Audi 100 Won't Start: Breakthrough ???
Robert Mangas
porter_t_dog at hotmail.com
Thu Jan 29 14:30:40 EST 2004
I hope it's safe to energize it directly w/ 12v; that's how I start it every
time ;)
On my 4kq the starter portion of that circuit wasn't working, but the
starter was fine, otherwise. I wired in a momentary pushbutton to fire the
CSV manually when needed. Works good, and though kludgy was way cheaper
than a new starter.
$0.02,
Robert
>From: "Marc Boucher" <mboucher70 at hotmail.com>
>To: "SJ" <syljay at optonline.net>, <quattro at audifans.com>
>Subject: Audi 100 Won't Start: Breakthrough ???
>Date: Thu, 29 Jan 2004 14:26:38 -0500
>
>Today I discovered something that has a strong likelihood of being the
>problem with my car's starting.
>
>I decided to measure the length of time that the cold start valve was
>energized for.
>
>Previously I had done the 'output' test of the ECU which essentially just
>shows that it can be energized. I'd also measured the resistance voltage
>across the thermo switch which measured at about 3.5k Ohms and was
>consistent with data supplied by others in this group. Today I got out a
>couple of radio shack resistors I'd never used in order to test.
>
>The results: REGARDLESS of what resistance was detected by the wire coming
>to the thermotime switch, each time the cold start valve was energized for
>only about 1.5 SECONDS !!! I have Hayes manual that shows that at current
>temperature (50F) the cold start valve should be energized between 2 and 4
>seconds. Here is a table of my tests, my expected, and observed results:
>
>Test Description Expected Time
>Observed Time
>Thermotime Plugged in, 50F 2-4 seconds
>1.5 seconds
>Thermotime Plugged out...open circuit ?
>1.5 seconds
>11 KOhms resistor (simulates 15 F) 4-10 seconds
>1.5 seconds
>22 KOhms resistor ?
>1.5 seconds
>wire shunted...zero ohms ?
>1.5 seconds
>FI box of ECU unit removed ?
>0 seconds
>
>So unless I'm missing something, the cold start valve is not being
>energized
>correctly according to the temperature. Is there something that I could
>have missed in order to get the cold start to be energized correctly
>according to the temperature?
>
>Would it be safe to energize the cold start valve with 12 volts directly
>and
>try to start?
>
>Anyone have any tips on where to go from here? i.e. anyone have a wiring
>diagram of the ECU's I guess the next step it to trace the wiring ???
>
>
>Marc
>
>
>
>----- Original Message -----
>From: "Marc Boucher" <mboucher70 at hotmail.com>
>To: "SJ" <syljay at optonline.net>
>Sent: Wednesday, January 28, 2004 8:03 PM
>Subject: Re: SJ Audi 100 Won't Start (Vacuum Leak?)
>
>
>It may be a few days before I can get starter fluid and a spark tester so I
>thought I'd add some further information. Each of these may be irrelevant
>but for what its worth, here goes:
>
>In lieu of an 'inline' spark tester, I pulled a plug wire, plugged it into
>a
>spare spark plug, and turned the engine over a few times. Each time, the
>spark plug generated a healthy spark from the time at which I engaged the
>starter until when the engine finally died. I know its hard to tell
>visually but it really seemed more like the engine died and so the sparks
>stopped, rather than the sparks stopped and so the engine rolled to a stop.
>
>I pulled one plug to check its condition. It had a thin coating of black
>suit, as I'd expect from a car that's been turned over for several days but
>rarely starts. Otherwise the plug was in good condition, the gap was
>correct, and there was no gap bridging or heavy deposits. Plugs are Bosch
>platinum 4477 with about 6000 miles on them.
>
>While working on the car I noticed fluid underneath the tranny on the
>garage
>floor. Confirmed it was transmission fluid. Not a lot but a noticeable
>amount. This car has never leaked a single fluid and the driveway and
>garage have until now been pristine. I wonder if repeated starting
>attempts
>can cause transmission fluid to leak?
