A tip to avoid piston damage

Posted by Michael 10/04/2017 0 Comment(s) Q & A,

Q. I own a 1993 80 series landcruiser wagon manual diesel with 280,000 on the clock. It has the naturally aspirated 1 HZ motor with an after market turbo fitted since new. Have had no problems with motor or turbo since new. About 102,000 k,s back at 177,000 I had the motor and turbo serviced and the pump and injectors done and watched as the vehicle was tuned on a chassis dynamometer to standard settings (no tweaking).
A week ago I was on a trip from the gold coast to Marree in Sth Aust and near Leigh Creek the motor developed a problem, after being towed to Copley and investigated it was found that the number two piston had split the top with a small hole burned in the middle, this resulted in the bore being scored so essentially a full rebuild is being done.
Initially we suspected a faulty injector and this may still be the cause but bench test did not indicate a problem. Can you tell me if it is possible for this problem to be caused by any fault in the fuel pump ( this is a rotary pump) affecting only one piston. I obviously want to make sure there is no repeat of this and will have the injectors serviced anyway. Any clues would be appreciated.

A. The injectors deliver fuel to each cylinder and if not spraying at the right pressure or atomising correctly, 1 injector could bring down a cylinder. The pump, whilst it’s a bit like a car distributor, could have some uneven fuel delivery if it’s a little worn. So in the end it could be the pump.
One major factor to consider though is the fuel loadings overall and how heavy they are. It’s very common for aftermarket turbo installs to be set what I could call rich in the fuel loadings. Now this would be a general issue and should affect most of the cylinders but you still can’t rule out the fuel being set a little too high originally.
My advice is once you get the engine repaired and the pump and injectors overhauled that you get the vehicles air-fuel ratios set on a dyno. As a guide the fuel pump should not be set much more that 5-6% higher than standard and the air-fuel ratios when on the dyno preferably above 20:1. Nice and lean and cool for a Diesel.