Some melting wire when I try to start
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Some melting wire when I try to start
I got some melting wire happening when I try to start the engine.
The engine does not want to start. It is on my 1989 F150 ext cab 4.9l straight 6cyl.
The wire location is as follows: On the right side in the engine bay at the front panel by the battery tray. Right in front of the negative battery terminal are two wires comming out of the main harness :a black/green wire and a black/white wire. Both are connected together to one wire that goes straight to the negative battery terminal.This is the splice that somebody did before. When I try to start the engine, the insulation is melting away here. It seems to me I have a grounding problem somewere and the starter tries to ground through this wire splice. Any ideas what I should do. Please help me out since the truck needs to be moved by the weekend.
Thanks in advance for any reply.
Martin
The engine does not want to start. It is on my 1989 F150 ext cab 4.9l straight 6cyl. The wire location is as follows: On the right side in the engine bay at the front panel by the battery tray. Right in front of the negative battery terminal are two wires comming out of the main harness :a black/green wire and a black/white wire. Both are connected together to one wire that goes straight to the negative battery terminal.This is the splice that somebody did before. When I try to start the engine, the insulation is melting away here. It seems to me I have a grounding problem somewere and the starter tries to ground through this wire splice. Any ideas what I should do. Please help me out since the truck needs to be moved by the weekend.
Thanks in advance for any reply.
Martin
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From: MA
It does sound like aground problem. My son had a similar problem with a 90 F250. When he changed the battery cables he couldn't get the ground off the block so he put it on the Aluminum A/C Bracket. Over time the Aluminum corroded an cause the bad ground.
If you have it attached in the same place move it to the block. If not then do this...
First Take off the battery cables. Disconnect the ground wire on the engine and clean surface. Sandpaper is good for scratching the metal bare. Do the same for the Cable end unless it looks like it needs to be replaced. Clean both end of the battery cables or replace them. Also clean the battery terminals to much gunk can mess them up.
If you have dual batteries try connecting only 1 at at time. If this doesn't work then it is either not a ground issue or it is another item causing the ground..
Hope this helps
If you have it attached in the same place move it to the block. If not then do this...
First Take off the battery cables. Disconnect the ground wire on the engine and clean surface. Sandpaper is good for scratching the metal bare. Do the same for the Cable end unless it looks like it needs to be replaced. Clean both end of the battery cables or replace them. Also clean the battery terminals to much gunk can mess them up.
If you have dual batteries try connecting only 1 at at time. If this doesn't work then it is either not a ground issue or it is another item causing the ground..
Hope this helps
Fleet Owner
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From: Easton,Ks
The Black/Green wire is the Actuators/Relay ground from the EEC pin 40 & 60 and goes to the NEG(-) post of the Battery.
The Black/White wire is the SIG Return (EEC pin 46) wire and this one is more than likely the one that goes to the Test Connector pin 2, not the Battery.
I do not think you have a ground problem, you have some wire that gets power shorted to some thing or some wire that is grounded over these wires.
Make sure you only have one wire, the big one on the starter side of the starter relay.
Note: These two wires are hooked togeather inside the EEC Computer.
Here is a Diagram:
The Black/White wire is the SIG Return (EEC pin 46) wire and this one is more than likely the one that goes to the Test Connector pin 2, not the Battery.
I do not think you have a ground problem, you have some wire that gets power shorted to some thing or some wire that is grounded over these wires.
Make sure you only have one wire, the big one on the starter side of the starter relay.
Note: These two wires are hooked togeather inside the EEC Computer.
Here is a Diagram:
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From: Virginia
If it only smokes and melts when you are cranking then I vote that there is something wrong with your large ground wire. You may find another small ground strap going from the engine block to the firewall. This may be getting hot and melting too.
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Note that these two wires are not normally grounded anywhere except at the battery for Black Green.
That is why if the Black/Green wire is not grounded the engine will not start, it provides the only ground for the Fuel Injectors, EEC Power Relay, EGO sensor.
It also provides the ground for the SIG Return. The TSP, EVR, MAP, PSP, and Clutch sensors use the SIG Ret. The Fuel Pump Relay also gets its ground from the Black/Green wire by way of a Transistor.
That is why I said and still believe you do not have a ground problem because these two wires do not normally have continuity to the Engine or Body surface.
That is why if the Black/Green wire is not grounded the engine will not start, it provides the only ground for the Fuel Injectors, EEC Power Relay, EGO sensor.
It also provides the ground for the SIG Return. The TSP, EVR, MAP, PSP, and Clutch sensors use the SIG Ret. The Fuel Pump Relay also gets its ground from the Black/Green wire by way of a Transistor.
That is why I said and still believe you do not have a ground problem because these two wires do not normally have continuity to the Engine or Body surface.
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Thanks everybody for your quick reply to help me out.
Unfortunally I can't see the diagram that Subford posted.
I would like to post a picture of the melted wire, but I don't how to do that. Any idea how to do that?
I will have a look at it tomorrow and keep you posted.
Unfortunally I can't see the diagram that Subford posted.
I would like to post a picture of the melted wire, but I don't how to do that. Any idea how to do that?
I will have a look at it tomorrow and keep you posted.
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Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
Here is a diagram of your system, notice the BLK/WHT (PIN 46) & BLK/LT GRN (pin 40 & 60) wire in the bottom part of the diagram.
http://www.autozone.com/images/cds/g...3d800a3a44.gif
I have no idea why you can not see the above diagram.
http://www.autozone.com/images/cds/g...3d800a3a44.gif
I have no idea why you can not see the above diagram.
Last edited by subford; Feb 10, 2006 at 09:34 PM.
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