Quote:
Originally Posted by Mike Noc
It might not be as accurate as using a gauge but you can. The engine turns over with the injectors not firing and T4 checks how the crankshaft speed slows as each cylinder comes up on compression.
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If it isn't accurate it is a useless test unless something is seriously wrong. The cranking speed will slow because of compression and the load on the battery massively increasing, with each crank the battery will be weaker and weaker so will skew any potential results. A slight crack that virtually seals up when warm wouldn't be found but is still head gasket failure. You would need to make sure that power is stable and on something to deliver it to the car, using a car battery will have huge voltage dips making it useless. Only using something that can provide 14v at 400-500amps would give anything even potentially usable as a result.
Just take the glow plugs out, do a test then fit new glow plugs (they will be knackered now anyway). Also make sure its a diesel compression tester as a petrol one won't read high enough.