Louie L

I have searched but haven't found an answer. Looking for an opinion.

400 plus ci LSX, fully forged engine built on a GM Performance LSX block. About 3000 miles and a handful of 1/4 mile runs.

During start up about 30% of the time, the engine will not show oil pressure in the oil gauge at start up. A small quick rev (2000-2500 rpm) and pressure will shoot up to normal. No problem with any subsequent start ups for the day. The issue may occur the next day..or not for the next month. This happens with the original sender and a new GM sender. As far as i can tell there is no wiring issues. I did not build the engine, so i am not sure what oil pump is inside.

The engine idles at 680-750 rpm in gear with 35-38 psi hot (coolant temp 195, oil temp 193).

It makes 60-62 psi at 80 mph 1500-1600 RPM (192 deg coolant temp,175 oil temp)
Valvoline Synth 10w 30.
Upon acceleration, the oil pressure follows the rpms.

Any advise on what may be going on here ? Oil pump pressure relief valve stuck?

ls1itldo

iTrader: (30)

Sounds like a gauge issue. Put a mechanial on it and see if they are they read the same.

BennyB

iTrader: (12)

yeah this would be the first thing i would try. hopefully it is just wiring or something going on with the sender.

loser98

iTrader: (3)

Oil pick-up tube seal (o-ring) is also something to think about. Put a mechanical gauge on it and confirm what's going on.

dogsballs

Mech guage. Personally prefer something like 10w 40 if any hint of oil pressure issues or to prevent

5 Liter Eater

iTrader: (5)

My vote is relief valve.

CAMSTER

iTrader: (10)

Try a different oil filter.

jcrankshaw

Hello - curious to the solution to your zero oil pressure intermittently on 30% of your starts. I have a very similar issue and would be interested in what you found?

thanks

kingtal0n

iTrader: (1)

The idea is,

install a mechanic gauge (even temporarily) to verify. Electric gauges are inaccurate much of the time; they can even read some number when the engine is off!

If the pressure is having trouble during a cold start (seems slow to come up)start with the simple things, like looking for leaks (both inside and outside the engine) i.e. Inspect the O-ring for the pickup and the pickup itself; look for damaged parts or holes where oil can leak. You might think about pressure testing the oil system. Then think about changing the oil pump.

patrick335d

your oil pump draining dry.
you have a leak where air allows to enter the pump once switched off.
Pickup tube/ seal, Too much clearance in pump, relieve valve, pump housing cover

jcrankshaw

I have been dealing with the problem since I have owned the car about 2.5 months. Started showing symptoms by the third day after oil change. After several oil changes since, with 5W-30 Mobil 1 and various filters including PF46 and Wix. Never saw an indication of the problem on the initial test drive, nor did an inspection observe it. Anyway, sender unit replaced and relocated with DPE kit and mechanical gauge. Have verified when zero oil pressure occurs the mechanical gauge is also zero. I do get what I call a slow oil pressure build up which trips the alarm, but goes away within 1-2 seconds.

Several places have suggested that it could be a spun cam bearing causing the issue, but that does not seem like it would cause a intermittent zero oil pressure at start.

At this point, it seems like it as you suggested and going down the path of pickup tube, oil ring, pump will most likely resolve the problem. That is why I was curious to the OP solution as more confirmation.

Appreciate the insight.

jcrankshaw

Sorry one more thought, it stands to reason then when oil temp is ~215-220 and at idle then the oil pressure may be lower than normal, like 15-20psi at 750rpm?

64post

iTrader: (5)

If you're willing to go through the work that is involved, you could get an oil pressure reading at the front of the block vs. the top rear where the pressure switch normally lives. On the left front of the engine is the first galley plug, it's pressure is right off the oil pump before it goes through all of your bearings, filter etc. A higher difference in pressure there vs. the rear will tell you: excessive clearance, cam bearing out of place, worn engine or something instead of wondering or chasing your tail. You'll need to make an adaptor, 16mmx1.5 plug center drilled with 1/8npt. for your OP gauge connection. you can run your motor for a few without the drive belt to get a reading. If you have a low reading up front at operating temp then of course you have pump/pick issues. Adaptor is available from Autometer if you can't make one.

jcrankshaw

Thanks! Curious why mechanics have not tried to use that to verify issue.

So I have the fitting but no crush sleeve. Trying to find a picture of the oil plug. Left side when standing in front of car facing engine correct? Why remove the drive belt?

64post

iTrader: (5)

Because the oil galley plug is behind the low mount alt bracket and the bracket and alt will have to be moved to access the plug.
if you have something else like a high mount bracket maybe you don't have to move anything, Fbody style alt. bracket is what I was referring to.