× Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

1995 Ford Ranger 4.0 V6, XLT 4x4- no spark

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
17 Jan 2020 22:04 #36698 by kvforte
I need some help diagnosing a no spark issue. The truck would occasionally cut off while driving, but immediately start back up. This time it again cut off while driving and will crank fine just has no spark. I could really use some help on this one since my son turns 16 in two week and is looking forward to driving this truck.

Parts Replaced so far:
crankshaft sensor
camshaft synchronizer & sensor
PCM


Vehicle has factory non-chip key anti-theft system.

Test results:
50/50 test- no start.(starter fluid sprayed into intake.)

in-line spark tester- no spark while cranking.

injector has 12 volts- key on, but no pulse while cranking.

fuel pump- primes with key on.

Coil- 12 volts key on, drops to 10 while cranking.

CEL- on with key on, goes off for approx 3 seconds while cranking then comes back on.

RPM monitor- reads 186 rpms while cranking, then drops to zero in about 3 seconds. RPM measurement is from OBD device. (Onboard tach doesn’t move.)

PCM pin 103 to B- has .6 ohms key off.

PCM pin 97 to B- has 12.1 volts key on.

CKP pin 21 to B- has 1.55 volts DC key on.

pins 21 & 22 at PCM -has .5 AC volts while cranking.

CKP at sensor - .5 AC volts while cranking.

CKP at sensor - 660 ohms resistance.

Tone ring visual inspection looks normal.

As stated about already replace crankshaft sensor, PCM, Coil Pack, and camshaft synchronizer w/sensor. Not sure what else it could be?
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
17 Jan 2020 22:17 - 17 Jan 2020 22:20 #36699 by John Curtis
Replied by John Curtis on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
No Injector Pulse and No spark...

A couple things. You need to make sure the PCM has powers and grounds. (Does check engine light come on for a few seconds during initial key on?)

Just realized you checked this.

How much voltage drop is happening during crank?

You need to verify crank signal is getting to the PCM.

Thinking out loud always helps me in the process.
Last edit: 17 Jan 2020 22:20 by John Curtis.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
17 Jan 2020 22:46 #36700 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
Yes I checked the voltage drop on the red wire at the coil pack. It has 12V with key on, drops to 10V while cranking. I tried to do a strobe test at the coil pack using the red wire and each of the three ground wire individually. With key on the test light was on. While cranking the test light flickered dimmer, but never actually went off/on completely. I think I was just seeing the voltage drop cause the dimming, not the PCM ungrounding/grounding. Also tested the crank signal at the sensor and at the PCM, readings were the same. I am attaching a few test procedures I found online along with results, but I’m not very experienced with electrical issues, so I’m not sure what they mean.
Thanks for your help, I’ve been working on this truck for several months when time allows. Getting a little hopeless.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
18 Jan 2020 10:16 #36705 by Cheryl
Replied by Cheryl on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
I’d recheck the grounds at the pcm. Continuity to ground is kinda a bad test I’d make sure the powers and grounds light a headlight bulb first. Also do you have a 5 volt reference at any sensor?? Tps maf
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
20 Jan 2020 10:54 - 20 Jan 2020 11:04 #36735 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
I’m attaching a picture of the PCM pin assignments, and have a couple of questions. I see the pins labeled power 97,71,55. I also see pin 90 labeled reference volt. Should all three power pins light a bulb with the ground pin 103? Sorry, like I said, electrical is not a strong point for me.
Attachments:
Last edit: 20 Jan 2020 11:04 by kvforte.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
21 Jan 2020 13:52 #36758 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
After some testing today. I do have 5V on the reference voltage pin back probing the PCM with key on. I also checked all power and grounds pins as labeled on the PCM chart, they all check out good and will light a test bulb. I have 11.5V with key on at red wire on coil pack. I assume the other three wires at coil pack harness are grounds that the PCM used to fire the coil. When testing each of these along with the battery positive, the test bulb will only light up very dim. Is this correct?
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
21 Jan 2020 15:36 #36760 by Noah

kvforte wrote: I have 11.5V with key on at red wire on coil pack. I assume the other three wires at coil pack harness are grounds that the PCM used to fire the coil. When testing each of these along with the battery positive, the test bulb will only light up very dim. Is this correct?


I'm sorry, I'm not following this part well...

Are you saying that with the test light connected to battery positive that while cranking the engine the yellow/xxx wires light dimly?

That would suggest good coil control. It happens so quickly that it's never grounded long enough to light the bulb very brightly.

Or, are you saying that with the test light connected to battery negative that all 4 wires on the coil light the test lamp dimly with the key on and engine off?
That would indicate a voltage drop on the coil feed circuit.

Sorry for the confusion on my part

-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
21 Jan 2020 16:14 - 21 Jan 2020 17:06 #36761 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
With key on engine off the power wire to coil pack has 11.5V. Then, testing the three yellow/xxx wires individually using the test light lead to battery positive with key on engine off. All three will very dimly light the bulb.

Shouldn’t these three wires be grounded completely while key is on but not cranking? Then the PCM would cut/uncut the ground to each along with the timing as the engine cranks.

