New injectors, now twice the smoke.

[MarioG]

From another thread:

I went to the rebuild shop and found out that the shop uses reconditioned parts for the injector overhaul. I got the bright idea of going over to Detroit Diesel in Miami and picked up reliabuilt N90P "premiums" at twice the price at $98.50 a pop. Before installing them, I took them over to get tested and the injectors were all even and well within specs. we installed them today and fired it up. eventhough the engine fired up on the first try and ran smooth, it smoked twice as much compaired the old injectors.

Back to the drawing board.

valves gapped to .15
injector calibraded to 1.460

what am I missing?

 

[JLR]

Get rid of the Reliabuilt injectors and get Interstate.

 

[Brian Degulis]

Mario read the spare injectors thread I just did the same thing 24 Reliabuilts in then mosquito control so 24 Reliabuilts out and 24 Interstate in and no problems. I FEEL YOUR PAIN!!! You can get the Interstates at Diesel Pro in Miami or PC Industries in Ohio around $50 each.

Brian

 

[MikeP]

This tells me that whatever is used to "test" the injectors is essentially useless. I still don't understand this issue - if these injectors are so bad, how are they still being sold? If an automotive product was so bad, it would be gone immediately!

Ooops - well that's not true, the Quadrajet is still around. But you CAN make a Qjet into a good, reliable unit.

But I have a question related to this (I don't have the service manual handy - it's 2500 miles away on the boat), is it possible that the injectors could be improperly installed which could cause this high failure rate? I mean if something tests ok and then, in place it doesn't work properly, what are the odds that it failed between the test and the installation? I'd say just about zero.

Or is the testing machinery at fault?

The fact that injectors are "rebuilt" should be meaningless. A rebuilt engine can ALWAYS be a better engine than a new one. I don't see any reason that a rebuilt one can't be as good as a new one. SOMEBODY/SOMETHING has to check and assemble them in either case.

One thing that occurs to me based on other types of applications is the torque when installing the injectors. So, based on the tiny internal clearances the installation torque is likely fairly critical. I realize that the injector is steel, not pot metal or Al but overtorquing might deform the body sufficiently to cause a problem, especially with the tiny clearances internally. Is that a possibility? Note that the torque reading the wrench is seeing (calibrated recently?) and the actual installation torque may be quite different based on the condition of the individual threads, the lubricant used (if any), etc. Another issue - maybe the fuel pipes to the injectors are getting contaminated with foreign material?

At the same time, I have to admit that when I was in the Army (Tank Battalion Maintanance officer at one point) diesel injectors on DDs were changed in the field (literally in a field!) with no apparent problems. Were the injectors better then or did we not really care if there was some smoke? I don't really recall - we just cared about getting non-running vehicles running.

I know it seems I may be beating this horse to death but I just CANNOT get my head around the fact that so many of these injectors are bad from the suppliers. ["puzzled" icon would be here if I knew how to generate one]

 

[REBrueckner]

Taking Brian's input at face value, Reliabilts just don't measure up: he got clean burn from Interstates and smoke from Reliabilts. That tells me the Reliabilt testing is probably useless ...unless he incorrectly installed Reliabilts and properly installed Interstates....not very likely.

Difficult to believe since this is not new and unique testing...but we have all seen crazier things I'll bet...

 

[krush]

Quadra-jets give you problems? I've never dealt with a better carb than the Q's. Holley's won't hold a tune for shit.

 

[MikeP]

"Quadra-jets give you problems? I've never dealt with a better carb than the Q's. Holley's won't hold a tune for shit."

Good one K, Pretty funny...

I had to hunt up one of my previous minor rants re Qjets that I posted on this subject a while back:

"Unfortunately, carbureted GM engines (Crusaders) came with Quadrajet carbs and the phrase "well adjusted carburetor" and "Quadrajet" have, to my knowledge, never appeared in the same sentence. And if they did, it was a typo.

As you can tell, I am not a Qjet fan but I assure you that a carb can be essentially trouble free and work perfectly if properly set up. My first reaction when faced with a Q jet is to immediately fill a trash can with it but have to admit that even a Qjet can be forced (admittedly with much kicking and screaming) into working quite well. But one of my minor fantasies is to see all the QJets ever made sitting together in one landfill! (Then we could melt them down to make pot-metal replica Chevy Vegas.)"

 

[krush]

I would choose a Quad jet over any other carb, especially for a boat. Powervalves are junk.

 

[TedZ]

To get back on the topic i'm assuming the injector tool was used to set the heights, and it was the right one???

Ted

 

[MarioG]

yes. injector height set to 1.460 assuming 1.460 is the proper height for N90's

 

[34Hatt]

Mario send Scrod a PM he does Injectors, pumps and turbos get his feeling on this also.

 

[Brian Degulis]

Mike Maybe I can explain it? Back in the 70s I worked as an aplication specialist for DD on military vehicles. I went to school for the 71 series engines part of that training was fuel injection. The instructor went through all the procedures for rebuilding injectors then everyone in the class was given an injector to rebuild. We were told you could get any new parts you needed but you had to explain why the part couldn't be re used if the instructor looked at and didn't agree with you you would not get the part. When we were done our injectors were tagged and put directly into a good running 671 and it smoked like hell and ran like crap. Cylinders were cut out one at a time to see if any were right out of a class of 23 only one injector was working correctly(It was not mine). Then each injector was tested and most passed. The test is the pop off pressure then total volume at 500 or 1000 strokes. The only test for spray pattern was visual.

