No Oil Pressure!
 

Just installed a 94 into my 90. When freshening up the motor the crank sprocket was fused on, and we had to drop the pan to take the crank to a machine shop to remove it. We installed new main, and rod bearings. The oil pump was damaged when removing everything so I bought one off Egay.

So here is the problem, when I started it today for the first time I'm not showing any oil pressure, and the lifter clatter didn't go away after about a min so I shut it down. I removed the sending unit and it shows 120 ohms with no pressure, when I blow some air through it they (the ohms) drop down to 20.

When I put resistance to the gauge it showed ~15 PSI at 47 ohms and 60 PSI at 22 ohms. So it seems like the sender and gauge are working.

I removed the oil filter and it was full of oil. I tried several more times running it for about a min to see if pressure would build without any luck.

So where am I? whats next? It obviously has SOME pressure or there wouldn't be any in the oil filter. Are the numbers I posted for the sender and gauge in the right ballpark. I'm going to get an external oil pressure gauge and see what I got.

Any other suggestions?

Don't buy oil pumps on fucking eBay?

Pressure relief valve comes to mind.

You're missing the step where you primed the new pump. New pumps will usually prime themselves on the Miata IF you crank long enough, but you have to admit that's an uncomfortable position to be in.

You can use (or make) a preluber and prime the system through the oil pump port.

This is how long it took on my new engine:

You cranked a fresh engine w/o oil pressure for 30 seconds? I'm not sure I could do that, even with assembly lube.

I've got a preluber made from a gas grill propane tank - probably cost $10 to make. Put a couple of qts oil in it, close up the valve, put 60psi air pressure in it, turn it up side with it hooked up to the pump and open the valve. Entire engine is lubricate (and pump primed) in a matter of a couple of minutes.

No shit! The car has been off the road for almost a year, family obligations got in the way of progress. this motor is just to get the car on the road while a proper build gets under way.

Thanks for the constructive help guys, I will try that when I get back into town on Monday.

*) at the turbo oil feed. It's not that drastic...

Picture of said device? Where do you plug it in?

Ok, you all know I'm a noob, but I'm working hard on this, and learning tons, so I found an old paint pressure pot, cleaned it up and drained several quarts of oil into it. I'm not turbo yet but I have most of the stuff, so I grabbed the turbo oil feed line hooked it up per Begi's instructions.


Attachment 204410


I have pumped almost all the oil into the engine at 55psi, but I don't know if it's pumping the oil into the pan or circulating it over to the oil pump. I searched for quite a while for a diagram of the path of oil in the engine I've seen here before, but couldn't find it. I turned the power on the car to see if the oil pressure gauge moved (it didn't). If I don't hear back soon I'm going to disconnect the coils and turn it over to see if its primed. I'm assuming the only way I'll know is the gauge will show some signs of life.

Attachment 204411

Attachment 204412

OR just yank out the pressure sender on the other side of the engine and crank over, (without coils. without plugs installed) and see if oil is moving where the sender is plugged in.

Just removed the oil filter and pumped a little more oil with the prelubber. oil was coming out freely. Thus I can assume that it must be getting to the pump right?

So if oil is getting to the pump, and its still not priming then that means the the oil pump, or its relief valve must be jackaloped.

Please tell me there is something else.

In most engines I've built, priming with a tank will show pressure on the oil pressure gauge. A couple of quarts of oil pressure fed to the engine should oil everything. Pull the cam cover and see if the pressure can is getting oil to the cams. Can you experienced Miata guys tell us if that is the case with this engine? I would not be inclined to start an engine without assuring oil pressure first.
Old guy, noob to Miata
Daryl

I'm stumped, gonna pull the motor and throw in an OEM oil pump.

While you have it on an engine stand, consider looking at the main, rod, cam bearings, cam lobes and the cylinder walls. It ran quite a bit with no oil pressure. If something is scuffed or galled better to find it while you have it right in front of you instead of back in the car. Pre-oiling before starting it the next time would be a good idea.
Daryl

Many lessons learned.