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 ancientbugger
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| posted on July 9th, 2010 at 08:12 AM |
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Ignition coil
Can a coil be breaking down intermttently? I've only had them work or not work. I can get the engine to start but not run. It's FI and I've
replaced the double relay and the fuel pump is working so I've ruled that out but with someone else cranking the engine there seems to be no spark at
the plugs>
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 matberry
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| posted on July 9th, 2010 at 08:35 AM |
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Coil or it's connections can give intermittant probs Barry. Chuck om another to test it, but make sure the connections are good as you go.
When it starts, it doesn't run at all, so just fires on a cylinder or two??? Doesn't sound like ign. but you can check spark as you've said, maybe
coil HT lead is a prob???
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
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Sides
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| posted on July 9th, 2010 at 09:27 AM |
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Also maybe check the earth strap from the trans to the chassis.
Have heard of cases where the strap was busted and the engine basically only earthed through the clutch and throttle cables... it'd fire once or
twice but that was it.
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ancientbugger
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| posted on July 9th, 2010 at 10:58 AM |
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I thought it would be the fuel pump circuit as the pump comes on only when the starter motor runs then the double relay keeps the pump running when
the starter is no longer needed. The engine starts up then dies as if the pump has stopped, so I checked first that the pump works, it does. I checked
that I was getting a spark at the points,I was but when I had someone turn the engine over there was no spark at the plugs. All that happened was one
day I drove to work-all fine, the next morning nothing, everything checked out fine, just wouldn't start, like no spark. I replaced the double relay
and it started so I used it for work, no problems, drove home. Next morning nothing. I have another new double relay but I may go get another coil as
they're not expensive and try that but I'm very tempted to get rid of the FI all together except that when it's running it is super
smooth.................for a VW!
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matberry
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| posted on July 9th, 2010 at 12:21 PM |
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Before you buy a coil, go step by step with the coil output. You said the points were sparking but no HT output, where did you test that. While you
test the points, the coil should output, so at the same time, hold the coil HT lead near an earth, arc the points, (preferrebly by rocking the engine
with the points just opening and closing), test for spark at the dissy end of the coil H/T, etc.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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68AutoBug
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| posted on July 9th, 2010 at 02:17 PM |
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| Quote: | Originally
posted by ancientbugger
Can a coil be breaking down intermttently? I've only had them work or not work. I can get the engine to start but not run. It's FI and I've
replaced the double relay and the fuel pump is working so I've ruled that out but with someone else cranking the engine there seems to be no spark at
the plugs>
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Hi
Yes, coils do break down internally, or the top can crack..
so, something is happening at the points...
so, I presume Your spark is there..?? maybe..
but not getting out of Your dizzy..??
or.. not getting to the dizzy, via the high tension leads...
high tension leads , [not the ultra expensive ones] can break down or short out..
test each lead with a multimeter...
check Your high tension lead is pushed right in at the coil and at the distributor..
PS: I do carry a spare coil... lol
cheers
LEE
- [size=4]Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY--- [/size]
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vlad01
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| posted on July 9th, 2010 at 02:26 PM |
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yep coil can and do break like that. a few types of failures are:
Primary coil open circuit.
Primary coil short circuit.
Secondary coil open circuit.
Secondary coil short circuit.
Sounds like you have a problem with the secondary as you are lacking output when clearly you have current draw on the primary.
Time for a new coil.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE |
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ancientbugger
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| posted on July 9th, 2010 at 02:59 PM |
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I've checked all the leads and they're good, the distributor and cap are fine. I haven't checked the HT from the coil to the dist. so I'll pop out
and check that now, I'll also change the points while I'm there and see what happens but what keeps on throwing me is it still feels to me like a
fuel thing-forget about the lack of spark for a moment but it'll fire up on all cylinders and then die like the circuit in the double relay isn't
keeping the pump going.
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grumble
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| posted on July 9th, 2010 at 04:42 PM |
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Are the points burnt a blue colour,it may be a condenser as they will break down intermittently,but grom your description it does sound like fuel
supply,on the main fuel rail there is a 7mm bolt in a T remove the screw and fit a fuel pressure gauge over this fitting,this will tell you if the
pump is stopping and you can work from there.Cheers Les
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ancientbugger
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| posted on July 9th, 2010 at 05:25 PM |
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That sounds like a good idea Les.
