need help with 1998 dodge ram....

[hrsp]

truck is a 1998 dodge ram 1500 5.9l 4x4 with 140kmiles.


truck was running great until yesterday when all of a sudden at a stop light i lost all oil pressure...light changed and i was gonna pull up out of the way and then it shot right back to where it normally sits...i was like 1 mile away from my dads so i said im gonna try and make it there..the whole ride home it was normal til i stopped and then it did it again...

today i started it and when it was cold it ran fine in the driveway...after it warmed up the oil pressure dropped to 0 again...if i brought the rpms up to like 1k the pressure would shoot back up...

So any ideas what it is? i dont wanna drive it a blow it up...it has 140k and ran great..i gave it an oil change last week and it has been taken care pretty good i knew the last 2 owners.. Thanks in advance!!!

[Moparjim]

Sounds like it may be your very lucky and its just an issue with the sensor/gauge/wiring. It seems odd that it would randomly lose oil pressure then get it back again.

First thing I would do is confirm that it actually is dropping all oil pressure... either get another gauge on it to be sure, or was it making any noise like lifter tick etc? If it trully had no oil pressure it would be ticking and etc like crazy.

[Moparjim]

I notice you seem to have the issue at idle. Its normal to have lower at idle obviously but you seem to indicate that it is either 0 or shooting back to normal. The sensor may have an issue below a certain pressure the variable resistor in it is shorted, or maybe something like the lower voltage at idle is affecting it.

[hrsp]

yeah its always been right around 38-40 at idle and a lil higher when cruising...but now its either at 38-40 or 0 and the check gauges light come on...when started cold it sounds normal...after it warms up it does sound different and there seems to be more engine noise... When it goes down to zero and i hit the gas to bring the rpm's up to around 1k the pressure goes back up to the 38-40 range and if i keep the rpm's at 1k the pressure stays up...when i let off the gas it drops instantly to 0... I just did an oil change last week but when i checked it the day this happened ( that was my first thought like i had no oil in it) it read high on the dip stick..i checked it a few more times and it always reads like there is to much oil in it...That cant be i just did the oil change myself and i know how much i put in...i dont know if that matters but im trying to give all the details i can think of...

[BR3W CITY]

I've had this issue on a few different vehicles;
My rx7 had this and it was just the sensor. The connection was a small female spade terminal that barely made a connection and the oil psi would jump around or go right to 0.
My chevy van also had the issue. We never found the cause but it would go to about 3psi @ idle and then go to 30ish while driving. You could rev and watch the oil pressure bounce. This started at 137k and did it up through almost 160k when we finally sold it out of the fleet.

[BR3W CITY]

what about dying oil pump/damaged impeller? This was the suspected cause on my chevy van but like I said, it never died so we never opened it up.

[WickedSix]

had this happen with guage on two vehicles and it was corrosion in the sensor connection.... the only thing that bothers me is on both vehicles I had this happen where it'd drop oil guage at a stop...mine never lit the idiot light

[Moparjim]

Sometimes the idiot light is a seperate simple pressure switch, and the gauge is a sensor. Some vehicles there is just a sensoror and. It runs the gauge and then the light is triggered by a low sensor reading as well. I still be this is your problem, find that sensor and its connection and check it out.

a problem with the pickup, oil pump or impeller, etc. In every case I've ever seen of or heard of doesn't just go from 0 to normal with a few hundred more rpms. A catastrophic failure in the oil system will result in 0 and stay there, and a wear type issue normally would have crept up as lower and lower oil pressure across the board and at all rpms, and again wouldn't just pop up nor would it fix itself with the enginee revved just a little off idle.

[Moparjim]

I can't remember if you were a dsm guy wickedsix, but indeed dsms and stealth/3000gts commonly have these issues. The sensor has a loosely connected blade connector, and they also have a seperate pressure switch so the sensor getting weird or a loose connection messes with the gauge but no idiot light...

[WickedSix]

gm guy had the issue on one of my s10 and on a ford f150

[hrsp]

thanks i will try to look it up on the web to find where the sensor is on the truck so i can check it out...if anyone has free time and feels like looking for it i would appreciate it...if not i will attempt to look for it later on tonight when i got some time...thanks as always!!!

[Plum Crazy]

Id throw a oil pressure guage on it and see if its actually loosing pressure. The bad thing is, the oil pressure sending unit is on the top of the motor, next to the distributor. I have seen those switches go quite often. I have also seen alot of clogged pickup tubes on those motors.

[Russ Jerome]

Dodge related issues: check valve in oil pump sticking at RPM, will hold open releif and oil pressure will not return until RPM is lowerd and valve slams back shut. There is no spring/ball in oil filter head , its all in the oil pump.

The 90's Chrysler victom above has a horribly failure prone 2 or 3 wire oil pressure sensor at the back of the intake manifold behind dist, feeds both the ecm and dash, causes the idiot light to come on as well. Install a mechanical gauge or replace the sensor.

[Russ Jerome]

I just pulled a 1996 B 250 oil pressure sensor out if it help, mechanical gauge showed great pressure while the factory gauge showed low...hope you find the same!

[hrsp]

well it really wasnt getting oil pressure...so im gonna put in a new oil pump and new screen and hopefully that will remedy it....hope this doesnt suck to bad..lol...never done one...

[-stew-]

well it really wasnt getting oil pressure...so im gonna put in a new oil pump and new screen and hopefully that will remedy it....hope this doesnt suck to bad..lol...never done one...


Might wanna pick up an oil pump drive as well. i had one break on my dads truck once. Possibly yours is broke and at lower rpm's it skipping? Just a thought, better to have it and end up returning it than to need it on saturday night and end up waiting until monday to get it. Truck I did it on was an 85 (?) with a 318. It was a pretty straight forward, drop the pan and install the new pump, pull the dizzy, pull the drive (magnet bolted to a loooong machine screw and a needle nose to remove it) and re-install everything ordeal. I don't think a new Mag motor should be much different.

[hrsp]

it looks like the pan will drop down with out lifting the motor?? anyone know for sure if it come off without lifting the motor?? thanks

[Prince Valiant]

Even if you've got to lift the engine, you'd only have to lift it a bit....probably wouldn't even have to unbolt the trans mount either.

My guess is to plan to lift the engine...if you don't have to, great. Might be able to unbolt only one mount to get the clearance to remove it too...

[hrsp]

no update yet...been crazy busy so it sits still...might just bight the bullet and take it in somewhere and let them fix it...my one free day and it rained all fukking day...of course it did..lol

[hrsp]

any shop recommendations for this truck? the closer to hwy 100 and layton area... the better! Thanks