Help, the dealer gave up.

starfighter13

New Member
Feb 12, 2010
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So my sister's mustang only starts when it wants too. Sometimes everything works fine. Sometimes.........Open the door and the light is on and everything but when you turn on the headlights everything dims and quits working (like the power seat). Put the key in the ignition and turn it "on" and all the dash lights come on. with the headlights on everything works normal. Not like before when the key wasn't in. Turn the key and everything goes black.

Then she tows it to the dealer and it starts fine. gets it home and it takes a fat one.

She is just giving it to me and hoping I can fix it. I'm pretty handy I have lifted my on pickup and always do my own maintenance. Just wanna get a good place to start from. It would really help alot. She's in med school and can't afford the dealer fixin it anyway.


Oh just to add, when it starts, it starts. When it doesn't, well no cranking or trying, just everything goes black when you turn the key. The battery was checked out by the machine at the auto-parts store and its A-OK.....
 
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Begin with an inspection of the grounds. Esp the grounding strap from the engine to the car frame. Consider removing the grounds and cleaning the lug and frame contact area. Pay particular attention looking for evidence of overheating or corrosion.

Inspect the starter cable through it's entire length. Look for evidence of burning or overheating. Also, ensure there is not any hidden corrosion inside the battery cables. Internally corroded cables will be soft and brittle.

On the battery junction box, there is a bolt/lug connecting the battery cable. Check to be sure it is clean and tight. Inspect the other connectors near and around the battery looking for any damaged, loose, or corrosion.

Try wiggling the battery cables when the problem is occuring. See if you can find a weak connection.

Next, measure the voltage on the battery before cranking and during cranking. Report. Getting a voltage reading while the problem is happening is going to be very helpful.

Considering getting a DC amp meter. The shunt type is cheaper but the clamp on is easier. It would be very helpful to know the current through the starter. This may be as simple as excessive drag on the starter, a bad starter solenoid, or bad starter bearings.

If you can not find any evidence of an external electrical problem, consider replacing the starter.
 
This is a classic bad connection problem.You should first check the tightness of all high current wires especially on your starter circuit around the starter relay/solenoid & at the starter motor. Check ground wires too, Check battery voltage while cranking the engine. Battery voltage will drop to below 10v while cranking the starter which is normal, if this does not occur then the battery is not supplying enough current to crank the starter because of a bad connection somewhere. However headlights may light normally. If the battery is bad you will not ever get correct fully charged voltage which will be around 12.7v.

Secondly you could have a set of worn brushes in the starter, which will be intermittently making contact at rest. Try smartly tapping the starter motor casing with a wooden hammer handle or soft faced mallet , get an assistant to twist the ignition key ,if it fires right up, you need the brushes replaced.....
 
So I got the car from my sister and I was trying to get it to start just long enough to get it on the trailer. Its started once. I was wiggling the light switch and it fired right up. So like an idiot I turned it off and removed the light switch and then it went totally black nothing worked. Then I found that if I wiggled the ignition where the key goes it I could get everything back for a sec but I never got it to turn over just a click.

So here's what I found. I'm going over the wires completely tomorrow but just thought I'd update so you guys would know I'm dedicated to posting about this.

I would get dashlights and a click from the starter solenoid when I went for a start. But no start. Sometime when wiggling the ignition or the light switch something would cause such a draw the whole freakin car went black. I removed the light switch just to see if that was the component causing the problem and it was totally dead then I got the dashlights back by wiggling the ignition switch.

I took apart the whole dash wiggling and inspecting everything. It all looked good. The car went from black to dashlights with no start again when started to remove the negative battery post. Someone replaced the positive wires thinking that would fix it. I just have this feeling its a ground. I have had some bad grounds cause funny ****er to happen. This thing has some major gremlins. I'm gonna fix this sucker though.

Any Thoughts????
 
Check Ground G203-G204 near radio

Check the following grounds:
G201, kick panel, LH side, (Near PCM)
G203-G204, behind dash panel (left of center console near radio)
G104 Check the CCRM ground engine compartment front right.

Grounds G203-G204 are shared with many devices including the RADIO. Does this car have a BIG sound system? Possible the ground became loose after radio install. Or a big audio system may have over loaded the ground. In any case, this is the first place I would look.

If the problem is not found after inspecting the grounds, continue wiggling the wiring harness. Esp around the ignition switch. It sounds like it can be re-created easily which will make it possible to narrow down. Keep after it. I am sure you will find it.

When the problem is actually happening, make a list of what works and what doesn't. This can help narrrow down where the problem could be.

Check the positive battery cable to the main bottom stud of the main junction box. Make sure it it tight. It is easy to miss. Also check all of the battery cables for internal corrosion. The cables will be soft and brittle.

How are you concluding the load is too high? Have you measured the voltage at the battery? Recommend that you keep a VOM on the battery to monitor voltage during the wiggle testing.

Do you hear the sound of electrical arcing? If yes, think short. If not, think bad ground/loose connection.
 
I'm thinkings ground but the problem is so intermittent. I fixed it once wiggling the neg on the battery. Once by wiggling the headlight switch and once by wiggling the ignition. I think this weekend I'm just going over the whole negative side of the system. Thanks for the wire numbers though! That helps
 
So the battery terminals had been obviously cleaned several times to try and fix this problem but I took the wires out of the terminals anyway and they were so corroded it was sick. I cleaned every freakin ground on the car and whammy!!!!! Fixed......now just gotta give the whole upper motor a good bath and this mo-franky is gonna be rollin again.
 
So the battery terminals had been obviously cleaned several times to try and fix this problem but I took the wires out of the terminals anyway and they were so corroded it was sick. I cleaned every freakin ground on the car and whammy!!!!! Fixed......now just gotta give the whole upper motor a good bath and this mo-franky is gonna be rollin again.

Well done!
A tip for the future, a corroded connection will always result in increased resistance, which in turn results in a voltage drop at the connection. The end result is HEAT. A good way to check for bad connection on a low voltage circuit is with your hand! if it feels warm or worse..... hot, you can bet the connection is poor, this is a signal to check the connection. It works!
Also a coating of vaseline on the battery connections helps slow down any corrosion. Use vaseline not grease since vaseline is neutral & will not react with any metal, all it does is reduce oxides forming.
 
So let me get this straight....The dealer couldn't find a corroded battery cable at the battery? :nonono:

Normally you would expect the dealer to do top notch work (expensive but top notch). Frankly, I would assumed that the fundamentals would have been ruled out by the dealer.

Glad it turned out to be somethng straight forward and fairly easy to fix (hard to find).
 
well I can't say why but it looks like the just removed the terminals and cleaned both the posts and terminals. Mine have a little plate with two bolts to clamp the wires. Under that the wires were all wrapped together in a peice of copper. That copper crimp was CUH-roded. The dealer charged my sister 100 bucks to not figure this out. And some other mo-franky charged my sister to replace the "starter harness". He cut the ends off of the wires and cleans them up so they look new.

I'm going to go visit these fine business men when I drop the car off at her house.