Large voltage Drop

[Ja.mc44]

Hey Guys,

1973 351C -

Car has new starter, new solenoid, new battery, all paired with MSD ignition box. I have 13.7 volts at battery with a jumper on it for extra power.

The problem I have is when cranking the car falls from 14v to 9 on the battery and cranks extremely slow. Though when I remove the starter + wire, then crank and test the starter side of solenoid I hear the solenoid trip and I get 14 to starter side of the solenoid. As soon as I attach that starter side solenoid lead back to starter it drops to 9V when cranking.

1. Does this sound like the starter itself drawing too much power? What kind of Voltage drop I should have when cranking, should I see 9V across entire system like i am right now?
2. Could it be a grounding issue? I have the starter separately grounded to the frame rail so is definitely grounded.
3. Would it be better to test amperage to it? Not sure how to do that or what secs it would be
4. Could this even be something like the timing being off?
Any info appreciated,

Thanks guys.

 

[Steve McMahan]

Where is the battery ground wire connected? Is it directly connected to the block and to the body? I think the ground may be the issue as well. Is the wire going from the solenoid to the starter “hot” after cranking it? That’s too much voltage drop. Check out, clean, etc the grounds and see what that gets you.

And as always, recheck the battery connections. And, even if it’s a new battery, doesn’t mean it couldn’t be the problem. Most auto part places do a load test for free.

 

[Cleveland Crush]

+1 on the load test (both battery and starter) suggestion from Steve.

 

[Ja.mc44]

Where is the battery ground wire connected? Is it directly connected to the block and to the body? I think the ground may be the issue as well. Is the wire going from the solenoid to the starter “hot” after cranking it? That’s too much voltage drop. Check out, clean, etc the grounds and see what that gets you.

And as always, recheck the battery connections. And, even if it’s a new battery, doesn’t mean it couldn’t be the problem. Most auto part places do a load test for free.

Battery ground is run straight to frame rail. What size wire do you use for solenoid to starter. I think the one on there now is like 6 gauge. Its not hot after cranking though.

Its a very weird situation and Ive been troubleshooting it for weeks now to no avail.

I ll take for a load test.

 

[Cleveland Crush]

Battery ground is run straight to frame rail. What size wire do you use for solenoid to starter. I think the one on there now is like 6 gauge. Its not hot after cranking though.

Its a very weird situation and Ive been troubleshooting it for weeks now to no avail.

I ll take for a load test.

Do you also have the engine  block grounded to the frame?

 

[Hemikiller]

Factory ground wire went from Battery(-) to fender apron to engine block. If you don't have it grounded directly to the engine block, that's your issue.

I've never been a fan of the factory setup, as it relies on the lower screw for the voltage regulator to ground the chassis.

 

[351c1971]

Could it be an internal short in the battery? You might try swapping the battery instead of jumping it.

 

[Retired2014]

+1 on Hemikiller’s response. The battery ground cable should ground directly to the engine block. Using your standard automobile jumper cable, clamp one cable to the negative battery post and the other end to the block at a non-painted spot. Then attempt to start while monitoring voltage drop.

 

[70cobrascj]

Factory ground wire went from Battery(-) to fender apron to engine block. If you don't have it grounded directly to the engine block, that's your issue.

I've never been a fan of the factory setup, as it relies on the lower screw for the voltage regulator to ground the chassis.


View attachment 71969

I didn’t think they used that style battery cable after 71?
And it seems Marti or anyone else makes that cable with the center tab anymore. I wish they did because I like that set up. I like it because it’s another point to anchor the cable in place. I usually add another ground from the engine to the chassis also.

 

[basstrix]

Battery ground is run straight to frame rail. What size wire do you use for solenoid to starter. I think the one on there now is like 6 gauge. Its not hot after cranking though.

Its a very weird situation and Ive been troubleshooting it for weeks now to no avail.

I ll take for a load test.

Per Hemikiller's post/picture, the ground must be attached to both the engine block and the body. The connections must be clean bare metal to metal. Confirming this or correcting it is the highest priority on the list.

 

[Bobby]

A new starter doesn’t necessarily mean it’s a good starter. Suggest you have it tested or better yet exchange it for another. Just make sure your engine block is solidly grounded to the frame and from there to your negative pole on yore battery. What kind of starter did you buy? Once you’ve verified that yore battery, frame and engine block are solidly grounded together, You can test yore starter by hooking up jumper cables from the battery negative to the starter case and the touch the positive jumper to the wire stud on the starter. If it doesn’t spin you’ll know for sure the starter is bad and also if there is a heavy electrical arc, yes it is shorted out.

 

[tony-muscle]

I like using 2 gauge cables rather than the skinny factory ones.

 

[Bobby]

Addendum to my earlier post. If there is a significant voltage drop when ignition is initiated, that is indicative of an internal short in the starter.

 

[Hemikiller]

I didn’t think they used that style battery cable after 71?
And it seems Marti or anyone else makes that cable with the center tab anymore. I wish they did because I like that set up. I like it because it’s another point to anchor the cable in place. I usually add another ground from the engine to the chassis also.

They used it up through '73.

You're right, I don't see the ground strap on the sets NPD is offering. That's odd and potentially a big problem.

I used 1GA welding cable to make a set of starter cables for my '71. I had the cable and the lugs and other parts from McMaster were about $20 at the time. I welded a stud into the apron to solve any potetial grounding issues.

 

[tpj71mach]

I bought the battery cable set from CJ Pony Parts that has the grounding tab on the negative cable. You can see it mounted to the bottom voltage regulator bolt.
https://www.cjponyparts.com/cj-clas...-351c-with-air-conditioning-1970-1971/p/BC11/I never thought of using a lug like that. That would have been better in hind sight.

 

[70cobrascj]

I bought the battery cable set from CJ Pony Parts that has the grounding tab on the negative cable. You can see it mounted to the bottom voltage regulator bolt.
https://www.cjponyparts.com/cj-clas...-351c-with-air-conditioning-1970-1971/p/BC11/I never thought of using a lug like that. That would have been better in hind sight.

That’s good ones like that are still available. Marti shows out of stock and has been that way for awhile.

 

[351c1971]

My 71 ground is bolted to the fender apron with a serrated washer. The fender apron was also brazed to the frame for additional stiffness years ago. This ground works well. A pix. is attached

 

[Steve McMahan]

I’m just wondering, after all of this advice, did any of it help? Did you find your problem? Inquiry minds want to know!

 

[351c1971]

Sometimes you have to choose between "100 Point Restored" and "More Better"

 

[basstrix]

Sometimes you have to choose between "100 Point Restored" and "More Better"

But should be grounded properly, in either case. Based on the OP's description, it is not grounded to the engine block...although that hasn't been clarified. Agree that proper grounding can be achieved by numerous means. In my application, I went with the "heavy duty" version of the OEM cables. As one might guess, they use heavier gauge cable...I'm happy with them.