1995 Ford Ranger - No Spark Condition

[Quasimo1]

Hi Everyone. I have a 1995 Ford Ranger with the 3L, that has a crank no start condition (no spark). I have performed the following tests so far.

* Verified the crankshaft position sensor is sending out a signal via a waveform test.
* I have verified the 3-wire camshaft position sensor is receiving voltage via a test light and verified there is a good ground. I have attempted to test the camshaft position sensor signal wire with a multi-meter and have observed very low voltage <1 volt with key on engine off. When I attempt to crank the truck the voltage jumps all over the place going as high as 7 volts.
* I have verified that the coil pack is receiving 12 volts and primary resistance is within speck.

Any idea on how to further troubleshoot the no spark condition?

-Edited to correct the model year.

 

[SenorNoob]

Doesn't 05 have PATS? What's the theft light doing?

 

[Jandro2004FX4]

My ‘04 has a PATS, which I have bypassed … (fairly easy to do) … just spitballing here, but have you checked the fuel pump? I’ve had two of ’em fail on my truck

 

[Quasimo1]

Sorry everyone, it is a 1995 Ford Ranger, so no PATS. I got the model year confused with a different vehicle. The Fuel pump is good as I have verified fuel pressure at the rail.

 

[SenorNoob]

Can you pull codes? Even if the light isn't on it might show something...

 

[Quasimo1]

Can you pull codes? Even if the light isn't on it might show something...

Can you walk me through how to pull codes? My truck uses OBD1 and I do not own an ODB1 scanner. Is there a way to manually jump the terminal to have it blink out a code?

 

[Quasimo1]

I did some additional trouble shooting on the truck and this is what I have learned so far:

* No spark at the spark plug. Verified through an in-line spark tester.
* No spark at the coil. Verified with a test light after pulling the coil cap off and creating a small air gap with the test light.
* 12 volts at the coil pack on the power wire with key on engine off. I later tried to measure the voltage on the power wire when cranking, but my battery was now weak at this point (11.4 volts with key on engine off and a steady 9.6 volts while cranking). I am not sure if this is too large of a drop or within specs.
* No control signal at the coil pack on ground wires 2-4. Verified with a test light a no pulse condition when I cranked the truck. Test light was connected to battery negative and remained lit when cranking.
* Primary resistance at the coil pack was within specs.
* Secondary resistance at the coil pack was within spec.
* Wire integrity from the coil pack to the PCM was verified good with a multimeter.
* Crankshaft position sensor sends out what appears to be a good waveform.
* Camshaft position sensor was verified with a multimeter to be sending out a signal via multimeter. I have not tried to capture the waveform on this sensor.

What should be my next steps for troubleshooting? I am thinking, check the PCM for power and grounds?

 

[Brain75]

Recharge the battery... a 12.00 v battery is a dead battery. Below 12.3 to 12.4 ish you will start to get issues like no spark/wont start. A fully charged battery is 13.8 (there is some debate amongst the younger folks) but a traditional lead acid battery has 6 cells and each cell should be 2.3v ( 6 x 2.3 = 13.8) and a charging system (alternator) should put out at least 14v.
huge portions of the truck get a regulated 12.00v - which is why they call these things 12v instead of something else.

Here's a bunch of info on OBD1 testing including how to do all the tests:

Testing EEC-IV Equipped Engines - The Ranger Station

The EEC-IV equipped engines use an older diagnostic system to monitor and report engine related malfunctions. This system is known as On Board Diagnostics (OBD-I). The Diagnostic Trouble Codes (DTC’s) are two or three digit numbers and can be … Continued

www.therangerstation.com

what the 2 digit codes mean:

OBD-I Diagnostic Trouble Code - 2-Digit Ford Codes - The Ranger Station

Differences in test mode noted as: (O) = Key On Engine Off test (R) = Key On Engine Running test (M) = Memory code Code Definition 11 System checks OK 12 Idle Speed Control motor or Air Bypass not … Continued

www.therangerstation.com

what the 3 digit codes mean:

OBD-I Diagnostic Trouble Code - Ford 3-Digit Codes - The Ranger Station

Differences in test mode noted as: (O) = Key On Engine Off test (R) = Key On Engine Running test (M) = Memory code Code Definitions 111 System checks OK 112 (O,M) Intake Air Temperature (IAT) sensor is/was low … Continued

www.therangerstation.com

might also edit the thread title... might help to get more brains on deck if they know you aren't looking at a 2005..

 

[alwaysFlOoReD]

Title changed.

 

[Quasimo1]

Battery has been recharged. I went to pull codes after charging the battery and discovered that my truck is ODB2 and not OBD1! So I put my OBD2 code reader on the truck and found zero active or pending fault codes. I tried cranking the truck over in an effort to trigger a fault code without any luck. However, I did manage to check the live data for the crankshaft position sensor and was able to verify the sensor is reporting engine RPMs to the PCM. In addition, I pulled a spark plug and was able to verify it was wet with fuel, so at least I know the fuel injectors are working.

I then took the time to disconnect the wiring harness to the PCM and checked all of the power and ground wires on the harness for any issues but the power and grounds were all fine. I then pulled out the PCM and gave it a visual inspection but everything looked ok. I have attached a PDF picture of my PCM with some areas circled that looked a little bit different than the other areas just to double check. Perhaps someone who is familiar with what the inside of a PCM should look like can chime in if there are any areas of concern.

At this point I am stumped. PCM appears good from a visual inspection, the wiring harness looks to be good, crankshaft position sensor work and the PCM sees the data. I have good power to the coil pack, but no ground control. From what I know the PCM should send ground to the coil pack if it receives a crank sensor signal, but mine does not. Does this confirm that the PCM is bad? Are there any additional tests I can run to confirm?

 

[SenorNoob]

I can't tell much about the topmost red circle in your pic, but the rest of that looks normal to me. I'm guessing those pads are for components not used on your truck.

The top circle, is that connector on the outside? That's what it looks like with a heavy spray of waterproofing.

 

[Mechrick]

PCM looks fine. Those brown spots are aging solder flux, nothing to worry about.

What do you have for test equipment?

Assuming crank/cam position sensors are working fine if you are getting fuel.

At the coil pack:

Coil pack powers up with the key through the instrument panel fuse box fuse 19 (red/green wire).

The PCM grounds three wires to create spark. Yellow/black, yellow/red, yellow/white. You'll need an LED test light, power probe, scope or something similar to see those ground signals. DVOM won't do it.

Those connectors that plug in to the coil pack are known for getting flaky with age.