running rich all of a sudden

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brian_wildcard
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Posts: 24
Joined: Mon Apr 13, 2009 1:50 pm
My tercel:: 1986 AE86 sr5
Location: Vancouver BC

running rich all of a sudden

Post by brian_wildcard »

hi guys,
my little car's been running smooth so far... until 2 days ago :(

that day i had my radiator cap changed, and put in 19L of husky 90-octane.
problem didn't even show up till i started the car up later that night.
car would stall when i decelerate or idle. (does it no matter engine hot or cold)
o yeah.. car has hard starting problems too

pulled the plugs out today and they were black with soot.
also looked at the carb when i shut the car off,
the mouth of the carb was excessively covered with gas vapor...

here's what i think could have gone wrong:
1) fuel pressure too high --> fuel pump?
2) bad gas
3) EGR stuck closed (not likely since there's excessive gas in the carb)
4) choke stuck closed (nope.. i checked it, it was wide open)

that leaves options 1 and 2.
the underlying Q: why is gas being dumped into the carb?

p.s. is there a fuel return line in our fuel pumps? could that be stuck?
what is your opinion, and thanks
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ARCHINSTL
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My tercel:: Goldie is a 1986 SR5 attualmente con Weber/also owned the first T4WD in STL in late '82
Location: Kirkwood, a 'burb of St. Louis

Re: running rich all of a sudden

Post by ARCHINSTL »

The fuel return line of the pump is the one at the front of the pump. Sorry I can't be of more help. Is it an ancient pump?
Tom M.
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takza
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Re: running rich all of a sudden

Post by takza »

Could be the float or inlet valve in the carb...or maybe the fuel pump which has a regulator built in. Choke might not be opening?
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splatterdog
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Re: running rich all of a sudden

Post by splatterdog »

Float bowl fuel level can be checked in seconds. Should be in the middle of the sight window.
brian_wildcard
Newbie
Posts: 24
Joined: Mon Apr 13, 2009 1:50 pm
My tercel:: 1986 AE86 sr5
Location: Vancouver BC

Re: running rich all of a sudden

Post by brian_wildcard »

ARCHINSTL wrote:The fuel return line of the pump is the one at the front of the pump. Sorry I can't be of more help. Is it an ancient pump?
Tom M.
according to my knowledge, the previous owner replaced the pump just before i bought the car
and it does look kinda new... still pretty shiny
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brian_wildcard
Newbie
Posts: 24
Joined: Mon Apr 13, 2009 1:50 pm
My tercel:: 1986 AE86 sr5
Location: Vancouver BC

Re: running rich all of a sudden

Post by brian_wildcard »

yeah, it occured to me last night that the float could have gone bad..
i'm gonna go check it right now

the thing is i bought the carb REBUILT back in december...
float should have been replaced i assume
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brian_wildcard
Newbie
Posts: 24
Joined: Mon Apr 13, 2009 1:50 pm
My tercel:: 1986 AE86 sr5
Location: Vancouver BC

Re: running rich all of a sudden

Post by brian_wildcard »

well, today i took the car on the highway and drove it all the way to white rock
and u know what, the problem just dissapeared
no starting or running problems whatsoever

i guess i need to attribute this to a severe case of bad gas
(mixed superstore 87octane with husky 90octane)
have to say it's the weirdest problem i've ever ran into :?
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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: running rich all of a sudden

Post by Petros »

It could be a bad gas cap, or your carbon canister, that are supposed to allow the tank to vent. If it can not vent, on a warm day the pressure in the tank will build and over power the float valve in the carb.

It should be easy enough to check, loosen the gas cap and drive it for a day to see if the problem goes away. also there is a test procedure for the carbon canister system in the FSM. I would start there.

Good luck
'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)
brian_wildcard
Newbie
Posts: 24
Joined: Mon Apr 13, 2009 1:50 pm
My tercel:: 1986 AE86 sr5
Location: Vancouver BC

Re: running rich all of a sudden

Post by brian_wildcard »

i've been running 87 from shell the past week,
haven't had a problem yet.

and yeah, the weather's gotten warmer than when i had the problem
don't think it would be the carbon canister although i wouldn't mind checking the FSM just for the heck of it :)
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