SAC injector whine?

turbo_bu

Member
Mar 27, 2007
195
6
18
Central IL
Recently installed new S&S SAC00 injectors in my ~112K mile, 2004 LB7. The stock injectors were still in there and just starting to give off that raw diesel smell (haze) out the tail pipe. I've driven the truck now for a few months, and noticed that it has a weird sound that it didn't used to have before the swap. When I stand on it, and the engine revs up around 3,000 RPM, there is an audible whine coming from the front passengers side area of the engine. At lower RPM's it is not there. Only when the engine revs up to around ~3k RPM.

Anyone ever had this happen before? Is this specific to SAC injectors?

One other random question - I always added 2 cycle oil to my fuel with the original injectors. With the SAC style tips, do we still need to do that? or does it harm these injectors?
 

Bdsankey

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Feb 1, 2018
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I've never heard injectors "whine", it more so sounds like you have something loose. I would start with a leak test by removing the intake and applying compressed air into the inlet of the turbocharger to 30-40psi. Spray all the intercooler piping connections (and intercooler end tanks) with soapy water to try and find any leaks that may exist.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
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X2 on checking for a boost leak. Given all the piping had to come off for the injector job, any of those joints could be leaking now.

Do be careful how you get the 30 PSI in there. On a stock turbo truck, you should only be seeing 25 PSI or so of boost, so I wouldn't go more than that. I've had a boost test adapter pop off at 30+ PSI and smack me in the hand, and it is not pleasant.

Personally, I discontinued use of two stroke oil when I put the SAC injectors in my truck and they are still going strong 8 years later. IMO it mainly helps a sticky fuel pressure regulator, so if that was a problem before and you didn't replace it, I'd continue using two stroke until you do.