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Changing the Oil Metering Pump ( OMP ) while in the car.... my how-to
A couple of weeks ago my car threw CEL #27 for Oil Metering Pump. I searched and posted a thread looking for more information on changing them out but didn't find much. http://www.rx7club.com/showthread.php?t=672512 . Apparently this particular CEL isn't that common....and thankfully so. It was a major PITA. Figured I'd post my experience and maybe help the next guy.
As most of you all know, the OMP connects to the engine wiring loom just below the intake elbow and just beside the alternator. Removing the elbow gave me room to access the connector in order to perform the resistance/continuity checks set out in the FSM on pg D-15. I'm not good w/electrical issues but all the checks I was capable of doing here were within spec. A note here, the FSM makes mention of the OMP stepping motor and position sensor. As far as I could tell, the OMP assembly is not made to disassemble and with my limited abilities with a multimeter, I decided to proceed with the replacement.
Having already removed the intake elbow, I also remove the intake box, cross-over and upper vac chamber. The alternator and tensioner bracket are also removed. Likewise, the battery, PS pulley and the three bolts securing the pump to the support were removed and the pump slid back out of the way. You can then access the two bolts securing the large vacuum chamber. A note here: Initially I couldn't access the top bolt for the chamber. It sets beneath the oil filler neck. I finally had to remove the bolt secured the filler neck that sets just aft of this blocked nut. Doing so allowed me to gently flex the plastic neck upward just enough to get a socket on the nut for the chamber.
^The connectors for testing
^The arrow points approx. to where the 10mm bolt securing the filler neck is located. I had to remove that in order to flext the neck up and gain access to the top bolt for the vac chamber.
Everything removed.
Now, just fish the loom out from beneath the WP housing and above the main pulley and your done with what can be accomplished from the top. Get your jack and stands or in my case a lift. It really gets fun from here...
This is the initial view from underneath with the belly-pan removed. It improved a little by dropping the sway bar and the RB sway bar mount brace...but not much.
I ended up accessing the pump itself both from the front and side but like the fuel filter change, be prepared to be pretty limber. Another note: I thought I'd have to remove the WG actuator, but did not. Fortunately I didn't have to remove much of anything below to access the pump.
Tools here are limited to a 1/4 inch drive ratchet, a medium extension and a 10mm deep socket. The OMP is secured by 3 bolts, Two on the aft side above and below and one toward the front of the car just above the oil lines. The oil lines must be disconnected to access that bolt. You are absolutely working blind on the car, and have to feel your way around. I found a 4 inch extension with the deep socket and ratchet was about the right length to get onto each bolt. While not easy, breaking them loose and removing the pump wasn't too bad.
In the above picture you'll notice masking tape on the tools. Because I was working blind, I found that putting tape over the socket before inserting the bolt held it securely enough while I attempted to find the hole. The tape on the end of the extension was to give my finger-tips enough grip while I started each bolt. For obvious reasons, you DO NOT want to cross thread.
The new one in. Both the old and new "used" pumps had 'O' rings, but they were a little flattened with time. BTW, I called Ray at Malloy for a price on a new pump. Had I thought about it, I would have asked about a new 'O' ring but given what they wanted for the pump ($1400.00), a new 'O' ring probably would've been at least $500. So maybe just to feel better, I augmented the seal with a little RTV being careful to stay outside the 'O' ring groove and away from the pump oriface.
Then I just fished the wire loom and connector back up, being careful to re-use the wire retainer that's just below the WP housing to make sure the wires stay away from the main pulley.
Everything reassembled. Cleared the code and, Voila! Piece of cake.......not.
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__________________
Jim
93 VR R1 How's that "Hope and Change" workin' out for ya?
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I'm not very fast and didn't do it all in one day. But adding up all the hours, ~15. The FSM doesn't give you any instruction on this, and obviously I'd never done it before so I was being pretty diliberate. I'm sure many can do it faster.
__________________
Jim
93 VR R1 How's that "Hope and Change" workin' out for ya?
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I ended up removing my OMP but not because it was bad, just because it was leaking oil. I replaced the factory O- Ring, and the the crush washers. The O ring would NOT stay inside during installation, so I ended up putting some RTV inside the O ring groove to hold the O-Ring in place during installation. After the O-ring dried to the OMP, I removed as much RTV as possible and made sure there was no RTV in the orifice. WOW what a job
Glad you got it done Ernesto. And glad you mentioned replacing the 'O' ring and washers. I didn't do it and got lucky, since nothing leaked. But looking back that was dumb. The smart thing to do is replace them. Mine were subsequently replaced during a rebuild.
__________________
Jim
93 VR R1 How's that "Hope and Change" workin' out for ya?
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- I'd recommend a new O-ring. They're actually really cheap from Mazda, like a few bucks at most. I'd hate to go through all that and have the O-ring leak!
- To retain the O-ring in the pump during assembly, you can coat the O-ring with Hylomar if you have some. It's a SUPER SUPER sticky non-hardening gasket goop. It's hard to find Hylomar nowadays, though - it's a case of you'll have some if you build engines . You can also coat the O-ring in Vasoline, that will do nicely. RTV can work, but when it hardens it can be the failure point for the seal. O-rings need to do their own thing to seal well.
- As stated, this is where 1/4" drive tools really shine. Sears also has a 1/4" drive 10mm that has a built-in universal joint, really handy in tight spots.
I've only installed OMP's with the engine out of the car, when it's FAR easier. This is definitely a job that requires patience. But, it's well worth it - the OMP is a critical part of the engine.
I'd also say to be careful with the plastic OMP lines - if one breaks, you'll have a REAL fun time pulling the upper intake manifold and rat's nest to replace it.
The wire to the OMP routes under the water pump housing, and getting it out of the retaining tabs can be fun as well .
Dale
__________________ | Dale Clark - RX-7 Bad-Ass
| '94 RX-7 R2 Brillant Black - Building the Perfect FD
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Good advice for the O- Ring sealing, I should have done that. Well I ended up using a brand new tube of "Permatex The Right Stuff" for the O-Ring groove. The purpose of using it is not to seal, but to hold in the O-Ring and plus I know that RTV is designed for oil. After the O-Ring dried to the groove, I removed as much RTV as possible from the O-Ring so that way it was only the O-Ring that was doing the sealing. However I will remember what you said next time around I run into a problem like this, because vasoline is a better solution
BTW getting the OMP out of the car took me about 4 hours, and getting it back in took about 3 hours. 1 hour for each bolt
So maybe just to feel better, I augmented the seal with a little RTV being careful to stay outside the 'O' ring groove and away from the pump oriface.
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