GolfGTIforum.co.uk
General => The garage => Topic started by: Mirage- on 25 April 2005, 10:13
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Guys
Just digging for thoughts and suggestions really as my gti decided that it wasn't going to start again yesterday having driven fine before parking up.
Noticed a few things when checking what was wrong.
- Battery leaked, corroding live wire connection to the battery.
- Starter motor causes power to the ecu to be cut and the clocks reset when attempting to crank it
- A LOT of Fuel is being returned through the air filter.
I've replaced the battery with a new one but I'm unable to continue investigating until I get a replacement starter motor tonight as even shorting the terminals produces only a clicking sound.
I'm thinking that it can only be one of three things:-
The battery leaking and corroding the main live feeds to the car it may be that it's just tripping the ECU causing it to fire the injectors when the valves are closed.
One or more valves are stuck/burnt out causing a free flow of fuel with no spark to be pushed back up and out of the air filter when the pistons crank over.
The leaking battery has totally buggered my ECU.
Any more thoughts/suggestions?
Regards
Ian
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Are you sure the battery is fully charged? If so try putting the car in gear and rock it back and forth. Perhaps something has siezed causing the starter motor to not be able to turn the engine over.
The fact that the ecu is cut and the clocks reset suggests that the batter lacks power, even with a knackered starter the clocks should continue working. Get a mate over and try jump starting it :)
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Tried jump starting it last night with no luck so knowing the battery had been leaking decided it was time to get a new one. New one fully charged and fitted, still cuts power when attempting to start.
It's hard to diagnose one problem when there are 4 more down the line before it :( Just when I thought things were starting to go right with a £590 FC insurance quote.
Will let you know later on about the starting problem after I replace the starter motor just wondered if there was anything else that could be causing fuel to be pushed back out of my air filter really.
Cheers
Ian
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Can't help with the fuel, but i had exactly the sam prob when turning the ignition key, everything electrical, went off then back on.
I traced the problem to the ignition live power the stereo! it was touching the body work! Worth a check as when you push your sereo in there it is very tight and those wires can get messed up!
Hope you fix it!
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Thanks I'll have a look at the stereo wiring tonight as I did remove it some time last week to connect the dvd player, could have possibly caught some wiring when pushing it back in.
Ian
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Hmm very strange! Unless the motor is well and truely siezed and simply draining too much current? You could try taking the motor out and jumping it direct from the battery to rule it out as the suspect.
The only other thing I can think of is either the ignition switch has gone, or possibly the cross over relay. Although I'm not sure where it is or what exactly it does, something to do with cutting pwer to non-essential components when starting the car I think.
Edit: Oh and double check all your earths are on tight, especially the gearbox and rocker cover connections. The gearbox lead is essential otherwise the ECU can get fried apparently :) Only on digifant models though, KJet has no ECU. I dunno what year digifant was introduced but I think 88 models have it anyway.
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The wires were corroded on the old battery so it may have had a poor earth :rolleyes:
Fingers crossed I haven't blown my ECU :embarassed:
Ian
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Well last night I managed to get the replacement starter motor fitted and the engine cranking over with the starter.
But.....
Now there's no spark. I've checked to see if there was a spark from each lead and then as none of them had a spark checked main lead from the coil, still no spark.
I'll have to have another go at it tonight and attack the lower voltage wires to the coil with a meter.
If there's no voltage going to the coil the only thing that I could think of was that the ECU is fried or a relay or fuse is knackered? Any advice appreciated.
Ian
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You should still get a spark even if the ECU was dead, if the obvious checks don't work out it could be a problem with the hall sender or wiring. The ECU only handles timing adjustments for engine speed/load etc.
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What more could I test to narrow it down and rule a little more out.
I wasn't aware that there would be a spark if the ECU was buggered as I was under the impression it controlled spark and fuel.
