1990 302 wont start

[tyothers]

I have a 1990 bronco that was leaking power steering fliud. I changed out the gear box and put new lines on.The book told me to unplug the coil wire and turn the engine while turning the steering wheel lock to lock(I know now not to unplug the coil wire). When I put the coil wire back on the motor turns over but will not start. I changed the spark plugs out and made sure I had spark. The fuel pump working fine,have spark,wont even try to start. Please help.

 

[Rons beast]

Hey TY, Welcome.

So you have spark, correct?

And have fuel preasure?

If yes to both, you may have had the coil spark to ground through a component for the ECU, and blown a fuse.

Check all the fuses, and if all are ok try an ecu reset by disconnecting the battery ground for 10 seconds.( be sure the key is off)

Good luck

 

[tyothers]

I took the batery off all night and will not start.What controls the timing of the spark?

 

[Rons beast]

Spark timing on a 90 is done by the ECU.

Did you check all the fuses?

If you have a fuse blown to the ecu, or injectors your truck will not start.

 

[tyothers]

I checked all of the fuses in the fuse box under the dash and all were good.Is there other fuses I need to check? I replaced the TP sensor and the MAP sensor.No start. Checked the codes and this is what I got after replacing both: ** p ** p * p ** p **. This (KOEO) key on engine off.

 

[90bronco86]

Did you check the coil and see if it's good?

 

[Rons beast]

Hey Ty ,

Here is the info on code 22. (Thanks to Miesk5, as posted on the FS Bronco fornum.) Read it dillegently.

DTC 22/126 indicates the Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) sensor is out of Self-Test range. Correct MAP/BARO range of measurement is typically from 1.4 to 1.6 volts.

Do NOT use an ordinary voltmeter to check a Ford BP/MAP sensor because doing so can damage the electronics inside the sensor. This type of sensor can only be diagnosed with a DVOM that displays frequency, or a scope or scan tool

Also make sure engine manifold vacuum is within specifications at idle. If vacuum is unusually low due to a vacuum leak, ******** ignition timing, an exhaust restriction (clogged converter), or an EGR leak (EGR valve not closing at idle).

A low intake vacuum reading or excessive backpressure in the exhaust system can trick the MAP sensor into indicating there is a load on the engine. This may result in a rich fuel condition.

A restriction in the air intake (such as a plugged air filter), on the other hand, may produce higher than normal vacuum readings. This would result in a load low indication from the MAP sensor and possibly a lean fuel condition.

A good MAP sensor should read barometric air pressure when the key is turned on before the engine starts. This value can be read on a scan tool and should be compared to the actual barometric pressure reading to see if they match. Your local weather channel or website should be able to tell you the current barometric pressure reading.

Check the sensor's vacuum hose for kinks or leaks. Then use a hand-held vacuum pump to check the sensor itself for leaks. The sensor should hold vacuum. Any leakage calls for replacement.

An outright failure of the MAP sensor, loss of the sensor signal due to a wiring problem, or a sensor signal that is outside the normal voltage or frequency range will usually set a diagnostic trouble code (DTC) and turn on the Check Engine light

"...The vacuum gauge should show 18-22 in-Hg @ idle, and maintain a steady needle. Rev it up to ~2500 rpm, hold it steady, and you should see the needle drop, then slowly increase to a level close to the idle reading (though slightly lower is normal)..."

Source: by SigEpBlue (Steve) at FSB

Gauge Diagnosis Source: by Craig U at http://www.classictruckshop.com/club...ts/vac/uum.htm

Possible causes:

circuit open between sensor vehicle harness connector and PCM.

circuit shorted to VREF, SIG RTN, or GND.

Damaged MAP sensor.

Vacuum trapped at MAP/BARO sensor.

Unusually high/low barometric pressure.

Kinked or obstructed vacuum lines (MAP).

Basic engine (valves, vacuum leaks, timing, EGR valve, etc.).

High atmospheric pressure.

Damaged PCM.

VREF circuit open at MAP sensor.

SIG RTN circuit open at MAP sensor.

The pinpoint test directs you to check the voltage to the MAP sensor. With the MAP sensor connected, use paper clips to back probe the MAP connector so you make contact with the terminals inside the connector by inserting the paper clips into the bak of the connector. This allows you to get voltage readings while the connector is plugged in. The other option is to use straight pins to pierce the insulation of the wires. First check the voltage of the outer two wires of the MAP connector by connecting a voltmeter to the clips or pins you have inserted. You should see 5 volts with the key on. This is the power to the sensor.

The BLK/WHTwire provides a ground called Signal Return (SIG RTN on EEC), it will show 0 volts with the black probe on negative battery terminal. The 5 volts VREF (ON EEC) (Reference Voltage) is supplied on the ORG/White wire. The Signal the computer reads is on the middle wire, DK BLUE/-Lt GRN (MAP on EEC). The correct MAP/BARO range of measurement is typically from 1.4 to 1.6 volts on the Signal (middle wire).

If any of the voltages are out of range, there is a wiring problem that needs to be tracked down and repaired. These three wires all go back to the computer. The signal wire (middle) is the only one not shared by other sensors, it goes straight to the computer. The Signal Return and VREF are also provided to other sensors

Good Luck