Gas In Oil

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rocketscience
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My tercel:: 1983 4WD SR5
Location: Tenino, WA

Gas In Oil

Post by rocketscience »

I started a thread in the general area https://goo.gl/H2BPzS to introduce myself and the car and ask a couple questions but now I have a more specific repair question... the car has been running rich which I'm trying to sort out but I just realized that I can smell gas in the oil. I already dumped the old oil but my question is would a rich running carb be enough to do this or is the fuel pump the prime suspect? The car has good compression but I'd think too much unburnt fuel could get by the rings. When I removed the carb there wasn't really any gas pooled in the intake. I have a spare fuel pump and am thinking I'll just replace it.
rocketscience
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My tercel:: 1983 4WD SR5
Location: Tenino, WA

Re: Gas In Oil

Post by rocketscience »

Could gas from the fuel pump leaking into the head seep past the valve guides and simulate a rich condition? Or up past the rings? I was running synthetic 5w 40 from winter, it didn't seem too horribly diluted but it's a bit on the thin side to begin with.
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Petros
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Re: Gas In Oil

Post by Petros »

sounds like you are indeed getting way to much fuel. have you checked the site window on the float bowl? if the float or needle valve are shot that would make it too rich.

are you by any chance running the weber carb? if so, you need to put in a fuel pressure regulation. the factory fuel pump puts out too much pressure for the weber. I can not think of a reason for a pump to put out too much pressure, the stock carb is designed to take the fuel pump pressure.

only other sources of excess fuel is the AAP, easy test is to cap off the vac line to the AAP and run it again. Usually if that is bad, only the #1 and #2 spark plugs get fouled.

best solve the problem, that much excess fuel will not allow the cylinders to lubricate the rings, and as you found, it gets in the motor oil.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
rocketscience
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Posts: 144
Joined: Wed Oct 28, 2015 12:46 pm
My tercel:: 1983 4WD SR5
Location: Tenino, WA

Re: Gas In Oil

Post by rocketscience »

I just took the top off of the carb and it looks very clean inside, like its been rebuilt. I forgot to check the site bowl while it was running but did after pumping the gas once to set the choke but it was hard to tell, like it was either pretty low or high. probably not the best time to test it. I'm not running a weber and the AAP is already disconnected. There was some fresh looking soot in the primary barrel, it was smoking pretty good the last time I ran it.

I disconnected the lines from the charcoal canister and there was a release of pressure, not a lot but definitely some. Could this cause too much pressure in the fuel system? The check valve on the canister doesn't seem overly restrictive but also isn't free flowing. I'm also at about 4000 ft and didn't have the vac on the HAC connected, would that do it?
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Petros
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Re: Gas In Oil

Post by Petros »

the HAC leans the mixture at high altitude, but I do not think it would cause it to run that rich.

My daily drive does not have a HAC, and I routinely drive it up to altitude without showing any signs of running rich.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
rocketscience
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Posts: 144
Joined: Wed Oct 28, 2015 12:46 pm
My tercel:: 1983 4WD SR5
Location: Tenino, WA

Re: Gas In Oil

Post by rocketscience »

I pressure tested the needle with the float resting on it up to 16 psi and it doesn't leak at all, float appears to be new and is plastic with no fuel inside. I'll check the jets in the morning but I'm leaning back towards weak spark, I need to test it again but found a used dizzy for cheap I'm going to get shipped here, none of the salvage yards in the area have one. another thing I did find is that the gasket under the heat shield was basically non-existent, the one above it wasn't much better
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Mark
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Re: Gas In Oil

Post by Mark »

Does your Tercel version have an oxygen sensor? If so, it has a feedback carb like mine. The carb is tuned to run slightly rich and the oxygen sensor/primitive computer/solenoid valve allow a small amount of air into the carb to lean out the mix, keeping the air-fuel mix within the proper ratio. If any of the components fail, the carb reverts to the slightly rich mix. If you don't have an oxygen sensor, then this all doesn't apply to you.
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Mark
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Re: Gas In Oil

Post by Mark »

By the way, I don't think a running rich condition would allow unburned fuel to build up in the oil. If the mix was that bad, the engine would probably barely run. I'd pull the spark plugs and smell them for unburned fuel, indicating maybe that that cylinder isn't always firing and the fuel isn't combusting.
rocketscience
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Re: Gas In Oil

Post by rocketscience »