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ernie norley
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| posted on July 9th, 2010 at 05:25 PM |
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Gday all does the car run a balast resistor it maybe wired incorrectly when you let it return off start and it stops theres a wire unpluged for ign
side of resistor this is my thoughts on it starting but not running
Ernie
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ancientbugger
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| posted on July 9th, 2010 at 06:04 PM |
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Ernie it does have a ballast resistor on the coil but that has never been unwired(?). Would it cause any damage to anything if I wired it the other
way round. In the past and present with all my cars the coils have never used one but this came with one and I've never had a problem so saw no
reason to change it.
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grumble
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| posted on July 9th, 2010 at 06:17 PM |
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is the resistor wire burnt out?
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matberry
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| posted on July 9th, 2010 at 06:31 PM |
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Or put a test light accros the fuel pump terminals, will proove it gets continuous supply.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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ancientbugger
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| posted on July 10th, 2010 at 12:09 PM |
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AND THE WINNER IS.....................none of you! It was an air leak! Where the intake boot connects to the plenum chamber it had slipped off but not
until I had given everything a thorough shake,pull or just a bloody good talking to. I'n no expert with FI but it all seems arse about face with the
symptoms, when there's an air leak it runs slower or in this case not at all. In Pauline Hansons famous words "Please explain?" BTW she's running
sweet again.
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68AutoBug
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| posted on July 10th, 2010 at 01:38 PM |
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| Quote: | Originally
posted by ancientbugger
AND THE WINNER IS.....................none of you! It was an air leak! Where the intake boot connects to the plenum chamber it had slipped off but not
until I had given everything a thorough shake,pull or just a bloody good talking to. I'n no expert with FI but it all seems arse about face with the
symptoms, when there's an air leak it runs slower or in this case not at all. In Pauline Hansons famous words "Please explain?" BTW she's running
sweet again.
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thanks pauline...lol
Must have been a BIG leak..??
although Fuel Injection is like rocket science... lol
everything balanced..??
LEE
- [size=4]Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY--- [/size]
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ernie norley
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| posted on July 10th, 2010 at 01:58 PM |
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Gday all glad to hear you have it running nothing worse than not knowing where to start. then finding an unrealated symptom to be the cause have a
nice weekend
Ernie
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bajachris88
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| posted on July 10th, 2010 at 05:50 PM |
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An air leak makes perfect sense. an FI system with a AFM (air flow meter) as opposed to a MAP will stall instantly after start up. Its the central
main component for the computer to make judgement on air/fuel ratios based on teh programmed air/fuel curves. Its like ripping a heart out of a human,
it doesn't work well lol (don't try that one at home kids!!) 
IE: ur afm wouldn't have registered air flow as it would be sucking through the vac leak (near complete bypass if large enough). the start up
injection does its job, then it just dies over because it doesn't register any air flow (or very little) and adjusts the fuel mixture to suit the
wrong air flow.
And if its next to no air flow in the afm, it'll spit out next to no fuel to suit. (like a fuel cut off at the injector)
(ô_!_/ô) (ô_!_/ô)
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ancientbugger
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| posted on July 10th, 2010 at 06:22 PM |
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Where the elbow fits over the lip of the plenum inlet there's not a great deal of overlap so when the hose clip tightens up it slips up and off. It
was only when I actually made the mad dash from switching on then back to the engine I actually heard the hiss before the engine died. All good
now
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grumble
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| posted on July 10th, 2010 at 06:29 PM |
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| Quote: | Originally
posted by bajachris88
An air leak makes perfect sense. an FI system with a AFM (air flow meter) as opposed to a MAP will stall instantly after start up. Its the central
main component for the computer to make judgement on air/fuel ratios based on teh programmed air/fuel curves. Its like ripping a heart out of a human,
it doesn't work well lol (don't try that one at home kids!!)
IE: ur afm wouldn't have registered air flow as it would be sucking through the vac leak (near complete bypass if large enough). the start up
injection does its job, then it just dies over because it doesn't register any air flow (or very little) and adjusts the fuel mixture to suit the
wrong air flow.
And if its next to no air flow in the afm, it'll spit out next to no fuel to suit. (like a fuel cut off at the injector)
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They also split the rubber and again run like crap.Glad you have it sorted out.Les
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ancientbugger
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| posted on February 2nd, 2011 at 09:54 AM |
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You've have to love this forum, this has just happened again and I couldn't remember what caused it last time but a search and sorted!
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