[brcidd]

Just to add to this thread- I have some new insight from an S-10 I worked on over the weekend.....

So another buddy needs his '98 S-10 Fuel Pump replaced- (tired of kicking the tank to get the pump to run) - So he tows it to my house- I jumper the test lead- kick the tank 5 times- pump comes on- pressure builds to 65psi- start the truck- pull it into my barn- Just for fun, I pull the jumper off- and pull out the FP relay- the fuel pressure starts dropping- the truck stalls- I am perplexed- figure the GM method of wiring (per the current wiring diagram) says this is a parallel circuit- FP should run off oil pressure sending unit switch- So- after I replace the FP (lifted the bed off the truck- 8 bolts super easy with a full tank of gas) I jumper the two big wires at the oil pressure sending unit- and truck runs without the relay now- as designed- so I figure a bad sending unit- I go by a new sending unit- counter person brings me one with a single terminal- I say no way that is for oil pressure only- mine has the wiring for FP as well- I need the three terminal unit- she looks up a '99 S-10- it has a different part number- brings me the sending unit- it has three terminals- I install it (tough to do- have to pull the distributor) and I find the OEM sending unit has only ONE terminal (duh- the parts girl was right). Since I have the wiring for the three terminal unit- I install the three pronged unit and everything runs as designed- pull the sending unit plug- truck runs, replace sending unit plug, pull the relay- truck runs.

Now the big question- Why was the OEM and replacement sending unit designed for oil pressure only? when the truck is wired for the FP parallel circuit (and the service manual shows it as well)- can certainally become confusing- So any of you out there that say the circuit is not in parallel- check your sending unit- for a single terminal!!! GM must have saved some money that year with the single terminal sending units.....Just my learning experiences...............