intermittent spark

[simwal 0]

hi looking for some help 

i have fuel pressure as it should be regulator working 

amf ok ecu ok as i have tried different ones 

i have intermittent spark sometimes i have 2 plugs sparking switch off start again other 2 spark some times all spark some times none spark

i have tried differnt amps no difference not sure if all good 

purchased a new one no difference

with ignition on i have 12v both sides coil is this correct ?

lead to dizzy good 

all earths good 

tried different tach relay 

running out of ideas 

cheers 

[jackherer 543]

If you're getting spark to some plugs and not others it is probably a distributor cap related problem.

[simwal 0]

hi thanks

new dizzy and rotor 

no cracks there fine 

am thinking its amp related 

have tried new wires from amp to dizzy no change

in fact now getting no spark at all

[jackherer 543]

I've never seen a problem like that caused by an amp FWIW.

 

I'd suspect the coil itself if it isn't dizzy cap related. I am pretty sure it is correct to see +12v on both sides of the coil with ignition on and engine not running, the ignition switch supplies power to the + side and until the amp grounds the other side you are seeing the same 12v through the coil of wire from the + side. When the signal from the distributor pulses the ignition amp it then grounds the - side of the coil to produce the spark.

[simwal 0]

yes i agree on more invesigation there should be power both sides

i have checked coil seems to be close to what it should be on ohms 

i had a new coil on it 

changed back to  old one no change

checked and re checked ever thing 

must be something simple i am missing 

 

[simwal 0]

hi 

can any one help 205gti

i have intermittent spark sometimes sparks, some times no spark sometimes 2 plugs sparks switch off and other 2 spark

these are the things i have checked / changed 

ecu

afm

earths

new dizzy leads 

fuel pressure good 

tech relay 

i have tried different amps 2 ducillers and bosch

and others too

seems not to make much difference 

tested coil with bulb on negative side coil and earth and bulb flashes 

it has  sprung in to life a couple of times for a few seconds 

i have even tried wiring making my own wiring from multi plug from amp to  dizzy to check wiring and still same 

hope some one can suggest something 

 

 

 

 

 

[Tom Fenton 1,542]

All the trigger signal information comes from the distributor, assuming yours is a Jetronic car?

Anyway I'd try a new distributor or you can change the pick up coil inside the distributor, but its a bit fiddly to dismantle.

[dcc 855]

Also to the above, the cap and rotor arm

[PhilNW 44]

Under what conditions does this happen?

 

Ticking over?

Driven hard?

Accelerating?

Other?

Have you tried a set of in line spark plug testers to see when it happens?

Edited July 25, 2018 by PhilNW

[Andy 105 1 Cars]

Simon. Andy. Sorry that I cannot Skype until Monday. You tried the bulb on the negative side of the coil and it flashed, as it should do as the amplifier grounds the coil and causes it to produce the high voltage . That means that the coil is being pulsed . When you previously checked the output of the coil in the distributor, you got about  5hz at cranking speed, which is about right. The pulse also means that the injectors will be firing as the ecu needs the pulse to time the injector earthing . If the spark is still intermittent, it does suggest an HT problem, although I know that you have previously checked the leads, arm, cap and plugs . The other option is the timing, with the engine at tdc on number one with those valves shut, the rotor arm should be adjacent to number one plug lead. Check again . And finally, the injectors. They are injecting ? Unbolt the fuel rail, with injectors still in place , plugs out and rotor arm removed, spin the engine over and the injectors should pulse away like there is no tomorrow . An intermittent spray would suggest an intermittent pulse to the coil , so worth a look . Oh. Whilst you are doing this , resist the temptation to strike a match and torch the thing . In the end it will go. At the moment it is still laughing at you ( and me ) 

[simwal 0]

hi andy 

and thanks every one at the moment i have constant sparking as it should be due to making my own plug and wiring to ignition amp

not sure if this was cause of inconsistent spark but seems ok for now 

fuel  rail full of fuel tried spare injector and pluses great  and have had rail off a few times 

checked timing again 

plugs wet with fuel

tdc mark on fly wheel rotor  firing at plug 1 piston no at top 

can the the coil  give a weak spark ?

what would cause over fueling could it be getting to much 

fuel air spark compression should run 

its on the verge of running most of the time just seems something stopping it going 

could any thing in wiring cause it to spark at the wrong time 

have change tech relay 

i can feel it switching on with key and off when turn key back 

oh yes andy its laughing a lot at us 

 

 

 

 

 

Edited July 27, 2018 by simwal

[DamirGTI 342]

Ignition leads correctly routed on the dizzy cap terminals/plugs as per firing order ?

 

Tried another spare dizzy ? .. could be something within the dizzy mechanism

 

Weak spark , seem to remember old ducellier amps often fail by creating weak spark intensity .. but can be all the ignition components coil , coil + amp (sometimes when the amp burns out it damages the coil as well ..) dizzy cap/rotor arm , leads , spark plugs ..

 

Me thinks you do not have an "overfueling issue" , just an fuel leftover in the cylinders as it doesn't ignite it properly ..

 

What kind of spark plugs are you using ?

Had an real jigsaw with my mates 1.3 rallye no start issue .. fitted brand new NGK's as per specs and the engine simply didn't want to fire up .. also the spark intensity was kinda weak too ... after a lot of checking , swapping parts , measuring , cleaning - did an search via trash can for the old Eyquem plugs which where in previously , cleaned them up a bit and back in the engine and the bloody thing started up on the first turn of the key !