>
>So I went and checked the other fluids...hydraulic fluid has dropped from
>max to middle of fill line in less than a month despite never going down
>before. Again I wonder if the repeated starting attempts, or the time we
>had to push it and steer without power assist can cause a leak to begin?
>
>One more point to add: almost the last day that I drove the car
>trouble-free
>also happened to be the coldest weather the car's ever been exposed to. It
>was parked outside for about 6 hours in -30C (-22F) temperature. After 6
>hours it turned over slower than usual but started on 2nd try (usually
>starts on 1st) and took me home fine. Its been in a warm garage since.
>Maybe one or two other short successful drives, but something just didn't
>'feel' right with how it started even then (given it was in a warm garage).
>
>Before I had any trouble, there was an interesting 'tick tick tick' during
>idle (actually a couple of them). One could be recognizable as the tappets
>and that would sometimes go away. But the other one was the fuel
>injection.
>I guess I'm gonna have to read up on fuel injection because I'm convinced
>that the problem is that fuel isn't getting through the injectors into the
>cylinders. I'm tempted to try adjusting the mixture or pulling an injector
>and if that doesn't work then getting it to a mechanic, or just shooting it
>:-)
>
>You asked if I had Bentley. No unfortunately. I have Hayes, which doesn't
>cover adjusting the mixture of the fuel injection.
>
>Marc
>
>ps below when I said "Thus the current flow would be about 100mA once the
>ignition was engaged," this was poorly explained. A clearer explanation:
>
>Once the ignition was engaged, the current flow was a steady 100mA. While
>cranking it remained at 100mA. Once the key was released (released because
>it seemed like the engine was starting) the current essentially followed
>the
>rpm...ie.descended from 100mA to zero just as the rpm descended from 1000
>to
>zero. Time between releasing key and zero rpm was almost always under 1.5
>seconds.
>
>
>
>----- Original Message -----
>From: "SJ" <syljay at optonline.net>
>To: "Marc Boucher" <mboucher70 at hotmail.com>
>Sent: Wednesday, January 28, 2004 5:03 PM
>Subject: Re: SJ Audi 100 Won't Start (Vacuum Leak?)
>
>
> >
> > Here are the results of today's testing (pulls out his log book :-)
> >
> > TESTING OF THERMOTIME SWITCH:
> > Both pins measured about 3.5k Ohms from ground to the pin. At about 50F
> > this is quite close to your results.
> >
> > TESTING OF IDLE and FULL THROTTLE SWITCHES:
> > Confirmed...on idle the switch is engaged (zero ohms) between pin 1 and
>2.
> > On full throttle we get zero ohms between pin 2 and pin 3. (I know its
>not
> > technically zero ohms...guess that's called 'closed circuit' ?)
> >
> > TESTING TO ELIMINATE FUEL PUMP RELAY AS CAUSE:
> > This had been done yesterday and results reported. Key point is that on
> > removal of the relay and shunting, the fuel pump can be heard to
>operate,
> > and is measured to draw about six Amps. Starting of car while using the
> > shunt produces a result that is NO different than using relay.
>Conclusion:
> > Relay is likely not the problem.
> >
> > TESTING OF FUEL PUMP OUTPUT:
> > The fuel pump was disconnected at the entry to the filter (filter is
>new-was
> > changed as a first step in trying to solve this problem) and carefully
> > directed into a container in which I could measure flow. Fuel pump was
> > energized for about 2-3 seconds...during this time it pumped about 60ml
>(2
> > fluid ounces). Note that I don't have the equipment to accurately and
> > safely test flow, or to test it under pressure. But this test gives me
>some
> > confidence that its pumping and more than likely the pump is not the
> > problem.
> >
> > TESTING OF CURRENT FLOW THROUGH DIFFERENTIAL PRESSURE REGULATOR:
> > Today I was not successful in getting the car started. Thus the current
> > flow would be about 100mA once the ignition was engaged, remain at that
> > during cranking, and once the key was released (released because it
>seemed
> > like it was starting) the current essentially followed the rpm...i.e.
> > descended from 100mA to zero just as the rpm descended from 1000 to
>zero.
> > Time between releasing key and zero rpm was almost always under 1.5
>seconds.
