Z_WAAAAAZ

As the title states: started up my built VVT motor for the first time today and noticed there was zero oil pressure. I only had about 30 minutes to diagnose it but here’s all the details and what I’ve done so far.

Built VVT motor, died a couple months ago due to a spun bearing. Got a reman crank with 0.010” machined off of mains and rods, new Mazda bearings all around, rehoned cylinders and new rings, polished cam caps and journals. Confirmed all bearing clearances are within spec. Cleaned the oil pump (BE stage 2 VVT pump) and replaced the oil pump gears due to mild scoring on the outer diameter. Replaced the donut oil cooler, blew out all oil and coolant passages on block and crank before installation. 15w40 Rotella T4 for break in oil and motorcraft fl816 oil filter

Motor is running a 25 row Setrab oil cooler with a sandwich plate from the TrackDogRacing oil cooler kit. I cleaned both in a hot solvent parts cleaner and flushed them with new oil, ran them in my OG motor for about 1,200 miles with no issue, then swapped back to this motor. I cleaned and flushed them when swapping back to this motor as well. I drove my car to work yesterday morning and oil pressure and temp was fine

Diagnosis so far:

Car turned over first crank, idled at normal rpm, a little under 1000 and didn’t show oil pressure. I shut it off after 5-6 seconds.

I knew I put oil in it but I double checked that. Oil level is within spec.

I pulled the connector to my oil pressure sensor to make sure there wasn’t an issue with the reading. Pressure gauge flashes dotted lines with the connector off, 0psi while connected. Again, the sensor/gauge was working yesterday.

Pulled all the spark plugs and injector fuse and cranked the motor over for ~30+ seconds. No pressure

Pulled one of the lines to my oil cooler off, set up my phone and took a video of the line/cooler while I cranked the car over (didn’t start it) for a couple seconds. No oil out of the line or cooler.

The engine previously died due to a spun bearing but I had to fire the engine up to get it on a trailer The day after it happened. Oil pressure was varying wildly at first but then settled to just slightly lower than usual right before I got it on the trailer. So I know the pump was making pressure still after the hearing grenaded.

My only idea right now is that sometime between the motor blowing and now, the pump’s pressure relief valve got stuck open. I’d really appreciate anyone’s additional insight however because I really don’t want to blow this motor I just spent months rebuilding. Are there any other things I should check before tearing the oil pump out?

Z_WAAAAAZ

Follow up question: I have a stock VVT oil pump laying around that I can use the pressure relief valve and spring from if there’s any damage to mine. Does anyone know if the BE stage 2 VVT pump relief valve/spring are different than the stock pump? I can’t imagine they are.

Another follow-up: The oil pressure shot up to 150psi then off the gauge’s max reading at one point after I cold started the car to get it on the trailer, before eventually settling down to 20-30psi at cold idle. This is my first rodeo here but I bet that could’ve done some damage to the relief valve and spring somehow. I should’ve thought to check before putting the motor together…

Also the block was hot tanked at the machine shop so I would hope they got all of the bearing debris out of it.

rjacobs

They are kind of notorious for this arent they?

Ive read to many stories of their pumps sticking the relief valve open and went with a bone stock OEM pump on my rebuild.

Z_WAAAAAZ

Yeah based on my research so far, it looks like it.

I’m gonna pull the subframe and oil pan within the next few days. Hopefully that’s what I find.

Z_WAAAAAZ

Ok now I'm super confused. I pulled the pan and the relief valve is stuck at the top of the pump. Tight, like I can't move it. This would mean the relief valve should be unable to bleed off any pressure at all right? I can still see the assembly lube I packed the pump with hasn't moved at all from the pickup tube inlet at the pump. Really not sure where to go from here. Maybe I just need to prime the pump from the top and crank it with no plugs again?

Z_WAAAAAZ

OEM VVT gears in BE Stage 2 pump for reference.

Update: I think I found my issue.

Pulled the oil pump this afternoon and realized I was running BE oil pump gears for an OEM pump in a BE Stage 2 housing. You can just barely tell in the photo but the gears sit just a little below the top of the housing. I put my new BE replacement gears in my OEM VVT pump and they sit perfectly flush with the housing. I’m gonna install the OEM pump with the BE gears and I think that should solve my problem.

Funny enough, the pressure relief valve was actually stuck fully closed.

I’ll update this thread when the motor’s back in the car. Hopefully it keeps somebody from making the same mistake.

LeoNA

Boundary uses cheap chinese aftermarket pumps with gears they machine. The Mazda std pump uses 9.5mm thick rotors and the vvt/mspeed use 10mm. There are no aftermarket 10mm pumps so boundary mills the bore deeper in the std aftermarket pumps for the higher flow application. The passages and relief system of the aftermarket are not as good as the oem. The best option would be oe pump castings with the boundary gears. Make sure you’re careful when installing the cover plate. The screws need to be very clean and red loctited only on the threads.

