1996 Dodge Ram No Saprk

[ajakeski]

So this morning I went to leave for work and my 1996 Dodge Ram 5.9 V8 wouldn't fire up. It cranks without issue, but no fire.
I noticed that the tach didn't move when I cranked it and remembered that this is a symptom of a bad crank position sensor.
I picked up a new crank position sensor after work and changed it out. Still no start, no tach.
I ran the codes and got code 11, No crank signal, (bad crank sensor). I checked for voltage going to the sensor and it's in spec.
I changed the cam position sensor too. (Hall effect in the distributor.) Stiil a crank but no start issue.

Tomorrow I'll pull the crank position sensor and trade it for another new one. Maybe this one is bad...

I've been all over Google and all I find points to the crank sensor. I doubt it's the computer, because every time I clear the codes, it gives me code 11 after I try to start.

Any ideas?

[jonnymopar]

Could be a bad splice somewhere. Check your major feeds. I had a Dakota from the same generation that had a corroded splice that took me absolutely forever to find.

[ajakeski]

I downloaded the service manual and I'm going over the wiring diagram. I'll start digging through the harness tomorrow.

https://docs.google.com/uc?id=0B0EBf...xport=download

[RattFink]

My dad's old 97 ram would do this whenever it rained a lot, but it would eventually start up and run fine. It always bugged me, let us know what you find.

[mopar-tech]

The aftermarket sensors are bad, ask me how I know!! Mopar only for the crank and cam.

I spent days chasing my tail due to a junk name brand sensor.

If you need a sensor, I have a used one you can have to do diag, it would get funky when hot and skip in reverse.

[ajakeski]

The local Chrysler dealer doesn't stock the crank position sensor and was going to charge me $165 for it. That reminded me why I don't do business there.
I ordered the sensor from an online Mopar dealer, RT Parts, for $70 shipped.
Since I had the multimeter out, I checked the wires going to the sensor. Purple supplies 5 volts from the PCM, Gray is the crank signal to the PCM and Black is ground to the PCM.
All wires have good continuity, no shorts. I found that both the Purple and Gray wires are receiving 5 volts from the PCM with the sensor unplugged. They are not shorted.
If I'm reading the wiring diagram right, the Gray wire should not receive voltage from the PCM, but should send a voltage signal to the PCM when the crankshaft sensor is triggered.
This is leading me to believe the PCM is bad. A replacement is on it's way.

Prior to this incident, the truck ran fine, no misses, no issues. This no start situation started literally overnight. It ran Sunday, no start on Monday morning.

[thedon809]

Don't order a pcm. What it's doing is normal. Do the same test to the throttle position sensor and I bet you get the same thing. Ground on 1 wire and 5 volts on the other 2 when unplugged.

[jonnymopar]

Don't order a pcm. What it's doing is normal. Do the same test to the throttle position sensor and I bet you get the same thing. Ground on 1 wire and 5 volts on the other 2 when unplugged.

Yep. Internal pull-up resistors making that happen. Even though it's a signal pin, it can't be left floating (as in when the sensor is unplugged), so the PCM has pull-up resistors on those signal pins which usually pull them to 5V when a sensor is disconnected.

[ajakeski]

Yep. Internal pull-up resistors making that happen. Even though it's a signal pin, it can't be left floating (as in when the sensor is unplugged), so the PCM has pull-up resistors on those signal pins which usually pull them to 5V when a sensor is disconnected.

Even with the crank sensor plugged in, the gray signal wire has constant 5 volts. It doesn't change when the engine is cranked.

[ajakeski]

A Mopar crank sensor fixed the no spark issue, but the fuel pump died. And the tank of is full, the tanks always full when fuel pumps go out...

[135sohc]

Try smacking the tank bottom with a rubber mallet. Get one last jolt out of the pump and use it to pump the tank out.

[thedon809]

No doubt that fuel tanks are ALWAYS full when the pump dies.

[ajakeski]

Fixed. The truck runs again.