| From | Message |
wil bridges
Dodge Dakota
JOIN HERE
5/23/2003
00:54:17
|
 Subject: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
Hello, I have heard the oil pressure guage does not directly measure engine oil pressure. The oil pressure is calculated by the ECU based on engine rpm and makes the guage register the guesstimated pressure....any one know if this is true. Supposedly dodge did this to solve a problem with people complaining about low oil pressure..
Thanks,
Wil
|
98Durango360
Dodge Dakota
JOIN HERE
5/23/2003
08:31:49
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
I really doubt thats true, but I guess its possible. If it is true then Dodge is pathetic and I don't want to buy any more of them. Oil pressure is very crucial in diagnosing many engine problems, not to mention if you are low on oil. Can't be true. Nope, don't think so.
|
Mike N
Dodge Dakota
JOIN HERE
5/24/2003
20:25:51
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
I have a '98 Dodge 1500 with 70,000 miles and a '88 Dakota With 187,000 miles both v6's and both of them register the same low oil pressure. The ECU "guesstimating" the oil pressure is an interesting question, is this a mechanical gauge?
|
NDakota
Dodge Dakota
JOIN HERE
5/24/2003
21:21:02
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
Hey guys,
I have a Chilton's manual, and the specs indicate that the minimum idle oil pressure is 6 psi for that engine. Other than being freaky, that would tell me that the gauge is way inaccurate, however there is an oil pressure sending unit, so I'm thinking that it does measure oil pressure, but you can disregard the numbers on the gauge face.
Hope this helps!
Ryan
|
Wil
Dodge Dakota
JOIN HERE
5/25/2003
00:03:54
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
It would be interesting to see the part number for the idiot lite sender and the sender for the guage packade with 0-110# guage. The Chiltons manual is correct for a typical idiot lite sender, usually they switch at about 6-10 PSI to say you have pressure. Does anyone have a wiring diagram for a '98 5.9 engine (or a 5.2) does the wire from the sender go to the guage or to the computer????/
|
jjj
Dodge Dakota
JOIN HERE
5/25/2003
09:19:12
|  RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
All newer engines idle with just a few #'s of oil pressure. Most idiot lights are set for 3# and 6-10 at idle is corrent, you just don't need more and it cost HP and mpg.
And 98Durango360 if you are expecting an oil gauge to tell you if you are low on oil.... well let's just say by the time you would notice the gauge it would be too late.
Jeff
|
jtha03
Dodge Dakota
JOIN HERE
5/25/2003
16:38:54
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
All 3.9, 5.2, and 5.9 engines send a signal from the sensor to the PCM relating to engine oil pressure, this info is from the factory service manual, tied into the same circuit is the fuel pump module. There is no mention of how pressure is determined, most likly by varying resistance of the sensor. If you doubt the pressure reading of the factory electrical gauge install a tee fitting and a mechanical gauge either temporary or perminate.
|
Wil
Dodge Dakota
JOIN HERE
5/25/2003
21:44:46
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
I think we are missing the point here...... historically in the automotive world if you had a analog guage, you also had a analog pressure sender (however cheap or inaccurate it might be)that DIRECTLY modulated the the guage to represent ACTUAL (again accuracy is questionable) oil pressure at a given rpm. If Dodge has changed this to represent whatever they choose to guestimate from the electronic control unit based on rpm, it is a fraudulent representation of a historical precedent. It is acceptable that the oil pressure signal go to the electronic control unit ALSO to allow control of the fuel pump upon oil pressure loss, but if the sender doesn't directly control the movement of the oil pressure guage, it is fraud!!!
