Lb7 injector return flow

check codes first, you would more than likely have a low fuel pressure code if you need to check for return flow, if you do, you'll need special fittings to tap into each head to figure out which head has the defected inj. and you'll need to measure and compare millileters to factory specs, the head that has more then spec has the defected injector(s), then your just better off replacing the 4 on that side, because to test each seperately gets really involved, and if you dont have hardly any fuel coming out either side you might have a weak injector pump!
 
The most simple way to test injectors is find someone with EFI Live or a tech 2 and read the balance rates.
 
To check for high return use EFI-Live, Snap-on Modis, tech2 or similar to command 160MPA fuel pressure. If it does not maintain within 2MPA of commanded pressure suspect high return rate or faulty relief valve.
 
LReiff said:
To check for high return use EFI-Live, Snap-on Modis, tech2 or similar to command 160MPA fuel pressure. If it does not maintain within 2MPA of commanded pressure suspect high return rate or faulty relief valve.
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is that accurate? if you use a scan tool to try and check return the injection pump is still in the picture and could be faulty, the scan tool would just confirm you have an issue!
 
Matt Hatfield said:
is that accurate? if you use a scan tool to try and check return the injection pump is still in the picture and could be faulty, the scan tool would just confirm you have an issue!
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Correct, basically you must use process of elimination.
Injector bodies crack, no fuel in crankcase = no internal leaks.
Fuel in oil = bad injectors or leaking fuel lines, this can be harder to pinpoint.
If you're suspicious the relief valve is weak check the return off of it or simply block it for the test.
If the truck hazes out the tail pipe and fuel pressure is low it most likely has bad injectors.
You'll also want to check engine data to be all the sensors are functioning properly.
With the proper equipment it takes less than 20 minutes to diagnose bad injectors.
The pressure drop method to test return rate is GM approved for warranty purposes.
 
return flow

:Cheer:thanks for all the info. it helps so much being apart of a web site where everyone helps one another. thanks guys
 
I just changed my cp3 due to hot no starts and no start when hot. But I have my ounce gm tec2 and have tested a few trucks for friends and have found even when balance rates are good dosent mean that the injectors are good . At least from my experience.I don't know where your from tommyracer but if your jeering central Ohio your welcome to use it anytime . I also have the fittings and catch cups to check the return rates manual .
 
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