2000 Ram Van 3500 - Crank but won't start
 

My flippin sweet van ( Named Vincent ) had an instant ability to crank but not start. I get P-0351 error code, and check engine light, ABS light and brake light while it fails to start.

Having done much troubleshooting and research, I've tried many things, so let me explain what I've done and what I know :

Starter engages, and strong crank, but no start. I've replaces the ignition coil first, as I was not getting spark. After replacement, I realized that I'm not getting voltage to the ignition coil, so the coil replacement was not necessary. I noticed at this point too, that I was not getting fuel ( pretty sure ).

Chasing the problem further, I realize that the Automatic Shutdown Relay ( ASR ) is not engaging. I was able to test I do get voltage to the coil of the relay, but not engaging. So I replace the relay, but no difference. Upon further investigation, I get voltage to the relay, but the ground portion of the relay's coil is not set to ground ( the Power Train Control Module sinks that to ground ). I decided to jumper the relay closed, and several other relays engaged, and now I believe I also am getting fuel, but still no start.

I replaced the ignition switch 1 year ago, however I've not ruled that out as the problem. It seems to me that the computer is missing an input, to tell it to sink the ground on the Automatic Shutdown Relay & likely to sink the ignition coil to create spark.

What should I try next? Can I test that the Powertrain Control Module ( PCM ) has all the signals it needs to sink the Automatic Shutdown Relay? Can I test that the PCM is sinking the coil, to create spark properly? Should the PCM sink the ASR before I crank, or during the cranking process ( For instance it sinks after getting an input during crank vs. should sink to ground with ignition switch engaged )

In looking at the diagram, makes me wonder if the crank sensor is not sending signal to the PCM, but unsure how to verify that idea. However if the PCM sinks the ASR prior to crank, that would throw out that idea.

Other thoughts?

Does the fuel pump prime at initial key on?

The PCM *should* energize the ASD, and Fuel pump relays for about 3 seconds at key on.

Yes, the fuel pump primes when I turn the key on.

I don't get ASD nor the fuel relay for the initial 3 seconds. Looks like they are connected on both the ignition switch ( for positive ) and sinked to ground with the PCM.

I just tried to force the ASR coil to ground, and it does engage the relay, and I get voltage at the ignition coil ( pin 1 ), same as when I jumper-ed the relay. So I'm confident the PCM is not sinking the coil relay to ground, when key is in ON position.

I have nearly all the same symptoms as this thread ( other than It has never started when cold ).

https://dodgeforum.com/forum/dodge-r...ml#post2228452

Perhaps I'll pull the wires from the alternator, and see if ASR gets a good circuit

ASD relay will only power things for a few seconds, unless the PCM sees the engine turning. (crank sensor.) If the ASD isn't re-engaged when the engine is cranking, (and the fuel pump should be running as well.) Probably a bad crank sensor, or the wiring between it, and the PCM. If you decide to replace the sensor, use ONLY a genuine mopar sensor. The dodge systems really don't care for the aftermarket sensors.

I super love the help and ideas. Thank you and I appreciate you. I do not get ASR for the 3 initial seconds, nor when cranking. With me short circuiting the relay, I would think that would take the need for the sensor input out of the equation. ( I'm only a mathematician, so don't know much about cars )

I just noticed that while cranking, my voltage goes down significantly ( on the dashboard meter/indicator ). It goes from 12v down to 9v really quick. So going to charge the battery ( less than year old ) up overnight, and pursue the alternator is grounding out the system next.

If you don't get the initial prime.... then something is seriously awry..... Try resetting the PCM, see if you get prime at least once...... If you don't, entirely possible the PCM itself is bad.

Ok gang, I decided to start fresh, as I was no certain that I was getting initial prime. After work I was able to put a meter on the relay, and I do, in fact get the initial prime, and do get initial voltage to the ASR and the fuel relay/pump. So good news there. I also checked to see if the alternator was shorted out to ground, and it is not.

So, I am getting good voltage from the ignition switch and I am getting good initial ground sink from the PCM to the relay. The relay does engage for approx 2 seconds then releases.

This makes me think ( from other forums and my diagrams ) that I'm missing input from a sensor back to the PCM to re-engage the relay. From what I can see the crank sensor is likely my next part to replace.

Yep. That seems perfectly reasonable. Use a genuine Mopar crank sensor ONLY. These systems really don't play well with aftermarket sensors.

yep - p0351 for me was the crank sensor a few years ago