I posted this on performance trucks and havent gotten any help yet, so I am cross posting here hoping for some more immediate help.

So, I just got done swapping cam//valvetrain/head gaskets on my LQ4 truck motor due to a bad lifter. I had bent pushrods a few weeks ago, that cracked the lifter trays and let one lifter go sideways (I guess) and grind itself and the cam down.

Put it all back together. and it fires up and runs good, my oil pressure is 60psi + cold as normal. I get out and check some things in the enginebay and go for a short drive around the block. I notice a light valvetrain tap at the first stop and then notice my oil pressure is less than 40psi. By the time I get back home I have to hold the throttle at stop signs to keep the oil pressure off of zero.

I go get some oil and figure maybe my old oil was diluted. I drained the old oil and put in 5.5 quarts of 20-50 and now I have zero pressure even if I rev it up slightly. I havent let it run more than 3-4 seconds at a time this way, and have tried 3-4 times to see if the pump will prime itself again.

When I did the cam swap I did not disturb the oil pump or pickup at all.

What the hell gives here?

The new oil filter had filled with oil. I have the oilpan off. I pulled the pickup tube off and found no obstruction, and the stock o-ring was in place and in good shape. I pulled a rod cap off and the bearing looked okay as did the journal. I was afraid to pull a main cap off because I read that the fasteners would need to be replaced and a special tool may be required to remove it.

Tomorrow I will pull the front cover off and pull the pump out, and see if I can figure anything out. I'd like to know what I should be looking for, though.

IF this v8 keeps treating me like **** then I might wind up with the first turbo rotary powered denali in the world, because I could have already built and put 500 miles on one of those during the time I've been screwing with this truck.

 

You might have bumped and broke your oil sending unit. Go get another sending unit before you check your pump. The oil sending unit sits behind the intake manifold in the back.

 

when you change your oil you will see 0PSI for a few seconds
until the system primes up.
install a mechanical gauge if you question your oil flow.

 

If you ground a lobe off the cam the oil pickup screen might have picked up all the chunks it can and now is starving the oil pump. Pull the pan and look in there.

Good luck with that, Tom

 

Sender is fine. As mentioned above I drove around for a few minutes and initially had good pressure, then it slowly dropped until there was none at idle.

Then i did the oilchange and never had any afterwards. I started it 4-5 times and let it run 3-4 seconds each time, blipping the throttle slightly to see if pressure would build. There was NONE.

I have done oilchanges before and know that it usually takes about 1-2 seconds for pressure to build. Hearing your engine idle for several seconds and seeing the gauge not so much as flinch is unnerving.

 

as mentioned above, the pan and pickup are off, and there were no issues with either. Whatever it is must be inside the pump, which I havent gotten off yet.

 

I would suggest checking out the valetrain, specifically the lifters. Other possible causes may be the front cover not sealing around the main oil passages and all the oil is spilling right back into the pan.

 

Rotary,
I want to offer up a thread where I helped a guy troubleshoot oil pressure problems https://ls1tech.com/forums/generation-iii-internal-engine/774926-help-no-oil-pressure-new-motor.html. Several people have used this information to go about the diagnosis of oil pressure problems in the past few months. Some have sent me a PM asking for my phone number and I'll be glad to help you if you like.

First, read and re-read the thread so that you understand the oil system. Then, the first thing that I would do would be to take the oil galley plug out of the front-left side of the block (requires a metric allen wrench). Then slightly thread the plug back in (one revolution) and crank or start the engine. If the pump is working, oil should be coming out from around the threads of the plug. You need to know to know if the pump is working at all. Then you need to determine why you have no or poor oil pressure.

Something is wrong here, but hopefully, nothing is hurt.

All my best,

Steve

 

The lifters are all brand new ls7/gm performance from sdpc. As mentioned above that is how this fiasco started, with a bad stock lifter. I replaced all lifters, cam, manley hardened pushrods, and ls6 valvesprings. I am confident that the valvetrain is as right as I can make it.

I also used a new front cover gasket and all bolts were tightened properly. Maybe I am misunderstanding, but other than an external oil leak, I dont see what role a bad front cover gasket/install would have on the oiling system.

 

Thanks for the help and the link. I took the pump out and apart and saw no real issues. The regulator piston was at the top of the barrell and when I took the spring out from underneath I was able to slide it out with reasonable pressure so I am not convinced that it was stuck open. There was a very little bit of sediment in the bolt at the bottom. I cleaned and checked everything. There is mild wear on the lobes of the rotors but nothing that looked bad. I put it all back together and am about to reinstall it on the engine. I did add 3 small flat washers under the spring as shims to perhaps bump pressure up slightly. This is a trick we use with some rotaries to obtain extra oil pressure from stock components.

