Considering engine swap in the Brum

Subydoug · Post by **Subydoug** » Wed Apr 03, 2013 9:27 pm

The ballast resistor has nothing to do with the points. Its the condensor capasitor that stops points from burning out. All the resistor does is drop the voltage from the alternator down to 12v for the coil. Sometimes cars have a relay, so when the engine isnt running, the battery bypasses the resistor. This assists starting because of the voltage sag during cranking. On the resistor there should be a rating in Watts. The resistance only determains how much the voltage drops across the resistor. To determain the correct wattage you need you use ohm's law. V=IR.

V=voltage (volts)
I=current (AMPS)
R=Resistance (ohms)

so, say you need around 2ohms to get 12v under full charge

12= I*2 or I= 12/2
I=6Amps

Now you need to know how many watts that is.

W=VI
So w=12*6

W= 72watts

So it needs to be 2ohm, 100watt resistor.

Make sence? Given that your resistor is going up in smoke its either wrong, shorted out (unlikely, usually they go open circuit) or the wiring to your points is faulty. Do your have a multimeter?

Regards

Doug

tambox · Post by **tambox** » Thu Apr 04, 2013 8:03 am

Those resistors, generally, do not change much with heat, milliohm changes are usually the specs, unless overloaded.

I would be heading down Jonno's path of a short somewhere.

The standard plastic plugs, like the one on the back of the ignition switch are more likely to overheat and become resistive, when they are overloaded, by running to much current due to a "short". Hence loss of supply voltage/current. They cool down and the outer contact shrinks and closes on the inner. More revs=more current, causing your problem.

Does your temp gauge work yet?
If not, this could be related to an earthing problem.
Coincidence???

Silverbullet · Post by **Silverbullet** » Thu Apr 04, 2013 5:15 pm

Thanks alot Doug, your electrical knowledge is much appreciated here

And we got a decent multimeter today, that decades old Dick smiths cheapie wasn't giving enough info. Haven't had a chance to measure things yet.
Couple of questions about your calculations though, apologies if these sound dumb since I know nothing about electronics

Where did the 2 ohms figure come from? When looking for parts everywhere that had Brumby ballasts said they were .85 ohms. When the engine is running and the ballast is hot it's putting out 11 volts, 14 volts going in. Open circuit, that's what the guy at the auto electrical place said when I asked what happens when a resistor fails...what exactly does it mean? Is it equivalent to a break in the circuit? I'm guessing once a resistor goes open circuit it's completely kaput ie no recovery possible?

Tambox are you talking about the ring and bolt method of electrical connection being the ones that overheat? (dunno what they're actually called, they're not spade connectors) I'm about to go out and search for shorts, resistance and continuity now with the new multimeter. Maybe there is a short somewhere in the distributor itself.

Thanks guys, appreciate it

tambox · Post by **tambox** » Thu Apr 04, 2013 6:02 pm

I meant the high current spade connectors, the other types are for lower power. I have seen a few times where the spade plug plastic has gone off colour, as one of the connectors is getting hot.

The primary resistance of the OEM coil is about 1.2 ohm.
The standard ballast is about .85 ohm.

1.2 + .85 = 2.05 ohm.
.85/2.05*14=5.8v across the ballast.
1.2/2.05*14=8.2 across the coil.
These voltages are measured across the pins on these devices, not refered to ground.
If you have 11v at the coil, it will get hot and cause misses.
Disconnect your condensor to see if it has any effect on the voltages, it should make little difference.

These are ball park figures. The coil should run somewhere between 6v & 9v on a ballast points system.

Going on Doug's formulas, V=IR or I=V/R, 14/2.05= 6.8 amps.
Points are designed to work at up to 8 amps (generally).
Your multimeter should measure up to 10amps, so you could test the ballast/coil circuit. If it destroys the meter, its more than 10amps:sad: Carefull if you do this.

W= VI, 14*6.8=95.2Wtotal.
.85/2.05*95.2 =39.4W your ballast resistor has to get rid of.

Also measure from the battery -ve to the motor/manifold and any other earth points you can find, to make sure they are earthed fully.

