So, I've got the classic oil pressure drop to zero issue that so many seem to have by my searching...

I have learned there's an issue sometimes with the pickup screen, and also sometimes a gauge problem...

What I haven't seem is, what's the general likelihood of being able to continue driving the truck with this issue. i.e., what's the most "likely" thing that is really the issue here.

It runs about 20 according to the gauge and (sometimes almost 30 when it's cold) - then when it's good and work it'll drop to zero every several minutes, and stay there for a few seconds, then slowly build back up to around 20....

97 Dakota Sport 180k on truck, just put in wrecking yard engine... sound ok, has NO power, and very weak oil pressure.

also, what kind of oil pressure do 318's generally run with 100k + miles??? I'd guess, by comparing to my Chevy's it should be 60 when cold and 40 when hot?

any help is appreciated

 

Looking up the 3.9 and 5.9, which should be similar, it lists 6 psi minimum at idle. At 3000 rpm, 30-80 psi. Sorry, no 5.2 in my 2000 FSM.

First thing, put a mechanical gauge on it and check the pressure. It could very well be a sending unit issue.

It could be sludge on the pickup screen, it could be a bad (worn) pump. Find out what the pressure really is, the factory gauges aren't very accurate to begin with, and take it from there.

If you haven't given it an oil and filter change, I'd start there too.

Good luck.

 

thanks for the help. it does have new oil and new filter. I'll try and get the mechanical gauge on it and see what's happening!

Thanks!

 

if the oil pressure goes up when the rpm goes up you are good. unless the oil pressure is very low. also are running one of those to thin of oil? or the oil sender might be bad. NOTE: ONLY use small steel break line tubing. DO NOT use nylon tubing. hose. copper tubing. this goes for oil lines, and transmission tubing. of course trans line is bigger.

 

it goes up slightly when it's colder with rpm... mostly floats around the 1st line (20).. it has brand new 5/30 in it, which I think it what it called for.

 

OK, mechanical gauge in place, took for drive (warmed up) -

started around 12psi, went to 18.... idle-1500rpm stays at 18... 2000 rpm + = right to 40 psi, take foot off gas, right back to 18... where it seems to stay...

(the factory gauge was showing 20, with drops to zero every few minutes, I'm presuming the factory gauge doesnt read as low as its actually running ~18psi)

Is there any chance I can drive this thing and have it be semi dependable to get to work with it running 90% of the time at 18psi?

 

I think if the pump was bad or clogged at higher rpms psi would drop for a second, maybe not sure. I run around middle of the gauge to 3/4's. Sometimes drops to a 1/4 at idle but as soon as you hit the gas it goes back up.

 

check the oil filter. it does sound low. i would use (Valvoline Premium Blue® Diesel Engine Oil
Advanced lubricant protection for diesel engines. The Premium Blue Advantage:

Unique dispersive polymer technology (DPT),with premium Group II baseoil, provides advanced soot control, and cold start protection.
Valvetrain wear protection and reduced oil filter restriction at high soot levels.
High temperature deposit control, including single and two-piece pistons, and ring/liner wear protection.
Higher TBN level and TBN retention for long-life performance, while meeting all chemical limits.
Endorsed and recommended by Cummins for use in Dodge Ram Turbo Diesels
For more information contact Valvoline Customer Service at 1-800 TEAM-VAL.) 15 -40 it works good in gasoline engines. DO NOT FLAME ME FOR SAYING USE DIESEL oil. the oil pump might be bad.

 

It's normal for the pressure to vary as you give it throttle. Your pressures are in spec so it is likely the sending unit that's going bad.

You could run a slightly thicker oil, 10w-30, if you want and see what happens to the pressure. Follow the owners manual recommendations. I wouldn't run 15w-40 in any modern engine.

 

Mine happens; mainly heat related; once you kill the engine and it builds up temps slightly; when you restart and the engine is past a certain temp; it seems the guage sits at 0 then climbs right above 20 but when i get moving the gauge registers appropriately.

I think its the sending unit. failing when the temps rise.. but thats just me. If its not real hot outside it never hardly happens.