Little back ground history on this unit..

1996 Dodge ram 1500 4x4 - 5 speed (NV3500) - 318ci 5.2l

Bought this truck 5 years ago and have never had any sort of mechanical issues until summer of 2019.

Truck started losing oil pressure after the engine got to operating temps.. yadi yadi yada.

Figured i'd spend some time and money on this and turn it into a project.

I pulled the motor and rebuilt it from the bottom up, Replacing every single part inside the motor and 75 % of the bolt ons.

After the long build, and many hours i finally had this thing running & spent approximately 2 weeks driving it with zero issues. however after about 2 weeks, my truck started sputtering and bucking while cruising at highway speeds. i drove it a few more times through the city without issue and then it began to get worse, Bucking and sputtering throughout the city. I figured it seemed like a fuel loss issue, maybe clogged filter or worn out pressure sending unit. none the less, i dropped the tank and replaced the pump/filter and pressure regulator. needless to say that didnt fix the issue and that would be why I'm here.

the only codes present were 02 sensors so i figured why not get those out the way. still no fix, as i didn't expect that to do anything anyways.....

however i went for another burn down the street, trying to get it to missfire, Buck, and sputter again, and of course it finally did after about 20 minutes of cruising around flawlessly.

This time it stalled out and would hardly start, only allowing me to get a few meters' at a time before dying.

This is when P1391 code became present.

While doing the rebuild, I hadn't changed my Distributor so i figured might as well replace that, along with the crank position sensor

I replaced one at a time, Starting with the distributor and the issue was still happening. the truck started and idle'd perfectly fine for about 3-5 minutes and then it would miss and drop a couple hundred rpms, Rev back up to compensate for the loss. this would happen until it finally died after running rough for about 30 seconds.

Next i changed the Crank sensor, And at this point it wont even start. I threw the old sensor back in and the pre existing issue happened again.


One thing i've just recently learned was the flywheel has a magnet and that's what communicates with the sensor (obviously) however when i installed this flywheel I never knew this information and i'm not sure if there is a correct way and an incorrect way to have this orientated upon installation...


Any idea's ? also wondering if the crank or cam sensors have to be relearned at the dealer.


Hopefully I don't have to separate the transmission again.


This is the first time i've ever posted on a forum,therefore i will do my best to keep you guys updated and to reply to questions, or if you have any ideas..


Thanks!!


Here's the motor after the rebuild

 

What brand O2 and crank sensor?

 

Not sure about the 5 speeds but the autos have cut outs on the flex plate witch the sensor reads. Sounds like the crank sensor is the issue though. Also did you address the plenum gasket issue?

 

Yeah, crank sensor is a hall effect switch. It reads the holes in the flywheel as they pass. If you put in a cheap one, not really a surprise it didn't work, need a genuine OEM sensor. You can source them from various places, and they are cheaper than the dealerhip.

Also, if you used bosch O2 sensors, that could be a part of your problem as well. Our trucks simply don't like them. NTK, or Denso only please.

 

Hmm, Good to know. I ordered both O2 sensor's through rock auto, and to get them from the same warehouse (just to cut shipping costs) I wound up having to get a Bosch Downstream sensor and NTK Upstream sensor.

The Crank Position Sensor is Ultra Power brand.

 

I don't think the downstream plays as big of a role in determining mixture as the front one does. In fact, I am not entirely sure if it has any affect at all........ and it's just to monitor the cat efficiency.....

 

Upstream O2 sensor is NTK
Downstream is Bosch

Crank position sensor is Ultra Power

 

Okay, Thanks for the tips ! & yes I heard that was a magnum issue with the manifold, So i layed a nice bead of RTV high temp gasket maker through it.

 

My thoughts exactly.. i'm going to roll with the OEM Crank sensor for the time being ( the one that at least allowed my truck to idle ) and I'm about to head out and play with the oil pump drive shaft.. My next guess is maybe its a tooth out on the cam gear.

 

Need to check fuel sync. Distributor has nothing at all to do with ignition timing, that's what the crank sensor is for. The cam position sensor (pick-up coil) in the distributor tells the PCM where in the firing order it is, so it knows which injector to fire. Fuel sync has a tolerance, plus or minus 7 degrees, get too far out, and things get weird, though, rumor has it, it will run at 180 out, just badly. (and consistently badly at that.)

Have you changed the cam sensor??

Think I might be tempted to check the wiring for the cam/crank sensors, and make sure it didn't get pinched somewhere.