 

Also , had intermittent misfire caused by the spark plug also ... was just one , started when the engine reached operating temp shunting on/off one cylinder .. toughly checked the plug but everything looked fine on the outside .

 

Can try an shoot of easy start spray too , if everything seems to be fine fuel/ignition related but the engine is reluctant to start and keep on running/idling .

 

 

D

[simwal 0]

hi thanks damir

yes i am running ngk plugs spark is weak so i could try different plugs 

leads rotor cap all new 

have tried  a spare dizzy 

dizzy is new as is the engine it did run had a problem with head so swapped for another new one 

it has ran for a few seconds here and there 

i have tried start you basterd lol thats what they call easy start in australia 

i was under impression that coils either work or don't work 

have got a bosch amp on atm this is the one that the engine ran with 

am staring to think that i have a intermittent fault in the wiring loom somewhere 

 

 

 

 

 

[DamirGTI 342]

NGK's are really good plugs for XU engines , and single electrode best .. Those NGK spec. plugs for 1.3 rallye engine simply didn't work .. they where 3 electrode plugs , bought later on proper ones some odd fancy looking curved 4 tip Eyquem for the rallye specific on which the engine ran great though it did as well on a single electrode Eyquem and Denso plugs , simply didn't like triple electrode NGK's like there's no ignition what so ever not even a cough .. was an strange engine that TU24 !

 

Blue Bosch amps are the best and most durable , so that should be fine . Cylindrical coils also , pretty good but not so much can be said for the square type coils (mounted on the inlet manifold) these fail more often .

 

Kinda out of ideas really , strange issue you're having ..

 

 

D

 

 

 

 

[simwal 0]

thanks damir

ok got new champion plugs cheap!!!

put them in and instantly ran

3 times 

then nothing 

now took injector plugs  off and it ran for a few seconds 

this has lead me to the real and last problem hopefully as there has been a few

it must be over fueling 

changed ecu no differance

changed afm no differance

checked coolant sensor ohms seem correct 

the plug that goes in i don't seem to have continuity on earth get reading when ignition is switched on for a few seconds hen returns to 0 any ideas 

 

 

 

[DamirGTI 342]

Seems like mixed problem both the fuel and the spark then .

 

On the ECU coolant temp sensor wiring plug you need to have on one terminal earth and on another 5v (roughly 5v) with the ignition ON .

 

D

[Tom Fenton 1,542]

It sounds like it could be the ECU temp sender, have you belled (continuity tested) the wiring from the sensor plug back to the ECU plug?

[simwal 0]

hi 

checked temp sensor all good 

the 2 wires that go to temp sensor  ignition on no volts  continuity on earth 

when start get 11volts and no continuity on earth and  jumps around  3.1 then 2.6 ohms

 

 

 

 

[Tom Fenton 1,542]

What I mean is, if the wire back to the ecu is damaged or high resistance then it will affect the signal.

I would unplug the ecu plug and the coolant sensor plug. Identify the cores in the ecu plug. Resistance check from ecu plug to sensor plug each of the 2 cores. You should see very low resistance if any at all.

[Tom Fenton 1,542]

Edit to add. It’s not “earth” on the plug. It will be a voltage feedback to the ECU of coolant temp. 

[simwal 0]

hi tom 

thanks did continuity test on wire that goes to eco no 10 mines orange

reading 0 so all good other wire goes  to maf then earths go 0 on hat to 

any other ideas that could be causing this to over fuel and fail to start 

starts as soon as un plug injectors and runs for around 5 seconds

damir says i should only have 5v in orange i have 10 not sure if this makes a difference 

form one yorkshire man to another 

regards 

[Tom Fenton 1,542]

Hard to diagnose these issues remotely.

 

What might help us, how has this fault come on?

e.g. is it a car that was running ok then has developed this problem? Is it a project that came to you as a non runner? Did you do some work such as timing belt and then it’s showed the problem? Etc!

[simwal 0]

hi tom 

long story really had problem with previous engine none starting drove it home and then next day would not start

after a lot of diagnosing turned out to be lost compression 

so rebuilt engine (professionally done )

started and ran seemed to be ok except head knocking 

so new head 

ran first turn for  a minute or so then wouldn't start had sparking problems which are resolved 

then as stated above is were i am at 

i am sure the problem is over fuelling as said here is a real smell of petrol and disconnect injectors and stars runs for approx 5 seconds

 

 

 

[Tom Fenton 1,542]

Couple of things, are you sure the inlet manifold gasket is the correct injection type, the gasket sets often come with the carb type inlet gasket in as well, which covers the injectors over hence not getting a spray but a stream running down the port floor?

Also is the bolt for the oil filler in the side of the inlet manifold, this causes a big air leak as it’s a through hole.

[Tom Fenton 1,542]

Final thing are you sure there isn’t a wodge of rag up the inlet manifold, had very similar symptoms on a mates rally car 15 or so years ago, which turned out to be a big wodge of blue paper towel up the inlet that someone had put there to keep debris out, and then forgotten about it and fitted the throttle body. It took us some finding, we tried all sorts, swapped pretty much every component,  even tried towing it up and down the road with a 4x4 trying to tow it off.