philwarner

I am chasing a lack of fuel pump running and tried direct 12V+ to the brown/white wire on the pump, but no joy.

Is the fuel pump grounded internally or do I need to ground one of the three wires at the unit and if so which one? (I would assume the black one but don't want to fry anything).

vetteoz

black wire at tank connector is the ground wire

Cliff Harris

…and that black wire goes to a ground on the passenger side near the rear compartment light.

…unless you have a convertible.

philwarner

No convertible, just a ratty black base coupe.

I tried direct power to the fuel pump and it makes a sound like a click but doesn't run. The resistance is 0.6 ohms across the tan/white and black wires and it draws about 10 amps with 12V+ applied, but it doesn't run. This car has very old gas in it, evidenced by the smell of what leaked when I connected my fuel pressure gage, so might the pump be gummed up? If I pull the unit might I be able to free it up?

I also spent part of the day re-wiring the fuel pump relay connector after discovering that some PO had reversed the two red wires from the harness in a forest of plastic splices and had put the lead to the ALCL G on A and the fuel pump fuse lead on D (before and after pics below), but when I plugged the re-wired connector into the new BWD R671 relay from O'Reillys, the connector seems to lock in before reaching the relay's spade contacts and won't push in any farther. Did the PO cobble in a wrong connector?

I did notice that if the relay's diagram represents its contacts in correct order, it DOES match the 8A electrical diagnosis diagram with the Fuel Pump fuse/supply on A, winding ground on B, winding + on C, ALCL on D, and Battery constant 12V+ on E, but A to E would be right to left looking at the front of the relay.

Cliff Harris

Pull the fuel sender/pump out of the tank and see what's happening. Have a new gasket on hand because the old one will probably be destroyed in the process.

The current draw and resistance readings seem about right.

philwarner

Thanks Cliff,

I have a service manual on the way but not in hand yet; pump removal looks straight forward with the cover flap already off, but are there any tricks to it?

I saw this FP connector listed for an 86 on eBay and it is longer than the one that was grafted to mine; I am guessing mine might be from an earlier year since the telltale panel was an earlier one.

So...buy the connector and start over on the re-wire? or is there a relay that would fit my current connector and work and mount the same way?

BTW, anyone have a photo of the oil pressure switch location? I can't seem to find it.

AGENT 86

Oil pressure switch is at rear of engine, driver side of distributor. It shares a "T" with the oil pressure sender.
Use the forum advanced search engine and I am sure you will find a pic.

Cliff Harris

This is what mine looks like (the connector has orange and red wires coming out of it -- there is a ring that holds the connector on and you have to unlatch it to unplug the connector).



The silver cylinder below the oil pressure switch is the oil pressure sender for the dash. In later years the two were combined into one unit (around 1989 or so).

vetteoz

same as

http://forums.corvetteforum.com/c4-t...h-article.html