Question : Urgent fuel pump still runs after car is off

[packardbell]

1988 cutlass supreme 2.8 MPFI, having problem of the fuel pump draining my battery dead. Tried pulling out the fuel pump relay but pump still runs, tried pulling off the oil pressure switch and pump still runs, pull out the 20 amp fuse and the pump stops.
what other switch is causing the pump to get +12V?? Here are some pictures of me probing the terminals with a test light with the car off.






































oil pressure switch is a 1 terminal so I don't understand how it can run the pressure gauge in the dash and supply +12V from that 1 terminal. Anyways I ordered the switch and will be replacing it.

[1988GTU]

Whats the condition of the chassis? Rusty but trusty or clean as a minty whistle?

Make sure the connector under the car above the tank isnt corroded jumping contacts.
You might pull the back seat and check the connector there by drilling out the rivets and pulling it thru the hole.

[packardbell]

Whats the condition of the chassis? Rusty but trusty or clean as a minty whistle?

Make sure the connector under the car above the tank isnt corroded jumping contacts.
You might pull the back seat and check the connector there by drilling out the rivets and pulling it thru the hole.

has some surface rust but not serious imo.
so how many wire connector am i looking for? what color wires? which ones are live or grounded?
does having a FE3 suspension make it more difficult to drop the gas tank?

[1988GTU]

has some surface rust but not serious imo.
so how many wire connector am i looking for?

1

what color wires? which ones are live or grounded?

I dont remember off hand. A OTC repair manual should ID that info for you tho.

does having a FE3 suspension make it more difficult to drop the gas tank?

If you are not removing the back seat to try at it from there then the other option will be labor intensive. If its rusty even the slightest, it might incur unexpected repair & additional costs/time.
To get to it by removing the tank, it'll all be the same level of difficulty. That will require cutting exhaust and I think all the heat shields.

[pocket-rocket]

1

I think he means how many wires in the connector, which would be a pump + and -, sender + and -, and possibly more depending on emissions equipment back there.

[packardbell]

I think he means how many wires in the connector, which would be a pump + and -, sender + and -, and possibly more depending on emissions equipment back there.

yes you are correct, i would like to know which of the wires in the back is giving a constant +12V. Like the other member said there is two or maybe more wires on top of the fuel tank that is shorting a +12V making the fuel pump run all the time.

[robertisaar]

EDIT: i'm blind.

[packardbell]

EDIT: i'm blind.

probably take a video and host it up on youtube for you.
I am going to swap out the oil pressure switch tonight after work.
Just wondering how a one terminal oil pressure switch can run the gauge in the dash plus supply a constant +12 volts to the fuel pump at the same time.

[robertisaar]

it can't. you should have something like 3 wires in there for either the switch(short) version or the sensor(long) version.

[packardbell]

it can't. you should have something like 3 wires in there for either the switch(short) version or the sensor(long) version.

that is what i thought as well and looking at a schematic diagram it shows that the switch is supposed to have one terminal giving a resistance for the gauge, then there is two terminal where one is +12V and the other goes to feed the pump the +12V once it supposed to see more than 4psi of oil pressure.
The oil pressure switch I have on my car is a one terminal long version, and the replacement oil pressure switch i got is the same one terminal long version one as well. So I think there is another switch somewhere on the engine that is supposed to supply the +12V but i don't know where.

[robertisaar]

http://imgur.com/s97FirI,EfIfHSk

oddly enough, alldata is showing two sensors? i'm familiar with the one near the oil filter, but the one at the top of the bellhousing? i've never seen an oil pressure sensor/switch there, or at least have never had to replace it.

[packardbell]

http://imgur.com/s97FirI,EfIfHSk

oddly enough, alldata is showing two sensors? i'm familiar with the one near the oil filter, but the one at the top of the bellhousing? i've never seen an oil pressure sensor/switch there, or at least have never had to replace it.

that could be it, so there is another sensor around the bellhousing? do you have a picture of it?

[robertisaar]

other than that second line drawing, no.

[packardbell]

other than that second line drawing, no.

okay thanks, anyways i will probe around on top of the bell housing area and see if I can find anything there.
so there is a second oil pressure which i assume is two terminal which controls the +12V to the pump. I was searching on rockauto for that part but i found 1 and 3 terminal ones.

ok i found the two terminal switch on rockauto.

[robertisaar]

curious...... looks like most 87 and 88 60V6 applications used that 1-wire switch/sensor? i wasn't aware anything other than the 3-wire setup was used.

i imagine you will find that oddball sensor on top of the bellhousing.