Compu-Fire Failed?

[gtkid2002]

Hi all, here's my situation.

Pulled engine a few weeks back, put in a new clutch put it back in. Engine didn't start. Fast forwards a few weeks, pulled compu-fire unit and I put in points. Car runs, but stumbles on hills and such. Reduced fuel economy from 35mpg down to a measly 20mpg. Worse if I drive worse. Fast forwards to yesterday, I pop in a new compu-fire unit. Car still doesn't start, so I buy a timing light, and after a little bit of tinkering, viola! It starts. Fast forwards a few more hours. I do some reading up on what it should be timed to, set it to 0 (far left notch on my rear pulley), engine runs well. Hop in the cab, engine dies. Refuses to start back up. Hook up the timing light again, and it doesn't flash. At all, from either cylinder 1 plug or the wire from the coil to the dizzy.

I'm running a bosch blue 12v coil, resistance is about 3.8ish Ohms, it is getting power, key out voltage from the alternator (converted to 75A from generator) is 12.38v. I have a 009 Dizzy (I know, timing should be at 7.5 degrees, or middle notch, I know that now), and the cable that goes from the coil to the dizzy is missing a little piece, but it was working earlier. Cap has some corrosion, but rotor is the only thing that bothers me slightly. Will be picking up a new one in the next few days ( I work night shift weekends, so we'll see).

Cranking voltage dropped from 12ish volts down to 10v from the (-) terminal on the coil. Dropped down to 7vish when I had the timing light plugged in. According to the troubleshooting sheet that came with the compu-fire unit, if the voltage drops to 1v when cranking, it's the unit. If it stays at "around 13v", then the unit isn't getting power.

I followed the installation instructions to a T (minus clipping the excess from the wires), and everything worked with points.

The bug is a '69 for reference.

So did I just have a friggin part that cost me almost $90 just fail on me with not even two minutes of run time, or is something else amiss?

Please save me the whole "points are better!" speech. I know they're reliable, I just liked having the car the way I got it. I was totally unfamiliar with points until now, and the non-bosch ones I got just looked awful after only a few hundred miles of driving. The timing was off a bit beforehand though.

[JerryMCarter1]

Not sure
In order to eliminate all the ign wires -- try just hooking up 12 volts directly from the battery and see how it runs

Might be something along the way that is using up intermittently the voltage

Jerry
_________________
Experience always triumphs over hearsay and You get to select which theory to believe

[gtkid2002]

Alright. I'll try that come this Monday when I've got some time off.

Another thing I should note, I've always seemed to have had electrical issues with this car. I'll fully charge a battery, and over time, it'll just kinda slowly drain. Never die and leave me stranded, but I'll listen to my music, flick on the blinkers, and the stereo will die now and then. I've had this when I had my generator and now with my alternator.

Mind you, I've got a basic stereo and two speakers. I keep it up at around 24ish, and I do a little bit of engine off coasting with the stereo on, but not more than five minutes for an hour of driving.

[JerryMCarter1]

Well, on that order I would put in new battery cables and of course grind the body on ground install and also replace the tranny ground

_________________
Experience always triumphs over hearsay and You get to select which theory to believe

[gtkid2002]

I replaced the battery ground strap, but I'll have to check the tranny ground. I also get the joy of waiting on testing for a parasitic drain because I fried my multimeter a few weeks back. Voltage setting works, but the amperage does not.

[JerryMCarter1]

battery cables can look perfect on the outside and totally corroded in the inside-- and they can also check ok (low on ohms) for no reason - The way I check them is to have one in my hand and flex it watching to see if the needle moves intermittently on ohms - even then it is a bad test -- One must put an electric load on the cable - which is nearly impossible -
So as a rule of thumb I replace it if it has more than a few years on it
Jerry
_________________
Experience always triumphs over hearsay and You get to select which theory to believe

[Late again]

The Compu Fire is just a switch, just like points. Can you try to use a static timing light and just rotate your engine while watching the lamp. If the Compu Fire is good, your static timing lamp with turn on and off. The DVM you "fried" is just fine. Open up the case and find the fuse that is blown and bring it to a radio shack. Learn about your meter, you can't measure more current than the fuse or the range setting.

