I have a fuel pressure gauge, so I plan to check the fuel pressure tomorrow. I can hear the fuel pump prime with the ignition on, so I have a feeling my issue is spark related (i suspect a bad crankshaft position sensor).

I hear you on Airtex...I've never heard anything good about them. I had to replace the fuel pump in my Isuzu Rodeo last June and went with a Delphi, and haven't had any issues since. I'm not sure who the OEM is for the Ram pumps....anyone else know?

 

lol **** a shop replaced my fuel pump with an airtec, i got the box with my old pump in it, well ****tttt. well i havent had an issue with it for over a year now. maybe i got lucky lol

 

You will only have power at the coil for a about three seconds when you first turn the key on, then, the PCM cuts out the ASD relay, and won't re-energize it till it sees the engine turning. (which I think can also include a switching signal from the cam position sensor.)

PCM controls ground side of the coil circuit to provide spark, so, while cranking the engine, you should see switching continuity to ground on the ground side of the coil connector. (a digital meter won't work here, has to be analog, so you can see the needle waving at you. )

If you don't see that, then chances are real good the crank sensor took a dump.

 

I spent some time troubleshooting this morning, but unfortunately I have little to show for my efforts, other than eliminating a few possibilities. I was by myself when I started, so I couldn't check for power at the coil since, like you said, the PCM cuts off the ASD after 2-3 seconds, which is not enough time to turn the ignition on and then run around and probe the coil connector with my multimeter. So, I checked for fuel pressure first. That checked out - I have about 46 psi with the ignition on, which may be a little low and not ideal, but should certainly be enough to get the engine to run.

So, I then decided to jump right into replacing the crank sensor, since I had already purchased it several months ago. I expected this to be a pain in the butt, and it was. I ended up going at it from underneath the truck, and finally got it, but it probably took me about 2 hours from start to finish. I then reconnected the battery, said a little prayer, and hoped that the truck would fire up.

It didn't. So then I had a friend come help me so that I could check for spark. I pulled the spark plug wire off one of the plugs and put an old spark plug into the end, then held it to the body and had my friend crank. The plug did not spark.

I don't have an analog multimeter, so I wasn't able to check for ground continuity at the coil plug (by the way, how do you know which connector "prong" is the ground?). Instead, I just decided to install the new coil I had purchased. I didn't really want to do this, but I was going to feel like an idiot if I didn't try and that ended up being the cause later, so I went ahead. As I suspected, still no change.

So now I'm kind of stuck. I'm thinking it's either a bad cam position sensor, bad PCM, some sort of electrical gremlin like a bad ground maybe. Or, is it possible it could be something simple like a bad ASD relay? Should I try swapping in a new relay just to see what happens?

I think I'm about to get in over my head, as electrical troubleshooting is not a skill I possess. But, I welcome any dumbed-down advice I can get!

Thanks to everyone that has chimed in to help me. I really appreciate it!

 

Yeah, electrical is 'fun'.... and I hate it. Unfortunately, it's what I got stuck with most of the time, as I could eventually bull my way thru it, and solve whatever problem the customer was complaining about....

Can you read wiring diagrams? Sometimes, being able to sit down, and look at how the circuit is supposed to work, the problem becomes obvious. Or, at least, gives you an idea of what you need to be looking at.

But, since a new crank sensor, and coil did NOT solve your issues........ Need to verify that you are actually getting power past the ASD relay. (powers the injectors, and the coil.) So, see if you can grab your buddy again, and check that.

On the 01 trucks you should have two wires, Dark Green w/Orange trace, power feed, should be 12 volts on that wire, and the Black w/Grey trace, with is the ground side, controlled by the PCM.

 

I wish all techs took your approach of actually trying to troubleshoot a problem by following logic and a process of elimination by doing some simple investigation, rather than suggesting to just start replacing parts one at a time.

I can probably follow a basic wiring diagram if I really study it for a while. It's definitely not something that I can glance at and grasp immediately, but hopefully I can comprehend it if I spend some time studying it. And, that's probably what I need to do if I'm going to solve this on my own. Good suggestion.

Thanks for the wiring information. Just to make sure I am understanding, I should first check for constant 12VDC on the dark green/orange trace wire going to the coil while cranking the vehicle. If that power is not present, then....I'm not sure what to draw from that conclusion. Loose/frayed wire somewhere?

If I find 12V on the power wire, then I should check for fluctuating continuity to the chassis on the ground prong of the coil plug using an analog multimeter, so I can see the needle bouncing back and forth? And if the ground circuit is not opening/closing, then I know the PCM has commanded the ASD to shut off, right? Then the question is why?

Am I understanding this correctly?

Thanks again for all of your help. I'm sure it can be brutally frustrating helping novices like me via the internet....but I really appreciate it!

 

Pretty close. You can find wiring diagrams in the factory service manual, you can download one from here.

If you DON'T have power going to the coil while cranking, check for power at one of the injectors. If you don't have power there either, then you likely have an ASD event. (ASD is not getting triggered.) If you do, then it's a wiring problem between the coil, and ASD relay.

If you DO have power there, but the ground is not switching on/off, then there is either a problem with the crank sensor, or the PCM itself.....

If the ground is indeed switching, time to check and see if you are getting injector pulse. Easiest way is with a noid light, that just plugs into one of the injector connectors. Most any parts store should have 'em.

 

I have a copy of the service manual, thanks to you linking it in another post several years ago. That has been a huge help with many of the projects I've done myself. So thanks for that.

Just to recap one more time for my simple mind:

1) Check for constant 12VDC at the coil
-If present, check for switching continuity on ground prong of coil connector
-If no power present, check for power at fuel injectors (should this be pulsating, or constant?).
-If no power present at injectors either, then suspect wiring issue between ASD and coil.

2) If power and switching continuity are both present at coil, then check for injector pulse with noid light.
- If there is no injector pulse, then where do I look next?

I think I have that right. If I had to guess, this will turn out to be related to the wiring between the ASD and coil, or the PCM itself. I am almost positive I can smell fuel after I crank the engine, so I'm guessing the injectors are getting a pulse and are doing their thing. I will try to verify though.

One more question, though - is it also possible that some mechanical failure could be at play, causing the cam sensor to not send signal, thus preventing the ASD from switching the ground circuit on? For instance, if the timing chain failed, then it's possible the cam sensor wouldn't see rotation and would not send the proper signal, correct? If so, should I pull the distributor cap to verify rotation of the rotor? That makes sense in my head, but it also seems that if the timing chain failed, my engine would have grenaded during cranking when the pistons and valves collided. Am I way off track there?

I'm sorry for asking a million questions. I owe you at least one case of beer already as it is!

 

If you DO have power at the injectors, but, not at the coil, look for the wiring issue. If you don't have power in either place, ASD relay isn't getting triggered, and we are back to the crank sensor. (which is new......)

If you are NOT getting the injectors firing, time to look at the cam position sensor. If it isn't giving a signal, the PCM may fire the coil, but, it won't have a clue which injector to fire, so, it won't fire any of them.

 

I've got some investigating to do. First, I need to get the truck towed from its current location in the shop parking lot, haha.