easy to check and verify with feeler gages but that little plunger that comes out of the side of the injector and connects to the 'rack' is another whole thing with respect to setting and adjusting.  Good luck with your project.  O es decir, buena suerte.


RE: Detroit Diesel 671 injection

There is a special tool required to set the injectors. White smoke in a diesel engine usually means burning engine oil or low compression. 2 stroke Detroit's have a problem with blower seals so motor oil is pushed into the combustion chamber.

Ed Danzer

RE: Detroit Diesel 671 injection

In 4 stroke diesel engines I always found burning oil to be bluish in color and white smoke to indicate unburned fuel such as when there were injector problems but I can't specifically remember on the Detroits that I had to fight with.  What I can remember about the last one and the only turbocharged one that I ever kept up is that after a prolonged period of idling it would smoke real whitish for a good bit until it was good and blown out and after that no smoke could be detected.  That smoke could have been from oil from the rings building up in the air box or oil from the turbo seals or, yes, even the blower seals.

With the thing rated to consume one gallon of oil for every 10 hours of operation when it was running normally, who would know where it all came from (if you discount what just leaked out of every potential leak point on the engine).

Question is; was any work done on the enging the last round that would have upset the rings and let oil bypass them into the air boxes until they reseat?

Second question is; is the smoke continuous or does it abate after some time running.


RE: Detroit Diesel 671 injection

Many thanks to all for your support. I went last week to see the engines. Checked compression rings for a broken or sized. Removed an injector to check if the right ones (DDs original reconditioned). Adjusted the valve's lash. Adjusted the injectors timing, not having the specific tool with a caliper. Started motors and no relevant smoke. Sea too rough to test the boat. The reasons for the owner's complaint about black smoke and lack of performance were evident: both turbos have problems: one misses part of a rotor and makes noise when hand turned (and a nice high pitch humming when engine running at revs) The other one has a turbo "refitted" from a truck engine...
I believe that with 2 new turbos things will get close to perfection. The only doubt then will be the governor's adjustment. There were so many fiddlers playing that  fiddle that everything is to be expected.

Thanks to this excellent forum

RE: Detroit Diesel 671 injection

Ah-Ha, black smoke.  Now that is a different matter.  The blowers should give enough air flow with the engines unloaded to prevent smoking so you might check for other air path restrictions.  If there are no air restrictions you shouldn't see black smoke at least until you put them under load.  On the other hand, if you crowd the throttles without the turbo's spooled up, you can make any engine smoke-and bad too.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close