Silverbullet · Post by **Silverbullet** » Thu Apr 04, 2013 7:33 pm

Primary resistance of my coil is 1.6 ohms, within spec. Secondary is 16.6, maximum spec in the book is 12.5. It's not the OEM coil but 16 ohms could still mean damaged?
I checked continuity with the earth(?) cable that goes to the dizzy. With the probe on that wire there's continuity with the engine, both pos and neg terminals on the battery and both pos and neg terminals on the coil with everything off. I thought this was odd but then there's continuity between both terminals on battery and coil anyway (duh

) There's no short in the engine wiring harness, and no short at any of the pins in the car side of the harness plug.

Also my old resistor is reading something like 1.6 ohms and the meter wouldn't settle down on the new one probably because it's still connected? Says in the booklet not to get the meter above 10 amps for more than 30 seconds and has a special probe socket for 10A.

You say points system should run at 6-9V, but when I ran it with both resistors in series (dead on 9V) it ran like crap and perfectly replicated my misfire symptom.

Anyway I've decided I'm not going to chase this much longer. It's seriously doing my head in and stressing me out. It's no fun when you're chasing a temperamental gremlin in your daily driver. So I will probably probe around a bit more but I'm ultimately changing to the electronic dizzy and coil, no resistor on Saturday. Swapping the engine harness over as well to make doubly sure there is no part of the old ignition system remaining. If it still misses and stalls...then I dunno what I'll do

tambox · Post by **tambox** » Thu Apr 04, 2013 7:37 pm

Is the coil a ballast type coil or a 12v coil?

Silverbullet · Post by **Silverbullet** » Thu Apr 04, 2013 8:08 pm

Bosch GT-40R

"R" for Resistor type

tambox · Post by **tambox** » Thu Apr 04, 2013 8:10 pm

Seeing your'e going to turf it, cut the wire on the condensor to rule it out,

Subydoug · Post by **Subydoug** » Thu Apr 04, 2013 8:30 pm

I used 2 ohm in my example because 2 is an easy number to work with. Remember, the resistance you need is determained by what the charge voltage is out of the alternator.

Yes Open circuit is essentially no connection internally. Just a ceramic paper weight

.

So now you've got your new beaut multimeter, time to put it to some good use. First things first, lets check the engine side of things. Get your multimeter and put one end on the negative side of the coil, and the other to a good ground. select "Ohms" on the multimeter, or if it has it, the audio beep mode for continuity. Slowly rotate the engine with a 22mm spanner. The meter will beep (or not) and show something like "0" ohms as the points connect withing the distributor. if it never shows 0 ohm then your points are either really dirty or they arnt closing properly. If its always showing a resistance then there is a problem elsewhere. If this is the case, I would unplug the engine plug (blue plug), locate the points connection within the plug (sorry, I dont know what pin it will be. You may have to use your multimeter to find it out) on the engine side and repeat the test. If now you have open circuit instead of a resistance then most likely there is a fault somewhere else inside the car's wiring, most likely something to do with the dash and tacho hookup. If it still shows some funny resistance then there is something up with your points. Before you dive head deep into the points make sure the condensor cap isnt skewing results. If it is points related They may be not opening far enough. I think from the top of my head they need to open about 1mm?? someone may be able to confirm that.

Now, if when you tested the engine wiring and It was good, then the problem lies elsewhere. The easiest way to find out what is causing your problem is simple. Put one side of your multimeter onto the negative of the coil, and the other to ground. This should be open circuit, though the tacho signal does come off here so you may see something in the order of kohms or mohms. Not sure what else comes off that coil negative as Ive rewired mine and it only has points and tacho.

man Im rambling. If you test all that, post back and throw up your results. If none of the above makes any sence let me know and Il try and illustrate it better.

Regards

Doug

Silverbullet · Post by **Silverbullet** » Fri Apr 05, 2013 10:35 pm

Just tried all that, with one probe on negative on coil or on the single earth wire at the plug the continuity doesn't stop when turning the engine over. Points open or closed it's always beeping. When I look at the earth lead into the dizzy it looks isolated from the dizzy body by non-metallic spacers for the spade terminals, and the rope insulation to the points inside. But since the points are bolted to the body of the dizzy anyway doesn't that defeat the purpose? Or are the points isolated from the body as well?

