Technical Tips > Post 84
C4 1987 Throttle Body Coolant Bypass
87Z51:
Power goes from battery through BOTH FP relay and OP switch to pump at same time once engine is running
Vettech:
I will be replying in full, but when I've found the info.
I must admit it took me awhile to find your cct pic in my books.
Stay Tuned. My biggest issue is squeezing my pics small enough.
P.S plus now you have sown doubt, I will do a test, but the 87 is in bits, and I'm reluctant to use the 90.
MY081:
Maybe 11PM is not the best time to fix the problems of the Corvette World. Uncle Doug. Ray
Vettech:
Only 22.56.15 not 2300hrs, so there Ray - get it right.
I know that 2200hrs (10pm for interlectuals) is past you Old Farts bedtime, but some of us keep on keepng on.
:therethere:
sirfixalot:
Fuel pump relay is shown in de energised position, relay is only energised by ecm for a few seconds to get fuel pressure for start up circuit 465. Engine starts and allows 12V+ via oil pressure switch to fuel pump 12V + goes to diagnostic plug when fuel pump relay is de energised only. Both circuits are never energised at same time it is one or the other 12v back feeds to all points of both circuits. If the oil pressure switch is disconnected engine will stop, this is a safety feature that if engine stops ie in a front crash pump stops and doesn't poor fuel into engine bay if fuel line is damaged.
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