Ignition system failure, trying to find fault...

[mike1980ra40]

Hi people, been Having some trouble with this motor,which has had me scratching my
head WTF...everything under the bonnet in brand new.
I think I have covered all the bases trying to find my problem there might be something I have over looked.

engine (18RG twin solex) starts up easy but dies anything up to 10mins later which would
normally indicate a failing coil, condensor or resistor (or all three) so i replaced the whole lot. carbs were checked out ok.
When I was driving car I would get say no more than 15 mins down the road the engine
would stall, sit on side of road for a while then start again go a bit more down the road etc.

spark plugs where gapped @ 1mm condition of plugs where (this set brand new only run for total of 15 mins NGK BP6EY):

No.1 Clean light tan
No.2 Black dry sooty
No.3 Clean light tan
No.4 Black dry sooty

ignition system is Lumenition optronic no faults found testing power module or optical switch. testing that involved having engine at TDC with IG on and making a short between
the black and blue wires from power module (optical switch disconected) that produced a
nice bright spark. optical switch reconnected and voltage tested on same wires. with beam uninterupted got 2.5v and beam interupted dot 1 volt so no fault there.

The dizzy I'm using came from my 18R-C which never gave me any problems before
and is the 16R type (with the advance/retard knob) tested vac advance diaphragm and
that held ok when vacuum was applied to it. no excessive play when turn rotor left or right.

so far I have run two setups

No.1 - (GT40R) with ballast resitorI
No.2 G coil without ballast resistor (GT40) (reccomended by lumenition techs)

I tested the resistance of the primary and secondary circiuts in first coil (GT40R)and found:
Primary 1.8 Ohms
Secondary 17.45K Ohms
Resistor 2.5 Ohms
Condenser 6.4 Ohms

in the second set up (GT40) (how its set up now)
primary 3.5 Ohms
secondary 17.25k Ohms
condensor 6.4 ohms (same one)

both of these have created the same problem, fowling up the plugs in 2 and 4 and stalling
after no more than 10 mins. are these coils the culprit? I read somewhere else on here
that GT40(R) coils were no favorable, I think I've run out of ideas at the moment

anyone have any thoughts?

TIA ..

[thechuckster]

grab a coil from an 4cyl Magna or a Camry with an external coil? neither of these requires a ballast resistor ('m using the magna one at the moment).

Personally, i'd suggest the VR pickup, igniter and Coil from a guts of a 22RE or 18RG that had electronic ignition.

Id also suggest you check that the lumination box output to the coil is changing from a short (or near-short) to ground (12V to coil) to open-circuit to ground (voltage drops off) when the trigger wheel gets to a 'spark location'?

Is the coil getting hot?

Do you get the same result if you use old-style points?

[mike1980ra40]

thanks for your ideas there i will try that,

strange thing is this IG system was running fine on my 18R-C then i did the RG changeover
and tranceplanted the the whole IG system (was the ballast setup) its only since the RG was
put in by someone else that the problems arose. first time round I found that the black wire
from first power module (too opt switch) was broken internally therefore the was not grounding
the switch properly so eventually the power module burnt itself out.

that was replaced so was everything else. neither coil wasnt getting hot, although i did notice the
+ve terminal on the ballast resister was quite hot (burning hot) however no wires where melting.

one other thing I did was borrow a borerscope and have a look at 2 and 4 when this problem
first started, and found a massive build up of carbon that looked like 100,000k's when engine
so far had only done 2,500

I'll try the 22R setup you suggested and also the magna and camery coils and see
what joy i get

cheers.

edit: one thing i'll do is double check if the coils get hot, i'll even measure the temp ...

[thechuckster]

are you sure the carbi's are OK? big carbon build does point a lot of finger at the carbi.

[mike1980ra40]

both carbs were checked twice, once on car and once off and the people who had them said there wasn't anything wrong with them and they were pointing fingers at ignition because
of the fowled plugs on 2 and 4.

[thechuckster]

suggestion? put the timing light pickup on each lead (one at a time) and see if all 4 are similar (in that the timing light is solid, regular, etc) ... if not the ignition, if they are consistent then re-consider carbs.

[brett_celicacoupe]

hard wire the coil to the battery and see what happens.

this should prove/disprove ignition thoery.


it does sound like it could be a carby problem, sounds like it could be running out of fuel. check fuel flow from pump in a bucket - disconnect while running.

[stradlater]

Those plugs are either real sus

OR

something funny is going on
BECAUSE,

you've got

1 - Lean(OK)
2 - RICH
3 - Lean(OK)
4 - RICH

Now, that, if I'm not mistaken is part of the firing order yeah? So it's doing SOMETHING on every second fire.

