Pennock's Fiero Forum
  Technical Discussion & Questions - Archive
  Fuel pump keeps running....

T H I S   I S   A N   A R C H I V E D   T O P I C
  

Email This Page to Someone! | Printable Version


Fuel pump keeps running.... by DavidStremer
Started on: 01-01-2004 01:39 PM
Replies: 9
Last post by: buddycraigg on 01-02-2004 11:52 PM
DavidStremer
Member
Posts: 372
From: Stevens Point, Wi, USA
Registered: Apr 2003


Feedback score: N/A
Leave feedback

Rate this member

Report this Post01-01-2004 01:39 PM Click Here to See the Profile for DavidStremerClick Here to Email DavidStremerSend a Private Message to DavidStremerDirect Link to This Post
I replaced oil pressure sensor with a new one. Sensor is OK per test of 0.00 on oil pressure guage tab.
I measured it at 200 ohlms.
Now the fuel pump is turning on(running). The battery went dead during the night. I suspect it is one of the wires on the plug that
is causing the problem.
I am getting 12 volts at the tan wire of the oil pressure sensor plug. This must be a constant 12 volts to keep fuel pump running, I think.
The tan wire on the plug which connects to the oil pressure switch gives me an ohlm reading of 1.00 with the key turned to "off". With the
With the key turned to "on" the reading drops to .5 ohlms
The black wire (according to the diagram I have) says it is the wire to the fuel pump. With the ohlm meter, I get the following readings: 1.00 with key on,
I.00 with key off.
Is it simplistic for me to assume that if the oil pressure sender is switching on the
fuel pump, that the problem is being caused by the black (fuel pump) wire?

IP: Logged
PFF
System Bot
scrabblegod
Member
Posts: 1009
From: Lexington, KY
Registered: Jun 2003


Feedback score: N/A
Leave feedback





Total ratings: 58
Rate this member

Report this Post01-01-2004 01:44 PM Click Here to See the Profile for scrabblegodClick Here to Email scrabblegodSend a Private Message to scrabblegodDirect Link to This Post
A defective oil pressure switch can keep the fuel pump running.

On my 4.9, if I start it cold then shut it off after a min, the fuel pump will run for 20 or 30 seconds till the oil pressure bleeds off.


Gene

IP: Logged
Indiana_resto_guy
Member
Posts: 7158
From: Shelbyville, IN USA
Registered: Jul 2000


Feedback score:    (15)
Leave feedback





Total ratings: 163
Rate this member

Report this Post01-01-2004 01:47 PM Click Here to See the Profile for Indiana_resto_guyClick Here to Email Indiana_resto_guySend a Private Message to Indiana_resto_guyDirect Link to This Post
It could be, can you hear the pump running?
The system was doing ok before the oil pressure switch change, correct?
If you can hear it running, pull the plug on the switch and see if it quits. If it doesn't, concentrate your efforts to the fuel pump relay.
IP: Logged
DavidStremer
Member
Posts: 372
From: Stevens Point, Wi, USA
Registered: Apr 2003


Feedback score: N/A
Leave feedback

Rate this member

Report this Post01-01-2004 08:14 PM Click Here to See the Profile for DavidStremerClick Here to Email DavidStremerSend a Private Message to DavidStremerDirect Link to This Post
First of all, let us be certain we are talking about the same item. I am referring to the large, black item by the battery as a
sensor. It is two or three inches tall and on V/6 engines w/AC is mounted vertically near engine oil dipstick. There are three prongs on
the top. You two are referring to it as a "switch", while I am referring to it as a sensor. Is this correct?

I installed a new sensor/switch because my oil pressure guage was not working properly. I then started engine and made certain oil pressure guage was
working.

While working with the three socket plug, I discovered that if the plug was wiggled, it sometimes turned on the fuel pump. So, I think I have a bad plug or a bad wire.

One other thing that has me confused: when I finished installing the sensor/switch, I hooked up the battery charger to the car and let the battery charge overnight.
When I left the garage the fuel pump was not running. This morning when I walked into the garage, the fuel pump was running and the charger was running.
When I tried to start the car, I found that the battery was dead.
I am recharging the battery now....with the plug disconnected from the sensor/switch.
The tests in my original posting, show the sensor/switch is good. I also know that the fuel pump works as I can hear it running. I know that the plug is getting 12 volts of power. and that the wire to the oil pressure guage is working.
MY QESTION IS: should I concentrate my search for a loose connection to the fuel plug wire?

