That X#$&^*@~* '75 still won't start--the saga continues

[Mike Self]

Some clarifications:  it is a stick shift car, BTW

• We're getting +12 v at the coil anytime the ignition is on, and also when the key is turned to start, so we know the coil is getting power
• We've tested the entire ground circuit at both the dizzy and at the coil, to the point of running a jumper wire from the - terminal on the coil to the dizzy.
• We've tested the points to make sure they're not grounding between the movable points and the fixed ones.  With the points closed we have a complete circuit; with the points open, the ohmmeter reads infinity.  We also made sure the movable (insulated) points aren't grounding against the distributor body when the points are open.  We performed a smiliar test on a set of used but identical points, and the tests were all the same.
• The point plate is properly grounded to the dizzy body.  
• To eliminate a problem with the tach, diagnostic port plug or the remaining emissions stuff, we disconnected all the wires on the coil's negative terminal, and ran a jumper wire to the distributor.

Since this is an electrical problem and not a timing problem, we've tested all the electrical components of the distributor (as opposed to the timing components) and they all check out.   However, given the trouble I encountered with my own car a few weeks ago that proved to be an elderly condenser, I have a couple of NOS Bosch condensers in my parts stash that we can try.  

 

Keep those cards and letters coming, folks.   This ain't over yet!

 

mike

[dlacey]

3 hours ago, Mike Self said:

To eliminate a problem with the tach, diagnostic port plug or the remaining emissions stuff, we disconnected all the wires on the coil's negative terminal, and ran a jumper wire to the distributor.

and still nothing? it can only be one of those three components: coil, points, condensor

I would bet condensor every time

['76mintgrün'02]

It's funny how many of the old distributors I've had come to/through the shop have had bad condensers.

 

+11 for you having bad condensers. 

 

"90% of your ignition problems are caused by condensers." 

( maybe not, but it reminds me of your father-in-law's quote.  )

 

The body of the condenser needs to be grounded to the distributor body through it's strap.  There was a thread a couple months ago where someone wrapped a small condenser in electrical tape, to make it fit the strap and that insulated it from ground.  It worked, once the tape was removed.  Surely that's not your problem, but a fun story.

Tom

Edited May 19, 2021 by '76mintgrün'02

[Buckeye]

@Mike Self, You need to find a loaner dizzy. BTW, what is correct dizzy for 75? Can't you borrow one from one of your cars and stick in there? That is 10 minutes job. 

Just my 2 cents.

Edited May 19, 2021 by Buckeye
.

[Hans]

1 minute ago, Buckeye said:

@Mike Self, You need to find a loaner dizzy. BTW, what is correct dizzy for 75? Can't you borrow one from one of your and stick in there? That is 10 minutes job. 

Just my 2 cents.

If only to see if it makes a spark at the plug.

[Son of Marty]

No real need for the correct distributor by year, your just looking to make a spark, not to drive it around.  

[Buckeye]

12 minutes ago, Son of Marty said:

No real need for the correct distributor by year

That is true. I am just curious and for archive 

['76mintgrün'02]

2 hours ago, Buckeye said:

what is correct dizzy for 75?

 

R.I.P.B.M.W. posted pages from his Bosch catalog that lists all the distributors for our cars, as well as the consumables that fit them.  I bought a 1983 version of the same catalog off of ePay after seeing his.  I'm too lazy to take my own photos right now, so I'll borrow his and then give the link to where he posted it, with all the other pertinent pages.

 

 

 

 

Tom

[JLENHAM]

Mike, what starter is in the car?  I am sure I won't get this right from memory... but if you connect the "12v directly to coil while cranking" wire (black red?) in the same location as you would on the stock starter to some of the "upgraded" starters it won't work, when the key returns to run, that connection goes to ground.  

Your description of the presence of 12v at different key positions doesn't support this possibility...  but....  

[Schnellvintage]

What is the dwell angle?  That will show the points are actually moving correctly. Opening and closing.  Also have you tried jumping a separate positive and negative wire from battery?  Positive to the positive side of coil and negative to body of distributor.  That isolated the 3 components, 4 if you count the spark plugs.   Just a thought.  Hoping it gets fixed.

 

['76mintgrün'02]

This may have been mentioned in your previous thread on this topic, (multiple threads on the same problem make it harder to keep track), but have you tried a different cable between the cap and coil?  I had two faulty plug wires (brand new). 

 

Tom

[ray_]

On 5/18/2021 at 3:36 PM, Mike Self said:

Some clarifications:  it is a stick shift car, BTW

•  
• We've tested the entire ground circuit at both the dizzy and at the coil, to the point of running a jumper wire from the - terminal on the coil to the dizzy.

 

I'm not quite sure what that does...

[dlacey]

11 minutes ago, ray_ said:

not quite sure what that does...

The coil charges when it is grounded via the dizzy points, the coil fires when the ground connection is interrupted,

 

by running that wire, all black wire wiring loom/connector/revcounter factors are eliminated... as long as theres volts on Coil+ it will work.

[ray_]

3 minutes ago, dlacey said:

The coil charges when it is grounded via the dizzy points, the coil fires when the ground connection is interrupted,

 

by running that wire, all black wire wiring loom/connector/revcounter factors are eliminated... as long as theres volts on Coil+ it will work.

He didn't say he ran that wire to the points.

[dlacey]

24 minutes ago, ray_ said:

He didn't say he ran that wire to the points.

Theres only one electrical connector on a 2002 dizzy