12v on both wires of injectors, but...

[carlosm180]

Hello Explorers from Italy
Yesterday My 1994 Explorer 4.0v6 suddently stopped to work, engine start but doesn't crank: so I run koeo test (1 1 1, no problems), fuse and relais are ok, fuel pump is ok, fuel pressure is ok, trottle position sensor is ok, sparkles work fine, crank position sensor have not problems (as this truck is bifuel - it run also with LPG/propane- i disconnected the sensor and the engine stopped), injectors... Oh, perhaps they have a problem! Disconnecting and testing the cables of injectors, infact, I find something of strange: both the wires show +12v (the ground of the multimeter is connected with negative of the battery).
In addition, check engine light never works (also turning key on or during koeo test)...I don't know if the bulb is broken (before Yesterday it works) but perhaps it is another symptom of the problem.
Any idea?

 

[boominXplorer]

If your check engine light isn't coming on when you turn the key to on check the pcm relay under the hood and swap it with another.

 

[carlosm180]

I swapped the Pcm relay, but nothing changes.... The problem is the same: when i turn the key on without starting engine, only one injector wire (and not both) has to shown +12v, isn't it? A bad ground could cause it?

 

[carlosm180]

Have someone got the wiring diagram of the injection system for a 4.0v6 explorer (1994)?

 

[Centaurious]

12v on both injector wires and loss of check engine light makes me think ECM or Engine Control Module has failed. Sometimes the capacitors inside swell and go bad, if so might be an easy fix for someone who can solder components. If the ECM is non repairable you will need to find an EXACT replacement.

If the bulb has failed, replace it and read the codes. Ford OBD/OBD2 Codes – TroubleCodes.net Will tell you how to read the codes and an idea what they mean. If you get codes post them here and we can help.

 

[carlosm180]

The koeo test is ok (1 1 1, no other errors), so I thought Ecm was ok. When Ecm fails, it is still able to run koeo test?

 

[410Fortune]

you should NOT have 12V+ on both injector wires
The red wire should be 12V+ when the key is in the ON position
The other wire is a - signal wire that comes directly from the PCM and should only "flash" a - signal for a moment as the injector opens.

Sounds like you have a short in your PCM
Yes sometimes a bad PCM can still perform the OBD test.........

 

[Marv]

you should NOT have 12V+ on both injector wires
The red wire should be 12V+ when the key is in the ON position
The other wire is a - signal wire that comes directly from the PCM and should only "flash" a - signal for a moment as the injector opens.

Sounds like you have a short in your PCM
Yes sometimes a bad PCM can still perform the OBD test.........

YES there is 12v on both wires.
The injector is feed 12v on one wire, the voltage passes through the injector coil and out through the other one. The PCM will ground that wire for a milli second completing the circuit. If you don't have 12v on both wires then the injector coil is bad.

 

[carlosm180]

Ok, i remove the Pcm.... Capacitors are not good. I hope this is the problem!

 

[Marv]

Hello Explorers from Italy
Yesterday My 1994 Explorer 4.0v6 suddently stopped to work, engine start but doesn't crank: so I run koeo test (1 1 1, no problems), fuse and relais are ok, fuel pump is ok, fuel pressure is ok, trottle position sensor is ok, sparkles work fine, crank position sensor have not problems (as this truck is bifuel - it run also with LPG/propane- i disconnected the sensor and the engine stopped), injectors... Oh, perhaps they have a problem! Disconnecting and testing the cables of injectors, infact, I find something of strange: both the wires show +12v (the ground of the multimeter is connected with negative of the battery).
In addition, check engine light never works (also turning key on or during koeo test)...I don't know if the bulb is broken (before Yesterday it works) but perhaps it is another symptom of the problem.
Any idea?

I have had that problem with my 94 explorer. Turned out that the deta pressure feedback sensor (DPFE) went bad and had a short inside that killed the 5 volt reference from the PCM. Simply unplug it at the sensor and try to start the engine.Only take two minutes to try that.

 

[carlosm180]

YES there is 12v on both wires.
The injector is feed 12v on one wire, the voltage passes through the injector coil and out through the other one. The PCM will ground that wire for a milli second completing the circuit. If you don't have 12v on both wires then the injector coil is bad.

When I tested the wires, the injector coil was disconnected.... I disconnected the coil, then I touch with the black cable of the multimeter the negative of the batter and with the red one a wire of the connector (12v) and then the other one (always 12v)....

Mmm... I hadn't test the DPFE sensor... I have to reconnect the PCM, then I'll try to restar the engine... I hope it run!!!

 

[carlosm180]

Strange.....my 1994 Explorer has no EGR....

 

[Marv]

Strange.....my 1994 Explorer has no EGR....

"wiring diagram of the injection system for a 4.0v6 explorer" posted here.
Wiring diagram also shows pressure feedback electronic module.
If you are in Italy, the Explorers maybe does not have the same emissions controls as in the USA.

"When I tested the wires, the injector coil was disconnected.... I disconnected the coil, then I touch with the black cable of the multimeter the negative of the batter and with the red one a wire of the connector (12v) and then the other one (always 12v)...."

Yes that is correct, red wire 12v always hot with switch on, other wire will only show ground for a milli second when the computer tells the injector to fire

 

[410Fortune]

In the USA 93 had no EGR unless it was sold in California then 94 the EGR was back. It seems a bit hit or miss in those two years......

let us know what you find, curious to see what your PCM looks like

 

[carlosm180]

This is the Pcm type:

.... And here you can see the capacitor broken:

When I touched it, it "collapsed"!

 

[Marv]

f37f-12a650-zb shows it's for a 92-93 explorer or ranger.
Look up the your vin number, that will show the year

 

[carlosm180]

Questo è il VIN report

 

[Marv]

VIN clearly shows it is a 1994
Without an EGR it should be pre 94
F37F-12A650-ZB ECM should be for a 1992 or 1993
Got me confused

 

[Turdle]

BAT1 is non egr , auto trans 1993 sequential Injector tune code--could be a very early production 94 ( I'm curious as to actual build date)





Have you tried replacing all capacitors? There are a few threads which result in replacing them for a fix.

 

[carlosm180]

:-( ..... I notice my engine has no cam position sensor, while 1994 models usully have it...


I'll buy the capacitors today, I hope to solve!