i have a w 126 mercedes and as they tend to do a chain guide went and moved cam timing result bent valves i had already owned a 1988 mercedes 420 witch i removed and fitted to the other car on start up the rev counter fluctuated and car ran normaly but high tick over . i have used car like this for a couple of months now but rev counter has stopped working altogether. and car starts then stops after a couple of seconds. have replaced fuel pump relay and checked fuel pressure witch at ignition on while pump runs is at 110 lb after that it drops to 40 please can some one help