Re: [doc] re still doesn't idle ok

[Nick Tomlinson <nickandkathryntomlinson@xxxxxxxxxxx>]

The resistance test is a simple one on a diode and you remember correctly.
  Diodes though can become 'leaky' when the PN junction breaks down which is why you check with the diode function. This will show the voltage drop across the junction and depending on type should show no voltage drop one way and between 500mV and 800mV the other.
   
  "
  "Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for throttle switch input 
(AT THE ECU MULTIPLUG) meter should read battery voltage with 
throttle closed (switch 
> operated) and no voltage with throttle open.""
according to the workshop manual, does this input not just earth
when the switch is closed (car at idle) so to test i earthed it with 
diode removed then tried to start car.
  "
  Yes, the unit does earth this switched point when the throttle is closed.
  The test  I give will show if there is any feedback voltage from the other circuit showing the diode has gone short, leaky or open circuit. I am presuming that you earthed this input at an earth point like the engine block or better yet the -VE battery post.
   
  Hope the circuit diagram I sent to you makes the connections clear.
  Chances are you have an earth lead off somewhere so the unit isn't earthing at the earth pin.
   
  It's always harder to explain in words what you could do yourself in 20 minutes.
   
  This problem will be fixed soon.
   
  NickT.

blackaddertoo <blackaddertoo@xxxxxxxxxxx> wrote:
    Hi Nick

thanx for the reply. Don't worry you can talk technical as i used to 
do a bit of hobby electronics, building transmitters etc, simple 
logic circuits etc.

i thought the screw which has a lead to it earthed the ecu.
i will recheck the multiplug earth.

i will check for continuity from ecu multiplug to idle motor. did 
not have any wire long enough yesterday, as the car is parked away 
from home.

"Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for throttle switch input 
(AT THE ECU MULTIPLUG) meter should read battery voltage with 
throttle closed (switch 
> operated) and no voltage with throttle open.""
according to the workshop manual, does this input not just earth
when the switch is closed (car at idle) so to test i earthed it with 
diode removed then tried to start car.

the diode, i must be wrong but i thought it would read continuity in 
one direction ie no resistance one way and 100% the other, but i 
couldn't remember back to my electronics days.

