Engine/Transmission (1994 - 1998) Oil Press. Ques

[Mr. Cummins]

I noticed the oil pressure gauge on my recently purchased 98 3500 takes a few seconds to register once the truck is started. I sometimes takes 3 seconds or so then jumps to exactly where it should be. Is this anything to be concerned about

 

[SEmerson]

It is normal. The oil guage is one of the last things the computer turns on. You probly had good pressure on start up.

 

[Hogan]

1998 or 1998. 5 (12v or 24v) ?



On my 97 (12v) it does take 2-3 seconds for the oil pressure to come up when first started that day.



Considering where the oil filter is and the distance from there to the pick-up in the pan, plus the "cold" 15-40 oil, it's reasonable to me that it takes a couple of seconds to pump the oil up and get it pressurized.



As for the computer turning the pressure gauge on, the gauge should be active as soon as you turn on the key. The computer doesn't systematically turn the gauges on for you after start-up (notice the other gauges are already working before the engine is started).



I wouldn't be concerned with it as long as your oil pressure is normal the rest of the time.

 

[MCummings]

I just feel I should chime in hear, as I rescently purchased a 12V for myself .



On the '98 trucks the computer does infact turn the oil pressure gauge on at startup.



If you will notice/ experiment with this. Before starting your truck, make sure the HVAC switch is in a position to run the A/C, and you will notice, upon starting, that the Oil Pressure, and A/C Compressor will turn on at the Exact same time.



You have oil pressure right at startup. I've heard the Cummins, in cold conditions can see up around 150PSI oil pressure, and Dodge decided to leave the gauge "off" for a few seconds on startup to show the customer what they want to see oil pressure building, not a peak on startup (which is what I understand they do)



BTW, the '98 12V trucks have the same computer controlled dash as the 24V trucks do (through the '02 model year).



Hope this helps, and feel free to correct me where I'm wrong



Merrick Cummings Jr

 

[dodgedude30]

the engine oil psi delay is normal for all dodge diesels.

im a dodge tehc in red bluff ca and all of r trucks r like that . .

 

[jlhartak]

My 99 takes 2-4sec. to show pressure on the guage, this is normal. I have had, do have mechanical pressure guages on most all of my vehicles over the years and they all take a few seconds for the pressure to build.

 

[Hogan]

Originally posted by MCummings

I just feel I should chime in hear, as I rescently purchased a 12V for myself .



On the '98 trucks the computer does infact turn the oil pressure gauge on at startup.

The sending unit is electronic, but I guarantee you it doesn't turn it on a few seconds after start up. Why? I have a 1997, no computer, and oil pressure doesn't build for a couple of seconds when first started for the day.

If you will notice/ experiment with this. Before starting your truck, make sure the HVAC switch is in a position to run the A/C, and you will notice, upon starting, that the Oil Pressure, and A/C Compressor will turn on at the Exact same time.

Coincidence, the oil pressure gauge and A/C compressor are controlled by different things. Likely the A/C clutch and relay are energized when the alternator goes live. No computer involved.

You have oil pressure right at startup. I've heard the Cummins, in cold conditions can see up around 150PSI oil pressure, and Dodge decided to leave the gauge "off" for a few seconds on startup to show the customer what they want to see oil pressure building, not a peak on startup (which is what I understand they do)

There's no spike in cold weather upon start up, for one it doesn't make sense that there would be one, for two the oil pressure doesn't drop until the oil is warm and the viscosity drops, which is more than just a couple of seconds and more on the order of minutes.

BTW, the '98 12V trucks have the same computer controlled dash as the 24V trucks do (through the '02 model year).

Doesn't explain why the lack of oil pressure showing on the gauge exists on pre-98 trucks, such as mine.

Hope this helps, and feel free to correct me where I'm wrong



Merrick Cummings Jr

Good reasoning, but too easy to disprove by way of experience, not only with the computer-free Cummins, but vehicles with mechanical oil pressure gauges with copper tubing going straight from the block to the gauge.



Same thing happens on the Mack CH612 I drive at work. No computer, all mechanical, no oil pressure for a few seconds. It's normal for this to be the case for any vehicle, the time it takes to build oil pressure is what varies.

 

[Hogan]

Just to follow up on this with some verifiable proof for you non-believers.



I'm looking at the wiring diagram for 1994-1998 trucks (Not 1998. 5, which is when the ISB 24v was introduced) and here's how the wiring goes:



oil pressure sensor -> oil pressure gauge

oil pressure sensor -> oil pressure warning lamp



In other words, the gauge reads exactly as the sensor sends, they are directly connected with no computer in between, nothing to "turn it on", etc. What the gauge shows is what you've got, any lack of oil pressure showing after initial start is just that, a lack of oil pressure. The only time the gauge will be incorrect is when the sensor is failing.



I don't have the schematics for the A/C clutch relay on the Dodge/Cummins, the only one I have is for gassers and those don't apply.

 

[BTanzini]

If I remember correctly the manual says If you do not see oil pressure in 10 sec shut it down.

 

[SEmerson]

Just adding this becouse I got cut to shreds stateing this before. TDR issue 35 page 93 touches on the guage not getting the sending unit info right away. I know I have heard it elsewhere but at less this adds a little credibilty to my case. How ever it does seem to be a 24v thing acording to the mag. :-{}

 

[Hogan]

Originally posted by SEmerson

Just adding this becouse I got cut to shreds stateing this before. TDR issue 35 page 93 touches on the guage not getting the sending unit info right away. I know I have heard it elsewhere but at less this adds a little credibilty to my case. How ever it does seem to be a 24v thing acording to the mag. :-{}

Want to be sure?



Start your truck first thing in the morning and time how long it takes for pressure to show on the gauge and then let it idle for 10-20 seconds, then shut it down and start it back up, again timing how long it takes for pressure to register.



Cold (Dry) starts always take longer to build pressure. It takes 4-5 seconds first thing in the morning for pressure to register on my 1997 12v. After driving to work, I can shut it down and start it back up again and have pressure register within 1 second of engine start.

 

[BTanzini]

Originally posted by SEmerson

Just adding this because I got cut to shreds stating this before. TDR issue 35 page 93 touches on the guage not getting the sending unit info right away. I know I have heard it elsewhere but at less this adds a little credibility to my case. How ever it does seem to be a 24v thing accordion to the mag. :-{}

I have a 96-12v and the oil pressure takes about 3-4 seconds to register also. One thing I have noticed when I change my oil filters, is the oil level in the filter is down about 1/3-this happens every time I change filter at least I do not have to worry about spilling oil out of filter while changing, not sure if it is normal or not or if it contributes to slow gauge pressure, no matter what the weather (hot or cold).