[T3] '73 Idle Test

Sun Sep 1 10:37:39 PDT 2019

" the DC current thru the relay is ~1/4 A with pulses up to ~3.75 A during
injector pulses"

 Quite a test Jim. On the power relay I got the same reading on it's coil
winding. The power relay contact didn't gave dirt on it and the case was
clean inside. The contacts looked like they had a bit of tarnish I would
imagine since the injector pulses draw 3.55 amps through time due to slight
arching this might be expected. They would not pit or burn as ign points
since the voltage is not the same.

 When I first checked the voltage drop from battery + engine off key on to
# 30 there was no voltage drop at all read 0.000 this to me means the wire
and connection are sound. yet on #87 I read less than battery voltage by a
bit over a volt since it was key on I imagine that was due to the contact
tarnish at that point the pump relay had already timed out and was not part
of the reading . Yet this was not under a load other than what the ECU was
drawing at that point. This would not include injector pulses. When I
repeated the test engine running I only saw mV on #30 & #87 , in this case
the injectors were firing yet never saw a higher voltage drop the 3.55 amp
injector pair pulse would offer yet the pulse is quick and may not show up
other than a unsteady reading and reading was not steady I didn't record
the high and low since it was so quick and I didn't know what the injectors
drew. If my meters had a mix max feature I may have caught this. I just
never saw any ready higher than mV.

 The power relay was never installed in any way other than the intended
contacts facing down. I did the voltage drops tests off battery + to the
relay on the volt setting always do . The resistance test using the ohm
meter was done with #30 & #87 removed from the power relay just the coil
energized key on.

 I will try to see what I read as a voltage drop at the ECU connector
engine running to see what I find on both leads #16 & 24 if I recall. If I
find an issue there after I check voltage drop on the power relay and find
nothing and I don't feel I will then I would suspect connector #20 between
the power relay and ECU . Even though it's never been a part and has no
frayed wires I just have to rule it out. I do know relays are rated by how
many cycles of course dependent of actual load running through them. I do
know when I got this car someone had accessed the ECU because the rear trim
panel hard board was cracked and also someone replaced the MPS because it
was screwed together and looked quite a bit older than any other part near
the engine yet it ran fine once I replaced the pile of rust the original VR
was . It worked yet I had a volt meter on the battery just because and once
the black smoke out the exhaust began I saw the meter dive in voltage then
return. I also saw quite a few of the red + battery post protectors under
the rear seat so they knew there was a running issue yet certainly missed
it and may be why the replacement MPS that looked like it was from a
salvage yard . After I replaced the VR and all the injector seals and
vacuum  lines and runner boots  intake gaskets and points cap rotor and
plugs it ran great for a good many years.

 I've had the engine out once then later the engine and auto trans to
repair the loss of all forward gears. I just unplugged the harness from the
engine and moved it to the side. I didn't abuse it and it still ran fine
after 2003 when I did the trans . It's possible that TS1 is faulty I did
check from pin the pin resistance and each pin to ground yet never checked
to see the full range of it's ohm reading per temp or pins to ground engine
running adding vibration into the mix I want to check this to rule it out
because if it does short to ground internally or has to low or high
resistance it could cause going rich or lean.

 I did drive it after the power relay and it always once hot has a 1000 RPM
in park yet now in drive I see 850 down to 500 RPM and don't know what
caused this change all I did was deal with the power relay . Before it was
always 1000 in park and 850 in drive when warmed up. This is with TS1
unplugged . It runs fine with TS1 connected until it warms up a bit then
the miss fire come in and if I give it gas and let of it pops out the
exhaust and I fixed the one exhaust leak I had because it used to pop even
with TS1 unplugged letting off the gas coming to a stop in both cases the
move I brought up the RPM driving then let off coast the worse the popping
was.Now with TS1 connected any time I bring the RPM's up and let off it
pops out the exhaust the more the worse this becomes.

On Sun, Sep 1, 2019 at 8:38 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 31 Aug 2019 at 16:24, William Jahn wrote:
>
> > Jim when I read resistance on #30 & #87 I had both wires disconnected .
> > What I saw was it was jumping around and I didn't record the resistance I
> > do recall seeing above 25 ohms and the lowest was 9 ohms. If I turned the
> > key off then on again it did the same thing
>
> Okay, that was a reasonable way to do that measurement, but flakey
> contacts often give erratic resistance readings. Read on below.
>
> > When I did the voltage drop test it was in mA on both #30 & #87 yet it
> > was not steady either.
>
> If you're looking for voltage drops at bad connections, the best way to do
> this
> is to use your voltage scale. That will actually tell you the voltage
> drop, and it
> avoids the problem of damaging your meter if you happen to touch ground or
> find a connection with a large resistance (large voltage drop.)
>
> > Once I took the cover off and manually closed the contacts keeping my
> > hands clear of the probes so not to introduce resistance I still got no
> > lower than 9.5 ohms and still was higher than 20 ohms just holding the
> > contacts closed , I found that odd how the resistance would vary not
> > moving the contacts and with no voltage or current to heat the
> > contacts.
>
> Yes, once you get dirt between the contacts, nothing is certain or clear
> again. I wonder how dirt got in there; could the relay have been turned
> terminal side up for some time? Cleaning the contacts, and cleaning inside
> the relay shell, should give you a good fix. You could also use a point
> file,
> but don't use any kind of abrasive paper, as that can leave behind tiny
> bits of
> non-conductive grit, which can just repeat the problem.
>
> > Once I cleaned them testing by hand and in the car with the coil
> > energized it was a consistent 0.02 ohm , I didn't try the voltage drop
> > again after cleaning the contacts.
>
> I suggest repeating the voltage drop test, using the voltage scale, just
> to
> confirm and see what you're getting. You'll be looking for voltage drops
> under 0.1 V. With the engine running, it will be interesting to see if you
> see
> jumps in the drop as the injectors fire.
>
> >  I didn't have good results with both temps sensors connected , I may
> just
> > pull the ECU and still connected engine running see what the voltage is
> off
> > the power relay .
>
> That would be another interesting test, but do it on the V scale, with the
> other probe on the battery + terminal. It will be interesting to see if
> you can
> see much larger drops on the wire that feeds the injectors. I don't
> remember
> which power input feeds which part of the brain, but you will probably be
> able to tell, but noticing which wire seems stable and which one your DVM
> has trouble reading. If they both have trouble reading, then you're still
> getting voltage drop back in the common part of the feed: in the relay, or
> the
> wire to the battery.
>
> > Then pull the connector and check to each component for resistance to
> > the temps sensors and injectors and see if I can move /wiggle wires to
> > see if I can find an intermittent . Then the ECU grounds and perhaps
> > with every wire unplugged see if any two wires have continuity , the
> > grounds should have but not any of the voltage feeds or the MPS even
> > the TPS on the TPS I can leave it connected and see if it reads the
> > same as testing at the TPS unplugged.  I know it's a lot of testing yet
> > I need to know if anything in the wiring is causing this .
>
> Yes, that's a LOT of work, and it's probably unnecessary, as those kinds
> of
> problems don't tend to happen unless the wiring harness has been severely
> abused. That kind of abuse shows up as obvious external damage: torn,
> frayed wires, melted or cut insulation, obvious repairs, etc.
>
> OTOH, the Bosch D-jet testers make most of those checks quick and easy
> to do.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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