Fuel pump power issues

[Kirbeh]

I own a 1988 ford bronco 2 4x4 and the fuel pumps do not want to work, I took out the external high pressure fuel pump on the drivers side and tested it by connecting it to the truck battery and it ran. I also replaced the fuel pump relay and it still would not start the pumps. I acquired infromation on how to test for the power from the self test connector by jumping the circut with a wire from the tan/light green wire to a ground and the relay switch should click, The relay switch indeed clicked but it also started running both the fuel pumps (the one in the tank and one on drivers side). so after that i am now stumped and why theres no power flowing to the pumps when i turn on the ignition, is it possibly a ground issue? or a onboard computer promblem?

any insight and/or help will be greatly appreciated.

 

[miesk5]

yo!

Ok, that Test you did shows that both pumps are ok; since "...Connect FP Relay to any ground to force the fuel pump(s) on when the key is in RUN..."

Also. do you have any Diagnostic Trouble Codes (DTC)s?

Connect STO to SIGRET to trigger diagnostic modes. Consult the 7th post on this page for more info:

http://www.fordf150.net/forums/viewtopic.php?t=71346

If the CEL is burned out, connect pin C to a 12V test light, and the light's other terminal to B .

This is in: Self Test - & Connector Location Info in 87-95; "...87-95 located under L hood hinge..."

Source: by Steve83 at http://www.supermotors.net/registry/media/245234

Also our pal BroncoJoe has the Self test here at http://broncozone.com/topic/14269-code-reader/page__p__74587entry74587

Suspect bad FP Relay &/0r socket; ck the tan/lt grn @ Relay to see if it has a bad ground or has corrosion in socket

See if you have 12v at FP Relays yellow (if not, ck for voltage @ EEC Relay) etc...using Yardape's diagram below

Consider swapping to BOSCH style relays as used in later years such as 92-96

Color Codes for Troubleshooting/Swapping to Bosch Style Relays

Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/507189

Bosch Overview, Schematics, etc.

Source: by Craig U at http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htmWiring Diagram in an 87

Source: by Yardape http://broncozone.com/forums/index.php?showtopic=15953

Backgrnd. FYI; Operational Sequence; "... When the ignition switch is ON, it turns the EEC power relay ON. The EEC power relay provides power to the powertrain control module (PCM) and the control side of the fuel pump relay. Power for the fuel pump(s) is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side). From the fuse link or high current fuse, current flows through the fuel pump relay and inertia switch to the fuel pump(s). When the ignition switch is turned ON, the fuel pump(s) will operate. If the ignition switch is not turned to the START position the PCM will shut the fuel pump(s) OFF after 1 second. The PCM will operate the fuel pump(s) when the ignition switch is turn to START position to provide fuel while cranking. After the engine starts, the PCM will continue to operate the fuel pump(s) unless the engine stops, drops below 120 rpm or the inertia switch is tripped...is used as a safety device in the fuel system. The inertia switch is located in the cab, generally under the dashboard on the right side. It is designed to open the fuel pump power circuit in the event of a collision. The switch is reset by pushing each of 2 buttons on the switch simultaneously (some models use switches with only one reset button). The inertia switch should not be reset until the fuel system has been inspected for damage or leaks." (under license from Delmar Publishers, combo of Chilton/Nichols/Delmar & Haynes); some may be incorrect, as reported by Seabronc, thanks Seabronc! NEW SITE URL!!! MUST REGISTER TO VIEW; select year, make, model, engine size and go to appropriate section

Source: by Chilton via AutoZone

 

[miesk5]

sorry for that long, uncoord post...

Since the pumps are running from that jumper job, figure on bad grnd as you wrote to each Relay, etc.