sctty84

I have recently bought a 1984 corvette. The problem I am having is the fuel pump wont shut off. I have to disconnect battery to get it to shut off. I have disconnected the fuel pump relay and I have also open up the gas tank and disconnected the fuel pump connection there. It still runs!. I have heard that depending on year some draw power from different points. Is it possible the power is coming off the starter?
Has anyone else had this problem?
I have tested the fuel pump and it is working and making contact it just seems like it is a wiring problem.
Any information on this would be greatly appreciated.
Thanks,
Scott

ex-x-fire

On early 84s, the oil pressure switch can go bad & cause the fuel pump to run on & on. Mine did that 20 yrs ago, I think mine was a 3 spade connector switch.

Cliff Harris

Look at the oil pressure switch on the back of the engine block behind the distributor. The wires for the fuel pump are orange and red.

jsatterf

Went into the garage this morning and heard a hum coming from my 1985, sounds like the fuel pump running.

Did changing the oil pressure switch fix yours?

Cliff Harris

Remember that the fuel pump relay and the oil pressure switch are in parallel. That means that if either of them gets stuck in the "on" position then your fuel pump will run all the time. Find out which one by unplugging...

wbdaily

Im fairly new to the forum, but recently had my pump out of my 84. You say you unplugged the conector at the tank and it still ran??? There are three wires on that connector. A ground, the ground to the fuel guage, and the power to the pump. If you disconected that connector there isnt any way the pump can run or recieve power. Are you sure you are hearing the pump?

Cliff Harris

There must have been problems with that combined oil pressure switch and oil pressure sender because GM changed to two separate senders for several years before going back to the combined part.

This is what I have (1986):



Later years have this:

jsatterf

Cliff, the set-up you have looks like what is on my 85, which of those components is the switch and which the sender? The switch is the one controlling the fuel pump correct?

When I realized it was the fuel pump running, I disconnected the battery and was looking at what all was involved. Hooked the battery back up, no issue. Engine fired right up and ran fine, some type of winter gremlin?? Haven't heard the pump run (with key off) since. Looks like I will add some items to my winter project list.

whalepirot

I once found a sticking relay, due to erosion of a contact surface. It had formed a hook-shaped surface that caused an intermittent ON problem, caused by arcing as the contact closed. The better relays have a capacitor that prevents that spark.

A few strokes with a small file fixed it; then a new relay.

Cliff Harris

The oil pressure switch is the one with the orange and red wires. There is lock ring on the connector that must be opened before you can remove the connector. Kinda melted in my picture after an engine fire...