Thanks in advance
Ian
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The ECU controlls only fuel :)
There is a seperare ignition module which handles the spark, and the coil gets a signal from the hall sender so it knows what the engine is doing. If the ECU is fried the injectors will just be stuck open flooding the engine. Stuff to check:
4 Switch unit - testing
1 When making this test, the coil must be in good condition.
2 Remove the plastic cover on the right-hand side of the plenum chamber for access to the switch unit (see illustrations).
3 Disconnect the multi-plug from the switch unit and connect a voltmeter between terminals 4 and 2 (see illustration).
4 Switch on the ignition and check that battery voltage, or slightly less, is available. If not, there is an open-circuit in the supply wires.
5 Switch off the ignition and reconnect the multi-plug to the switch unit.
6 Pull the multi-plug from the Hall sender on the side of the distributor (see illustration), then connect a voltmeter across the low tension terminals on the coil (see illustration).
7 Switch on the ignition and check that there is initially 2 volts, dropping to zero after 1 to 2 seconds. If this is not the case, renew the switch unit and coil.
8 Using a length of wire, earth the centre terminal of the distributor multi-plug briefly. The voltage should rise to at least 2 volts. If not, there is an open-circuit or the switch unit is faulty.
9 Switch off the ignition and connect the voltmeter across the outer terminals of the distributor multi-plug.
10 Switch on the ignition and check that 5 volts is registered on the voltmeter.
11 If a fault still exists, renew the switch unit.
12 Switch off the ignition, remove the voltmeter and reconnect the distributor multi-plug.<p>
5 Hall sender - testing
1 Check that the ignition system wiring and plugs are fitted correctly.
2 The coil and TCI-H unit must both be in good condition.
3 Pull the HT lead from the centre of the distributor cap and earth it to the engine or bodywork.
4 Pull backthe rubber boot from the switch unit and connect a voltmeter between terminals 6 and 3 (see illustration).
5 Switch on the ignition and turn the engine by hand in its normal direction of rotation. The voltage should alternate from between 0 and a minimum of 2 volts. If not, the sender is faulty and must be renewed.
(http://www.moddin.net/images/temp/golf/ignition1.jpg)
(http://www.moddin.net/images/temp/golf/ignition2.jpg)
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Hmmm if the sensor/switch in figure 4.6a was broken would this prevent a spark from being produced even when testing that a spark is coming from the coil lead?
Just wondering as I seem to remember the last guy that owned this car saying something about that switch cracking. I've been meaning to replace the cap/arm and sender for months but never got around to it.
Won't be able to do the tests till tonight now as I'm at work.
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I'm pretty sure it will, as looking at the diagrams it looks like it provides the only signal to the coil/ignition module from the engine.
I don't think you can replace the hall sender seperately though, I think its a dizzy out job! Not 100% on that though I've never really looked into it.
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If this is a PB engine, isn't the ign amp switched by the ECU thru the green wire?, this is how it controls the ign timing as the distributer has no advance mechanism in it. (now putting my asbestos pants on in anticipation of being shot down in flames :wink:)
Steve.
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Yeah apparently the ECU does control the ignition advance, you are correct there is no mechanical/vacuum control on the dizzy. I'm pretty sure you should still get a spark even with a fragged ECU, but I could be wrong :)
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I thought the digifant system and motronic all have ignition controlled by ECU, as Steve said, there is no advance mechanism in the distributor. So buggered ECU will mean no spark.
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I think there is a good possibility the ECU is toast due to the earth problems, the engine would not crank due to the cylinders filled with fuel and hydraulicking from the injectors being held open by the ECU.
Steve.
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So the verdict is its f**ked then :laugh:
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Well after reading the Haynes manual again, the transistorised ignition system is controlled by the TCH-H switch. on Digifant engines ignition advance/retard is controlled by the ECU as we have said, but it is not clear wheather or not having a fried ECU would prevent a spark completely.
Personally I would think not as you can still get the engine running on a carbed engine with the transistorised type ignition when the vacuum pipe to the vacuum unit is disconnected.
But this is only theory on my part, if I had a digifant GTI I would be outside trying it right now :)
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I wouldn't think it would spark if the ECU is f**ked, it would be the same as unplugging it.