Either way I don't think there should be a continuous circuit when turning the engine over, but I've been wrong on so many occasions with this problem. I don't really care anyway the electronic dizzy is already bolted up, just need to wire it and set timing.

Subydoug · Post by **Subydoug** » Fri Apr 05, 2013 11:54 pm

Just doing the same test on my engine now......

Subydoug · Post by **Subydoug** » Sat Apr 06, 2013 12:29 am

Just shot a quick video showing how I would test it just to hopefully make it clearer what your distributor should be doing. While it uploads Il just blab about a few things I think I should have mentioned in the video but didnt. Firstly, I rotated my crank all the way around, every time a lobe came around on the dizzy shaft the points closed. They stayed closed for only a short period. This duration comes down to the condition of the points and how well they have been adjusted. Looking in the FSM reveals point gap to be 0.3-0.4mm.
Notice that when the beeper went off and I looked at the multimeter, it showed "0". That is the circuits resistance. It should be 0 ohms or it will inhibit the discharge of voltage out of the coil, leading to poor coil performance. Usual cause of high resistance is dirty points. 1 ohm on the meter is fine

.
Looking into the distributor, notice where the point arm pivots has a plastic bush? If that is clapped out it could potentially be shorting out your points.
If your points are visually opening and closing, then the chances are the problem is in that arm assembly. You can lift out the whole points plate I believe (been a while since I have done it) for better access to the points.

I see your going for an electric dizzy setup now anyway. That should probably give you a less erratic spark and hopefully a bit more reliability. Optical sensor one? Personally I kind of have a soft spot for the points....dead simple and pretty effective

.

Here you go,

http://www.youtube.com/watch?v=QfriKXdv ... e=youtu.be

Regards

Doug

Silverbullet · Post by **Silverbullet** » Sat Apr 06, 2013 1:05 am

Thanks for the effort Doug, specially at this time of night

My points must be cactus then since I get a full circuit whether points are open or closed. Would never have suspected them since they're probably less than 2000k's old. Or maybe it's shorting out somewhere else in the distributor body, maybe I'll pull it apart more and have a look. Maybe maybe maybe hehe

I'm putting the electronic dizzy from the old engine that was in the ute on this engine, and the coil to match. I have no idea how it works, there's a module in the dizzy and 4 steps around the shaft a bit like the lobes for points. I agree I also never had a problem with points based and actually preferred them because I understood them at least a little bit, but this little saga suggests I didn't know squat about them in the end

steptoe · Post by **steptoe** » Sat Apr 06, 2013 7:37 am

It is a joy not to have to set and reset points however basic they may be. Doug likely has a good theoretical explain of how the ignition module and its magnetic pick up works. Reason I suggested in the points , from one experience of a set of points by Bosch for a Lucas dizzy in an old Holden six - for some reaon the non points contact end of the spring - the post end? a little plastic electrical insulator had softened and was shorting to earth occasionally and not recall its symptoms but suspect intermittent was du to spring tension on and off for the six lobes.

I think Kettering has been long dead so must be time to learn the newer technology dizzies before you step up to distributorless ignitions

, the first of Subarus came out 1989 - 24 years ago !!

Nice is that you can still buy ignition modules for them $100 here or 40 bucks on ebay in the US

steptoe · Post by **steptoe** » Sat Apr 06, 2013 7:46 am

Doug - I have been tricked (i think) at some times when using that continuity function with basic non electronic components - sample was chunky gearbox hi lo rev switches, sent me off on a wild goose chase until I came back with plain 12V to send through switches to find everything was fine. Have since left continuity function alone , reserving it for electronics or at least recalling it was not a be all end all test.

Am I wrong in thinking what a plain DMM continuity function is meant for? is used for ? Surprised and

to see you , an electronics handy dude use it for the youtube above, so may have to rethink my findings before.....