>***** "Thus"?? "would be"??
>Did you measure the current or not?
>Current should be at 100ma with igniton "on", but engine not cranking. Is
>it?
>
>
> >
> > TESTING OF POTENTIOMETER DURING STARTUP:
> > Previously I'd tested the potentiometer resistance with the bonnet open.
> > I'd found that The resistance between the bottom and the middle contact
>is
> > about 2 kOhms at rest and rises to a max of about 13kOhms near full open
> > falling slightly to 11kOhms at full open. Today I decided to measure
>this
> > resistance during an attempted start just to ensure that the plunger is
> > actually moving. The resistance moved from about 2 kOhms up to about 4
>or
>5
> > kOhms. when it appeared that the engine was about to start and then as
>it
> > sputtered the resistance fell back to 2kOhms.
> >
> > TESTING THE EFFECT OF UNPLUGGING OXYGEN SENSOR:
> > O2 sensor disconnected (heater and sensor plugs). Result...no change in
>any
> > observed behavior.
> >
> > Two of your suggestions...the inline spark plug tester and the starter
>fluid
> > will have to wait until I can get a ride to a car parts store. The
>spark's
> > been verified but you're right, it could be intermittent. I'll try to
>get
> > both as soon as practical...note however, with regard to the starter
>fluid,
> > its really too cold to barbecue up here right now :-)
>***** Ok, we need to check these two items in order to eliminate spark as
>the problem and fix the fuel system as the problem.
>
>After you do the above > spark plug tester, starter fluid:
>Verify again that you have no vacuum leaks. You said two lines had leaks .
>.
>pinch them off to make sure the intake has no leaks. Since this is the #1
>problem with hard starting, really make sure this is not the problem.
>
>Redo the ground connections at the back end of the intake manifold. Take it
>apart, sand the lugs, reinstall.
>
>Do you have the Bentley manual?
>
>Does the Cold start valve fire? You said it tested ok when you did the
>diagnostic tests.
>If its not too much trouble, take out the cold start valve, and see if it
>squirts when you crank the engine. If the engine fires up with starter
>fluid, this will be the area to check next.
>
>Take out the plugs also and check them. See if they are fouled or wet. If
>they are wet(fuel) I would get a new set. Clean and dry out the old ones in
>the oven.
>
>
> >
> > Marc
> >
> >
> >
> > ----- Original Message -----
> > From: "SJ" <syljay at optonline.net>
> > To: "Marc Boucher" <mboucher70 at hotmail.com>
> > Sent: Wednesday, January 28, 2004 11:38 AM
> > Subject: Re: SJ Audi 100 Won't Start (Vacuum Leak?)
> >
> >
> > Theoretically, the car should run without the fuel injection ECU. The
>system
> > will run in a mechanical mode.
> > Basically, all the ECU does is vary the Diff Press Reg current to fine
>tune
> > it for emissions.
> > The other ECU outputs are minor, ISV, vapor canister, cold start valve,
>etc.
> > Many of the inputs to the ECU can be "faked" . . ie, resistor in place
>of
> > temp sensor, jumper for idle switch, etc
> >
> > Are you keeping a log of your tests?
> >
> > Things that you arent doing and should be doing.
> > 1. Get that $7 in line spark plug tester . .and leave it on. Just in
>case
> > you have an intermittant ignition problem.
> >
> > 2. Hook up the ammeter for the Diff Press Reg. I use a cheap analog
>meter
>
> > radio shack. You can calibrate the analog against the DMM. Always
>monitor
> > this current . . . you should have a list of current values and
>conditions.
> > I sent you an email with these values.
> > Both my cars have insulated male and female spade lugs crimped on one of
>the
> > regulator wires. And I made up lug type test leads to interconnect to
>the
> > wiring and my meter. Now its very simple to hook up a meter.
> >
> > 3. Get starter fluid and rig up rubber hose so you can inject the fluid.
>Its
> > a lot easier to troubleshoot if you can get the engine to run. The
>starter
> > fluid will bypass cold start valve and lean mix from pressure regulator.
>
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