95 4.0 no start no spark

[Tonyt22]

Hey guys just picked up a 95 4.0 4x4 first ranger in a while guy I bought it from said he parked it came out the next morning and no start so far I determined its getting fuel at the rails but no spark at the coil any tips and where I should start

 

[RonD]

First, do 50/50 test
Spray gasoline or starting fluid into the intake
Crank engine <<<< this is the only way to test for spark and spark timing, spark testers don't work well on Fords Waste Spark system

If it fires up and dies you have spark but no fuel from injectors
If it doesn't fire up then you have no spark
50/50 instant results



Spark system is really simple
On the front of the engine next to crank pulley is the Crank Sensor
It reads what looks like a "gear" on the pulley, this times the spark AND fuel injectors
So computer will only start spark and injectors when this sensor starts to send pulses from crank spinning

Crank engine over and then pull out 1 spark plug, see if its tip is wet, if its wet then crank sensor is working, if its dry AND no spark then could be crank sensor is bad, these rarely fail but rarely is not never

Only thing left for no spark is Coil Pack power, pull off 4 wire connector, test RED wire for 12volts with key ON
If no 12volts then check fuse #19 in cab fuse box, 25amp fuse


Do the dash lights come on with key ON?

 

[Tonyt22]

First, do 50/50 test
Spray gasoline or starting fluid into the intake
Crank engine <<<< this is the only way to test for spark and spark timing, spark testers don't work well on Fords Waste Spark system

If it fires up and dies you have spark but no fuel from injectors
If it doesn't fire up then you have no spark
50/50 instant results



Spark system is really simple
On the front of the engine next to crank pulley is the Crank Sensor
It reads what looks like a "gear" on the pulley, this times the spark AND fuel injectors
So computer will only start spark and injectors when this sensor starts to send pulses from crank spinning

Crank engine over and then pull out 1 spark plug, see if its tip is wet, if its wet then crank sensor is working, if its dry AND no spark then could be crank sensor is bad, these rarely fail but rarely is not never

Only thing left for no spark is Coil Pack power, pull off 4 wire connector, test RED wire for 12volts with key ON
If no 12volts then check fuse #19 in cab fuse box, 25amp fuse


Do the dash lights come on with key ON?

Yea all lights turn on check engine will turn on then off and after a few moments on cranking will turn back on but scanner doesnt pick anything up
Grabbed my test light ,multimeter, and some starting fluid going to test when I get home

 

[Tonyt22]

Ok so I tested the 50/50 definitely no spark
Brand new cks nothing tested the plug no power from the hot went all the way to the pcm and nothing from the wires so I'm assuming bad pcm or is there something else that would cause the pcm not to send power out everything else is getting powered

Can I bypass the pcm and run a hot from the battery to test out the cks

Pcm looks like it's been swapped recently has remanufactured marks dont know when that was tho

 

[RonD]

The crank sensor generates its own power, you should see .5vAC(not DC) when engine is cranking

Crank sensor is a VR(variable reluctance) sensor so when a metal tone wheel(reluctor ring) with "teeth" passes by close to it the magnetic field causes it to generate a pulsing AC signal, the pulsing is a timing signal
In the case of the crank sensor there is one missing "tooth" on the tone wheel that denotes #1 cylinder at TDC, the PCM sees each pulse and sees the missing pulse, the gap, this is how it times spark and injectors

You can test crank sensor by setting volt meter to AC volts, then crank the engine, at 200rpm(crank speed) you should see .5-.9vAC

 

[Tonyt22]

Thanks for the info and reply so went back and tested the cks and was good figured out which pin on the sensor was pos and traced the wire back to the pcm looks like the po crossed the wires when he spliced in a new plug cut the wires and re soldered them truck fired right up no gotta finish re painting this beaut camo isn't really working for me

 

[RonD]

Good work

Thanks for posting the FIX

 

[Tonyt22]

painted it this weekend

 

[RonD]

Looking Good