Truck problem

[Dragsterhund]

Can I post about an issue I'm having trouble diagnosing with my truck in here?

[ducpainter]

Why not?

[Dragsterhund]

Didn't want to be a jerk


I'm having an electrical problem that I'm having a difficult time diagnosing. Came out to my truck the other night, and it wouldn't start. It was doing this:

https://www.youtube.com/watch?v=xfy-vkMkpM4

In that video, I'm trying to start the car, and it looks like the ECU keeps tripping and resetting.

I get some jumper cables, and get the car started. Starts right up. The voltage on the scan gauge is jumping around all over the place:

https://www.youtube.com/watch?v=nV25BhdCty4

In this video, the engine is just idling in neutral. Notice the voltage.

I decide to start driving, thinking the battery just needs to be charged under load. The voltage is still hopping around:

https://www.youtube.com/watch?v=weFZJbeVxII

Usually, the voltage is 14.1 or 14.2, rock steady.

After about 30 minutes of driving, I park the car, turn it off, and try to restart it immediately.

https://www.youtube.com/watch?v=AEjbPB5uqVs

Same thing as above.

Truck is a 2005 V6 4.0L 4X4.
Battery is about 5 months old. 

Does this appear to be a battery problem, an alternator problem, or a regulator/rectifier problem (inside the alternator in this vehicle, if I understand this correctly)?

[ducpainter]

Seeing the battery voltage on shut down and restart attempt I'd suspect the battery/connections.

The no load voltage didn't look great after a 30 minute drive.

Just a guess.

[brimo]

Yep I second that, it's unable to pull current out of the battery to start, yet with a jump start it fires right up and runs ok, with current probably being supplied by the alternator. Check the battery voltage with motor off with a seperate multimeter too as the battery could have failed.

[Howie]

First try ducpainter's advice, probable, cheap and easy.  Check the engine ground too.  Make sure the starter is tight.  Also have the battery load tested since over 14.5 volts is not good and it is always a good idea to confirm the battery is good before further diagnosis.  Check engine light on?

[brimo]

Engine ground and starter are probably ok as a Jump start got the car going. (assuming the connection was battery to battery)

[Rameses]

Checking your battery (load test), along with all of your connections, is a good place to start.

If nothing comes to light from that, it would be a good idea to test the resistance of your cables.

A wire or cable can look perfectly fine and still have issues internally.

I recently had a charging problem with one of my trucks and I was able to deduce that the voltage regulator wasn't sending any juice to the alternator to excite the field.

Testing the regulator revealed that it was fine though, and the problem was that it wasn't getting any input voltage even though the supply wire had voltage at the far end of it.

After systematically probing the wire, I was able to narrow down where the fault was, and cut out that portion of the wire and splice it back together.



Everything looked fine with the wire from the outside, but the inside was a different story...








So if you have a problem developing inside a wire or cable, you could have a situation where you have high resistance or intermittent continuity while everything looks fine.

[Dragsterhund]

Thanks for all the replies. I'm going to tear into it on Saturday and figure it out.