1969 Engine Wiring Harness Replacement - will not fire

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Peter, Good work....

Battery may have been ok but with the cranking lost it's energy. Because of this I'm more suspicious of the Yellow circuit during Crank. If it was bad, it'd cause what's going on.

To do the ohms test for the Yellow, just do a ohms test between the Solenoid R stud up to the Yellow/Pink connector in the engine bay. This just checks if the wire is good. Never know, a new harness could be defective.

And 583 ohms is ok for the PU coil. But also best to wiggle the wires under the distributor to be sure it's constant. Also I forgot but a good idea to ohm test each wire to ground too. If ~0 ohms, PU is shorted to ground.

Rich

Hi Richard - Yellow wire resistance tested well = 0.1 ohms.

Wiggled the distributor white/green and white wires while checking resistance across this circuit - maintained right at 587 ohms.

How do I ohm test each wire to ground?

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Hi Richard - Yellow wire resistance tested well = 0.1 ohms.

Wiggled the distributor white/green and white wires while checking resistance across this circuit - maintained right at 587 ohms.

How do I ohm test each wire to ground?

Ok good x2...

Place one meter lead on engine ground and other lead to touch each terminal on the connector one at a time. Should read infinite/open.

Rich

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Ok good x2...

Place one meter lead on engine ground and other lead to touch each terminal on the connector one at a time. Should read infinite/open.

Rich

I get an O.L reading, which I'm assuming means "open lead".

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

I get an O.L reading, which I'm assuming means "open lead".

Yes, Open. It's good.

I'd now wait for good battery and retry.

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Well Richard, no luck. Same exact symptoms.

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Well Richard, no luck. Same exact symptoms.

Ok, Let's do the same Sep1 Step 2 voltage tests from before.....

At Bat+ during Crank, then at Yellow during Crank. Record the results.

We have to make sure you're getting good voltage for the TI before we go any further.

Also, You may have missed the earlier questions about the TI Module, Original Delco or Reproduction?

Rich

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Ok, Let's do the same Sep1 Step 2 voltage tests from before.....

At Bat+ during Crank, then at Yellow during Crank. Record the results.

We have to make sure you're getting good voltage for the TI before we go any further.

Also, You may have missed the earlier questions about the TI Module, Original Delco or Reproduction?

Rich

Hi Rich - I'm still at 10.6 V at the batter, 8.6 V at the yellow wire. Where could the two-volt drop be coming from? Is this a potential starter solenoid issue? Anyway to est that?

I'm on the assumption that this is the original delco TI module, but I have no evidence to support that.

All I can say is that before the harness replacement, the motor ran perfectly, and now it doesn't. The only change is this wiring harness. Frustration is heavily mounting in my fruitless efforts, but I really do appreciate every bit of help you are giving in helping me solve this issue.

[David H.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

... the new harness matched up very well with the unit in the car, with exception to the TI connection, which another member pointed me towards the modification to the harness. ...

Peter

What was this modification?

Dave

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Peter

What was this modification?

Dave

Hi Dave,

The factory cuts off the wire end of the yellow lead of the stock wiring harness that is supposed to be threaded to the coil and replaces it with a plug connector to tie into the TI system. Here was my previous thread about this change:

https://www.forums.ncrs.org/showthre...d-Ignition-K66

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Hi Rich - I'm still at 10.6 V at the batter, 8.6 V at the yellow wire. Where could the two-volt drop be coming from? Is this a potential starter solenoid issue? Anyway to est that?

I'm on the assumption that this is the original delco TI module, but I have no evidence to support that.

All I can say is that before the harness replacement, the motor ran perfectly, and now it doesn't. The only change is this wiring harness. Frustration is heavily mounting in my fruitless efforts, but I really do appreciate every bit of help you are giving in helping me solve this issue.

Yes TI can be frustrating but you'll figure it out... Heading to dinner soon, and maybe you need a break too, but for now here is what I suggest for next steps when you get back to it.

10.6v during Crank at Bat+ is too low, but this is a C3 with longer cables than I'm used to. Ensure that you have a good Bat+ cable connection at the starter itself, and the battery+, and since this is a C3, that Bat- Ground Cable goes to the frame underneath. It may be with all the cranking, if there's any corrosion on that ground it could be worse and now affecting Crank voltage at the starter.

-You can eliminate that by using a good heavy duty jumper cable between the Bat- post behind the seat and directly to the engine, a good ground point, alt brace, manifold bolt, etc.

That 2 volt drop is a problem. You should see that to be almost identical to the Bat+ reading at Crank. It could be a bad Solenoid.
-To bypass it, add a jumper wire(~16Gauge) from Bat+ directly to the yellow wire up top at that connector. This would eliminate the Solenoid internal R terminal copper contactor during Crank. If it runs with this jumper, you solved your problem, albeit time for a starter/solenoid.

Edit... BTW, that jumper is exactly what the solenoid does during crank. You could add it before or after IGN On, but I would after IGN On.

Rich

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Yes TI can be frustrating but you'll figure it out... Heading to dinner soon, and maybe you need a break too, but for now here is what I suggest for next steps when you get back to it.