Or it's just co-incidence..

I don't see how a spark plug failing could cause it to run rich or lean, HOWEVER, a plug will get very wet if the plug is failing to spark properly, as you'll have fuel build up on the electrode area.

Just my 2c.

[brett_celicacoupe]

twin carb 18rg = 4 main jets.

its not uncommon to have one, 2 or three problematic mixtures


clean light brown tan doesnt sound like lean to me. sounds stoich

[mrshin]

Are you having fuel issues, e.g. is the fuel tank not breathing properly, therefore turning into a vacuum and not letting fuel out. Also, is your pump rooted?

Plus, if you have points, just get rid of them. No excuse is good enough to not use electronic ignition.

[stradlater]

That's why I said Lean (OK). It's probably fine, just if anything going towards the lean side, which is ok.

[river]

Hi,

Are you having fuel issues, e.g. is the fuel tank not breathing properly, therefore turning into a vacuum and not letting fuel out. Also, is your pump rooted?

I'm with the Shinmeister. I'd expect the ignition to give you trouble either starting or immediately after starting. And, as you've changed everything for the ignition, I'd be looking at a fuel delivery issue. Check the feul pump and filter. Run the engine for 15mins without the fuel cap on, and if it goes for longer than there could be a blocked vent or something that causes the vaccum in the tank and starves the engine for fuel. And, I know they've been checked, but check the float levels in the carbs.

seeyuzz
river

[mike1980ra40]

Hi to all, thanks heaps for all your posts has given me lots of food for thought. +rep to all

I have been at it since 7:30 am thursday morning and just finished up for now about an hour
ago 11pm. (i'm nuts) I ended up taking my laptop out side to cruise around the net while
fault finding. I have made some progress...hooray!!!, and have been concentrating on the electrical side for now.

Brett: fuel pump is ( I forget the name of it) a brass square flow thru type mounted
next to fuel tank.

mrshin: pump was installed a week after engine was rebuilt, so it's just on 2 months old.
on the weekend will take the hose off and check the pressure anyway jus to be sure
i didnt get a dodgy one.

I went to and auto parts store today and took my old coil with me with my multimeter
and tested two coils side by side plus the ballast resistors (old and new).
values I typed out in first post show a slighly stuffed coil and resistor, as the new coil
showed 1.2 ohms primary and 15.1K ohms on the secondary, new resistor at 1.3 ohms.

I went home changed over back to GT40R setup. Started engine first pop. 3 mins later
it stalled. I cursed car (discon the battery) went inside and had a CC'n'dry came back and tested under dash.

I traced the fault back to the central locking and keyless entry. WTF....I disconnected all
the power to that and the engine is now running with out stalling and when engine is
turned off it starts up again afterwards no problem. before it would not at all untill everything was cold.

thechuckster: did the timing light after I got engine running and got a constant solid flash on
all 4 leads, plus put tach on all 4 leads and got 850-900 rpm on each of them. Also
will be keep an eye on the carbs like you mentioned, I'm still convinced theres an issue
with them even though the've been checked twice

stradlater: sus plugs not sure ont that, the fowled plugs are next to each other on the
dizzy (2-4) firing order 1342, plus Ive used so far are Denso w16exu, w16exu11, and now
NGK BP6EY ... so next step (weekend probly) is to take plugs out and clean them and run engine again and see if theres any change in colour on 2 and 4.

diagram below roughly shows how its running now and how it pretty much the same as it
was when it was on my 18R-C



me needs to spread a bit more rep around ;-) I've already repped before ...

[mike1980ra40]

Hi,



I'm with the Shinmeister. I'd expect the ignition to give you trouble either starting or immediately after starting. And, as you've changed everything for the ignition, I'd be looking at a fuel delivery issue. Check the feul pump and filter. Run the engine for 15mins without the fuel cap on, and if it goes for longer than there could be a blocked vent or something that causes the vaccum in the tank and starves the engine for fuel. And, I know they've been checked, but check the float levels in the carbs.

seeyuzz
river

thanks river, theres no harm in checking again thats for sure ...

[Mundoolun]

Chech your Voltage Regualtor is not faulty, Chech alternator is working properly and all engine earth wires and battery terminals leads. I had a similar problem for years with a Turbo 18rc and it turned out to be a combination of things. worn alternator poor wiring and voltage regulator was not charging anywhere near required amount battery moved from boot to front also helped voltage drop as well as new battery leads and terminal clamps. I hope this gives you a new directon to go on. A good auto electrican can save alot time if you get to the point of totally frustration in working with you to ensure trouble free running.