Testing the Crankshaft Position Sensor

[Postal_Dave]

1996 Ford Explorer XLT 4.0 pushrod engine.
I have a Crank, No Spark, problem and I'm chasing wires. I already replaced the Crankshaft Position Sensor with a new one and I bench tested it to make sure it worked. I do get AC voltage when passing a piece of metal in front of it. The Ohms were 660. (If I read that right. .660 K)

Now I'm checking the wires. The CKP is not installed right now.

With the wiring clip disconnected from the CKP, I put sewing needles into each of the two connections, then used the alligator clips on my multimeter to test it. There is a blue wire that is supposed to be the positive wire and a grey one that is supposed to be negative.

With the multimeter set to DC Volts, I get nothing if I connect to both wires. If I connect to just (+) wire and then to the frame, I get 1.5 volts. If I just connect to the (-) wire and then to the frame, I get 1.5 volts.

When using a continuity test from the (-) wire to the frame, I heard the fuel pump pressurize. That doesn't happen with the (+) wire.
* (This is strange to me because I heard the fuel pump pressurize when I turned the ignition to "On".)

With the Negative Battery Terminal off, there is no continuity from either wire to the negative battery wire other grounding points.

I just unplugged the PCM wiring connector, The (+) wire does have continuity for the #21 pin and the (-) has continuity for the #22 pin.

I don't understand why I'd get the 1.5 volts from both the positive and negative wires. I also don't understand why I'd get the fuel pump to pressurize when I connect the negative wire to the frame.
Any ideas?
Thanks ,
Dave

 

[410Fortune]

Crank Shaft Position Sensor 1993 Ford Explorer. 4.0 , push rod type.

My fuel pump keeps running before starting. It should cut off with in two or thee seconds and then stop until the engine starts. However, when I turn the key to the run position, the fuel pump keeps running and the engine will not start. If the pump stops the engine will start. I am...

www.explorerforum.com

How To Test The CKP Sensor (1991-1997 4.0L Ford Ranger And Mazda B4000)

Important Tips And Suggestions. Symptoms Of A Bad CKP Sensor. Where To Buy The CKP Sensor And Save. Testing The CKP Sensor Signal With A Multimeter. 1991, 1992, 1993, 1994, 1995, 1996, 1997 4.0L V6 Ford Ranger And Mazda B4000

easyautodiagnostics.com

might be helpful!!

 

[Josh P]

With the CKP unplugged you get continuity on pins 21 and 22?

 

[Postal_Dave]

Josh,
I didn't test that. I was dumbfounded by the fuel pump pressurizing and didn't test that. lol

Fortune, I followed those links. The one from easy auto diagnostic, I read before I started looking at the CKP. The link to the one from the Forum seemed to have the best lead for my problems, so I opened up the PCM hoping to find something obvious like a blown capacitor. Everything there seemed to be fine. No obvious scorch marks or blown capacitors. Here is what the inside of the PCM looks like in case anybody wants to know. The case uses 6, 7/32 bolts.
In the first pic, upper left hand corner the second chip is the EDIS module.

I'm going to back probe the CKP connector tomorrow. I still don't know why I'm getting 1.5 volts from both CKP wires though. The struggle continues.

Thanks guys,
David

 

[Postal_Dave]

I back probed the Crankshaft Position Sensor. I got 1.06 Volts AC. So that seems to be fine.

 

[Josh P]

I back probed the Crankshaft Position Sensor. I got 1.06 Volts AC. So that seems to be fine.

Do you get the same reading at the sensor and on pins 21, 22 at the ecm connector?

 

[Postal_Dave]

I never thought about doing that. I'd have to unplug the ECM then connect the multimeter to those wires. The harness has too much stuff there to back probe it. Will the Explorer crank without the ECM connected?

 

[Josh P]

I'm not sure, if it doesn't you could jump the starter solenoid with the key in the run position

 

[Josh P]

Reading all the posts in this thread, you stated you had strange readings on the CKP wires. I haven't seen where you stated those wires have been ruled out as ok.

 

[Postal_Dave]

I checked the signal from the CKP back to the PCM. I cranked it by jumping the solenoid like you suggested, not because I had to, but because I just wanted to try jumping it that way. (BTW: That was interesting.) I got the 1.4 volts AC. I attached a pic showing how I used sewing needles for probes.

As for the strange reading from the CKP wires, I haven't ruled out anything there. The links that Fortune gave me mentioned the same readings but when they looked at their PCM, they had blown capacitors. My capacitors seem fine. It's hard to check capacitors on a board and I really don't want to try to replace them unless they had popped heads or showed some other sign of damage.

 

[Josh P]

The ecm is getting the signal from the crankshaft, I doubt any problems with the wire to the crankshaft sensor. I was thinking it might be shorted out, if it was you wouldn't get a reading from the sensor. Next thing to rule out is the 3 wires that go to the ignition coil pack. You confirmed 12V on the 4th wire. If the wires are ok, then I'd suspect the edis module in the ecm.

 

[Postal_Dave]

I'm thinking that some how, when I changed out my spark plugs and wires, I fried the PCM a little. My dashboard indicators work fine, and the Explorer ran great for a few minutes after I changed the wires and plugs. However, after 5 minutes of running, it acted like the computer overheated and shut the engine down.

My fear here is buying a new PCM and then have the car work for 5 minutes again before shutting down again.

 

[Josh P]

I'm thinking that some how, when I changed out my spark plugs and wires, I fried the PCM a little. My dashboard indicators work fine, and the Explorer ran great for a few minutes after I changed the wires and plugs. However, after 5 minutes of running, it acted like the computer overheated and shut the engine down.

My fear here is buying a new PCM and then have the car work for 5 minutes again before shutting down again.

car-part.com has 12 pages of them. Buy 1 or 2 of the $50 ones, shipping won't be too expensive. Since you posted pictures of the ecm, the one you are looking for is F67F-DC. I suspect the ecm, but I'd still rule out the wires to the ignition coil pack.

 

[Postal_Dave]

I did a continuity test for the wires 3 control wires from the PCM to the coil pack. I'm going to double check the 12 volts to the coil pack. If it's providing power then I'm going to order the PCM and hope that is the problem. Will this PCM need to be programmed in any way?

 

[Josh P]

I did a continuity test for the wires 3 control wires from the PCM to the coil pack. I'm going to double check the 12 volts to the coil pack. If it's providing power then I'm going to order the PCM and hope that is the problem. Will this PCM need to be programmed in any way?

96 didn't have pats, should be plug and pray.

 

[Postal_Dave]

"Plug and Pray"?!?!? HAHAHA There's going to be a whole lot of praying that this works, otherwise, LKQ junkyard might get a new vehicle.

 

[Josh P]

"Plug and Pray"?!?!? HAHAHA There's going to be a hole lot of praying that this works, otherwise, LKQ junkyard might get a new vehicle.

With the price of things these days, finding the issue is cheaper than a replacement