10.6v during Crank at Bat+ is too low, but this is a C3 with longer cables than I'm used to. Ensure that you have a good Bat+ cable connection at the starter itself, and the battery+, and since this is a C3, that Bat- Ground Cable goes to the frame underneath. It may be with all the cranking, if there's any corrosion on that ground it could be worse and now affecting Crank voltage at the starter.

-You can eliminate that by using a good heavy duty jumper cable between the Bat- post behind the seat and directly to the engine, a good ground point, alt brace, manifold bolt, etc.

That 2 volt drop is a problem. You should see that to be almost identical to the Bat+ reading at Crank. It could be a bad Solenoid.
-To bypass it, add a jumper wire(~16Gauge) from Bat+ directly to the yellow wire up top at that connector. This would eliminate the Solenoid internal R terminal copper contactor during Crank. If it runs with this jumper, you solved your problem, albeit time for a starter/solenoid.

Edit... BTW, that jumper is exactly what the solenoid does during crank. You could add it before or after IGN On, but I would after IGN On.

Rich

Peter, Replying to my evening post after some thoughts....

The 2v drop may be the solenoid but may be connection issues as I mentioned above.

At Crank I had you measure Bat+(at the Battery itself), then Yellow wire at Crank.

I should have had you measure Bat+ at Crank... at the Starter Cable stud on the solenoid itself. This would be a more accurate measurement to calculate the delta of the two. Your solenoid may be ok, but it'd be worthwhile to retest as I described here.

But.... My gut is telling me you have a bad Ground cable connection at the Frame.

A good way to test that is to put your ohm meter between Bat- post(at battery, before the clamp), with a wire jumper if needed for length, all the way to a engine ground. You could also do that test for the Bat+ cable, to the solenoid stud.

Overall battery condition is still a big factor. I know you said it was new earlier, but did it ever completely discharge since you got it? If so, it's compromised.

Also, since you're TI Module may be a original Delco, remember to never pull more than 1 sparkplug wire to test for spark. The old units can self destruct. Best way to test for spark with TI is a inductance timing light. Also, never try to connect a electronic tach to TI(coil+). It has been proven by others it will damage the original TI circuits.

Rich

[Peter S.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Peter, Replying to my evening post after some thoughts....

The 2v drop may be the solenoid but may be connection issues as I mentioned above.

At Crank I had you measure Bat+(at the Battery itself), then Yellow wire at Crank.

I should have had you measure Bat+ at Crank... at the Starter Cable stud on the solenoid itself. This would be a more accurate measurement to calculate the delta of the two. Your solenoid may be ok, but it'd be worthwhile to retest as I described here.

But.... My gut is telling me you have a bad Ground cable connection at the Frame.

A good way to test that is to put your ohm meter between Bat- post(at battery, before the clamp), with a wire jumper if needed for length, all the way to a engine ground. You could also do that test for the Bat+ cable, to the solenoid stud.

Overall battery condition is still a big factor. I know you said it was new earlier, but did it ever completely discharge since you got it? If so, it's compromised.

Also, since you're TI Module may be a original Delco, remember to never pull more than 1 sparkplug wire to test for spark. The old units can self destruct. Best way to test for spark with TI is a inductance timing light. Also, never try to connect a electronic tach to TI(coil+). It has been proven by others it will damage the original TI circuits.

Rich

Hi good morning Rich - seeing both your messages this morning. I was thinking the same thing - potential issues w/ the battery cables themselves. I was going to check resistance of each this AM. I was also going to inspect the engine ground, if that could even be a potential issue. Hopefully can take care of some of these items today, but I have a busy day w/ my kiddo as he's got a hockey tournament. I appreciate your follow up!

[Terry M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Just a Sunday morning thought here: Is the cable between the frame and engine (jumping over the passenger side engine mount) well connected?

BTW: This is a very nice systematic troubleshooting thread. Nicely done by both of you.

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Hi good morning Rich - seeing both your messages this morning. I was thinking the same thing - potential issues w/ the battery cables themselves. I was going to check resistance of each this AM. I was also going to inspect the engine ground, if that could even be a potential issue. Hopefully can take care of some of these items today, but I have a busy day w/ my kiddo as he's got a hockey tournament. I appreciate your follow up!

Ok Whenever you get back to it is fine. I think we're on to something. Best tool to check grounds is your ohm meter between frame and block. I think there's a separate ground from frame to starter, not sure though. Maybe the C3 experts can help with that.

Hope he does well at the game. Have fun. I love hockey too.

Rich

[Richard M.]

Re: 1969 Engine Wiring Harness Replacement - will not fire

Just a Sunday morning thought here: Is the cable between the frame and engine (jumping over the passenger side engine mount) well connected?

BTW: This is a very nice systematic troubleshooting thread. Nicely done by both of you.

Thanks Terry. I'm not too sharp on the C3 cars when it comes to the physical details. That ground cable you mention is worth checking. Good lead.

What's odd is everything was fine until he swapped the engine harness. We'll see when he gets back to troubleshoot some more.

Rich