[ashman40]

[gtkid2002]

Ashman - I did not adjust the timing, because I got it to run. I did install a condenser, and I did gap the points to .016, which got it running. Did not know that about the difference. I tried the timing light off of the alternator terminal, and it still didn't fire. The only thing I have on the (-) side of the coil is the points. No tach.

Full battery voltage -SHOULD- be like 12.72v, right? I was wondering about that the other day.

I don't think the battery is bad, but that makes me wonder about my charging system. I always seem to have issues with it after a few weeks of driving, so I should probably re-charge my battery and try again.

Late again- Can't open the compu-fire units. The're sealed with a white epoxy. They're hall sensors anyhow, and I don't want to mess with those. Could be interesting to find one that can handle that much current and make my own though.

JerryMCarter - Is there a specific size my battery cables should be? Because the one that runs to my alternator is oddly small. Maybe six gauge, if that. Probably more like ten to eight.

Sorry for the late response, was almost late to work yesterday.

[JerryMCarter1]

your alt wire is ok
_________________
Experience always triumphs over hearsay and You get to select which theory to believe

[Cadaver]

as it says in the compufire manual and all like kind.
you can not have a super low Ohm (impedance) coil or it will blow up the
sender in the disty.
also if you connect the points to the coil positive , same blows it up.

the former overloads the transistor switch.
the latter sends current to infinity and same results.

what coil are you running.... measure it.
how many DCR (dc ohms) is the primary of your coil. 1 ohm, or 3 or 5?
read the warnings at their web site.. there are many a coil. not all are a go.

you can also , crank motor and monitor the sender wire. (black see manual)
12v , 0v, 12v , repeat as you crank
if that dont happen.
then,
1: no power to coil
2: coil primary open
3: coil minus lug not wired to sender.

it works just like stock but the points (a switch) is not a transistor that acts the same.

I Run MSD, so when my points fail i see the LED stop flashing on the MSD box.
you can add the same LED , i can teach you.
1x led
1x 510 ohm resistor green, brown , black color code.

the LED will be off when charging coil (transistor is on)
the LED will go oN ,just as it fires. (transistor is OFF)
an analog volt meter or scope work better....

if you need a schematic, can do, of led idea.
put it in a box and keep it in the engine bay and now you have a monitor for the points or for the compufire.

(never for CDI (my CDI uses a current monitor to pull this trick off)

ART:
coil minus >>> LED anode LED >>> LED cathode (longerleg) >>> 510ohm resistor engine ground. (ASCII art , piss poor)
some stores sell 12v LEDs that have the internal resistor already.
The LED lamp comes on at the instant of the firing.

News flash:
i see the walmart sells busman fuses now. with internal LED that
makes it glow, when it blows ( in the Military 40 years ago , all fuses had this. took 40 years to leak in the the civvy world , funny that)
I put them on all my external wired , fuses, (like back up lamps, fuel pump, etc)

[gtkid2002]

Candymustang - Not sure if I mentioned it earlier, but I'm running a Bosch blue. A: it's what my older compu-fire was running on for some time before I apparently knocked it out of timing, and it says anything lower than 2 Ohms is a "low resistance". Last I checked, the coil was about 3.3-3.8 Ohms. Depends on how my multimeter is doing (fried it, still kinda works), and I did measure it before I fried it. Also was about 3.8 Ohms, so I don't think it's the coil.


So just curious, with my old one, if I were to connect BOTH wires to the (+) coil terminals, could it fry it, or would it just not work? Because that's why I thought I fried my first one, which is why I replaced it.

And for that little LED circuit, I should have it run in parallel to the compu-fire wire, and not in series, correct?

I know the coil is getting power, because the wire is ran right to it. I can see it physically get a connection.

I'll play around with it this Monday and try and get a ride to Avery's Air Cooled down in woodland. Pick up some new plug wires among other things hopefully.