Z_WAAAAAZ

Thanks Leo. I now have an OE pump with Boundary gears in it. Screws were clean and red loctite'd. Gonna start 'er up in a few hours. Hopefully all's well now.

Z_WAAAAAZ

Confirmed the issue was the gears. Cranked ‘er over with the plugs out and saw pressure within 15 seconds. Disconnected the turbo oil feed line as well and confirmed flow from there.

Don’t make the same mistake as me lol.

LeoNA

There seems to be some confusion on the pumps that you have. If you originally had the 9.5mm thick gears in a 10mm pump housing then that was 1991-2000 pump gears in a 2001+ VVT 10mm pump housing. You now have installed a non-vvt lower output pump.

Z_WAAAAAZ

If that’s the case, then two mistakes were made. This oil pump was attached to the VVT motor when I purchased it and the pump gears I ordered were for a VVT as well.

So if that’s true, the motor was running the wrong oil pump AND Fab9 sent me the wrong gears. (Fab9 has messed up multiple of my orders so that wouldn’t surprise me…)

Of course I already threw away the packaging weeks ago so I can’t confirm this.

This is never a question I thought I’d have to ask. How f*cked am I if I run the motor with a non-VVT pump? I’m planning on running 15W-40 oil in it and it’s gonna see a lot of track use. I’d assume disabling the VVT solenoid would alleviate the absolute need for additional oil pressure right? Mama didn’t raise no quitter but I don’t think I have it in me to remove the engine or change out the oil pump with the engine in the car again anytime soon…

Z_WAAAAAZ

Did some digging and found this. So there’s three different gear sizes depending on whether you have a non-VVT, VVT, or stage 2 BE pump.

I believe I have the correct stock VVT pump and BE standard VVT gears installed currently. This would also make more sense than having received the wrong gears AND the motor I bought having the wrong oil pump.

The pump I removed was a BE stage 2 (deeper housing than stock VVT) so it makes sense why the stock-sized VVT gears were too small in that housing.

LeoNA

The claim in that post is there are 3 different thickness gears. I have only seen two. Maybe indeed you had a housing that was for .43 thick gears and now have a vvt housing with (.393, 10mm) thick gears. Which is what you want. Can you explain how you ended up with a bare housing from boundary? Also if you can measure the depth of the gear housing with a depth mic or dial caliper.

From my experience there is not enough room to go thicker then the .393, 10mm gears because it starts to interfere with the front seal drain. Also anything larger than the vvt 10mm gears will not produce more flow to the bottom end because the oil passage from the pump to the filter is a limiting factor. Any higher flow would also cause the pan to run dry at high rpm.

Z_WAAAAAZ

I’ll measure the boundary housing with a depth gauge this week if I get the time and can grab one from my coworkers. I bought the Boundary pump for my last motor from another user on this site. It was on my last motor that spun a rod bearing and I found some mild scoring on the outer diameter of the gears during teardown so I ordered a set of VVT Boundary pump gears from Fab9 to replace them. Unfortunately the gears that were originally in the Boundary pump have long since been thrown away.

I do still have the stock gears that came out of the pump that is currently in the car (this is the pump that was installed on the VVT engine when I bought it) and can mic those as well. I bought the motor as a running unit from Satisaii @ 949 Racing. It was in his car “Mental” for years and actually had a fresh OEM rebuild not too many miles before I bought it. Dude is super high and tight with his vehicles and I can’t imagine he rebuilt the motor with a non-VVT pump.

However, for science, I’ll make a point to mic the stock gears this week.

I got the car running yesterday and did the initial Flyin Miata ring seating procedure on the dyno, changed the oil, then drove the car 8 miles. Oil pressures looked like what I’m used to seeing but I’m gonna drive it some and monitor more closely today.

Z_WAAAAAZ

I just mic'd my OEM gears with two different micrometers. One read 0.385", the other read 0.392".

LeoNA

I measured the OEM and Boundary gears that I have from the 94-2k 1.8 and they measure .373" (9.5mm). I'm assuming that boundary makes a stage 1 (9.5mm), stage 2 (10mm) and a hi-flow that is (.430" 11mm).

The box from the last stage 2 that I have lists it as a stage 2/hi-flow. The gears in that one measured .393", 10mm. The casting was a chinese sourced ITW early 1.8 bored deeper from 9.5mm to 10mm.

It appears you got gears that were .393", 10mm and ended up installing them in an actual VVT oem casting which is good. The other casting must be the .430", 11mm which I have never physically seen, nor would it be a good option in my opinion.

Z_WAAAAAZ

I concur with everything above.

Case closed. Glad I'm in the clear. Drove the car another 100 miles yesterday and confirmed oil pressures are within the same range that they were before. It seems the Stage 2 pump wasn't giving me any additional pressure than my current pump, at least at a glance.

Thanks for the input regarding the .393 vs .430 housings. I'll probably just run the OEM VVT housings with the upgraded gears from here on out, and I'll always check gear fit within the housings haha.