IP: Logged
Francis T
Member
Posts: 6620
From: spotsylvania va. usa
Registered: Oct 2003


Feedback score: (1)
Leave feedback





Total ratings: 119
Rate this member

Report this Post01-01-2004 10:42 PM Click Here to See the Profile for Francis TClick Here to visit Francis T's HomePageClick Here to Email Francis TSend a Private Message to Francis TDirect Link to This Post
when it sticks 'on' again, pull the connector from the sensor, if stays 'on' go to the fuel pump relay amd pull that. if it stops then, replace the relay they can get stuck. I had the same problem and it was the sensor, only mine was very intermitent. the damn thing worked fine when ever I tried to fix it. Interm I pulled the fuel pump fuse, put it in a fuse holder and then wired a toggle switch to kill the pump. Here's the neat thing, the sensor fixed it, I left the togle switch (which is out of sight onder the dash) as an anti theft device!! If someone tries to still the car, even with keys, it start via the cold-start but not run! Do fix the circuit, don't use a switch as a perm fix.
IP: Logged
Indiana_resto_guy
Member
Posts: 7158
From: Shelbyville, IN USA
Registered: Jul 2000


Feedback score:    (15)
Leave feedback





Total ratings: 163
Rate this member

Report this Post01-01-2004 11:36 PM Click Here to See the Profile for Indiana_resto_guyClick Here to Email Indiana_resto_guySend a Private Message to Indiana_resto_guyDirect Link to This Post
 
quote
Originally posted by DavidStremer:

First of all, let us be certain we are talking about the same item. I am referring to the large, black item by the battery as a
sensor.


Yes, we are talking about the same item.
The unit does both, reads oil pressure and it also acts as a switch for the fuel pump that will provide power to the pump in the event of a relay failure.
Follow the advice given here, all of it points the same drection.

IP: Logged
DZ
Member
Posts: 747
From: Jacksonville, FL 32217
Registered: Nov 2001


Feedback score: N/A
Leave feedback

Rate this member

Report this Post01-01-2004 11:49 PM Click Here to See the Profile for DZClick Here to Email DZSend a Private Message to DZDirect Link to This Post
Just installed a rebuilt 87 2.5 but the oil presssure is kind of low. The Fuel pump was running after I shut off the engine, so I pulled the oil pressure switch and now the fuel pump shuts off as soon as I turn off the engine so the pressure switch must be a problem. It is brand new since I did not want to mess with a used one. Pressure is 35-40 won't go lower or higher even if I rev the engine. I know the guage is good since I tested it in another engine. Guess the new switch could be bad, any other ideas. I was ready to pull and tear the the engine down looking for a problem, but I know it was done right.
IP: Logged
DavidStremer
Member
Posts: 372
From: Stevens Point, Wi, USA
Registered: Apr 2003


Feedback score: N/A
Leave feedback

Rate this member

Report this Post01-02-2004 09:13 AM Click Here to See the Profile for DavidStremerClick Here to Email DavidStremerSend a Private Message to DavidStremerDirect Link to This Post
Thanks: The battery is charged now, so I will attack problem with info you have given.


DZ: I have a topic on page 3, 4, or 5 in which a person gave me a page to access info on switch/sensor. It explains three
tabs on switch and tells how to test switch to make certain it is working.

IP: Logged
ka4nkf
Member
Posts: 3702
From: New Port Richey, FL USA
Registered: May 99


Feedback score: N/A
Leave feedback





Total ratings: 148
Rate this member

Report this Post01-02-2004 10:15 PM Click Here to See the Profile for ka4nkfClick Here to Email ka4nkfSend a Private Message to ka4nkfDirect Link to This Post
What year car do you have? I have a 1986 V-6 and my wires going to the sender are pink/white which is the 12 volts
Tan which is the Guage
Orange/blk which is the fuel pump
Don
IP: Logged
buddycraigg
Member
Posts: 13353
From: kansas city, mo
Registered: Jul 2002


Feedback score: (5)
Leave feedback





Total ratings: 475
Rate this member

Report this Post01-02-2004 11:52 PM Click Here to See the Profile for buddycraiggClick Here to Email buddycraiggSend a Private Message to buddycraiggDirect Link to This Post
david, your problem is the oil pressure sending unit. (unless you have a very obvious problem with frayed wires in the plug that goes to the sending unit)

what year is your car?

i am pretty sure that the sending units are different at some point in the years.
on my 84 the two veritcal connectors are the fuel pump circuit.

but on my 85 they make an "L" shape.
maybe the parts store gave you the wrong sending unit.

IP: Logged



All times are ET (US)

T H I S   I S   A N   A R C H I V E D   T O P I C
  

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock