Well the last post was in July, and it's now September... but here's some more info on the no-longer-available GM 15528707 fuel pump relay.
By the way, the bare frames for the motor homes of that vintage were delivered without a tank installed. The individual builders had the option of an in-tank pump or an external pump mounted on the frame rail.
As to the relay... it's a normally open relay wired so that contact closure on the relay applies power to the electric fuel pump. There is a 5-10 second timer built inside the relay housing. Applying power to it closes the relay for a few seconds to supply fuel to the carburetor. Once the oil pressure comes up the relay stays on for as long as power is applied AND there is oil pressure.
These GM relays have an internal design flaw BUT ARE REPAIRABLE. I've done it.
DO NOT THROW AWAY THE OLD RELAY.
The flaw is part of the circuit board inside... the design engineer did not take into account the possibility of a short circuit on the load side. If there is a overcurrent situation (even momentary) on the pump side (like an accidentally grounded power wire to the pump) it will vaporize a bit of the copper printed circuit on the circuit board inside the relay (it's called a "trace"). That trace can be repaired with careful work with a fine-tip soldering iron.
I'm going to design a replacement using a standard relay and a small timer circuit board.
Mike
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Semi-retired technogeek...electronics / computer / 2-way / ham radio... WA6ILQ (45+years)
1985 Fleetwood 32' Southwind (Chev P30/454/TH400), dubbed "Lazarus" by friends... I resurrected it from the dead...
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