ok so i work at a shop which rarely works on diesels but recently we have a 97 6.5 come in with a cranks no start...narrowed it down to a no fuel to the injectors..i got on here and got some good info from everyone about the fsd..i condemned the fsd..my boss on the other hand wanted more prof..so i did more research and more research..we he found a company that had a test list to go down and one of those tests was to see if there was a 12v pulse leaving the module goin to the fuel solenoid..when i tested for the pulse..there was one..so we replaced the fsd..and that fixed it..but just to be sure we tested at that red wire agian for a pulse and what do you know there was one...now you probably could only see this using a scope..which most people dont' have but maybe some of you guys have tried this method before..or does it sometimes send a pulse but technically not still work..or did i just miss a post somewhere..thanks for help..this site is amazing..haha

could finding out be so easy?

i guess if you had a known bad pmd/fsd then you could preform this test..as long as you had a labscope(modis/sun machince) who knows i dont' work on enough deisel's here so just thought i'd see if anyone else had tried that

no disrespect intended but your boss sounds like a guy who will take any job even if he knows he cannot fix the issue. by your own words "we rarely work on diesels" says alot, perhaps your boss should invest some of that cash into buying some proper diagnostic equipment. that's not saying you, yourself are incapable of fixing a diesel but are, were you trained to work on them. just my opinion. Ed

Thats common that shops take on things that they dont normally do, I take on a 6.5 from time to time but have no intrest in them. It pays the bills! Have i been Trained on them? Nope ! Am i ASE Diesel Certified? Yup! Can i fix em ? You betcha!

no i'm not trained on them..i just know enough to get me introuble..i worked on a lot of diesel engines when i was in the golfcoarse feild..everything we used had a diesel engine...so i understand the basics...and well they think im a diesel mechanic cuase i own one..haha i just understand what it takes to make most of them run..and trust me..you haven't offended me at all..but im only 24 so im sure i'll get to learn a lot about them. what kinda special tools do you need to do basic fixes on a diesel..anyways yeah

Hang 'round here a while, all you'll have most of the dealership folks beat.

I'd venture to say you'd have to have some type of test bench that will mimic the PCM and IP. Then use some program commands and compare FSD signal wave etc. To know its really working correctly. I doubt you could catch it on an Oscilliscope.

Many kinds of failures symptoms dead, stalling, hiccups etc a lot of which are intermittent. A lot seems heat related so again bench test can't match real world. And by the time you buy that kind of equipement and spend that kind of time diagnosing you'd better be doing it a lot. Much cheaper to have a spare FSD and try it.

Good that you did not automatically condemn the IP. Thats already better than most dealers.

well we aren't a dealer..but anyways..you can catch the pulse on a modis(which is a snap on scanner) if you jsut back probe the red wire goin to the fs. but in our case this fsd just wasn't workin period. so it was an easy tell when i pluged the new fsd in and tested it again..it was a clear 12v spike..i can't remember what settings i had it on..but i think it was around 50ms which i doubt you'll see with a test light..hahah although i guess it's a possibility.but i agree if i worked on alot of 6.5 i would have a spare fsd...and yes we did remounted the fsd to a new place thanks for all the help guys

As long as remount included: nice cool location and a heat sink, I think you've got her covered.