Here's one for ya! 1993 850 cranks over,has a couple of sparks from coil and then nothing until you let the key go.The wave pattern from the cmp and crank sensors get dirty after the starter is engaged,but if i jump start the car (its a manual)it ALWAYS starts perfect.The computers have been checked,the sensors have been replaced,the harness in the engine bay was replaced (it had been soldered in a couple of places and when we jumped the wires in this harness it started fine,we thought we found the problem),volt test done on ignition switch and computer powers and ground,the fuse panel grounds and powers checked,the anti-theft relay exchanged,ground wire replaced and moved to starter bracket to block ,starter was replaced with factory unit in September and is ok as is battery.All grounds have been cleaned and checked .... I get 4 codes with the VST (Volvo Scan Tool)both cmp codes and both crank sensor codes but these units are ok as i said before(they have been changed and checked again)This problem showed up 2 years ago for a short time and i cleaned a few grounds then and the problem corrected itself.This problem has slowly started to show up again in the last year and is here now again.4 mechanics (2 are Volvo mechs.and 1 a GM training expert in electrical)have given me a hand with this in the past month + but we are all stumped.Any ideas would be gratefully appreciated.I have worked on Volvos since '85 and have NEVER had a car like this!!!

Ready to set fire to it ...pb90125