Fuel Pump wont turn on

[nhbroncoguy]

iv got a 1996 forb bronco just dies going down the road. put in new pump still no power to pump. where do i start?

 

[miesk5]

yo NH;

Operational Sequence; Power for the fuel pump 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 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.

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.

---------------

Do you have anyone around with an OBD II Code reader? it needs to be scanned for Codes, free at a local parts store if you can drive it there; all lights and accessories must be off

have em do the KOEO = Key On Engine Off portion first

& Remember that the engine has to be @ Normal Operating Temperature before doing the KEY ON ENGINE RUNNING (KOER) portion; so see if you can run it in driveway to heat it up.. if it won't run long enuf, then do KOEO and post codes found here.

Corrosion is prob for the 2 relays; so ck them and if ok, try swapping each with the Horn relay; they are in the Power Distribution Box;

Location pic in 92-96; Miesk5 Note; Located under the hood on the drivers side fenderwell, on driver's side of the air cleaner housing

Source: by Froggmann (Ken P) at http://www.froggmann.com/Bronco/Tech/ABS.htm

Diagram in a 96;

Source: by Ford via Roadkill (The Beast) at http://www.supermotors.net/clubs/superford/vehicles/registry/media/533918

Relay Socket Corrosion Info; "...if you had corrosion in your relay socket, then you probably have it other places. one at a time unplug all relays and connectors on that fender and spray them down with contact cleaner. then after you let that do it's job for about 30min-1hr, go back and unplug each relay and connector again (one at a time) this time put them together with di-electric grease. you can buy a tube of it from any electrical/electronics supply or auto store. make sure you get everything plugged back in..."

Source: by datrimm

Since it does run, we can assume fuses are good,

 

[Seabronc]

There have been reports of the inertia switches going bad and just opening up for no apparent reason. The solution is to replace it. You can bypass it for testing purposes, but DO NOT leave it bypassed. If it is bypassed in an accident, the fuel pump will provide plenty of fuel for the fire that may start.

Good luck,

>-

 

[nhbroncoguy]

iv check for 12v on fuses 9,16 & 22 all have 12volts i was told they should have. iv checked continuity on the yellow wire that runs from the fuse panel to the solenoid on the inner fender near the battery that is ok as well. iv swapped the relays out w/the one for the horn so i know thats good as well. do you think maybe the PCM is bad?

 

[miesk5]

yo,

Sorry, I didn't see your reply earlier!

Hardly ever, will the PCM be the cause.

Did you do what Seabronc advised?

Use following to test for voltage, continuity and the Inertia Switch Bypass.

Inertia Switch Location pic in 92-96; as Steve83 pointed-out, "...The module I MIS-labelled as "Airbag" is actually the Wiper Control Module (WCM). The Airbag Diagnostic Module (ADM) is light blue, wrapped in black foam, above the gas pedal..."

Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net



I don't have a 96 wiring diagram direct LINK for some reason; use this (print it out);

Wiring Diagrams & Component Location Diagrams in 86-96 Bronco & Fords; Agree and enter year, make/model, etc.

Source: by Airtex at http://www.showmetheparts.com/airtexts/

Select; 7201 - Engine Fuel Controls -> Part 8

& compare it to this;



by seijirou for 94-95 Bronco & F Series (2 pumps in F Series)

Ignore the Front/Rear Selector switch

All colors look ok except from Inertia Switch to the Fuel Pump which should be Pink/Black instead of Red/Yellow

 

[2percent]

I was a lucky one and it was my PCM. A simple test for this is simply remove the PCM and smell for a burnt wire smell. If evident may need to swap it out.

I am actually going through this right now with a 95 bronco. Runs great but just dies with no reason or forewarning.