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Luke
Dodge Dakota
JOIN HERE
2/06/2009
01:26:01
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 Subject: The big mystery - SOLVED!!
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My 93 Dakota 3.9 started having issues about 7 or 8 years ago. It would poof out white smoke at startup, idle rough for a minute after a cold start, power was very poor, gas mileage was below what it should be. I tried everything! New intake gaskets, new plugs, new wires, new cap and rotor, new coil, new timing chain and gears, new injectors. Nothing helped! I just lived with it.
So, here a couple of months ago, I got the idea to replace the gas cap for good measure because it was old. Well, low and behold, ALL of the above problems have totally disappeared!!!
Apparently, the gas cap wasn't sealing properly and rather than the engine pulling a vacuum on the gas tank, it was sucking air through the tank constantly. After it sat a while, lots of gas fumes in the tank were immediately sucked in causing the smoke and rough idle at startup.
I have seen no more smoke from the exhaust. The engine idles smooth right from a start. Gas mileage has gone up. Power is much improved.
I have read on this board where others had similar problems. I just thought some of you may find my experience useful. If you are having these problems, REPLACE THE GAS CAP!
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Bucket
GenII
2/06/2009
13:47:31
|  RE: The big mystery - SOLVED!!
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Message:
Aint that a bitch when a stinkin gas cap can totally take yer truck out of commission !!! Lucky you found the problem before a dealer or mechanic ripped you off for unknown repairs that werent needed.Glad you figured it out and gave us a heads up Luke.
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Dakota49
Gen I
2/07/2009
19:29:51
| RE: The big mystery - SOLVED!!
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Message:
Luke, I can see where the gas cap can cause some problems, but the gas tank can't have a lot of vacuum, if it did the pump wouldn't be able to draw fuel from the tank to the engine, if it did the tank would impolde. There has to be a vent to allow some air into the tank as the gas is being used. I am glad you found the problem though.
Good Luck
Dakota49
dakota49
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TexasTodd
GenIII
2/09/2009
19:22:24
|  RE: The big mystery - SOLVED!!
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Message:
I too find it hard to believe that a gas cap caused those problems. But, stranger things have happened!
01 SLT QC, two tone paint,
OEM fender flares
Cab high Leer cap w/ double slider window,
Infinity sound,
Tire and handling pack,
R/T sway bars
Trailer towing pack,
3.92 LSD rear end, 2WD
Ransho RSX shocks
4.7 manual,
HO cams,
HO intake,
Ported the stock 68mm TB,
Homebrew 'true' CAI, w/ K&N
No belt driven clutch or cooling fan
No third cat.
SuperChips Tuner
Max dyno, NO short belts, etc.
227 RW HP
300 RW TQ
Drive it like its paid for!
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Luke
Dodge Dakota
JOIN HERE
2/09/2009
21:13:18
| RE: The big mystery - SOLVED!!
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Message:
Thanks for the replies. I find it strange too. But, after the gas
cap being replaced and no other repairs having been done for
quite some time, it runs so much better. I know the tank isn't
designed to hold a lot of vacuum. But, the gas cap is supposed
to let small, metered amounts of air in as gas is sucked out so
that the gas vapor in the tank is sucked out through vacuum
tubes to the EVAP system, thus burning the vapor and not
releasing the hydrocarbons into the environment. When the gas
cap has gone bad and is apparently letting air to be constantly
sucked through, not only is it a massive vacuum leak, huge
amounts of gas vapors are constantly being sucked into the
engine causing a very rich condition.
All I can say is that I am glad the engine runs so much better
and smoother now.
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Forseti
Dodge Dakota
JOIN HERE
2/09/2009
21:14:08
| RE: The big mystery - SOLVED!!
IP: Logged
Message:
The leak detection system put the tank under PRESSURE to test for leaks ... not put it under vacuum... the gas cap allows air to enter into the tank when there is even a slightest amount of negative pressure in the tank. And an excess of fuel would cause black smoke not white .... oil and or water burning would cause white smoke ..
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Luke
Dodge Dakota
JOIN HERE
2/09/2009
21:17:39
| RE: The big mystery - SOLVED!!
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Message:
All I can tell you is that is has never burned oil nor has it lost any
coolant. And, it no longer smokes and runs smother with better
power. I'm just sharing my experience.
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BWBluegrass
Dodge Dakota
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2/23/2009
21:00:13
| RE: The big mystery - SOLVED!!
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Message:
This is a common suggested fix for the problems you described. Some have found this to correct the problem as in your case, and some have not. Another tip that is similar, and may start to affect you is the vacuum tubing going to the vapor recovery system from your fuel tank filler neck. It will build up with liquid fuel over time, and rot. Once this happens, you get the huge vacuum leak that is very difficult to find. Watch for this if you start having problems again.
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Ric
Dodge Dakota
JOIN HERE
3/05/2014
18:24:54
| Fuel problem
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Message:
Have a 2004 Dodge Dakota that is emitting fuel
vapors into the cab. Originally, took truck to
shop for a burning oil vapor entering the cab.
They replaced valve cover gaskets and knocked
something loose on the fuel rail resulting in a
fuel leak. They repaired the leak, they say there
are no more fuel leaks, but still have fuel vapor
entering the cab. The fuel problem was not an
issue before taking the truck to them. What could
this problem be and should they be liable?
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Ric
Dodge Dakota
JOIN HERE
3/05/2014
18:27:25
| Fuel problem
IP: Logged
Message:
Have a 2004 Dodge Dakota that is emitting fuel
vapors into the cab. Originally, took truck to
shop for a burning oil vapor entering the cab.
They replaced valve cover gaskets and knocked
something loose on the fuel rail resulting in a
fuel leak. They repaired the leak, they say there
are no more fuel leaks, but still have fuel vapor
entering the cab. The fuel problem was not an
issue before taking the truck to them. What could
this problem be and should they be liable?
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dale
Dodge Dakota
JOIN HERE
3/07/2014
00:19:22
| RE: The big mystery - SOLVED!!
IP: Logged
Message:
Yes.
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