TheSamba.com :: View topic - Can you fry your coil & still be driveable?

Wed Jul 02, 2008 2:43 pm

Background: I just bought a '73 SB w/ a 1600 DP, 009 dizzy and a center mount weber prog that I just finished rebuilding a couple of days ago. Cap and rotor appear to be newish, haven't checked points yet, but she starts immediately (even cold) and idles smooth.

Also, haven't been really able to figure out how to adjust the electric choke. Put the cap on making sure that the hook engaged the thing and turned clockwise until butterflies opened all the way, turned counterclockwise until they closed and then back clockwise just a tad. Tried adjusting choke again today and checked it after starting and the butterflies were wide open (this is why I think something is amiss) and no fast idle.

Situation: I was heading up a hill yesterday at about 40mph and it started shuddering/hesitating pretty bad until I backed off the gas. I was able to limp home and could get up to 55-60mph on level ground if I gentle, but no more than 35-40 mph uphill.

Also, at some point before/during this episode my choke walked over a bit and grounded out on the fan shroud frying the lead from the coil and popping a couple of fuses.

I have since fixed the wire and the grounding issue, replaced fuses, but she is still a pig going over 40mph.

Questions:
1. Is it possible to only partially fry your coil and/or condenser if one of the leads off of the coil gets melted in this manner?

2. Is it somehow possible that I first fried the choke, then it started running like crap bc the butterflies were closed (heard this happens maybe when pull pwr from choke?), and even though I have re-wired it, I still have something ass-backwards or the choke is toast?

3. If my choke is toast, any quick ideas to bypass for next month or two until I can get a better fix (it is well over 90deg here and I think I might be okay for a little while w/o it)?

I would appreciate any insight you may have to offer. Sorry for the novella and sorry for being such a flaming noob.

Wed Jul 02, 2008 3:33 pm

Eliminate the choke entirely,take the choke plate out of the throttle body...warm your car for 30 seconds or so before driving and you'll find that whole choke thing is nonsense......redo your tuneup proceedure....

Wed Jul 02, 2008 3:58 pm

Just after posting this, I thought to go remove the choke from the mix. So, I disconnected the linkage to the butterflies, locked them open and went for a drive (didn't think about disconnecting power to choke, that was still on).

First time I took off and tried to accelerate med/hard, it started to stutter/hesitate, blew a fuse (tach died) and the gen light came on. Also, same as before, I couldn't get above 30mph w/ aggressive accelerating. Below 30mph, however, it pulls nice and has good power.

Not sure what blew the fuse this time bc the new wire I put in wasn't fried and still had a good connection (wasn't grounded out).

Wed Jul 02, 2008 7:13 pm

i fried mine as well some time ago and mine wouldn,t crank up let alone drive but the motor did turn over

Wed Jul 02, 2008 7:30 pm

BTW, also checked resistance on coil and the results seem to be normal. The
middle terminal to one of the externals reads at approx 9k and across the two externals I get what appears to be zero (cheap reader only does 1k readings).

Thu Jul 03, 2008 6:50 pm

Another update:

Put in new condenser and points (cap and rotor look fine), started right up and went for a drive. Same thing, hesitates/shudders above 30mph and blows a fuse about 1.5 miles later down the road.

Constants:
1. starts quick and idles nice
2. good pwr and acceleration through 30mph-ish
3. starts shuddering/hesitating and will not accelerate further
4. back-off the throttle, coast a bit and driveability returns
5. about five minutes (approx) it blows a fuse and gen light comes on and tach freezes, but is still driveable.

I need help, suggestions please.

Thu Jul 03, 2008 7:41 pm

Run it without the tach and see what happens. Disconnect the power to the tach and remove the wire on the negative side of the coil. Years ago my tach would short out on my worktruck and do the same thing you are describing. Good luck.

Thu Jul 03, 2008 8:22 pm

Another update:

Okay, pulled the tach lead off of the coil and cut the positive pwr wire coming out of the back of the gauge (left more than enough wire to hook back up later).

Went for a test drive and no change- even blew another fuse.

Thu Jul 03, 2008 8:43 pm

To answer your specific question------NO

Fri Jul 04, 2008 7:04 pm

So you didn't say, but did the car run normally at first but then at some point you started having problems? Or has it always been this way?

A couple of things to check:

First, make sure that the wires are all hooked up to the coil correctly.

