Date: Mon, 26 Sep 2005 13:35:18 -0700
Reply-To: Tom Young <tomyoung1@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tom Young <tomyoung1@COMCAST.NET>
Subject: Re: 82 won't start when hot
Content-Type: text/plain; charset="iso-8859-1"
From: "Higginbotham, David A." <dhigginbotham@HAZENANDSAWYER.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, September 26, 2005 10:14 AM
Subject: 82 won't start when hot
OK, I have finally replaced all the vacuum lines and the temp head
sensor on our 82 and the engine is still hard to start when it is hot.
Although, it is better about not dying when I let of the accelerator,
like at a light or something. When I try to start it the engine turns
over and over and over and I feather the accelerator pedal and finally
it starts and I have to feather the pedal a little more until the revs
get up and then it's OK. If it were a carb'ed engine I would think it
was flooding as that what it acts like but I don't smell fuel. When the
engine is cold it fires right up no problem. What should I check next?
I think you're on the right track with you thoughts about a too-rich
situation. One cause of this is simply the effect of time and use on the
AFM. The AFM in these things has an air-vane that twists against a spring
in response to the engine's demand for air. The position of the air-vane
affects a signal to the ECU which provides more or less fuel in response.
Over time the spring in the AFM weakens which leads it to signal to the ECU
a demand for fuel which is TOO HIGH AT ALL SPEEDS. The vehicle starts up
fine when cold because it can use all the gas that's dumped into it. But,
when the engine is hot, the engine 1) won't start when warm unless you
provide it with LOTS of air, typically by holding the gas pedal to the floor
while cranking and 2) tends to stall out it idle and bog down when climbing
hills.
There's 3 fixes:
1) If you're lucky, you lean out the mixture with the CO adjustment screw in
the AFM
2) If things have progressed to the point where you can't lean out the
mixture sufficiently with the CO adjustment screw you either
A) Open up the AFM and tighten the spring (details in the archives)
or
B) Buy a reman AFM
If you have a California van you can set the mixture properly by monitoring
the O2 sensor (details in the archives) and if you have a federal van you
should really take the vehicle to somebody with an exhaust gas analyzer.
Of course, before doing anything involving spending money you first check
over the FI system thouroughly as a bad TempII sensor or too-high fuel
pressure will also lead to a too-rich situation.
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Tom Young
Lafayette, CA 94549
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