[T3] Bad day at the (FI) office

Keith Park topnotch at nycap.rr.com
Sat Apr 9 16:31:35 PDT 2016


Jim, you left us in suspense,
what WAS causing your 2 cylinders to flood?

Having a fuel pump switch does add a way to deal with certain situations
like this.

Keith


Topnotch Restorations
topnotch at nycap.rr.com
http://www.a383ina68.addr.com/radiorest/main.htm
71 Squareback  "Hothe"
65 Notchback  "El Baja Rojo"
93 RX7  "Redstur"
87 Golf  "Winterat"
 

-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org]
On Behalf Of Jim Adney
Sent: Saturday, April 09, 2016 12:05 AM
To: type3 at vwtype3.org
Subject: Re: [T3] Bad day at the (FI) office

Daniel,

I have a theory. While you've been having trouble with your '69 I've 
also been having trouble with my '73. It finally occurred to me that 
your problem might be similar to mine. Your symptoms are similar, but 
I'm guessing that your FAR meter has been leading you to make the 
wrong guess about the problem.

My '73 has developed a tendency to flood 2 cylinders when started up 
from cold. In this condition it has almost no power and I'm sure that 
leaves two spark plugs black. When I finally get all 4 cylinders 
going, the idle speed comes up (naturally) and the full power 
returns.

Here's what I've been doing to get the engine "unflooded."

With the engine running well above idle, I turn off the fuel pump 
leaving my foot at the same place on the throttle. As the engine 
continues to run, the fuel pressure drops and the engine first speeds 
up, indicating that it likes things a little leaner. After a few 
seconds of that, the rpms start to drop and, just as I think it's 
going to die, it suddenly picks up again. This is the 2 flooded 
cylinders kicking in. So 2 cylinders die just as the other 2 come to 
life. This continues for a few seconds, the time depending on how 
flooded they were. Then the rpms drop quickly and the engine will 
die.

If I can turn the fuel pump back on just before everything dies, 
sometimes I'll get 4 cylinders back. I repeat the whole process until 
I get 4 cylinders. Sometimes it helps to crank with WOT and the pump 
off, just to flush out those cylinders, then turn the pump back on 
while cranking and see if you get 4 cylinders.

It's a pain, but, with practice, you can do this by reaching under 
the dash and unplugging the FP relay. It takes practice to be able to 
pull it off just far enough that one terminal is still connected, so 
you can push it back on easily when you need to. But, I have a better 
solution:

I've been working on a different form of fuel pump primer switch. The 
first version, which you have, is just a push button which turns the 
pump ON. This 2nd version has a 3 position toggle switch: 
OFF/Normal/(Run.) (Run) is momentary; the equivalent of the 
pushbutton. OFF turns the pump off. It's a LOT easier to reach under 
the dash and flip this switch between OFF and Normal than it is to 
plug and unplug the FP relay. I haven't really put this version out 
for sale, but this sounds like a good time for a beta test.

I suspect that your AFR meter is lying to you because it's getting 
treated in ways that it was never meant to operate under. It's 
expecting hot combustion exhaust, but instead it's getting fairly 
cool combustion exhaust mixed with fuel-air mixture that never 
burned. Plus it's seeing gasses that are varying in temp so that it's 
never steady state. It will be VERY interesting to know what it says 
once you get things working right, but for now I think you have to 
either turn it off or learn to ignore it.

I'll make up a 2nd version primer switch to send you, but that will 
take me a few days. By that time I should have 1 more brain that 
might work for you. I'm afraid only 1 of yours turned out to be 
fixable given my incomplete knowledge of the schematic. You should go 
thru the A & B brains you have there, because some of them that 
you've rejected in the past are probably just fine. The switch and 
brain can ship back to you next week. In the meantime, play with 
leaner mixtures. Start with no resistor and the pressure sensor back 
to /. Then if you get the bucking (missing), try the pump relay 
trick. You might want to try your other CHTS, too, because if this 
one goes open (R= infinity) that will push things very rich.  

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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