And uhm, funny story. I should have looked on the unit before I ordered my new one. I bought the one for the 009 because that's what I have ,but the one on it was for the vacuum advance dizzy's. I was wondering why it had a C.A.R.B. number and the new one didn't.

[Cadaver]

there is more than one system. (4 total,. points,electronic points, CDI, and distributor less ignition (with 4 coils or 2 with wasted spark)

one system just replaces the points function. yours?
the other is CDI, where the points or a trigger coil send a sync signal
to the CDI box.
the CDI box then sends 400 volts to the coil primary..
they are not wired the same at all.

http://www.vw-resource.com/compufire.html

you can not wire either system wrong or risk burning it up.

just try wiring your car radio backwards, boom.

do you have ,
21100. ? or 21101 P/n

http://www.compufire.com/index.php?option=com_cont...p;Itemid=9

this is the manual. did you do the 3 tests on page 2?
for diagnosing this (test light)?
http://www.compufire.com/index.php?option=com_docman&task=doc_download&gid=10&Itemid=35


the red wire is power / (compufire 21100)
there must not be a ballast resistor before the red wire.
before means, between the Plus coil lug and the ignition switch
this red wire powers the compufire electronics.
the black wire wires to the coil minus and emulates POINTS. (21100)


THE IGN COIL HIGH voltage tower: term:
never ground the coil HV output and crank (get shocked and can over load the system)
never run it open circuit . very bad idea, this cause progressive destructive break down of most the parts. (wires and coil too)
but do always have a spark plug as a load when testing, always, gapped
to the VW spec or the maker of the electronic ignitions recommendations.
some run a wider spark plug gap like .035, (my CDI does that)
of running CDI? use real resistance park plug wire, mag coil is best,never use
sold core, no resistance wires. I use Bosch mag, 500 ohms per foot.

the gap for the trigger neads to be .060 inches.
with 2 wires right. and 12v on the red wire.
and black to the minus coil , you must get spark.
if not test the coil for bad.

[ashman40]

Just as a note...
The two wires from the CompuFire unit are:

RED wire = 12v+ power. Usually connect to the coil (+) #15 terminal or a known good ignition switched source. Below 10v the unit will stop working.

BLACK wire - ignition trigger; coil (-) #1 terminal. THIS IS NOT A GROUND WIRE. Current coming in on this wire must be protected by a ballast resistor in the 3-4ohm range.

<GROUND> - The CompuFire unit is grounded by the distributor body it is attached to. This is the same as with mechanical points. If the ground strap inside the distributor is loose you will have grounding problems.

Also, mu CompuFire unit came with a small ring spacer that fit below the magnetic disc. When installed on my SVDA this is installed. I believe the instructions said it is NOT installed for the 009. So maybe the same kit can work for both?
I thought the "vacuum advance kit" was for the SVSA "vacuum-only" distributors (late '60s / early '70s), but I might be mistaken??
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[Cadaver]

[Cadaver]

there are lots of pit falls.
12vdc not steady to the +coil and module. monitor it. while crankiing
(in the instructions)
no ballast up stream to coil (coil will run at 8v and so will compufire and compumfire fails at 8v.
the CF module must be grounded ( base) if the disty has poor ground
the CF will fail.
the ground must stay a 0v all the time (use battery minus post to refr this ground and see that error)
the trigger wheel must be calibrated .060"

Using a volt meter. measure + coil , 12vd cranking , never wiggling ,steady 12v all times.
measure the Black wire , cranking, it must pulse 12,0,12v over and over.
if not the Compufire is not firing. (mag trigger, or?)
if it is wired correctly , it fill fire, (if not blown out already, as may returns show)
it fill fire, if it has power and is grounded and wired correctly
if not the trigger is failing, make sure the trigger wheel is set correctly.
these tests are in the manual. (pdf linked above)

never trust ground. on any vw, (weak link) always use battery minus
for your meter and see true ground errors at the test points.

[gtkid2002]

Candymustang - I'm not sure exactly which coil I have, so I'll have to take a look and pull up a model number. All I know is that it worked with my older compu-fire unit just fine. The one I have installed right this second is a 21100 and the one I had installed prior is a 21101.

