Just finished off installing tt engine. Found out that 2 injectors seem block, and one is filling up bore. engine was running at idle on 3 pistons....just... So here's the technical bit. Had to do cold compression test.. The pistons that was not firing was around 106 and ones firing was around 150. Engine has been sitting around for 3 years. So could compression on 3 pistons just be low because they have not fired in 3 years? And will it get better if fix injectors and break them back in. Another thing added oil to piston with block injectors. Went to 155 psi. But one where its dumping fuel hardly improved? If had leak down tester would use but short on cash Thanks
Injectors have NOTHING to do with compression..... Compression rises with the addition of oil down the bore because the rings are worn. Fix the injectors and the motor will run better (firing on 6 cylinders is always preferential) but nothing can be done about your low compression.
it could be an injector issue if the seal is gone. it could also be a stuck valve (carbon/debris) holding it open a bit. what work did you do on the engine before putting it in the car (i.e. after it had sat for 3 years). maybe best to pull the plenum and have a good look...
It could be stock rings. I had a z once with low compression on two cylinders. I added marvel mystery oil and soak the cylinder for a day or two. Google Saturn piston soak. The Saturn owners do that once in a while:br:
Injectors do not fit in the head. They mount in the lower plenum, just before the inlet valves. If an injector O ring has broken then fuel would leak. If a fuel rail seal is broken (between fuel rail and lower plenum) then a boost leak would be a problem. Compression is: rings, valves, and head gaskits.
Sitting 3 years...... "may" have rust/crap on the valve seats of the cylinders that were left open along with the matching injectors which may explain no compression increase with oil down the bores....... Oil down the inlet of the offending cylinders would be the next test to confirm cruddy valve faces/seats if you could be bothered. Plenum pull for that... YAY! Youll have to pull the injector that is sticking open regardless so plenum pull here you go! If they are stuck closed they usually release after running time and heat cycles but stuck open....... pretty slim chances that theyd come right on their own Im predicting that once you get the thing up and running with 6 clean and working injectors then the low compression cylinders will come back up once any rust/crap on the valve face/seat is bashed away, which it will. 100psi is pretty average but not that bad to begin with. E
A leak down tester if you can borrow one would be the go, or get one of the cheap eBay ones, they're not real accurate but good enough to help diagnose where you're loosing pressure.
Thanks for replys. So hoping that comes good once fix injectors. im currenlty pulling plenum. Putting in 740 nismos, 360 rail, turbosmart fpr and nistune. Had stuff sitting around from other engine. Bit less hassel than trying to rebuild stockies