Also, just for good measure I tested the crankshaft sensor signal again. Got .4 AC volts at the sensor and at the PCM while cranking. Is this enough signal to tell the PCM to fire the coil?
Last edit: 21 Jan 2020 17:06 by kvforte.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
22 Jan 2020 09:07 - 22 Jan 2020 09:44 #36788 by Noah
The pcm will give the coil control circuits ground as it is triggered. So there should be 12v on all of the wires key on engine off, coil plug connected. Try a volt meter instead of the test light.
I'm not sure about the test light for that test, doesn't sound right. I would think that it should not light at all, but I suppose it could be finding a ground path through the pcm?

As far as .4vAC on the crank sensor, I think that should be sufficient. I've never checked one with a meter, but according to the Engine Performance and Diagnostics book: pg15 21-8,
"Amplitude must be a minimum of +/- 500mv for the AD converter to "see" the signal."

So your .4v (400mv) is course enough for me to think it's working, remembering that a voltmeter gives you an average reading. So at an average of 400mv, I would assume that when viewed on the scope that the signal is likely crossing that 500mv threshold.


-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-
Attachments:
Last edit: 22 Jan 2020 09:44 by Noah.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • juergen.scholl
  • juergen.scholl's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
More
22 Jan 2020 09:35 - 22 Jan 2020 09:37 #36791 by juergen.scholl
Replied by juergen.scholl on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
Make sure the two crank sensor wires are not inverted! Check that the respective wires from terminal 1 and 2 of the crank sensor connector go the right ecm pins (21 & 22 I think) and that they are not the other way round. Although a VR sensor, it features "polarity".

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 22 Jan 2020 09:37 by juergen.scholl.
The following user(s) said Thank You: Noah, aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
22 Jan 2020 11:35 #36793 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
You are correct retested this morning. With key on, all four wires at coil pack harness have 11.5volts with the harness connected.

When harness is disconnected with key on red wire has 11.5volts, and the other three have .02volts.

Any ideas what else could be causing the no spark?
The following user(s) said Thank You: Noah, aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
22 Jan 2020 16:16 #36808 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
Update: was able to hook up an Obd2 scanner to the truck today and have a few questions about the results. Once the key is on and connected the CEL is on. Has the engine is cranking the scanner reads the RPM’s at 180-190 and the CEL goes off. Approximately 3 seconds later the RPM’s drop to 0 on the scanner, and the CEL comes back on. At that point the CEL stays on and RPM’s stay 0 as the engine continues to crank. The key is then returned to the on position for a few seconds. Then try to crank again and the CEL stays on and the RPM’s read 0. In order to get the RPM’s to register again and the CEL to go off while cranking, the key must be returned all the way to the off position before beginning to crank. It seems like the PCM is initially getting the crankshaft signal, then the signal is cut off and remains cut off unless the key is turned off. What could cause this signal to be shutting down? Could the computer be looking for a signal from another component and shutting the system down because that signal is missing?
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
22 Jan 2020 19:19 - 22 Jan 2020 20:58 #36810 by stioc
Replied by stioc on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
What does the scanner read when the CEL is on? any codes? Sounds a bit like an immobilizer issue.

When the RPM reads zero is the crank sensor still sending the .4v?
Last edit: 22 Jan 2020 20:58 by stioc.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
22 Jan 2020 19:30 #36811 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
No engine codes are present. I didn’t check the crankshaft voltage after the RPM drop. I just assumed the signal was still there. I’ll check that tomorrow.

Is the spark and injector pulse related? I’m just wondering if there could be an issue in the fuel system that is causing the computer to shut down the spark.

If feel like the computer has to be killing the RPM signal after the 3 seconds. Because it will do it exactly the same every time as long as the key is turned to the off position before cranking. However, I guess the crankshaft signal could be getting shorted out. I’ll check voltage after RPM loss tomorrow.

Thanks
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • kvforte
  • Topic Author
  • Offline
  • New Member
  • New Member
More
23 Jan 2020 13:45 #36832 by kvforte
Replied by kvforte on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark
Looks like the crankshaft ACVolts signal is dropping at the same time the RPM’s go to zero on the OBD scanner (after about seconds of cranking).

Maybe one of the crankshaft sensor wires is shorted somewhere? Thought?
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
24 Jan 2020 11:25 #36866 by stioc
Replied by stioc on topic 1995 Ford Ranger 4.0 V6, XLT 4x4- no spark

kvforte wrote: Looks like the crankshaft ACVolts signal is dropping at the same time the RPM’s go to zero on the OBD scanner (after about seconds of cranking).

Maybe one of the crankshaft sensor wires is shorted somewhere? Thought?


I would suspect a bad crank sensor first especially if it's aftermarket. If you still have it I would put the old CKP sensor back on and see if it's also dropping out so quickly. If it shows the same exact behavior then I'd chase the wiring possibility or some other reason.
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

More
25 Jan 2020 10:49 #36897 by Noah
I'm on the crank sensor band wagon.
I like Juergen's suggestion about polarity, especially if you had to repair the connector when you changed the sensor.
check out this Ford crank sensor video:


While cranking the engine on your Ford, the CEL should go out as long as the PCM is receiving the crank signal. You say it goes out but then returns just as the RPM stops displaying. This seems to confirm a crank sensor signal dropping out. Possibly an air gap issue. Do you get maybe one or two spark events during the first couple seconds of cranking?

-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-
The following user(s) said Thank You: aboudi.naddaf

Please Log in or Create an account to join the conversation.

  • Not Allowed: to create new topic.
  • Not Allowed: to reply.
  • Not Allowed: to edit your message.
Time to create page: 0.541 seconds