Wil
Analog Sender...................analog guage
|
|.....Elect.Cont.Unit......fuel pump
|
jtha03
Dodge Dakota
JOIN HERE
5/25/2003
22:17:44
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
I dont follow your reference to analog gauge and analog sender, an analog gauge is one that shows its readings with a dial ( as on Dakotas ) vs a digital readout but a analog gauge can be either electrical ( as on a Dakota ) or mechanical. Mechanical gauges are more accurate. For years oil pressure, water temp and other gauges have used variable resistance sending units to transmit the signal to your dash gauge.
|
Wil
Dodge Dakota
JOIN HERE
5/25/2003
22:42:38
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
There are two methods used for the past several years to indicate presence of oil pressue. One being the idiot lite and its associated sensor which is a pressure switch, ie, when a certain pressure is reached, it opens or closes a circuit causing the idiot lite to turn on of go off as the case may be. The other method using a analog sender(perhaps a variable resistance) that goes to a guage marked off in oil pressure increments, ie analog. The movement of the needle is proportionate to the resistence of the sender. A third version which is not typically used by detroit anymore is the pipe/tube from the oil pressure source going to the analog guage....been know to break and squirt oil everywhere...messy but typically pretty accurate.
|
sandman
Dodge Dakota
JOIN HERE
5/26/2003
00:52:43
|  RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
It is irelavant were the signil goes from the sender before getting to the cluster. All that is important is that the information is accurate.You might notice that your cold oil pressure is maxed out even at idle. After driveing 20 miles when you go to idle the oil pressure drops to 12 o'clock postion even though the RPM are the same at idle cold as when warm for the most part. You might also have noticed that different oil's,grades, and temps make the oil pressure guage read differently. Their is proably some buffering of the guage to make it more linear and to reduce eratic reading but it seems to be close to real time. If they were going to go off RPM then they would not have installed a senderright next to the oil filter! Their also would not be an idiot light of switch to the fuel relay because if you idea was right then as long as you had RPM's then the computer would always predict an oil pressure and show it even if the crank case was empty. Buffering yes, little bit of funny math to make it less eradic yes but all out false readings hard to belive!!! I belive 3-4 members have already tested your theory about 2 years ago by T'ing into the sender port and hooking up a mechanical guage.
|
Wil
Dodge Dakota
JOIN HERE
5/26/2003
22:44:58
| RE: Oil Pressure 5.9L 1998 1500
IP: Logged
Message:
It is irelavant were the signil goes from the sender before getting to the cluster. All that is important is that the information is accurate.
So its ok for the doctor to guess at your BP, just as long as he is lucky enough to guess the actual pressure?
You might notice that your cold oil pressure is maxed out even at idle. After driveing 20 miles when you go to idle the oil pressure drops to 12 o'clock postion even though the RPM are the same at idle cold as when warm for the most part. You might also have noticed that different oil's,grades, and temps make the oil pressure guage read differently. Their is proably some buffering of the guage to make it more linear and to reduce eratic reading but it seems to be close to real time.
The characteristics of cold/warm oil vs rpm should not be dampened out of the pressure indicator, engine oil pressure variations vs temp and rpm are valuable indications of whats going on under the hood, especially if you tow anything in hot weather.
If they were going to go off RPM then they would not have installed a senderright next to the oil filter!
What engine are you talking about, the 98 5.2 does not have a sender next to the oil filter.
You missed the logic, AFTER the pressure switch trips at 6-10 psi (or whatever) I a suggesting they use RPM to calculate a oil pressure to suit their purpose.
Their also would not be an idiot light of switch to the fuel relay because if you idea was right then as long as you had RPM's then the computer would always predict an oil pressure and show it even if the crank case was empty.
I would presume dodge is honest enough to turn off the fuel pump if the idiot switch doesn't show any pressure.
Buffering yes, little bit of funny math to make it less eradic yes but all out false readings hard to belive!!!
If you think the pressure variations that occur because of temp/rpm is 'eratic' then you would do well with a lite, the point of a analog gauge is to see it move based on the conditions.
I belive 3-4 members have already tested your theory about 2 years ago by T'ing into the sender port and hooking up a mechanical guage.
You still missed the point, you can average enough new engines to build a pressure profile and duplicate that profile to the gauge based on rpm, problem is the profile doesn't change as the engine ages and gets greater bearing clearances, etc, is your oil pressure really the same at 300k as 1k miles, I also find it interesting that there is damn little difference between oil pressure in my engine cold vs hot at specific rpms, its about 30# at idle (hot or cold) and 70 psi at 2000 rpm hot or cold..
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