Open up the distributor and check the points and the point gap, or check the dwell with a dwell meter. If there's anything at all unusual about the points, then start by fixing that.

Keep in mind that the wire that supplies the positive side of the coil (and from there the two wires to the carb) HAS NO FUSE. So whatever's blowing that fuse is something else; possibly an unrelated problem. Which fuse is blowing?

With the fuse blowing, what happens when you turn the key to ON but without starting the engine? Do both the oil light and generator light come on?

Do any of your tach wires go to the coil? If so, it might be worth disconnecting them too.

Sat Jul 05, 2008 6:04 am

1. Bought bug about 60 days ago and it ran fine at first. After a few weeks it started hesitating pretty bad when accel from a stop, I suspected accelerator pump might be bad and I rebuilt the carb.

After rebuilding the carb, I drove it the next day for about 40-50 miles with a good mix of in-town and highway- everything was fine and it was actually running better after the carb rebuild but I think I still had some tuning to go.

2. Points and condenser are new and I'll check the gap again, but I spent a while installing them and making sure I had it set right.

3. Not sure which fuse it is other than it is the one on the far right of the fuse block (all the way over on the passenger side) and its an 8amp. When it blows, I can't find anything that stops working (haven't gone hunting, though).

4. After the fuse blows... I'll have to check.

5. Tach is disconnected at the back of the gauge.

New idea/theory: From my experience as a chevy guy (yes, I'm sorry), I seem to think that the only thing that would make a car shudder/shake like this at speed would almost have to be ignition-related only, right? Fuel/air issues, I think, would still make it run like a pig- just not so violent.

Sat Jul 05, 2008 7:51 am

raynman1972 wrote: After rebuilding the carb, I drove it the next day for about 40-50 miles with a good mix of in-town and highway- everything was fine and it was actually running better after the carb rebuild but I think I still had some tuning to go.
Ah, that sounds like a lot of my experiences. Dirt/crud in the carb tends to cause a lot of problems that are fixed by cleaning.

Quote: 2. Points and condenser are new and I'll check the gap again, but I spent a while installing them and making sure I had it set right.
I understand that, but a big surge of current or voltage spike might well mess up the points (unlikely but possible). if the surface of the points is messed up, that will change both the dwell and the timing point.

Quote: 3. Not sure which fuse it is other than it is the one on the far right of the fuse block (all the way over on the passenger side) and its an 8amp. When it blows, I can't find anything that stops working (haven't gone hunting, though).
I can't read the 1973 and later wiring diagrams very well, but at a guess from the ones posted on this site, I would say fuse 12 runs the fuel gauge, the seat belt warning system and the turn signals.

Quote: 5. Tach is disconnected at the back of the gauge.
So the gauge is totally disconnected from the rest of the car, particularly the coil? Disconnecting it from power will NOT necessarily remove it from the system. If the tach connects to the ground side of the coil, even without power, it could draw current from the distributor side of the coil and mess up the running of the car. This is much more likely if there's been spikes of current through it (when your choke grounded out).

Sat Jul 05, 2008 7:40 pm

Update:
1. replaced cap, rotor plugs and wires (condenser and points a couple of days ago).
2. Still need to check timing and valves.
4. Tach is completely unhooked at back of gauge.
5. Removed lead from coil that I am not really sure where it goes (doesn't go to choke), doesn't have power (batt or ignition) and has an inline fuse about a foot after it leaves the coil- fuse was an 8a and it was blown so it wasn't doing anything anyways.

Resutls:
1. Still starts quick an idles nice.
2. Still stutters/shakes at about 35mph, but is not as pronounced and seems to have a little more power. Now, the engine seems to shudder- before it seemed like it was about to shake something loose.
3. Doesn't blow fuse anymore and Gen light stays off.

Sat Jul 05, 2008 7:51 pm

raynman1972 wrote: Update:
2. Still need to check timing and valves.

Check the dwell too, before setting the timing. If you change the dwell, re-set the timing.

Quote: 5. Removed lead from coil that I am not really sure where it goes (doesn't go to choke), doesn't have power (batt or ignition) and has an inline fuse about a foot after it leaves the coil- fuse was an 8a and it was blown so it wasn't doing anything anyways.

That's usually the line that powers the reverse lights. Be sure to put the dead fuse back in the fuse holder so that it's tight and doesn't come apart and short out on something.