Engine/Transmission (1998.5 - 2002) '01 Oil Pressure Gauge Wild Fluctuations?

[CYauch]

I own an '01 Quad-Cab 2500, and this is my first post to the TDR ( subscribed 3 weeks ago). I have a question, and as such, I will try to include as much detail as I possibly can.



Over the past few weeks, I have noticed that my oil pressure gage 'appears' to have been acting funny. Normally when I start the truck, the needle pegs to the right after a second or two (well, not all the way to its stop, but to around the first hash mark to the right of 40). Once the engine has warmed, and I have driven a few miles, the needle sets between 40 and the first hash mark left of 40 (at idle). Normal to me. About a week ago, I started the truck as normal, and drove for a while, then noticed that the gage was reading 40 (which was odd to me because usually it stays to right more until I get closer to work than where I was). While sitting at a stop light, I then noticed that the gage jumped to the first hash mark right of 40, stayed, then dropped to what appeared normal after a few minutes. And, I tried to rev the engine to see if the needle would move, it did not, stayed on 40 until it jumped on its own. )



Fast forward today.



I left home this morning, made a stop, got on the interstate, and after about 20 miles or so, I noticed that the oil pressure gage was still on the first hash mark right of 40. I continued to glance at the gage, then noticed that it dropped to 40, stayed, then jumped back to the previous position. It did this about 6 times, then stayed there the rest of the trip, 40 miles about. Even at stop lights, the needle stayed off to the right.



Now get this, after I parked, I turned the ignition on, not starting the motor, and the oil pressure needle moved to the hash right of 40! I'm not that mechanically inclined, (I'm a computer programmer), but I'm thinking that the needle should have stayed on 0 since the motor wasn't turning?!? It puzzled me, but I went in to work. Came back out a few hours later, turned ignition on, needle moved to around first hash left of 40 this time. I had to drive, so I started the truck, ran my errands, then noticed that the gage was reading normal (rise on accel, fall on decel/idle).



I am assuming that I have a faulty sending unit and / or gage? I was going to ground the connector to the gage to make sure that the needle would max deflect (indicating a good gage, right?) but have no clue where the connector is at. With the needle deflecting to the right when only the ignition is turned to ON and not start tells me that the oil pump is OK, but that it is either the sending unit or gage. Are my assumptions correct? Is there anything else that I should be looking at, or has anyone else had this problem?



Now, the truck only has 50,300 miles, and I have the extended warranty to go with the 100,000 on the engine, so everything is under warranty. However, how do I explain this to Dodge, when it seems that this happens only when it wants to? I mean, I could take it in there and it work fine, then get charged the labor to look it and find nothing wrong.



I live in Mississippi (between Biloxi and Mobile, AL) right on the gulf. We did have a little cold weather last night (there was a little frost on the vehicle when I got in it at 5:00a), but I have not really paid attention if the other incidents coincide with cold weather.



Is there anything else that I should be looking at, or has anyone else had this problem?

 

[Texas Diesel]

My bet is on the sender being bad. Dont let the dealer reflash it, there is some stupid TSB about it. They will reflash your ECM and tell it to ignor an out of range oil pressure signal which means you will NEVER have an oil pressure gauge again. It will read 40PSI IF the sender fails or you lose oil pressure. Ask me how I know



By a new sender from Cummins *OR* INSIST that the dealer check the sender FIRST and NOT to reflash.

 

[ramman]

It will most likely be the sender,can be replaced or as I have learned after the second one,remove the sender from the engine and gently remove the cover from the end opposite the threads with a small screwdriver,once removed you will see the wipper arm and the the rheostat coil and most likely you will see grease bunched up around the the arm contact. Take some electrical contact cleaner and clean it and snap the cover back on. If you were so inclined it can be tested before and after with an ohm meter and a air pressure regulator as the pressure is increased from low to high and the diaphragm moves the wiper arm the resistance will change proportionally. On the two of mine the pressure would drop to zero on the gage at idle and the bell would go ding ding. This my not work for all but mine has worked fine for five months now and I have a spare also. This was on a 98 12 valve which has the same sender as the 981/2-2002 I think. Good luck it may save you $40. Tim

 

[CYauch]

Thanks for the quick response.



I do not have a repair manual for this truck, and was thinking about getting one. Are there any that might stand out better than others? And would I be able to pick it up at the local Barnes & Noble book store?

 

[Texas Diesel]

Get the OEM manual, it's the best IMO. There is a number in your owners manual somewhere.