It does have the o2 sensor, its possible that the EBCV isn't working right, there actually is one of those in the yard here. But what you say about it running rich not building up gas in the oil is what I've been thinking about, the plugs are sooty after idling with some smoke from the exhaust, quite a bit when reved, it seems like unburnt fuel. None of the plugs seem any worse than the others. I tested it with a sooty plug and the spark was yellow and inconsistant in placement (not a very good test cause it was partially carboned up) and again with an iridium plug which gave a white spark, but I'm not sure it was snapping strong enough. The plugs were more of a regular tan color after highway driving which made me think that I do have weak spark at low speeds or that the engine was dumping way too much fuel at idle. The o2 I replaced about 3000 miles ago, I pulled it to look at it and its pretty sooted up, I blew it out but haven't tested it.
rocketscience
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My tercel:: 1983 4WD SR5
Location: Tenino, WA

Re: Gas In Oil

Post by rocketscience »

I've read that on some carbs a leaky power valve can leak fuel when it shouldn't making it run really rich at idle but ours seems like its set up different. I tried to blow through it like the fsm says to and it checked out and didn't pass air until I pushed it in but if I suck through it it leaks a little bit when closed, is this normal?
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Mark
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Re: Gas In Oil

Post by Mark »

You could check to see if the engine is running rich by putting a volt meter on the carb feedback test connection. When the engine is warm, rev the engine at about 2000 rpm. The volt meter should show the output from the oxygen sensor varying from between 0-700 milivolts about once a second. This means that the system is adjusting the mix correctly. At idle, you could disconnect the oxygen sensor and hook up the volt meter directly to it. If the reading is anywhere near 900 milivolts, the mix is too rich.
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rocketscience
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My tercel:: 1983 4WD SR5
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Re: Gas In Oil

Post by rocketscience »

I've been looking into that, I asked a question about it on a really old thread here viewtopic.php?f=4&t=3703&start=15#p102742. I've never measured an o2 sensor but was reading that the voltage directly off it should cycle back and forth between lean and rich somewhere between .1 and .9, .45 being the average. If its staying toward one end that would indicate lean or rich. Have you tried it? That page from the FSM actually says 0-7 volts, it must be amplified by the ecu at that connector
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Mark
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Re: Gas In Oil

Post by Mark »

I tried it a week or so ago. It only cycles back and forth when the oxygen sensor is hooked up to the carb feedback system. The primitive computer is what causes the intermittent vacuum leak causing the mix to sway between lean and rich. If you disconnect the connector from the oxygen sensor (which disables the carb feedback system), the voltage off it should be mostly steady. If you pull off a vacuum hose, causing a lean condition, the voltage should quickly drop. If you take off the air cleaner lid and put your hand over the carb throat, choking off the air, the mix will go rich and the voltage should increase.
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Mark
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Re: Gas In Oil

Post by Mark »

rocketscience wrote: Fri Jun 01, 2018 11:02 pm I've been looking into that, I asked a question about it on a really old thread here viewtopic.php?f=4&t=3703&start=15#p102742. I've never measured an o2 sensor but was reading that the voltage directly off it should cycle back and forth between lean and rich somewhere between .1 and .9, .45 being the average. If its staying toward one end that would indicate lean or rich. Have you tried it? That page from the FSM actually says 0-7 volts, it must be amplified by the ecu at that connector
I just read your question on the other thread. I'm guessing that the difference in voltage (0-.7 vs .2-.9) is caused by voltage drop along the wire run to the test connector (it's a long way from the actual sensor). If you measure directly from the oxygen sensor, the voltage would probably be slightly higher. There is a tach sensor. It is the other wire that comes off the distributor (if I remember right, there are 3 wires: Power supply, test connector, tach signal to the computer). There are also 2 switches that have to be working: Vacuum switch #2 near the windshield washer fluid reservoir (disables the carb feedback system at hard acceleration) and one of the temp switches (activates the system when the coolant is warm). The vacuum switch #2 is operated by a small diaphragm that failed on mine. I replaced it with a generic one from a furnace supply store.
rocketscience
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My tercel:: 1983 4WD SR5
Location: Tenino, WA

Re: Gas In Oil

Post by rocketscience »

Huh, sweet, thanks for the info! Now I remember that capacitor on the distributor is the tach noise filter, just didn't realize it went to the ECU. That FSM page says 7 volts not .7 volts, does it measure .7 volts? It looks like the signal actually comes from the ECU unless I'm reading the diagram wrong. I'll have it running again on Monday so I can test it then.

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