• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

87 STX Highrider fuel/electrical issue


memorex402

New Member
U.S. Military - Veteran
Joined
Mar 31, 2010
Messages
52
Reaction score
0
Points
0
Age
36
Location
North Carolina
Vehicle Year
1987
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
So I sold my ranger to my neighbor. When he got it he decided to fix the nasty solenoid wiring it had before me. He got it cleaned up and looking better but now the fuel pump will not cut on. He called me over to help him figure it out but honestly I am at a loss. I think a few of my questions here will be kind of duh. During troubleshooting we have found some odd things.

The oxygen sensor is a 3 wire. One of the pins from the harness side is showing almost 12 volts. Should this be the case?

Which relay is the fuel pump relay? We are having a tough time identifying the relays at the wire colors are either impossible to tell due to the age or the wire colors are wrong in comparison to the schematics.

One of our relays was warm with the key off. We also noticed that the alternator got warm as well with this relay plugged in. We think this is the EEC relay.

I honestly am thinking he has something hooked up wrong as we have a back feed somewhere. When I owned the truck it did not have this issue. I hope the PCM is not toast.

Does anyone have the diagram of the fuseable links and where they terminate.

Any ideas would be great. Thanks. :icon_confused:
 


RonD

Official TRS AI
TRS Technical Advisor
Joined
Jun 2, 2012
Messages
25,363
Reaction score
8,369
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
EEC relay has a Brown Base, Fuel pump relay a Green Base, WOT relay Black Base(if it has one)

Fusible links will be hooked to Starter Relay on the fender, same post as the Battery "+" cable.

Google: autozone 1987 ranger 2.9l wiring diagram

Autozone has quite a good repair library

You can try this direct link but not sure it will work:
http://www.autozone.com/repairguides/Ford-Ranger-Bronco-II-1983-1990-Repair-Guide/WIRING-DIAGRAMS/WIRING-DIAGRAMS/_/P-0900c152800781b2


EEC relay powers the EEC(computer) of course, but also powers fuel injectors, TFI(spark) and the Fuel pump Relay, not the fuel pump itself, just gives that relay's coil 12v, EEC then grounds this relay to close it and send fuel pump 12volts from it's own 30amp fuse.
 
Last edited:

adsm08

Senior Master Grease Monkey
Supporting Member
Article Contributor
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
34,623
Reaction score
3,613
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
The three wire O2 sensor should have 5V on one pin, one pin read 12V, and one pin read ground.

The 12V and the ground are for the heater circuit. O2 sensor don't read well below 400*F, so the engineers put a heater in them to get them to operating temp quickly.

The 5V line is the signal reference from the computer, and the ground side of that comes from the computer to the back of the passenger side head.
 

Sponsored Ad


Sponsored Ad

Staff online

Members online

Today's birthdays

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Shran
April Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top