Engine/Transmission (1994 - 1998) Oil pressure

[Philsram]

I have a 1995 3/4 ton diesel 12v with an auto transmission with about 133k miles on it. The problem I have been having lately is the oil pressure droppes :{ out after the engine oil warms up. When the truck is cold and first starts up the oil pressure will climb to over 40 psi and hold. When the engine warms up the pressure just bottoms out. The engine sounds normal and temp in normal. Is this an oil pressure switch problem or something else. :{

 

[rabsyeeha]

I have an '01 that's doing something similar, except there is no real pattern to it. So far all of the research I've done points to a faulty sending unit. Hope that helps.

 

[RT66DOC]

It's usually the sender. You can check by putting a (real) mechanical gauge on it at the port on top of the oil filter housing.

 

[JGK]

Philsram,



What do you mean by "bottoms out" and "drops out" when it warms up? Do you mean it goes to 0? Do you get a 'check engine' light and/or alarm when this occurs?



Mine used to drop to 0 when I was shifting between reverse and 1st or 2nd and low revs as in maneuvering around in parking lots, aftef it was warm. But I bumped the idle up just a tad, which raised the oil pressure at idle slightly and I haven't had the problem lately. But I'll check the oil pressure with a mechanical guage as suggested just to double check.



-Jay

 

[CumminsPower98]

I had/have this problem on my '98 12v. First time I replaced the sender with one from Carquest and that fixed the problem for quite some time. It then started doing it again some so I got a sender from the dealer for a lot less money (looked the same) and this time it didn't fix the probem but only got worse. So today I am hoping to get the TSB 08-22-99, which is for my year truck and involves updating the PCM software with calibration changes. http://dodgeram.info/tsb/1999/08-22-99.htm



I don't see a TSB like this for your '95 so you probably just need a new sender.

 

[K5IP]

Normal pressure when it is cold and low pressure when warm has all the indications of something other than insturmentation.

An external (manual) pressure gage will give you the information you need.

Even if the pressure drops to very low levels when warm and at idle. I think the Cummins will live.

Rog

 

[CumminsPower98]

Well I went to a five star today in Indiana for the first time to have the TSB done and had a bad experience. I went in with the TSB number in hand and told them what was wrong and what needed to be done. How hard is that?? Well they get done screwing around and tell me there is no such TSB for my truck and that my sender is bad and they want to replace it for over $100. I said no way, I have already replaced it twice and it needs the PCM reprogramed. I didn't have time to mess around cause I had a trip to get going on so I left. I took off and noticed my fuel pressure gauge was now at 0 so I pulled over and find they pulled my pressure sender hose off while fishing around in there checking oil pressure, which was fine by the way at 60 PSI idling. So now I have fuel all over the place. Anyway I replaced the hose cause it was getting tired anyway, hosed the mess off and headed out. I called up my dealer in SLC, UT and they told me that yes this TSB does apply to my truck. Anyway this Indiana dealer charged me $41 and change for diognostic work that wasn't even needed and didn't fix the problem. I will go back with laptop in hand and show them the TSB and hope they can get it right. I'm sure glad I do all my own work!!! I don't know how they got 60 PSI at a hot idle but that's what the invoice says???

 

[RKraiza]

Hi there. Had the exact same problem with mine. Here's the fix. Locate the oil filter houseing. Looking at it from the front of the truck, look at the top of the filter housing, you will see a3/4 inch plug/nut, under this nut is a spring. The spring regulates the oil preasure. More tention on the spring, more preasure. Place a flat washer or to on top of the sring and retighten the 3/4 inch plug. You will notice around a fifty pound increase in oil preasure. Be carefull not to overdo it on the washer spaceing. Start with one, then two and note the difference. Most likely the spring is week and is collapseing early as in mine. let me no how it goes.

 

[CumminsPower98]

I'm stilling going to get the PCM update somehow. My oil pressure is fine. Too much oil pressure is a bad thing and can wash out the bearings, blow up oil filters and such so I'm not going to mess with that.

 

[norcalram]

How does the TSB work? is it like a recall. My 98 has been doing this for some time, mostly when slowing down at a light at idle. I have the DC sending unit, just haven't had time to replace it. since my pressure only drops while slowing , I find it hard to try the pressure guage. if I take the TSB to my local dealer, is this someting they are obligated to fix?

 

[CumminsPower98]

Update: I finally got back to the dealer here in Elkhart, IN and gave them a print out of the TSB #08-22-99 and they finally reflashed the PCM like I asked them to in the first place and it apears to have fixed my problem. My oil pressure gauge now sits just above 40 rather then well below when idling hot. The reprogram just changed the calibration settings for the gauge.



JLusher, TSB stands for Technical Service Buliten and is not like a recall. If you are under warrenty some TSB's are free otherwise it costs just like everything else. TSB's are basically updates and fixes to problems that show up after a vehicle is released. I sugest you take a printout of this TSB to your dealer in case they can't figure out how to look it up like the one here, that way you will be able to proove that you need a PCM reprogram. Here is the link again: http://dodgeram.info/tsb/1999/08-22-99.htm

 

[Andy Redmond]

Tom:



Isn't one of the quirks with the 98 up is that once the reflash (TSB) is performed and a real problem occur (true low oil psi) is that that the oil pressure gauge will not register 40 psi, even say if it was 20 psi? Maybe I'm confusing it with the Cummins fix of my desc. on a 2001 a customer went round and round with Cummins and Dodge over locally.



I will admit that it would be frustrating to hear the ding ding on the dash when it fritzes out when nothing is likely wrong other than a dummy reading to the dash.



Usually a new sensor solves the problem. . although not always as tom points out.



Good luck

Andy

 

[biggy238]

TSB's don't always point out something that DC feels obligated to replace. They just go out to point out a problem to dealer service centers and the likely fix for them.



Go to the chrysler website and fish around. Somewhere there you can enter your VIN number and all of the recalls for your vehicle. Those they are required to replace whenever the vehicle comes in for work.

 

[norcalram]

I replaced my sender a few days ago and have not had another problem with it. as for the reflash, Andy is correct. It basicly tells the guage to read 40 psi when the is any pressure greater than 6 psi at the sending unit. any pressure lower than 6 psi, the PCM tells the guage to read 0. By having the reflash done, that "GUAGE" in the dash just becomes another idiot light. After much research, i have found that to acually lose an oil pump is extremly rare, and even with the reflash, if internal pressure drops to 6 psi or lower, it will still send the guage to zero.

 

[CumminsPower98]

I am not aware of what would happen upon low oil pressure. I guess the only way to be sure is to put a real gauge on it. All I know is that it gets real annoying when the thing is chiming all the time. I did replace my sender twice. First time it lasted quite some time and then started acting up again, the next one was not much good at all and started acting up within a short time. If this reprogram prevents the gauge from reading actuall low oil pressure then I will have to put a gauge on it.