No oil pressure!

[m37jarhead]

Newly rebuilt engine was started Saturday. No oil pressure shown on gauge. Removed sending unit from the oil tube coming out of left side of block.
No oil comes out of the tube when engine is running. Removed lines to oil filter; no oil comes out of the block from either of these connections when
engine is running.
Removed the new oil pump and inspected. Meets all specs for a new pump. Primed pump and installed. Still no oil pressure with engine running.

I fear doom and destruction.

Any advice appreciated.

JB

[HingsingM37]

JB,

Odd that there would be nothing? Is sounds almost as if you are not pulling oil from the sump? The flow is as follows:
Oil strainer to pump, pump to steel line (you didn't leave this on the bench did you? just kidding ) which flows to cam , block, and crank galleys , oil filter input (side line on can) and
check valve port. Then it all comes back via the bottom line of the oil filter. This is to the best of my recollection. The guys will correct me if I am inaccurate.

When you say "Newly rebuilt engine", what all was done? Was the crank turned? Oil galleys & block cleaned thouroughly ? Oil pressure check valve functioning? There should be some oil pressure somewhere if the pump is functioning correctly, which leads me to believe perhaps something is amiss on the suction side?

My two cents. Good luck.

[powerwagontim]

When I was getting ready to start my rebuilt engine, I tried cranking it without the ignition on to build pressure. I couldnt get anything. I took an oil filter cannister and made a pressure oiler out of bits and pieces around the shop. Forced the oil through the system and then showed pressure on the gauge. When I fired it up, I had good pressure. I also had a good mechanical gauge connected rather than trust the old unknown electric gauge.
Tim

[m37jarhead]

Block "dipped", crank was ground, cylinders honed, new bearings for cam, rods, mains, and new rings. Washed block, rods, pistons, crank and other internal parts with hot soapy water. Used "bottle" brushes on all oil holes and gallies. Towel dryed and forced air pressure through all orafices. Coated all bare metal surfaces with either oil or assembly lube. My goal was a medicinally clean short block assembly. As I said, new oil pump was primed with oil before installing.

The oil strainer was throughly cleaned and installed along with the "crossover" (?) pipe. But maybe there's still some kind of suction problem. I'll pull the
oil pan today and take a look. Not a big job but still a pain. More on what I see later.

I don't have any kind of rig to pressure up the oil system but maybe I can put together something. Not a bad idea to pressurize the oil systems before
starting a new engine.
Thanks for the input and any other thoughts.
JB

[Carter]

I know this will sound dumb but you did add oil didn't you? Your posts do not mention it.

[m37jarhead]

Not a dumb question at all. I've certainly had my senior moments before. Yes I did add oil to the crankcase and
also filled the oil filter canister before starting the engine. Dip stick showed almost to the "full" mark.

This morning I drained the oil and dropped the oil pan and found the "L" shaped pickup tube was loose.
This is the tube that holds the round intake screen. The tube was not ready to fall out or anything close but I could
turn it quite easily by hand. Gave it another full turn or two and now it's tight as a drum. Aligned the tube with the bolt on
the bearing cap as shown in the TM. Maybe the oil pump was sucking air through this not to tight threaded pipe.

I also jury-rigged a pressurized vessel to pre-load the gallies with oil before attempting to restart.
Thanks for that tip.

Hope to have good news for all of you tomorrow. Will advise..............
JB

[powerwagontim]

Good luck, we are keeping our fingers crossed for you!
Look forward to hearing the results
Tim

[MSeriesRebuild]

Loose tube was likely the issue if loose enough to allow for an air leak.

My biggest concern at this point would be wondering what damage has been done due to running the engine with no oil pressure. I'm sure that time was short, but it only takes a moment to create big issues without direct oiling to critical areas.

[m37jarhead]

Charles and other people posting responses:

I've started pulling rod bearing caps and so far have found no unusual wear. Next the main bearing caps.
Hopefully nothing major there. After removing the bearing caps on the rods they dripped plenty of oil.
No telling about the cam bearings. I'll also re-prime the oil pump and pressurize the gallies before
restarting.
The interior parts of the re-built engine were generously slathered with a special assembly lube.
That may have helped.
More on the final results when I get it all back together.
Thanks for the input from all..........
J B

[MSeriesRebuild]

1 other thought that comes to mind, did you apply thread sealer on the threads of the oil pick up tube? The threads are NPT (pipe threads), they will leak and come loose if not sealed. Use either high temp thread sealer or a premium quality teflon tape to seal and lock the threaded connection. The fittings that the cross tube nuts thread into are also NPT where they thread into the block, they should be sealed also.

The assembly lube likely saved your hide, no engine should be assembled without it.

[m37jarhead]

Charles:
Thanks for the tip and reminder. I used Permatex Ultra Grey RTV Silicone gasket maker on the down tube this time.
Torqued the tube very firmly and aligned it with bolt head on the main bearing cap as shown in the TM. My hesitation
to over-torque the NPT threads lead to a mistake. Another lesson learned and stored in the memory bank.

I used Permatex Aviation "Form-A-Gasket" sealant liquid on the horse shoe shaped tube. Also torqued these fittings
and nuts very stout.

I'm told the Permatex Ultra Grey is the latest and greatest silicone gasket maker used on Hondas and other
high temp motors in place of traditional gasket material. Supposedly has "outstanding oil resistance" and
625 degree F. heat resistance. We'll see how that goes.
I've always believed that we shouldn't be the first to try or the last to buy but Ultra Grey has been getting good
marks from the automotive community.

Checking main bearings tomorrow. Pray fur me........
Thanks again for your input.......
JB

[MSeriesRebuild]

Silicone on threads is not a good idea. That type of sealer is for sealing flanges. You need to use a sealer that is designed for threads, such as Permatex high temp thread sealant. It is designed to seal the threads and lock the fittings from vibration loosening also. I would strongly suggest removing the fittings, clean off all the silicone and redo the job using a product that is correct for the job.

[m37jarhead]

OK, good. I've got several of those small tubes of Permatex High Temp Tread Sealant. Item# 765-2648.
Since I'm still checking the mains today, I can remove the down tube, clean it and apply the above
recommended Permatex Sealant. Thanks for catching me on that error.
JB

[Wayne64]

I have scratched my head for years wondering way Dodge elected to drive the dizzy off the pump, instead of the the distributor driving the pump. If the 230 6 was more like say a SBF or SBC then you could prime the engine before the fire up and check there is ample pressure. BTW years ago when we would build a SBC that pickup tube would get brazed to the pump housing. They had a tendency to vibrate loose in race conditions.

[m37jarhead]

The oil pickup tube was removed, cleaned and re-installed with Permatex High Temp Sealant.
Getting the tube oriented to the main bearing bolt was difficult. The threads on the tube are
NPT's and almost prevented the correct positioning of the tube. It tightened up well before
the correct position. A little more friendly persuasion, or call it "un-friendly", finally got the
tube oriented spot on. Oil pan installed and re-primed the oil pump. Not trusting the old
oil sending unit or gauge, I temporarily installed a 0 to 60 psi gauge off of the same oil
port used by the sending unit. Happy to report 40 psi almost immediately after re-start.
Now the old, rebuilt 251 c.i. purrs like a kitten.
Thanks to all for the help on this post. It's much appreciated.
JB