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Melted Battery Cables (No Crank)

X

XJ?2010

NAXJA Forum User
Location
Michigan
I just swapped in a new Engine into my 87 Comanche 2WD 4.0L. (the motor was from a 99 but I swapped all the sensors, and brackets over...except for the block coolant temp sensor which the block was not drilled for.)

So upon startup for the first time I plugged up my battery (which is the optima red top I use in my XJ...I used it cause the Comanches battery is weak and I knew it would take cranking the engine for awhile before it would run. This because I couldn't get the distributor timing lined up exactly so with someone cranking the motor I was going to turn it to set the timing.)

Anyways I connected the battery and all seemed well my idiot lights and radio fired up just like the normal starting procedure (for this truck at least) Then I went to start it and I look up and from the other side of the hood is white smoke meanwhile all the dash and other lights went dead like a total power loss...I quickly took the key out and went around to look. Apparently the Positive wire from the battery to the starter got so hot it actually melted the insolation around the wire and the Negative was almost as hot but not as much damage. My knowledge of this happening would mean that I have a short to ground somewhere but I don't know where considering the only main ground wire is from the negative post on the battery to the ground on the starter. Should there be a 2nd Ground wire running to the body from the Negative post? Im stumped on this one guys any help would be great.
 
XJ?2010 said:
I just swapped in a new Engine into my 87 Comanche 2WD 4.0L. (the motor was from a 99 but I swapped all the sensors, and brackets over...except for the block coolant temp sensor which the block was not drilled for.)

So upon startup for the first time I plugged up my battery (which is the optima red top I use in my XJ...I used it cause the Comanches battery is weak and I knew it would take cranking the engine for awhile before it would run. This because I couldn't get the distributor timing lined up exactly so with someone cranking the motor I was going to turn it to set the timing.)

Anyways I connected the battery and all seemed well my idiot lights and radio fired up just like the normal starting procedure (for this truck at least) Then I went to start it and I look up and from the other side of the hood is white smoke meanwhile all the dash and other lights went dead like a total power loss...I quickly took the key out and went around to look. Apparently the Positive wire from the battery to the starter got so hot it actually melted the insolation around the wire and the Negative was almost as hot but not as much damage. My knowledge of this happening would mean that I have a short to ground somewhere but I don't know where considering the only main ground wire is from the negative post on the battery to the ground on the starter. Should there be a 2nd Ground wire running to the body from the Negative post? Im stumped on this one guys any help would be great.
Click to expand...

There is not, from the factory - but there should be.

Also, the primary engine ground from the battery doesn't attach to the starter motor (although it can, through a mounting screw,) but to the side of the engine block. The stud is just below the deckline, slightly above and behind the distributor (even with the #4 cylinder, or about, passenger side.)

Also make sure you've got the ground between the cylinder head and the firewall up to scratch.

If the smoke settled down and stopped after you let go of the key, it's not a "dead short." It's involved in the starter motor cranking circuit - which narrows down your field considerably. If it did not, it should have started smoking almost immediately, I'd think.

What modification have you made (if any) to the starter motor circuit during your engine swap?
 
XJ?2010 said:
the only main ground wire is from the negative post on the battery to the ground on the starter.
Click to expand...

this sounds like the problem^^

the neg. (-) terminal needs to run to the engine block-- if it's running anywhere else (like the starter terminal) it will use whatever it's attached to as part of the ground circuit and create a short to ground when the item it's attached to is used.
 
Since you are in the need to replace your battery cables, please go to
Jon's (5-90) website: www.kelleyswip.com/

He makes the best set of battery cables available for our Jeeps. Love mine!!
 
Ahh okay that makes sense I will run that ground to the engine block and im assuming the ground I have connected to the ground point at the #4 cylinder goes to the starter.

I haven't done any electrical mods on this truck but at some the PO has its a birds nest in some areas (thats my next project)

Thanks guys
 
XJ?2010 said:
Ahh okay that makes sense I will run that ground to the engine block and im assuming the ground I have connected to the ground point at the #4 cylinder goes to the starter.

I haven't done any electrical mods on this truck but at some the PO has its a birds nest in some areas (thats my next project)

Thanks guys
Click to expand...

The starter grounds through the mounting pad and screws - there's no ground that runs to it from the factory. The ground path for the starter is case-engine block-primary ground.

(I have seen - and rarely added - a direct starter motor ground where necessary, but it's rarely necessary. I only had to do it with large Diesel engines, where the starter cranking current was 300-400A or more...)
 
Alright so I got a new harness and installed it the correct way with no ground running to the starter then I connected all my grounds to the block. Went to start it and it still would not crank just a click followed by 2 quiter clicks like I had a dead battery. I know my battery is good. Is there a chance I fried the starter when the wires overheated?
 
