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When replacing the injectors due to a moderate drop in fuel pressure after cycling the pump, should the 9th injector (the cold start injector) be replaced at the same time, or can it be replaced later, if necessary, without removing the runners and plenum again?
The CSV and tubing, can be replaced without removing the runners and plenum. Just curious, did you test the the system to verify where the pressure loss, was ?
I feel fairly confident that the injectors are leaking down, and that it is not a problem with the pump or lines (pulse dampener) in the tank. Since: It has a bit of an extended crank time on a warm or hot restart, and there is a bit of dark exhaust, with about 7-10 seconds of rough idle until it clears. Cold starts are flawless.
The fuel pressure gauge shows a steady decline in pressure when cold, and the rate of decline is faster, when hot, after 7-10 minutes.
As far as determining whether it could be a faultyleaky CSV, no I do not know how I would isolate or diagnose that.
Your description does sound like possible leaking injector(s), but I would still perform the fuel line pinch tests, to verify. I don't see any way of testing the CSV, without removing it.
I used a rubber tipped air gun at inlet and a shot of WD40 on the outlet, to see if it would displace the WD40. I used this method on all the injectors and found 4 leakers at just 20 psi, the CSV passed that test.
Here's some info on testing the fuel system http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
A few years later, I had another pressure loss, it was at the pulsator.