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Thread: Is the condense tank necessary?
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chuyler1
Hauling
Posts: 140
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posted June 06, 2012 11:36 AM |
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Is the condense tank necessary?
I was filling up at the gas station last night when I noticed fuel leaking from under the truck. After closer inspection, one of the lines connecting the condense tank had a crack in it. Out of curiosity I started tracing all the lines to check for other cracks and figure out how the system works.
I see 3 lines that come out of the condense tank.
The top line links right to the fill spout. This is likely where fuel spilled into the tank when I was filling the gas tank.
The bottom rear connects to what the shop manual calls a check valve (I think). This is the line that was leaking in my truck.
The bottom front connects to a metal line that goes into the engine bay. On my truck this doesn't appear to be connected to anything in the engine bay.
The other end of the check valve connects back to the gas tank.
So I guess my question is, if all the emmissions equipment and lines have been removed from my engine, should I have the condense tank connected at all? Isn't any fuel that ends up in there just evaporating?
The shop manual shows hoses connected to a ventilation valve on the carb as well as a ventilation valve on the oil filler pipe. I have rubber caps on both of these outlets (previous owner did that) and I'm wondering if the truck will run better if I connect this stuff back up.
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kansei
Redlining
Wankelized
Posts: 423
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posted June 19, 2012 05:21 AM |
 Edited By: kansei on 19 Jun 2012 05:23 |
If memory serves, the system essentially provides the same function as the can-style charcoal canister on other models (Cosmo, RX-4, RX-7, etc.), allowing fuel vapors from the carb/intake/sump to recondense back into droplets on their way to or in the tank. While the truck can obviously run without the system in place, it can help significantly reduce (or eliminate) the possibility of having fuel in the oil, hard hot starts (weak vapor lock), and flooding out when starting cold.
I know a lot of rotary owners plug off the ports like your truck has done, but personally, I prefer leaving the system in place and maintained.
Neal.
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Neal A.E. Swigert
Greenville, Michigan
1974 REPU Resto Project
1976 808 Wagon
1977 Cosmo
1978 Savanna RX-7 GT
1980 Leather Sport RX-7
1980 Petty Targa RX-7 #11
1985 GSL-SE RX-7
1988 RX-7 10th Ann
1993 RX-7 VR Touring
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chuyler1
Hauling
Posts: 140
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posted June 19, 2012 05:51 AM |
Edited By: chuyler1 on 19 Jun 2012 06:01
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Thanks Neal. I found a more detailed diagram of all the connections in the '74 online shop manual (the '75 manual had an abbreviated version). The diagram showed the path that gas flows and how the system handles positive crank case pressure, intake vacuum, and the evaporation tank. I used some fuel line to make the missing connections and noticed a slight improvement with my idle.
Now the pressure is relieved through the intake manifold instead of through the air filter unit when the truck is running. I'm guessing the charcoal canister has a bit of oil in it from the pressure traveling in the wrong direction for a while though.
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Brad
Rotorhead
Posts: 1672
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posted September 28, 2012 04:32 PM |
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I get more consistent fuel pressure with it in place. And less fuel vapor smell after shutoff.
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