I will then put the pickup back on, thread the front cover and oilpan on with a few bolts, install the crank pulley and oil cooler lines and fire it up to see if I can get pressure.

I was nervous as hell trying to let it run after the oil change with no pressure and the engine tapping and clacking loudly. Maybe the 4-5 seconds of runtime was not enough to fully fill all the gallies? The oil filter was full of new oil after the cranking, even though I had not filled it with oil myself.

How long is too long to let an engine idle (1200rpm cold idle) without oil pressure?

 

let it run if you dont see anything in at the most 7 seconds kill it.

 

Well wtf. I reassemble the oilpump, packed it with a little vaseline to help it generate suction (I do this on some rotary builds with long pickup tubes). Reinstall the pump, pickup, front cover, crank pulley and oilpan and put the 20-50 back into it. Hit the key and I have immediate oil pressure.

However it is still a little lower than normal. On cold startup using 5-30 synth, I would usually see around 70. I saw about 50 this time. I have not yet installed the waterpump housing and such so I only let it run about 30 seconds, and pressure seemed stable at 45-50.

Could the new lifters not be fully filled, and thus resulting in lower (than before) oil pressure somehow?

Before I put that f((*&*nt front diff and steering stuff back together, does anyone here think that I should wait a few days to get my hands on a new ls6 or melling oil pump? OR just put it back together and run it as is?

 

RotaryResurrection,
I'd just go with the pump that you have, get the oil up to normal operating temperature and drive around at moderate engine speeds for 20 to 30 minutes. The lifters should get quieter within five to ten minutes and then sound pretty normal by the end of the 20 to 30 minutes. With this engine series (or any other) the main thing that I replace every time is the oil pickup tube O ring. It needs to be lubricated and pressed together with some duck bill pliers (or similar) before installing the bolt. The intent of the bolt is to hold things in place, not to be able to pull the pickup tube into place within the oil pump.

Keep us posted in a few days as to how things are going.

Steve

 

did you not submerse them in motor oil before you put them in? If so they probably wont pump up right away when you run the motor...I always soak mine in oil first.

 

Is this the first time you have run 20-50? It is possible that even though it is a thicker oil, that it could cause your o/p to be slightly lower than it was previously until it warms up. Since it is thicker, the pump will have a harder time pumping it and will not pump as much of it while it is cold.

 

Thanks again for your continued help. Seems that every post I read during searching, regarding oil pressure was "the oring this, the oring that, you screwed the oring up, replace the oring, and if that doesnt work then replace it again!". My oring was blue and looked perfect, was still pliable and still fit the pump and pickup snugly on both surfaces. I used some of the vaseline that I packed the pump with to hold the oring inside, then just slid the pickup tube inside it and put the bolt through the retainer plate. I don't really see how this is such an issue for a lot of people...on the engines I build there are much smaller orings that tend to slip out of place much easier, so I am used to having to use assembly aids to hold them in place.

IN any case I am confident that the o-ring was not an issue before nor will it be now. For some reason my pump would not prime with oil after the oil change...but this time I literally had oil pressure within 0.5-1 seconds of startup.

I will probably run this 20-50 oil for a day or 2 as a "rinse" and then do another change to the standard 5-30 castrol synth that I have been running.

 

Most of the posts i read regarding the subject suggested that it would be pretty useless to do so, other than just coating them with oil during assembly. And the hole inside seemed so small that I did not think oil would simply drain into them without being forced in by 40-70psi of pressure. Is it standard procedure to soak them?

 

When I first got the truck I put some 20-50 in it for a couple of days to see if it changed the "GM sewing machine" click clack at idle, but it did not, so I just went back to standard 5-30 as recommended and have run that ever since. Oil pressure at the time did not change that I noticed.

 

alright now, I'm about to get really pissed.

I put it all back together and let the engine run until it warmed up, and then probably about 20 minutes more while I cleaned up my tools and such. Then I went for a drive up the road, keeping it out of overdrive so the rpms stayed between 2000-3000 to help pressurize the lifters.

With the oil warmed up I am once again seeing VERY low pressure. At idle I see 10psi steady and from idle until about 3krpm (I havent went any higher) I see steady 20psi.

I guess I'm about to order a f*&^ing oil pump and prepare to do the same job all f*&^ing over again.

 

You might want to replace the cam retainer plate.