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RE: [T3] Idles on 2; runs on 4 (Update/recap/ SOLUTION!)


Nice troubleshooting!
Note however, that there are 2 'E' Brains. And 028 and and 048, the latter
for a 73.  These were different in the aspect of timing and the distributor
used.

The old distributor in my Square (a 73 system) was completely shot, the
breaker plate was VERY loose and for the most part the car ran pretty well
but what clued me off was not just the timing floated a bit but the cruise
control kept kicking off, as it reads the steady stream of pulses from the
points.  The idle was a bit ragged but not too bad.

Keith


Top Notch Restorations
topnotch@nycap.rr.com 
71 Squareback
65 Notchback "El Baja Rojo"
65 Squareback "Eggcrate"
87 golf "Winterat"
93 RX7 "Redstur"

-----Original Message-----
From: Elroyyy@aol.com [mailto:Elroyyy@aol.com] 
Sent: Wednesday, March 15, 2006 3:13 PM
To: type3@vwtype3.org
Subject: [T3] Idles on 2; runs on 4 (Update/recap/ SOLUTION!)

Here's the recap of my problem and a few tests that were run to try and
solve 
it:
And like any good puzzle or riddle, the solution is at the bottom.


>> She's a 1973 FI MT Squareback.
>> I ran the tune up; it consisted of an oil change, valve adjustment,
plugs, 
>> points and condenser, adjust timing, check idle. This was not my first 
tune up. 
>> Everything was great for a little more than a week and then she began to 
run 
>> rough. At first, she just wanted her accelerator pedal feathered at the 
light 
>> to keep the RPMs up. A little later, she wanted the pedal tickled to keep

from 
>> stalling. Eventually she would stall and I'd have to crank her over and 
over 
>> until she'd catch, blow petrol-smelling smoke, then continue.
>>
>> Since I'm an avid reader of the type 3 list, I knew immediately that if 
the 
>> car runs rich it must be a problem with the Voltage Regulator or the Cold

Start 
>> Valve. I ruled out the CSV because I live in Southern California and the 
>> problem doesn't happen until after the car has been started.
>> So I connected my trusty VOM to the battery and got 12V. As the car 
>> approached medium RPMs, the VOM began to read higher and higher and 
leveled off >>just shy of 14V. But that's what it's supposed to read! The
Voltage 
Regulator is not 
>> my problem.
>
>Make sure that the CSV wiring between the CSV and the temp switch has 
>not gotten shorted to ground. This can mimic cold weather. The best 
>way to eliminate the CSV as part of the problem would be to just 
>unplug it temporarily, as a test.

Yes, as a test, the CSV was unplugged. No change.


>It's possible that your VR only goes bad as it warms up, so try to 
>take the car for a drive and then check the voltage after the drive.

A new VR was tested but the problem continued.


>> He (my mechanic) tested a known-to-be-good Pressure Sensor and nothing 
changed. >> He cleaned the trigger points and nothing changed. He retested
for 
spark -- it's fine all 
>> around.
>
>Is there any chance that the PS on this car is the wrong one. The one 
>for 70-1 has a couple of vent holes in the "cover" and these indicate 
>a style of PS which has a brass diaphram which can crack and leak. 
>The 72-3 PS came with a black cap over the adjustment screw, but 
>sometimes these have been broken off to tamper with that screw. You 
>really want one which hasn't been tampered with.

The PS is the right one. It's an "E" PS with an unmolested black cap.


>>Check the dwell and timing with a dwell meter and timing light?

Dwell and timing checked with meter and light. Timing is set to 5d before
TDC 
-- the third mark from the left (she's a 73) per Bentley. Dwell fluctuates 
ever so slightly. I think the bushing around the shaft is beginning to show
its 
age. But that shouldn't cause my problem.


>> But he discovered that the injectors for 1 and 3 were spraying too much 
fuel on 
>> each impulse. This is particularly troubling because the paired injectors

are 
>> 1&4 and 2&3. The injector wires were reversed on each side and 2 and 4 
>> started shooting too much fuel while 1 and 3 were fine. This tells me
that 
it's not 
>> a problem with the injectors themselves.
>
>Yes, sounds weird. How did you tell this? It's hard to see this 
>visually, did he actually measure it? If this is true, I agree that 
>it sounds like a brain problem, but such problems are actually 
>exceedingly rare. Were these injectors all genuine Bosch?

The injectors are all Bosch 007 yellow injectors. The test was done by 
allowing the injectors to spray into a jar. Same thing was done after
reversing the 
wires.


>> Next, he called to ask if I had another ECU we could try. The short
answer 
is 
>> no. She's a 73 with an "E" system (brain, pressure sensor and throttle 
valve 
>> switch all match). The only ECUs I have are a "D" and a blank. There is
no 
>> part number anywhere on the blank. So we tried them both.
>> The "D" brain didn't seem to affect anything. The blank, however, was 
another 
>> story altogether. Instead of pushing out too much fuel, this brain allows

no 
>> fuel to 1 and 3 while she idles. But when she gets a little gas, she'll 
run 
>> fine on all four.
>> 
>> Personally, I don't think the problem lies within the ECU. But I'm open 
>> minded enough to consider it as a possibility. I have a spare "E" ECU on 
the way 
>> but it won't arrive until some time next week. Anybody have any ideas?
>
>I also have E brains here.

Thanks, Jim. I have an "E" brain on the way. I'll let you know if the one I 
get doesn't work.


>I assume you checked the hose between the intake air distributor and 
>the pressure sensor, just to make sure it hadn't fallen off.

Yes, checking that hose for a leak was one of the first things I did before 
taking it to the shop.


SOLUTION:

If you read closely, you saw where the dwell was fluctuating. After 
accumulating three more black sticker "E" brains (none of which solved the
problem) and 
testing known, good spares at literally EVERY point in the FI system. The 
problem was solved by testing another distributor. I don't know if it was an

electrical issue inside the distributor or not. The best I can wrap my brain

around is the worn bushings allowed the dizzy to spin out of round at idle,
and 
then spin true at speed. The bottom line is that the distributor was the
problem.

Jim, are you still rebuilding distributors? May I send you two that I have? 
One would be the "problem child" described above and the other would be one
I 
picked up a few months ago -- condition unknown. Both are 311 905 205L.

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