Could I get away with running another ground wire from the dizzy to the engine block by any chance?

Also according to that schematic, if I'm reading it right, there is no ground, so it's still a 2 wire unit. Although if that's not a compu-fire schematic, then it still could be. They should really mention that in the manual though.

I'll check the rotor again and make sure it's attached well.

Thanks everyone for your help, I really hope I can get this thing going this week sometime. Kind of out of a car if I don't.

[Cadaver]

yes, the manuals mostly suck, "proprietary paranoia ,etc , or ..?"
at the least , they should show a drawing with what is called in this business
a "functional equivalence schematic".
(with no values )
or just show a trigger, then an Amp and the driver transistor.
in block diagram form
what i posted is the FREE WIKI drawing. (the coil is shown wrong)

but all you need to know is:
the module is not just a plastic lump
it has a Mag trigger (unless optic) most likely a Hall sensor.
then an amp . (this amp shapes the signal for the next stage)
that amp part, drives the main Coil driver transistor. (points emulation)

this main driver is just a ultra low RDs(on) hex FET. that has a very low resistance
tuned on. This transistor makes the perfect points replacement. (new age)

It runs cool and does not over heat if you never do 2 things:
never hook black wire to power
never run ultra low ohm coils (racing coils, there are many , vast numbers)
(not saying , higher voltage is bad or higher turns ratio is bad (blue is 80:1)
saying the primary coil resistance must not be TOO LOW. (ask them the limit, each brand and model has different limits....)
many can not handle 1 ohm primaries. as the manuals state.

Thank about that, as the coil primary impedance is reduced the current can reach infinity, and the transistor goes boom. (some racing coils cause that)
the transistor can handle (me shooting from my hip) 5 -10 amps.
exceed that and boom. same if someone, wired it wrong, boom.

the module has metal on the bottom, and that is ground.
there are 3 wires.
1 power
2: coil
3: ground.

Sure grounding any Distributor can help. (cars that use body for ground are not too good. and was corrected in the 80s)
in fact the 1968-70 205M disty has one inside. a ground strap.

if your disty is a 009 or some other distributor? lots there are...
ask your self , what is my path to ground. ?
just look inside.
is the breaker plate bolted to the casing (some are) is it loose? or rusted.?

The breaker plate must be solidly grounded, how you do that is your job.
keep in mind , rust ,age and missing parts.
the clamp on the base , goes to ground (good), the bore in the mag engine case is piss poor. (Mag/oxide rules here, and is bad.)
never rely on the Disty main shaft bushing for ground , ever...

if the unit don't make spark we can diagnosis it.
while cranking (meter minus lead to battery minus term via a long wire)
measure the voltage on the power pin, 11-12v typ. (disty PLUS)
measure the ground of the actual compufire module, it must stay at 0v cranking.
measure the coil minus wire (compufire, black) it must toggle, 0,12,0,12v.
or 11,0,11,0 ( (load on starter dictates actual voltages)

the trigger wheel must be gapped. the Hall effect sensor is very forgiving and is not like tuning in a Marconi radio. not at all.

the trigger wheel must be solidly fixed , then timed to TDC 0 , to begin.
later we can advance the timing to your cars spec.

you can also test this whole setup on a bench.
with jumper wires and a battery.

i think you coil is ok, 3.5ohms primary is AOK.

btw that electronic ignition must work , on the coldest day.
when cranking currents are way high and battery voltage is lowest.
if not , it's junk. 9v is a good goal. some newer cars it can drop to 8v.
not saying i know compufire spec. (they don't say)

[Cadaver]

[Late again]

Late again- Can't open the compu-fire units. The're sealed with a white epoxy. They're hall sensors anyhow, and I don't want to mess with those. Could be interesting to find one that can handle that much current and make my own though.

Maybe I wasn't clear. Nobody should open up a Compu Fire. I wanted you to open up the Voltmeter and find the fuse for the Ampmeter portion of the meter. You tried to measure more current than the fuse is rated for. Good luck on gettting the car running. I'm running the Pertronix and it worked right out of the box!