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RX-7 3rd Gen Specific (1993-2002) RX-7 1993-2002 Discussion including performance modifications and Technical Support Sections.

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Old 12-31-2018, 01:41 PM   #1
speedjunkie
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Default Fuel getting into catch can

I developed a strange issue recently on my way back home from SevenStock. We stayed the night in southeast Utah and in the morning I noticed I had oil sprayed all over the intake elbow and other things in the area. I'm using one of Adam Griffith's catch cans so the filter is right next to the oil filler cap. The can was overflowing and spraying out through the filter. I drained the can and went on my way. When I stopped for fuel a few hours later, the can had overflowed again. I drained it again and just left the drain open for the rest of the drive home.

Typically I'll drain the catch can every oil change and I'll get maybe a few drops of water with barely any oil. But now, if I take a drive that lasts a couple hours, I'll drain the can and I'll get about a tablespoon of mostly fuel.

When I first built the engine (sometime in 2014) I started out by using 20w50 and some Lucas oil additive, so it was SUPER thick. My buddy that helped me build the engine that time used to build them for Tripoint and he suggested using that oil and additive so I used that for the last few years until recently. Talking to another friend who has done a lot of research into oil, he suggested I use something thinner so it has protection on startup. He suggested 0w30 but I found 0w40 so I used that and no additive, and I changed that right before the trip to SS. That's the only thing I changed before the trip. I do need to get tuned again and I'm running pretty rich right now.

I was wondering if my oil control rings were bad, but I'm not burning oil. I'm thinking maybe the fuel is bypassing the oil control rings due to lower viscosity oil? But when it gets hot it's about the same as the thicker oil I was using.

I installed a boost gauge recently and my vacuum is reading around 10-12in/hg at idle, which I feel is a bit low, but the car starts up fine and runs fine. My idle increased to around 1800 while I was at sea level in California, and I thought it would drop back down to 900 when I got back home to 6000ft, but it didn't. This is the only other change I've noticed since the trip, not sure if it's related to the catch can issue.






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Old 01-02-2019, 10:16 AM   #2
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Don’t have an answer but maybe something in the fuel system mods you described here http://rotarycarclub.com/rotary_foru...ad.php?t=19257 failed?
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Old 01-03-2019, 11:20 AM   #3
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I never did anything with that, not yet. lol And I've changed plans a bit on that front also.
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Old 01-03-2019, 12:28 PM   #4
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That's weird, so it was behaving fine before the trip, and nothing was done to the car (mods, repairs, whatever) before the problem started? Do you still have the stock purge valve (I assume FD's have one) plumbed in correctly? Link to a FC version of this part for ref:

https://www.atkinsrotary.com/store/7...tegory_id=1060

Maybe posting up some detailed pictures or a diagram showing exactly how the catch can is plumbed into the engine would help figure this out.


Also, regarding the fuel in the catch can, do you still have the factory charcoal canister and its associated plumbing intact?

Last edited by Pete_89T2; 01-03-2019 at 12:31 PM..
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Old 01-03-2019, 03:25 PM   #5
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Yep, was working perfectly before the trip. I didn't do any mods before the trip. I had pulled the engine a couple months before to reseal the oil pan and install heat shields on the turbo bits, a few things like that, but nothing that would cause this and it was working fine on the test drives I took right before leaving for the trip. It was running much richer at sea level, and I chalked it up to that originally, but it would still have to be bypassing the oil seals or something.

I've never seen anything like that purge valve on the FD, and I can't think of what we would have that would be similar.

I'll take some pics, but basically the catch can is sitting where one of the stock vacuum tank was, right next to the power steering pump and behind the pulleys and right on the front of the engine. One vacuum line comes straight from the filler neck, and I have another tube coming up from the rear oil drain for the stock turbos, and that line goes across the top of the engine to the catch can.

No, I pulled the charcoal canister a few years ago and used that as an extra line for getting fuel to the engine. I did reinstall the canister itself to try to kill some of the fuel smell, but I don't have any lines hooked up from it to the engine.
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Old 01-16-2019, 01:34 AM   #6
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Shit, I forgot to take pics before I left the US haha.
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