Of course a carb engine will work with the vacuum unit unplugged on the dizzy, this is because ignition advance is also controlled by centrifugal weights in the dizzy.
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rubjonny, these are two completely different ignition systems, disconnecting the vacuum pipe to a distributer on a carb setup is only removing the vacuum advance unit, it has nothing to do with the distributers ability to make a pulse from the hall sensor to switch the ign amplifier to make the spark at the coil. The hall sensor on a digi setup sends a signal to the ECU that is used to calculate engine RPM and this also used in the calculation to fire the injectors. The ECU makes a load calculation from engine RPM, throttle position, temperature and air mass then triggers the ign amp to fire the coil at the correct time to suit the conditions. So I think that if the ECU was filling the cylinders with fuel and you have no spark, to quote another regular forum member,
So the verdict is its f**ked then  :laugh:
Hope this makes my train of thought a bit easier to understand.
Steve.
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The ECU says no :grin:
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Thats basically it, digifant is fully electronic fuel injection, so the ECU controls the fuel and ignition completely.
Carbs are a mechanic setup.
Well done to Steve for a much more technical explanation  :laugh:
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Oh ok then :grin:  It would be nice if the Haynes gave you a bit more info on how the digifant system works, I need to dig out my copy of the Bentley really! :laugh:
The Haynes doesn't give any way of testing the ECU either, it just says 'take it to a VW specialist' :(
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Plug in another ECU :wink:.
Steve.
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Oh ok then :grin:  It would be nice if the Haynes gave you a bit more info on how the digifant system works, I need to dig out my copy of the Bentley really! :laugh:
The Haynes doesn't give any way of testing the ECU either, it just says 'take it to a VW specialist' :(
Don't rely on Haynes for information :laugh: :laugh:
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Oh ok then :grin: It would be nice if the Haynes gave you a bit more info on how the digifant system works, I need to dig out my copy of the Bentley really! :laugh:
The Haynes doesn't give any way of testing the ECU either, it just says 'take it to a VW specialist' :(
Don't rely on Haynes for information :laugh: :laugh:
So dont rely on haynes or gfs parts what can we rely on????????
The size of the portions in fish and chip shops?
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So to clarify, my engine is PB and it's a 1988 1.8 8v running Digifant injection.
I've replaced the battery with new, replaced the starter motor, 8 months old coil (gsf).
Are the above mentioned tests no good for the Digi then? if not are there any other tests which I can do to pin point the problem and get a replacement part?
Thanks in advance
Ian
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All those tests are still valid for the digi ignition system, but non will tell you if the ECU is blown.
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So...
Check for spark at plug leads
Check for spark at coil lead before distributor cap
Check coil is receiving power.
Check Ignition Switch
Check Hall Sender
Check wiring.
If all fail ECU knackered?
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Oh ok then :grin: It would be nice if the Haynes gave you a bit more info on how the digifant system works, I need to dig out my copy of the Bentley really! :laugh:
The Haynes doesn't give any way of testing the ECU either, it just says 'take it to a VW specialist' :(
Don't rely on Haynes for information :laugh: :laugh:
So dont rely on haynes or gfs parts what can we rely on????????
The size of the portions in fish and chip shops?
Oi, stop stirring you troublemaker :tongue:
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I'm being really good :cool:
just a few gay people trying to stir things up :laugh:
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That was aimed at Paul...........not you Corin :wink:
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Well having still not manager to get her started last night and being the short tempered bugger that I am I ended up giving up and hitting the Autotrader. 2 nice looking golfs later, both sold so decide ANY MAKE/ANY MODEL <£500 and end up buying a Rover 216 Gti.
Guess now I have a runabout I can finally take the beast off of the road and do all the things that I've been planning on doing for the last 2 years! (money permitting).
Don't think that I did too bad with the Rover tbh, £300, 1991, FSH, 2 owners, leather interior, full electrics and £550 TPFT insurance.
Ian
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as said, why didnt you just get a 2nd hand ecu and try it?
£5'er of ebay here (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=9889&item=4546317778&rd=1&ssPageName=WDVW)