Well, I replaced the number 7 injector and that cylinder still fails the contribution test. While I had the valve covers off, I ran the engine and pulled the connector on each injector. It is fireing on all cylinders, but there is still this very very small sensation and very slight shake when it is at idle and in gear. I did not do a compression test, I need to find a gauge with the correct adaptor however when it cranks I don't hear any difference while it is cranking that sounds like a weak cylinder.
I did remove the schrader valve and plumbed a pressure guage to the regulator. While at idle, the guage fluctuats so fast between 20 and 80 that you could not read it. It appeared to be in time with each stroke of the pump. An increase in engine speed only makes it worse. I pulled the filter bowl, found that the vaccuum switch was leaking and that the regulator screen was totaly blocked. Cleaned everything and replaced the ageing hoses, but guage still reads the same. Also blew air through the return line to the tank, so no blckage there. I am sure if I had some type of metering device in the line with the guage, I could make it steady enough to read, but I am wondering if this is normal or if using a guage with the schrader valve in place would read different.
If this is abnormal, then is is possible that when the pressure is on the low point, could this be happening at the same time that the number 7 injector fires and could the slight weakness or shake be that it is not getting quite as much fuel pressure as the rest of the injectors?
Also, what is the max pressure that the guage should show at high engine speeds or wide open throttle?
All help is much appreciated, I have learned alot from this forum, it is great!!