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Re: TQC fuel system wierdness
> Hi all,
> I have been trying to find the Sunpro engine tool. The couple of auto parts
> places I have checked don't know of it. Is 7678 the right model number? Any
> other numbers someone can give me? Or maybe a description of what it looks
> like? I am looking for it because my 83 TQC started acting funny a few weeks
> ago. Here are my symptoms.
I have a SunPro Model CP7678 meter. It comes in an yellow/orange case.
It looks like a standard DVM, with an LCD display at the top, a large
rotary function select switch in the middle and three sockets into which
the test probes can be plugged. The function selector has settings for:
DC Voltage, DC Current (15A), Resistance, Diode Check, Lo Tach, Hi Tach
(x10), Dwell and Duty Cycle. The Tach and dwell settings have 4,5,6 and
8 cylinder settings. It is water resistant and will automatically shut
itself off after not being used for a few minutes.
I definitely saw them for sale in the Sears Auto department, but I managed
to get mine on sale at Grand Auto a couple of years ago. You're probably
primarily interested in the duty-cycle readout ... I saw an article in EC
(that talked about VW idle debugging) that showed what looked like a Radio
Schlock meter that had some duty cycle measurement capability. I haven't
been able to see a similar item for sale in the store or catalog ...
> Driving along and I notice the air/fuel LED meter is pegged on rich and not
> moving. Nominal running it is bouncing between lean and stioch(middle). It
> was rich under accel, idle, etc. All of a sudden the engien cuts out for a
> moment, the tach bounces and the meter goes full lean, car acts like it has
> no power. Floor accel, no response. After jabbing at the accel peddal a few
> times the fuel comes back and proceeds to work it way to full rich. It
> repeats this type of behavior a few times. Then finally the car stalls. I
> turn off the ignition and restart and everything is back to normal. A/F
> meter bouncing like normal and car is fine. It repeats this behavior later
> the same day. I haven't drove it too much since then.
> At this point I haven't done any diagnostic checkout or even looked into it.
> I am planning on going through the maint & adj manual procedure and seeing
> what turns up. Any thoughts?
My first thought is the ground lug that attaches to the back of the intake
manifold. I had similar symptoms a number of years back where the car total-
ly lost power, but I could get it to come back with the throttle. Finally
the car wouldn't do much more than idle and it finally died. Shut off the
ignition and started it up and I managed to get home (<1 mile), and I cleaned
the ground connection @ the I.M. No problems since ...
> I also seem to have a similar electrical anomaly where the oil temp changes
> with voltage. In may case, I have the LED diff lock panel from an 85 4000q
> installed in my 83 TQC and am using the voltmeter and oil temp LED meters.
> It seems that with varying electrical loads, my oil temp can change 50
> degree C on the LED meter. The characteristic is, the lower the system
> voltage, the higher the oil temp. I haven't done anything yet, but have been
> told that I should install a voltage regulator on the supply voltage to the
> oil temp LED bargraph. Is this functioning of the LED bargraph similar to
> what other see in their 4000q's and 85 TQCs? Has anyone had to fix an LED
> display for this behavior?
WRT voltage fluctuations ... I would assume that the digital gauges are
similar in nature to their VDO analog cousins. The gauge has an internal
voltage regulator, but this regulator doesn't seem to be too robust. As the
supply voltage decreases the relative value of the sensor input increases,
as does the gauge reading. If the problem is truly one of the battery volt-
age changing there ain't much you're gonna be able to do, but if it seems to
be related to the fresh air fan, cigarette lighter, stereo, etc. you can try
installing an independent +12 supplies to the gauges. If it is related to
the stereo, I'd recommend providing a separate, small gage wire to the stereo
and leave the gauges as they are. If it is a supply to the gauges alone,
wire gage isn't too important, but you do need to find a point that is
switched on and off with the key (HEY ... THIS VOLTMETER IS ALWAYS REGISTER-
ING A VOLTAGE!) Make sure that you install an in-line fuse near the battery
(or switched +12 source), things could get nasty if the insulation got
rubbed off otherwise. On the TQC it wasn't too tough to snake a power wire
for the stereo under the carpet when I had the seats out.
BTW ... is the diff lock switch on the new panel vacuum or electrical? There
was some discussion about this at the meeting on Saturday. Some people were
saying it was actually electric, but I'd be really surprised if it wasn't a
rotary vacuum switch.
> Looking forward to hearing from you all.
> Dave Lawson firstname.lastname@example.org