XJ?2010 said:
Alright so I got a new harness and installed it the correct way with no ground running to the starter then I connected all my grounds to the block. Went to start it and it still would not crank just a click followed by 2 quiter clicks like I had a dead battery. I know my battery is good. Is there a chance I fried the starter when the wires overheated?
Click to expand...

Wire doesn't overheat on its own (in general,) if your wiring got hot that means that something was drawing too much current for the wire.

As far as the starter motor being "tested" - bear in mind that it's a "no-load" test. It's mainly going to check to make sure that the motor hasn't frozen, that the bearings/bushings are still good (indicated by a rise in no-load current,) and the like.

Just for giggles, have you tried turning the engine manually? Put a 3/4" socket on a breaker bar, grab the crankshaft snout screw head, and turn the engine manually. Doesn't matter which way - just make sure you can actually move it.
 
Where exactly did you originally have the ground wire attached to the starter? You mention having it hooked to the ground on the starter but, as was pointed out, there is no ground terminal on the starter. You didn't by chance have it hooked up to the solenoid terminal? Or to the starter positive terminal with the positive cable from the battery attached to the solenoid terminal?

Having the ground cable from the battery somehow attached to the starter case would not cause a problem provided the other two wires (battery positive and solenoid positive) were attached correctly.
 
5-90 said:
The starter grounds through the mounting pad and screws - there's no ground that runs to it from the factory. The ground path for the starter is case-engine block-primary ground.

(I have seen - and rarely added - a direct starter motor ground where necessary, but it's rarely necessary. I only had to do it with large Diesel engines, where the starter cranking current was 300-400A or more...)
Click to expand...

I did notice the OP said he had the ground cable on the starter and thought it was unusal but did not comment. I figured ifhe bought the XJ like that it would/may be OK having been modified by someone earlier.

And 5-90, you are correct,....I have only seen (British) Lucas starters and large diesel engines especailly in boats haveing a ground wire attached directly to a stud put there for that purpose. Because the Comanche have the Renix system, I am unable to comment since I not familiar with that system.
 
as long as everything is safe (no melting wires or fires) remove the small wire to the starter solenoid and check for power there (at the end of the wire) when "cranking."

-- power there should equal cranking of the engine since the starter is known to be good

-- no power there will begin the process of working backwards 'til you find power-- the item stopping the power will be where power enters but doesn't exit

check for power at the solenoid and report back.
 
I had the ground hooked to the solenoid stud it was a stupid move on my part I should have known better. After I cleaned up all the grounds with a wire brush she started right up.

Thanks for all the replies guys.
 
techno1154 said:
I did notice the OP said he had the ground cable on the starter and thought it was unusal but did not comment. I figured ifhe bought the XJ like that it would/may be OK having been modified by someone earlier.

And 5-90, you are correct,....I have only seen (British) Lucas starters and large diesel engines especailly in boats haveing a ground wire attached directly to a stud put there for that purpose. Because the Comanche have the Renix system, I am unable to comment since I not familiar with that system.
Click to expand...

RENIX doesn't have a ground to the starter motor. I'm sure of that - I've had five of them.

You've worked on Brit cars? My condolences (I still have set of Whitworth sockets somewhereabouts...)
 
5-90 said:
RENIX doesn't have a ground to the starter motor. I'm sure of that - I've had five of them.

You've worked on Brit cars? My condolences (I still have set of Whitworth sockets somewhereabouts...)
Click to expand...

Thank you. Condolences accepted.

Yes, I am from the caribbean, former British colony. I those days, 90% of imports were from Britain with the remaining from Canada and the US. Just about every British made vehicle ended up on our door steps and most of their small to mid size construction and earth moving equipment. I started out as a trainee mechanic with a construction company whose vehicles included Land Rovers 90 series, Austin Champs http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGHP_enUS429US429&q=austin+champ and an odd mix of regular British cars and trucks as well as construction equipment.

I could tell you stories about those Whitworth tools mixed in with some AF sizes with Metric ( to use on the VW bugs) thrown in for good measure when I was still wet behind the ears in a mechanic shop :confused1 . Just think,... 1/2" AF equals to 13mm or about 7/8" ( on a measuring tape) Whitworth IIRC.

Well, that was many moons ago. I have since moved to the Virgin Islands and worked as a marine mechanic then to the US and now work in the wireless communications industry.

Back to topic: I am happy the OP got it figured out. My assumption is he had the ground connected to the solonoid out terminal. Connected that way the positive out from the solonoid would go to ground when he attempts to start the engine. Any other way and he may not have had time to trouble shoot. :flame:
 
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