1HZ Injector Testing

Supra88

Supra88

Joined
Jun 6, 2011
Messages
1,141
I've been slowly working on my 77 series that has a 1HZ in it. I get some black smoke when under load and the idle is somewhat rough on cold starts. The engine RPM is steady, but the the truck has a noteable vibration until it warms up. I know the 1HZ is gutless, but this thing is very slow. This lead me to think that the injectors are contributing to the problem and I needed to pull and test them. I also have a turbo/exhaust I'm plannng to install so I figured I should square away the injectors before doing that.

I have no history on the injectors, but the truck had 275k km on it. In all likelihood they could be original. The video attached shows my testing on all 6 injectors. They all seem to crack around 2000 psi, but some of their spray patterns seem very problematic. I have a new set of genuine Denso nozzles from High Tech in Australia that I plan to install.

Should I target the upper end of the spec for crack pressure (2200 psi)? Will the new nozzle add psi or should I plan to buy new shims to achieve the desired pressure? As it looks right now I'm 200 psi under the upper spec. Is there anything I'm missing on the injector R&R?




Okay, I went ahead and swapped out the injection nozzles. All of the crack pressures hit 2200 psi and the nozzles "chattered" at a much higher frequency. Here's the video:

 
Last edited:
hiluxjeremy

hiluxjeremy

Joined
Jun 25, 2012
Messages
400
Location
Delburne, Alberta
Very interesting, thanks for posting this. I have previously replaced nozzles only without testing, accepting that I was taking my chances, but with the expectation that if the thing ran with worn nozzles it could only be happier with fresh ones.

Your process supports my seat of the pants assessment. Happy trails.
 

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