Oil Pressure question

[jasond29]

I have a odd issue going on with my oil pressure. Cold start is is around 50 and once warmed up it is about 40 on the gauge. The weird thing is when I start to make WOT pull the pressure shoots off the charts. Rises with rpms straight up to 80+. Normal driving it stays were it should be and rises and falls like normal. Is this a sender issue possibly?

This is a heads/cam car, runs great, no weird noises, no oil leaks anywhere. I just pulled the oil cooler to check for blockage and it was good. I replaced the oil cooler lines while I was at it. Also replaced the oil pressure sender about 3 months ago (broke it during the heads/cam swap).

Anyway, just curious if anyone else has seen something like this.

Thanks

[Tom, F&L GoR]

You might consider a 1/8" pipe "T" at the oil pressure sending unit and temporarily adding a mechanical gauge. I had oil pressure questions due to low pressures during ~10°F cold starts and learned the gauge read 10-15 psi lower than the mechanical.

Obviously the oil pump does not know if you are at WOT or not; it pumps based on engine RPM. Have you safely (snicker) gone to the same higher RPMs on the street as you do on the dyno? It would be very, very odd if oil pressure at 5000 RPM on street is different than 5000 RPM on dyno.

Have you pulls with the engine cool: moderate to low coolant temperature could be very cold oil temperature. Now that I have an oil temp gauge (replaced voltmeter, installed another OEM coolant temp gauge, added sending unit to oil cooler hose) I know that in normal moderate weather, highway driving, the temperature never gets above 150°F. If your dyno runs are cold oil and on-road data is warm oil, that would explain some of this.

There are two oil pressure regulators, both under the oil filter adapter. With the adapter off, you see the freeze plugs that keep them in place. Have to drill a small hole in them, screw in a machine screw and pull to get them out. The parts book is very confusing to replace relief valve springs - first time I ended up with the spring that goes inside the oil filter adapter. Perhaps the relief valve is sticking when the timing chain cover is cold?

Speaking of oil coolers, it is a huge restriction. During my winter investigation I plumbed an oil pressure gauge before the cooler and the pressure was 20-25psi higher than on the outlet. The dash gauge is after the cooler, so it only sees the low pressure outlet side. Have you added an oil thermostat or relocated the sending unit location?

The oil pressure is also measured after the filter, so the filter experiences at least 20 psi more than the gauge (cooler restriction) and maybe you want to get a good, high pressure capable filter if you're really pushing 80 psi gauge (i.e. 100+ psi in the filter). Finally, remember that pressure means resistance to flow, not more flow.

I have an extra timing chain cover (because that's where the oil pump is) and oil filter adapter from figuring out my oil pressure. If you want parts to swap in and out (or the comfort of knowing where you can get parts quickly just in case...) let me know.

All just my $0.02 from recent similar experience.

[dave6666]

try a new sending unit. They're about 15 dollars

Exactly what I was thinking Tom!

[Tom, F&L GoR]

Exactly what I was thinking Tom!

Your Honor, taken out of context! (Although kudos for the forum "reply with quote" trickery.)

Why make it simple when you can do it the long way and justify some hard-earned beer?

[Luisv]

Gauges are also known to be flaky. Mine always reads the same pressure. I may be going to the t fitting and secondary gauge.

[jasond29]

thanks for all the info, I will change the sender first and then start troubleshooting from there.

[Edward 96GTS]

what is normal oil pressure if using 0-40 mobile 1? 5-30?
tia ed

[Hathoway]

Bump.

So I decided to just take a quick trip in the Viper and got the oil can light and engine stalling from idle with subsequent fails to start and oil can light. I do not have the manual for the car and it seems like the pressure is a bit higher than when I got it but level is good. I noticed that the oil filter is a K&N and got parts like the proper filter and was going to change all fluids as soon as parts come in, then this happened today. After many failed starts and attempts to get out of a parking lot to get home I eventually parked it before it could die a 3rd time and low and behold it stayed on. I wasn't sure wtf was happening as oil pressure may have been a bit high (60psi or so) but whilst running I checked level and was good, nothing seemed out of the ordinary. I made it home through red stop lights and car never died again. Very odd. Perhaps the filter just needs to be changed as it has some blockage or perhaps has failed...

I'm just wondering if the car is being nit picky as far as the filter or perhaps is there a larger problem. I imagine it's difficult for anyone to diagnose via online forums but any speculation is welcome.

[ICPREY]

Probably got the light because your car was stalling. It's not a filter problem, that will not cause your car to stall. I would start with checking your battery then the IAC.

[Hathoway]

Probably got the light because your car was stalling. It's not a filter problem, that will not cause your car to stall. I would start with checking your battery then the IAC.

I sort of panicked when it happened as I had no cell phone on me and nowadays I don't remember anyone's phone number and no help with no tools. Car has been idling at around 500 lately, although I'm not certain it may have been that way since I purchased it. You're probably right about the battery though. Thanks for the reply.

[stuntman]

I would use an OEM Mopar filter on the Viper, which uses a bypass valve specd for the engine.

http://www.motoiq.com/MagazineArticl...intenance.aspx

Might be worth screwing one on and see if you have different readings.

[Hathoway]

That's the exact part I ordered from Roe Racing's website amongst some other things mentioned in that article.

Just started it, idles at 500, no issues, oil pressure around 50-55psi, battery at 14 volts according to the gauge, although I think it's been taking more and more cranks before the car finally starts. The previous owner(s) installed some...odd stuff imho. Ridiculous Amp, unsure what subwoofer, Hertz speakers. I even left the mirror light on the first night as I didn't even notice it being on once I got home. I'll probably replace the battery anyway. Odyssey batteries sound fantastic.