Subydoug · Post by **Subydoug** » Sat Apr 06, 2013 10:05 am

Silverbullet wrote:Thanks for the effort Doug, specially at this time of night My points must be cactus then since I get a full circuit whether points are open or closed. Would never have suspected them since they're probably less than 2000k's old. Or maybe it's shorting out somewhere else in the distributor body, maybe I'll pull it apart more and have a look. Maybe maybe maybe hehe

I'm putting the electronic dizzy from the old engine that was in the ute on this engine, and the coil to match. I have no idea how it works, there's a module in the dizzy and 4 steps around the shaft a bit like the lobes for points. I agree I also never had a problem with points based and actually preferred them because I understood them at least a little bit, but this little saga suggests I didn't know squat about them in the end

hmm, I suspect steptoe may be right. Given that your engine runs pretty much rules out a fatal fault with the points. For eample, clip a ground wire directly to the negitive of the coil and try and run the car. It wont even fire.
Did you happen to see the resistance thru the points to ground? Very possibly shorting out somewhere else in the disty body. There are a few little plastic insulators that could wear out. Id maybe investigate a little further if your interested, or just put it aside and go with the Electronic points.

I assume the new disty guts has a 4 point star looking object rotating in the middle and a flat sensor like this?

These are very simple and work in a simmilar fashion to some types of crank angle sensors. The star induces a voltage into the little coil as its point comes closer.Then as the star finally passes the sensor's apex the voltage drops creating a falling edge. This falling edge tells the electronics to trigger a spark. Do you happen to have the other part of the disty? that part that pulls the coil low?

Regards

Doug

Subydoug · Post by **Subydoug** » Sat Apr 06, 2013 10:15 am

steptoe wrote:Doug - I have been tricked (i think) at some times when using that continuity function with basic non electronic components - sample was chunky gearbox hi lo rev switches, sent me off on a wild goose chase until I came back with plain 12V to send through switches to find everything was fine. Have since left continuity function alone , reserving it for electronics or at least recalling it was not a be all end all test.

Am I wrong in thinking what a plain DMM continuity function is meant for? is used for ? Surprised and to see you , an electronics handy dude use it for the youtube above, so may have to rethink my findings before.....

Yep, has happened to me too, though thinking about it just now, never with my fluke meter, only cheapies. One classic one I remember clearly was my roommates old ford brake switch. His brake lights stopped working and he pulled out the switch. Stuck a multimeter across it and it seemed to work just fine. Got a new switch and the brake lights worked again. It is usually always better to test something like it would operate. With the disty points example, you could connect a light bulb to the positive of the battery, then run the ground thru the points. The light bulb should illuminate when the points close. That is a far better way of testing it. Then if the bulb doesnt light, or stays lit, you can go in and investigate further. Given that the car actually runs, the points may need adjusting, or there is a worn bush, but deffinately not a direct short to ground.

Il be honest though Steptoe, out of the millions of times Ive used the cont feature on a multimeter, I may have had 2 or 3 where it didnt give accurate results. Thats a pretty good ratio. Also remember, light bulbs will mess with the cont mode as they have resistance.

Regards

Doug

Silverbullet · Post by **Silverbullet** » Sat Apr 06, 2013 11:34 am

Doug that's pretty much what the electronic dizzy insides look like. As for resistance when testing; the number would not settle down in any position so would be jumping from 9 ohms to .3 ohms then to 3.7 and all over the place. There must be a trick to testing resistance accurately

Anyway, points are in the past and in a couple of hours I'll be driving a pointless ignition system

All this time under the bonnet has given me the chance to notice 2 seeps leaking my new expensive (relatively anyway

) 90+ coolant all over the driveway...time to drain it and replace some hoses

Subydoug · Post by **Subydoug** » Sat Apr 06, 2013 12:33 pm

Awesome, will be interesting to hear how it goes. That sucks about the coolant leak. Hope its something easy to fix.

Regards

Doug

Post by **TOONGA** » Sat Apr 06, 2013 12:35 pm

Make sure you use the coil from the brumby with out the ballast resistor.

the pointy star thingy is called a reluctor

TOONGA