91 Bronco wont start

[Thumper22866]

I have a 1991 Bronco, 5.0 A4OD transmission, it wont start.  After pulling the codes I get 21 and 95.  Can anyone offer any tips ?

 

[miesk5]

yo

21 X X X ECT out of self test range 0.3 to 3.7 volts Engine Coolant Temperature Sensor (ECT) Testing; "..."But due to its simplicity of design, the ECT is rarely at fault when problems occur. Before testing the ECT or any other EFI component perform a self-test, trouble codes received during test can be used as a __af_placement_id--[AFF-PLACEMENT-ID].html]diagnostic tool along with other indicators. To test an ECT sensor you will need a volt meter. You can test the ECT by back probing the harness while reading the voltage returning to the EEC. Or you can removing the connector completely and test the resistance between the 2 pins on the ECT..." READ MORE


Source: by Ryan M (Fireguy50) at


http://oldfuelinjection.com/index.php?p=28http://oldfuelinjection.com/index.php?p=28


 

 


DTC 21, 51, 61 or 116, 117, 118 "...Failure in either the circuit or temperature sensor will show code 21, 51, 61 or 116, 117, 118.Unplug the http://motors.shop.ebay.com/i.html?_nkw=harness+connectorharness connector. First, check the signal voltage at the connector with the key on, engine off. Should be approximately 5.0v. Then, check the resistance of the sensor cold. Should be between 58,750 to 40,500 ohms. Plug in the harness connector and warm up the engine to normal operating temperature. Then, unplug and check the resistance of the sensor hot. Should be 3,600 to 1,840 ohms...

 


http://api.viglink.com/api/click?fo...ons, ...&jsonp=vglnk_jsonp_13879864207638Wiring Diagrams (Partial, Bronco similar) for F 150 in 86, 89, 91 & 95; EEC, Start/Ignition, EFI/Fuel System, Emissions, E4OD, AOD/C6 (+ clutch interlock switch), etc. & MAP, TPS, ECT, ACT, KS), Start/Ignition, Fuel System, Emissions Source: by Ryan M (Fireguy50) ECT at http://oldfuelinjection.com/?p=36http://oldfuelinjection.com/?p=36


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95 X X   Fuel pump secondary circuit failure. The EEC senses infinite resistance to ground from the fuel pump on the Fuel Pump Monitor circuit.


http://web.archive.org/web/20110704105113/http://broncozone.com/forums/index.php?showtopic=11544DTC 95 - bad ground or always on. Possible bad fuel pump ground or open between fuel pump and pin 8 at PCM


 


EEC IV Connector Pin Depiction Pic and LEGEND by Ryan M (Fireguy50) 

 


Legend @ http://oldfuelinjection.com/truckpinouts.htmlhttp://oldfuelinjection.com/truckpinouts.html


 


http://web.archive.org/web/20110704105113/http://www.supermotors.net/registry/media/245234Test & Diagram at the Diagnostic Link Connector in 84-95; "...Connect FP Relay to any ground to force the fuel pump(s) on when the key is in RUN..." MIESK5 NOTE; from Ford EVTM; The Control Module (PCM) runs the pump{s} for one second when it receives an ignition- on signal. It also runs the pumps as long as it receives a PIP signal from the Hall-effect devices, it continues pump operation even after the key is released from START. If the PIP signals fall below 120RPM, the control module cuts off the signal to the fuel pump relay or the integrated relay control module. The pump will also run when the terminals of the fuel pump test connector are jumped. the Control module signals the pump when it receives a CRANK signal, and when the Control module gets PIP signals that the engine is running. the pump does not run if the PIP indicates the engine is not running even with ignition ON {except for that first one second}.


Source: by Steve83


 


 

 

[miesk5]

Part 2

The FP electrical circuit has a fuel pump control relay controlled by the powertrain control module (PCM), which provides power to the fuel pump under various operating conditions. When the ignition switch in the OFF position, the contacts of the PCM power and fuel pump relays are open.

When the ignition switch is first turned to the ON position, the PCM power relay is energized, closing its contacts. As a result, power is provided to both the fuel pump relay and a timing device in the powertrain control module. The fuel pump runs through the contacts of the fuel pump relay and the inertia fuel shutoff switch . If the ignition switch is not turned to the START position, the timing device in the powertrain control module will open the relay ground circuit to the relay after approximately one second.

Opening the ground circuit de-energizes the fuel pump relay (opening its contacts), which turns the fuel pump off. This circuitry provides for pre-pressurization of the fuel system.

When the ignition switch is turned to the START position, the powertrain control module grounds the fuel pump relay to provide fuel for starting the engine while cranking.

After the engine starts, the ignition switch is returned to the ON position, and power to the fuel pump is again supplied through the fuel pump relay. The powertrain control module senses engine speed and shuts off the fuel pump by opening the ground circuit to the fuel pump relay when the engine stops or is below 120 rpm.


DTC 95/542 indicates that one of the following has occurred:

No Start:

- Inertia Fuel Shutoff (IFS) switch not reset or electrically open (if in secondary circuit). Ask if you need info on how to test

- Open circuit between the fuel pump and FPM circuit connection to the power-to-pump circuit. Ask if you need info on how to test

- Poor fuel pump ground. Ask if you need info on how to test

Ground Location - (pump and fuel level sender share connector C442 @ rear cross member) and at G100 @ LH front of engine compartment on upper radiator support - check G100 for corrosin, loose wires, etc.  Same for C442, etc.

- Fuel pump electrically open. Ask if you need info on how to test

Engine Starts:

- Fuel pump secondary circuit short to power.

- Fuel pump relay contacts always closed. Ask if you need info on how to test the relay

- Open in FPM circuit between PCM and connection to the power-to-pump circuit.

- Left/front HO2S short to power (dual HO2S applications).

- Damaged Powertrain Control Module (PCM). Last Resort!