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EFI fuel pump relays

dyeager535

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I've been thinking about this one for awhile now.

Anyone have any idea why GM used the odd rectangular relay for the fuel pump, but typically used the oval ones for other stuff, like electric fans and the like?

Not sure if the early TBI stuff used the oval relays too, but on the '88+ body style trucks, the oval bodied relays seem to be the only ones used. Never got a good look at a pristine '88+ wiring harness (only semi-butchered ones in the wrecking yard) but any time I've seen relays still in the rig, they are all oval. The EFI Camaro stuff I've dealt with ('87-88 only) used the same rectangular relay, while using the ovals for everything else.

I'm trying to figure out why they used two different ones. I'd love to ditch it for the oval style I've already got 4 of (that many?? wow) underhood. I will probably do the headlight harness/relay conversion, using the same style relay for all would be great for out of town quick fixes.
 
My 89 used an oval relay for the fuel pump, internally they are identical, just that one is a weatherpack style, and one isn't
 
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