Re: [SOLVED]Re: 2008 Buick Lucerne Fuel Pump Relay
I own a 2008 Lucerne and have the EXACT same problem as Century61. Exact same burnout of the fuse block at the exact same location. Car wouldn't start and I was lucky to find the problem myself without paying a lot of money. Replaced the relay and it works for now while I'm waiting for a new fuse block. I ordered an OEM one from the big auction site for $19.95, far less that the $300 the dealer wanted.
Here is what I think is going on. The original relay coil gets hot normally or gets hotter than normal because of an internal coil short. In the original relay design, the coil housing is part of the switch circuit and basically pin 30 is a continuation of the coil housing. Thus the heat of the coil is transferred preferentially to pin 30 because of the way the relay is designed. This heat causes a loss of temper in the connector in the fuse block which leads to a poor connection and more heat. The loss of connection may be exacerbated by plastic insulation which melts inside the relay and flows down the pin. Eventually, the connection is lost and the car won't start. I think Buick is aware of this because the new relay I bought from them has been redesigned so that there is no longer thermal continuity between the coli housing and pin 30, and the coil housing is no longer part of the switch circuit. Also, the new relay coil ohms out at 145 ohms vs. 90 ohms for the old relay. The coil wiring on the new coil is finer than than it was on the old coil so I think this is a design change to cause the coil to run cooler, rather than just indicative that the old coil was shorted. Moreover, if you take the cover off the relay and run the engine, you find that the coil housing is the first thing to get hot, not the switch. So, again, I think the design of the original relay was flawed because it allowed this heat to be transmitted freely to the connector in the fuse block.
Fixing the problem requires replacing both the relay and the block because the connector in the block has been irreparably damaged by the defective relay.