Engine/Transmission (1994 - 1998) Oil Pressure HELP ASAP!

[STPdieselhp]

I have a early 98 dodge 2500. The oil pressure guage in the cluster goes haywire when not pressing the throttle. Sitting at an idle at a redlight or in a parking lot the oil pressure will drop down to zero and the light will come on, then it will go back up to around 40 by itself. If it ever drops down to zero and you press the throttle it will come back up to where it is supposed to be. Or if you are sitting at idle and the pressure is like it is supposed to be and you pull it down into gear then the pressure will drop down to zero for a few seconds and will go back up by itself. If just does this spontaneously and sometimes it wont do it at all but it is starting to do it more often now. I have already put 2 different oil pressure sending units in the truck to try to cure the problem but it persists. Does anyone have any ideas as to what my problem is? It kinda acts like it has a short of some kind. Do you think that it could be in the guage cluster? I know that the truck has oil pressure because I have put a manual pressure guage in it and the pressure stays the same when the truck acts up so I know that something is just making the electric guage go crazy. Any help with this would be greatly appreciated. I am about to run out of options here. Thanks alot

 

[JGheen]

It could be your wiring somewhere but I personally would recommend going to a mechanical gauge for oil pressure. Just run a -3 steel braided line off the pressure tap on top of the oil filter housing and feed it to a good Autometer mechanical gauge.



Joe

 

[STPdieselhp]

well here is the only problem with that. if it were my truck i would totally agree with you on the oil guage because anything electronic has a great margin of possibility to take a ***** on ya. but the only problem is that it is a really good friends truck and he doesnt want to go that route, trust me I have tried. He wants his guage fixed but the biggest problem is that I have to figure out HOW? But thanks alot for the quick response. You guys have always been a big help on here so Im sure that we can get it figured out.

 

[esamuelson]

Mine does the same thing. I was told I need to have the dealer reflash the pcm. The oil pressure sender goes to the pcm and the pcm outputs to the gauge. If the pcm sees less than lets say 35 psi it sets the gauge to zero and trips the chime and check gauge light. If you get the pcm reflashed with the update supposedly it resets the pressure gauge to like 40 psi and you won't see it drop below until you are real low on oil pressure than it will do the same thing it is doing now. I talked to my dealer about it and he looked it up and said " what do you know you are right there is an update for that" I didn't get it done yet mainly because I don't like the idea of paying someone to make my gauge lie to me, at least this is my understanding of what is really going on. I would like to do this and than put a aftermarket gauge in so I know what the oil pressure is really doing and not some pcm telling what it thinks is going on. If I am wrong please let me know but this is what I was told about this problem. I too went through numerous sending units trying to resolve this and it would get better for a short time that back to its old tricks

 

[champspa]

put a new sending unit it , I had that happen .

 

[pwerwagn]

Mine does that too, but does it way worse if the oil level is not dead on full. Even slightly below makes it worse for some reason.

You might also contemplate raising the idle 50rpm or so. It should help a little. I realize its an auto, so you gotta be careful how far you raise it though.



--Jeff

 

[STPdieselhp]

I put a manual guage on it and when its hot in park it has 33 psi of oil pressure. Do you think that is whats causing the light to come on? So that reflash, how does it make the light not come on. What does it just add 5 psi to the oil pressure reading that you are getting electronically?

 

[esamuelson]

That is my understanding as to what the reflash does it just sets the gauge at 40 psi so the chime and light doesn't come on.

 

[CumminsPower98]

Mine started doing this a long time back so I replaced the sender and that fixed it for quite a while but then it started again so I replaced the sender once again but this time it didn't last long. Next I had the TSB done (long story about the dealer having no clue, finally having to print out the TSB and hand it to them). Anyway the others are correct in that all it does is set the gauge to about 40 psi. I think I have read that if it drops to zero at 6 psi after the flash. Anyway here is the TSB: http://dodgeram.info/tsb/1999/08-22-99.htm. Mine now stays at about 41 at hot idle where before it was a little under that.