Class B RV on a 1997 B3500 1 ton heavy duty. I posted here for the obvious reason of more eyes on my question. I hope that's okay. Van was running fine. I hooked up a loaded twin 3500# axle enclosed trailer for the first time and was very pleased at how easily it pulled. Made a few run's back & forth to storage. Then one run it felt like a brake was dragging. Now it's a dog. At that end of the run I noticed a CEK (obscured by the tilt steering) for misfire #8 and high volts fuel level (I just put in a new fuel pump ~250 miles ago). Other than low power, it runs smooth. I hooked up my OTC genisys scanner and observed max timing at speeds up to 65mph was 20-21 degrees. I'm in the middle of a short notice move and don't have much time to search the forum. Can anyone direct me to a sensor fault or possible other failure that might be causing this?

 

Are the fuel trims maxed/O2 sensor reading somewhat lean ? Between the fuel pump recently replaced and the fuel level sensor voltage high I'd suspect a problem with the replacement fuel pump and/or the wiring. Ideally check the fuel pressure at the rail.

 

Are you aware of the plenum gasket issues? Low power and multiple misfire codes are a sign. Wouldn't be a bad idea to check the fuel pressure.

 

I' ll have to record some data-stream so I can look at in detail. Fuel trims looked good (add up to less than 12, I think), but I need to review diagnosing them. One thing though, long term trim seemed to change more than I remember it should.... although I did recently disconnect the battery (it ran strong after). O2 sensors appeared normal, but I'll take a harder look. I was thinking the high volts fuel level was normal after dropping the fuel tank although I'm not sure why the cek didn't show up earlier. The replacement pump was made by the (or one of the) companies that make them for Mopar. It's a Delphi or Denso or ...? BTW, I have CRS (= can't remember... stuff). It was an open box discount from Amazon, but I'm 99% sure it was not swapped with a cheap pump. I did notice that it seemed to be a little louder than I remember. I'll take a look at fuel pressure.

I checked the plenum a few thousand miles ago, but I'll check it again. I'm kinda of thinking the plate was steel (magnetic) so I can't be sure if it was ever repaired in the past. I didn't see any more misfires (yet??) on a round trip to storage made after resetting the cek. I have to remove the passenger seat to remove the dog-house, so I have got around to checking it again.

FYI, I changed the fuel pump because the sending unit had failed, not because the pump had failed.

 

So I took a look under the, and put the cold air snorkel back on (I don't believe it has anything to do with my problem). I pulled it off a few months ago to fix something and I didn't get around to putting it back on. I started it and connected my scanner and looked at the data stream while sitting in park. I looked at the numbers at idle, 1500, and 2500. Everything looked good. Later I loaded up the trailer and made a trip to storage with the scanner hooked up. Again, everything looks good and it runs strong. I made a bunch of recordings.

A couple of years ago I was working on the AC. Using the Diagnostic procedures manual I traced a problem with the clutch not engaging to one of the 3 fire wall mounted connectors for the ECU (that is, after unsuccessfully throwing a few parts at it of courseRed face). I sprayed some Deox-it on the terminals and the problem has not returned. I wrote about this in the Ram Van forum a while back. Last summer my cruise control acted up. Once the system was energized I could not turn it off (unless I turned the key to off). I could only disengage it with brake pedal. I assumed it was the steering wheel switch, but I ruled it out using the steps in the manual. Then one day after idling for a few hours in the Mayo Clinic parking lot in Jacksonville in August (hot, hot, hot), that problem went away. Since that time it has returned, and then gone away after idling in stop and go traffic in high ambient temps. I never traced it down, but I suspect a bad connection somewhere.

IIRC, the ECU connectors are not designed to hold up to repeated connecting and disconnecting. My van has a long and mostly unknown history. My hunch is that my poor performance problem may also be an intermittent bad connection at the firewall, and the misfire is probably unrelated.

 

Timing is controlled through the ground of the coil. I have experienced a few odd things with bad coils in the past. If you can get a hold of a spark tester to see how good your spark is and go from there. Might be wires, plugs, cap/rotor, coil. Verify the your spark is good first. If it is then look at the fuel system and its controls. Also make sure your PCM grounds are good.