71 351 Cleveland starting/cranking issue

[FirstMach1]

I'm an average mechanic and have accomplished more in the last week than I thought possible. I hate electronics. But now I'm at a dead end and need your help.

1. Had no spark
2. Tested battery and coil. passed
3. Diagnosed a bad magnetic pickup in a relatively new distributor and replaced it. whew that was a job
4. Got spark again!!
5. Found TDC and roughly aligned timing
6. After a few attempts at starting I'm getting some carb backfire. Not the problem here but confirms fire in the hole.
7. Battery seems to run down quickly. ie.. cranks normally for a few seconds then acts like the battery is dead and doesn't crank at all. "The problem"
I continuously keep the battery charged up before trying to crank. I get one good crank for a few seconds if I'm lucky.
8. Battery checks out ok at auto shop and fully charged. Cables get hot when it does crank.
9. Pull starter and have it tested. It's one year old and passes test easily
10. Clean all contacts. Nothing looks awry.
11. Suspect starter relay. I jump the relay and at first it cranks normally and then slows down to no crank as before.
12. I'm out of ideas and need some help here please.

Thanks,
Eric

 

[Zach]

In terms of starting maybe too much timing maybe can cause extra stress? All you need is spark air/fuel and compression. Verify the rotor is hitting the right contact when you are at TDC of the compression stroke of cylander 1, out your thumb over the spark plug hole and feel for the blow, wait till it’s at the top. The rotor should be at spark plug ones connnection. You can put the spark plug in the boot and ground it and physically see the spark to make sure. Also make sure the carb is getting fuel, use some type of fluid if need be. Should at least fire.

It does sound like an electrical issue somewhere but even then it should still start. Have you tested the right voltage is being sent to the coil, distributor etc, not too much not too little.

 

[FirstMach1]

Thanks for the reply.

I have fuel (rebuilt the carb)
I’ll re check the voltage. I’ll search here for that.
I know timing isn’t right yet but without more than 2 seconds of crank I can’t experiment much. Dizzy is pointing to #1 at TDC. I’ve tried to get about 10 btdc roughly.
But again it just won’t crank long enough to give it a chance.

 

[Hemikiller]

First thing to check is that you actually have an engine to chassis ground path. Very common for this to be missing on our cars. Factory chassis ground point was the lower screw for the voltage regulator (#9)

If yours is present, or an alternative is present, and the cables and connections appear to be in good, clean condition, then a cranking voltage drop test is needed. If it's not present, add a temporary ground from battery (-) to the radiator support or fender apron and try again.

 

[boilermaster]

FirstMach1,
How well did the engine crank when you had no fire ?.
If in doubt, simply disconnect the distributor and take the timing out of the equation.
With no fire the engine doesn't know or care what the timing is.
If the engine still does not crank well the issue is with cranking.
Once that is sorted you can go back to timing the engine.
Boilermaster

 

[FirstMach1]

Thanks guys! It’s definitely a crank issue. It started just fine with good crank a few months ago. Then lost spark. Now this.
I do have a good ground cable. Cleaned all connections even though they looked ok.

I definitely need to check the voltage drop. Ok stupid question but I’m not sure so….
Which setting do I use on the multimeter when checking the drop?
DC v I assume