Regards

Steve




--- In doc-uk@xxxxxxxxxxxxxxx, Nick Tomlinson 
wrote:
>
> You said you checked the earth by:
> "earth check with continuity tester from screw into base to car 
body, 
> to ecu multiplug"
> 
> This mounting screw just holds the ecu to the metal frame which 
is earthed.
> The earth on the ecu is actually one of the pins on the 6 pin 
multiplug so check this first using the test:
> 
> "Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for earth at ecu MULTI 
PLUG, meter 
> should read battery voltage."
> 
> Check continuity of all wires from the idle speed ecu plug.
> Especially those to the idle speed motor.
> 
> "so how do i check the input from the coil/distibuter (which i 
assume 
> gives the rpm signal (also runs the rev counter input?)"
> 
> Said this in last message 
> "You can check for continuity using the resistance setting on 
the 
> multimeter and check for wire continuity between the switched side 
> of the coil to the ecu plug, (remove the ecu first). If there is a 
> suppressor, temporarily disconnect it in case this has gone bad."
> 
> Your test on continuity test through the diode would give a 
result dependant on the positive feed from your multimeter for the 
continuity test. This will be blocked or passed through (in laymans 
terms) due to the characteristic of the diode itself, hence the 
diode test.
> 
> Put the diode back in the circuit and do the test as in my 
previous message
> 
> "Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for throttle switch input 
(AT THE ECU MULTIPLUG) meter should read battery voltage with 
throttle closed (switch 
> operated) and no voltage with throttle open."
> 
> Do you have a circuit diagram of the idle speed ecu ?
> 
> NickT.
> 
> blackaddertoo wrote:
> hi Nick
> 
> thanx for the post...i know a long one but here hoes..
> 
> earth check with continuity tester from screw into base to car 
body, 
> to ecu multiplug
> 
> connected test light to main power ecu multiplug...lights with 
> ignition each time (tested fuse-ok)
> 
> check throttle switch input before/after diode, continuity before 
> (with earth) non afterbut reads about 700 on doide test on meter
> from your comment this looks about right but removed diode 
> completely to test further. does not activate continuity buzzer on 
> positive or neg current...thought it should.
> 
> have not checked coil to ecu or ecu plug to idle plug
> 
> thermister has been replaced a couple of weeks ago...reads about 
> 1800 ohms cold so that is ok i think.
> 
> tried earthing the throttle input and starting the car....car did 
> the same...runs for 15 secs then chugs and dies.
> 
> car idles ok (1500rpm) with brass screws adjusted so i assume co 
> adjustment is ok otherwise it would not run?
> 
> 
> so how do i check the input from the coil/distibuter (which i 
assume 
> gives the rpm signal (also runs the rev counter input?)
> 
> i'm running out of things to test but surely my problems are here 
> somewhere.
> 
> Regards
> 
> Steve
> 
> --- In doc-uk@xxxxxxxxxxxxxxx, Nick Tomlinson 
> wrote:
> >
> > How did you check the earth connection at the ecu multi plug?
> > 
> > Have you checked for a switched connected at the ecu multiplug 
> from the throttle switch?
> > 
> > Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for earth at ecu, meter 
> should read battery voltage.
> > 
> > Put your multimeter to volts. Connect the red cable of meter to 
> jump start post. Use black lead to check for throttle switch 
input, 
> meter should read battery voltage with throttle closed (switch 
> operated) and no voltage with throttle open.
> > 
> > With the ECU plugged in, check the multiplug that goes to the 
> idle speed motor, the centre pin should have 12v on it (with key 
in 
> ignition and tuned to position 2) continuously. The ecu 
momentarily 
> earths the outer pins to open and close the motor.
> > 
> > You can check for continuity using the resistance setting on the 
> multimeter and check for wire continuity between the switched side 
> of the coil to the ecu plug, (remove the ecu first). If there is a 
> suppressor, temporarily disconnect it in case this has gone bad.
> > 
> > The white lead from the distributor to the ecu is from the 
> negatively switched side of the coil. If this was short then the 
car 
> would not run at all.
> > 
> > 
> > The Diode should be tested using diode function on the 
> multimeter ideally not resistance.
> > Reading should be between 500 and 800 with test leads one way 
> round on the diode, and no reading (ie infinite) the other way 
round.
> > The diode is there to stop feedback voltage going to this 
> circuit, as the throttle microswitch operates a couple of other 
> circuits too.
> > 
> > I would say from your resistance tests that this diode would 
> appear to be open circuit.
> > Temporarily connect this wire to permanent earth for idle 
> testing purposes only. Does the car idle now?? If it does then the 
> diode will need replacing. Note which way round the diode is when 
> you removed it and replace it with another the right way round.
> > 
> > I am presuming that you have check for wire continuity between 
> the idle speed motor multiplug and the idle speed ecu multiplug.
> > 
> > Have you measured the thermister resistance?
> > Do this by using your multimeter on resistance and connect to 
> the 2 pins on the idle speed ecu multiplug. If you get no reading 
> (open circuit) then the connector to the thermistor connector plug 
> may have fallen off or the thermistor itself has gone bad.
> > If you get no resistance, you can make some short fly leads to 
> enable the multiplug to be connected to the ecu by 2 pins (on the 
4 
> pin block) and the thermistor ecu inputs to a 10 kilo ohm resistor 
> to simulate the thermistor. If the car now idles then this is the 
> problem.
> > 
> > NIckT.
> > 
> > 
> > blackaddertoo wrote:
> > Hi all
> > 
> > an update on my idle problems
> > idle ecu and idle motor checked and working by martin at DMUK.
> > now removed motor, blocked pipes and adjusted screws...car idle 
ok 
> > at 1500 rpm.
> > checked power to ecu ok at plug, checked switch ok at engine but 
> > diode reads no resistance either polarity. (should it?) n moved 
> for 
> > further testing.
> > checked ground connection at ecu - Ok.
> > put Eecu and motor back in, shorted the diode/microswitch input 
to 
> > earth...car idle 30 second then dies. exactly the same problem.
> > removed diode short...idle 30 secs then dies.
> > 
> > so i am left to check the input from the distributor (should the 
> car 
> > idle if this is dead and hence the ecu does not know engine 
> speed??)
> > and if the leads from the ecu to motor are OK.
> > 
> > if i put a test light on the connector at engine end and switch 
> > ignition, should there be a short positive signal on the one (to 
> > either close the motor or open?)
> > 
> > then remove the microswith...do the same and the other lead 
should 
> > go positive.
> > 
> > that is correct is it not, middle lead to motor is ground and 
the 
> > other run motor positive one way and positive the other to close 
> the 
> > air valve??.
> > 
> > Thanx for reading this!! and sorry to bore you. i am determined 
to 
> > resolve this (and enjoy it really!!)
> > 
> > 
> > 
> > 
> > 
> > 
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