We were then told to go back and rebuild our injectors again but this time pay attention to detail and cleanliness. It's mostly the lapping and fitting that makes the diffrence and it has to be done to a higher level than anything else you might do on an engine. The second time around about 80% passed (mine was one of them) No one was permitted to move forward without completing a passing injector. Of those that passed some were noticably better than others.

Brian

 

[MikeP]

Thanks Brian, interesting info...

Sounds like the test procedure is not particularly valid!

Do you think it's possible - maybe not practical(?) - to disassemble the bad injectors and correct the problem? Is it mostly cleanliness that's the issue or is it truly incorrect machining? Were they (replacement injectors) always this bad?

 

[Brian Degulis]

yes. injector height set to 1.460 assuming 1.460 is the proper height for N90's

Yes 1.460 with standard cam timing. Check the option plate or call DD with the searial # to confirm you have standard not advanced cam timing

Brian

 

[Brian Degulis]

Thanks Brian, interesting info...

Sounds like the test procedure is not particularly valid!

Do you think it's possible - maybe not practical(?) - to disassemble the bad injectors and correct the problem? Is it mostly cleanliness that's the issue or is it truly incorrect machining? Were they (replacement injectors) always this bad?

No you really can't do it witout the right shop set up you need magnifiers and lapping tables etc. and it's all got to be super clean and dust free.

No to the best of my knowledge they were not always this bad. We stopped using rebuilt engines around 8 years ago but back then we installed lots of Reliabuilts with very few rejects.

I think the test procedure is just to limited you can prove the valve is opening at the correct pressure and closing tight and you can prove the calibration is within spec. But that's about it the rest is pretty much dependant on good workmanship.

Brian

 

[Traveler 45C]

I remember reading on here that the Reliabuilt’s were coming out of Mexico. Do ya’ think that may have something to do with the increased failure rates?

 

[MikeP]

On my travels here in Mexico one day I passed by a little town in the middle of nowhere. There was a "garage" with a standard DD sign out front that had "V71" written on it. There were two guys sitting out front at benches working on some small parts. We went by so fast that I couldn't see what they were doing. Maybe they're the injector rebuild guys!

 

[Avenger]

I will not use expletives... I will not use expletives....

I went to the rebuild shop and found out that the shop uses reconditioned parts for the injector overhaul. I got the bright idea of going over to Detroit Diesel in Miami and picked up reliabuilt N90P "premiums" at twice the price at $98.50 a pop.

You're buying a rebuilt injector, why would you be afraid of a rebuilt part in it?

I'll tell you why. Because of someone's reman product that's junk. And then when you tell them it's junk they say it's because you need new parts. Then they proceed to ream you for the new parts that they should have been installing in the first place.

This tells me that whatever is used to "test" the injectors is essentially useless.

Does a dyno tell you if the guy that rebuilt the engine re-used old valve springs?

I still don't understand this issue - if these injectors are so bad, how are they still being sold? If an automotive product was so bad, it would be gone immediately!

Because it's got the two little arrows on it and people make the mistake of thinking that it's done by the OEM so it must be good. You should see the truck guys nearly stain themselves over something that's got a bulldog's @$$ on it. I'm not even going to get in to what I think of the bulldog.

Most OEMs are trying to make the same margins on rebuilding that they make on building. Rebuilding things correctly involves skilled labor and a fair amount of new components, scrappage rates are high. The bean-counters can't figure out that it is a low-margin business compared to manufacturing. And the last thing any big corporation understands is the value of skilled labor. Just ask Passages.

The fact that injectors are "rebuilt" should be meaningless. A rebuilt engine can ALWAYS be a better engine than a new one. I don't see any reason that a rebuilt one can't be as good as a new one. SOMEBODY/SOMETHING has to check and assemble them in either case.

Ah HA! Plenty of shops do good remans, just like plenty of guys build good race motors. Did you have any competitors that did lousy work? I do.

One thing that occurs to me based on other types of applications is the torque when installing the injectors. So, based on the tiny internal clearances the installation torque is likely fairly critical. I realize that the injector is steel, not pot metal or Al but overtorquing might deform the body sufficiently to cause a problem, especially with the tiny clearances internally. Is that a possibility? Note that the torque reading the wrench is seeing (calibrated recently?) and the actual installation torque may be quite different based on the condition of the individual threads, the lubricant used (if any), etc. Another issue - maybe the fuel pipes to the injectors are getting contaminated with foreign material?.

Since a DD injector is held in with what is essentially a tin clamp I'd say generally no. But contamination or other installation errors are always a possibility.

 

[Traveler 45C]

On my travels here in Mexico one day I passed by a little town in the middle of nowhere. There was a "garage" with a standard DD sign out front that had "V71" written on it. There were two guys sitting out front at benches working on some small parts. We went by so fast that I couldn't see what they were doing. Maybe they're the injector rebuild guys!

ROFLOL!!!

 

[Brian Degulis]

It does amaze me that the DD dealers keep right on selling them. Wensday I brought mine back all 26 I had purcased and I was ready for a fight. I was sure they would be telling me they aren't all bad we will replace only the bad ones and not issue a credit just a replacement. Well I got just the oposite they were very nice about the whole thing and even credited back the air freight. The counter guy said they get quite a few back I think the other guy who I bought them from the guy that told me they see very few problems was hiding somewhere? Never again the Interstates were even cheaper $50 vrs $66 for the reliabuilt and $20 core charge vrs $50 for the reliabuilt. Before I brought them back I put a few in a vise and poped them The Interstates foged more than the reliabuilts they were more of a stream than a fog?

Brian