04.5 oil pressure question

[Lmoore1624]

My new 3500 dually diesel has just over 2K miles and I notice at hot idle the oil pressure drops off to the low side of the "U" that surrounds the oil pressure needle. At normal cruise, it carries around 40lbs. Is this a matter of

concern? Thanks!!

 

[jwilliams3]

No matter, the chrysler gauge in the dash is dummy gauge and it not accurate.

The engine's only sensor for pressure is a switch that reads "ok" when it hits 7psi or greater of pressure.

The needle moves with RPM to simulate things.



--Justin

 

[Dog Licked Racing]

My 3500 dually diesel does exactly the same thing (450 miles), the dealer (their value is still TBD) says all is fine, the manual specs at least 10PSI oil pressure at low idle and this seems to be the guages reaction to idle level oil pressures.



Does anyones 04. 5 oil guage react differently?

 

[sag2]

The gauge is a virtual gauge. It really does not matter where it reads, as long as it reads above zero. As it was said, the gauge is really a 6-7 psi switch. as long as there is more than 7 psi, you are fine. The cluster is making up the reading based on temp and rpm.

If you want to prove it, pull the wire off the sensor (drivers side in back of the pump) and the gauge will read just like it always does!

 

[Bertram65]

I have a hard time believing the gauge is not accurate, mine varries pressure on outside temp, engine temp, and RPM if it is very cold it reads higher, it the engine is cold it reads higher, once it is warm as the RPMs rise it increases. Perhaps the gauges in earlier trucks were just enhanced idiot lights but based on how many varriables mine seems to react to it would be a greater effort to make it appear real then just read the presure.

 

[rbattelle]

I have a hard time believing the gauge is not accurate, mine varries pressure on outside temp, engine temp, and RPM if it is very cold it reads higher, it the engine is cold it reads higher, once it is warm as the RPMs rise it increases. Perhaps the gauges in earlier trucks were just enhanced idiot lights but based on how many varriables mine seems to react to it would be a greater effort to make it appear real then just read the presure.

It's fake. Get yourself a service manual or do what Sag2 said in order to prove it to yourself.

 

[Pawpaw]

I have a hard time believing the gauge is not accurate, mine varries pressure on outside temp, engine temp, and RPM if it is very cold it reads higher, it the engine is cold it reads higher, once it is warm as the RPMs rise it increases. Perhaps the gauges in earlier trucks were just enhanced idiot lights but based on how many varriables mine seems to react to it would be a greater effort to make it appear real then just read the presure.

Believe it. According to the wiring diagrams, it's not an "Engine Oil Pressure Sending Unit", it's an "Engine Oil Pressure Switch".



The entire engine is run by a computer that has access to ambient temperature, coolant temperature, engine RPMs, and that switch to tell it that there is oil pressure. It only takes a few lines of code to make the gauge needle dance so well it'll fool ya.



Bob

 

[JMcCoy]

Can a sending unit be put in it's place or will this set off engine codes?







'98 12 valve 4x4 47RE 2500 BFG M/T

 

[Pawpaw]

Can a sending unit be put in it's place or will this set off engine codes?

Since the switch feeds directly to the ECM, removing it would set off a code. Having a sending unit feed the computer would proably do no better.



You could put in a tee and run the switch off one side and a sending unit to an aftermarket gauge on the other side.



Actually, that's what I would like to do. I want to put an x-monitor on the dash with EGT/boost/transmission temp, and an analog oil pressure gauge in a SRT-10 pillar.



Bob

 

[rbattelle]

What size is the oil pressure port where the factory switch is located? I know someone on here has a pressure gauge installed there but I can't remember who...

 

[Lmoore1624]

Thanks gentlemen for all the info ... . I still need to decide if I need a REAL oil pressure guage or not !!

 

[DrDeltic]

Need 3rd Gen ecm/pcm wiring&pinouts

Hi
anyone have 04.5 wiring diagrams, ecm/pcm pinout positions for crank and cam sensors?
Got into a mess following up on "repair" started at out-of-town shop, but not finished. They replaced CP3, fuel pressure sensor, lift pump in tank (which runs), wires to crank sensor and new sensor (cam/crank sensors look like same part number, are identical)
found twisted 3-wire groups to crank and cam sensors with broken wires, routed to front plug at ecm/pcm pins 24, 32, 54 are supposed to be crank signal. Wires look like (1) dark green, (2) tan/yellow, (3) brown/orange
Cranks, No Run, No Start.
Thank you!

 

[sag2]

This should help.

 

[RVTRKN]

I have a hard time believing the gauge is not accurate, mine varries pressure on outside temp, engine temp, and RPM if it is very cold it reads higher, it the engine is cold it reads higher, once it is warm as the RPMs rise it increases. Perhaps the gauges in earlier trucks were just enhanced idiot lights but based on how many varriables mine seems to react to it would be a greater effort to make it appear real then just read the presure.

The dash oil pressure gauge is not accurate nor is it real, the reason it seems to be, is the computer uses an algoretheum to simulate the pressure. It's designed to simulate the pressure to fool you into thinking oil pressure is good and it has no accuracy what so ever. As posted, when the pressure goes above the closing pressure of the sending unit, it sends the signal to the ECM to tell it that pressure is present and it's safe to run the engine.

I installed a sending unit above the oil filter housing where a 1/8" NPT port is located. My dash gauge will show @ 35psi, when the actual pressure will be @ 20psi and at 2000 RPM the dash will read @ 40psi when the actual pressure will be @ 65psi. Also, the oil pressure at a cold idle will be @ 65 psi, and at a warm idle, it'll read @ 18-20 psi.

 

[brods]

Lol quoting a 12 year old post. Tons of ancient threads pulled up lately, probably that stupid "similar thread" crap at the bottom of the page. We all need to look at the post dates before trying to help someone who has probably already go rid of the truck in question!

 

[promisedland]

Ahhh, but like good wine.... it just gets better with time...

 

[sag2]

Diagnostic info for no start