2008 Ford Explorer XLT Won't Crank

[brinkster]

Been living with the issue for about 3 years now until last week, it was same ole same ole for the approach to get the Explorer to crank.

Working Theory: When the fuse box under the hood in front of the driver gets warm, the truck won't crank. The heat can be from driving it or even just sitting in the sun.
In order to get the truck to start, you can spray canned air onto the starter relay / starter diode area of the fuse box and the truck cranks 99% of the time on just one 2 second spray burst.

Last week, the truck just stopped responding to this approach of spraying canned air and I found that the starter relay was completely dead. After replacing the relay, we are back to the spray and run situation.

If the truck is cold and its cold outside, it starts every time without being sprayed with canned air. So during the winter months, the truck is extremely reliable.

Checked power to the starter and all is normal. Starter purchased 06/2018
Battery purchased 06/2018 and a load test Saturday showed it was in great shape.
Situation exists with both keys so I don't believe this is a security issue. Plus the winter reliability also rules this out.
Checked wiring harnesses in and around the PCM and all look to be in good shape. No rubbing or exposes wiring.

You can hear the starter relay click when the key is moved to engage the starter but the starter is not engaged.

Any thoughts on troubleshooting this issue? Does anyone possibly have wiring diagrams that would show me what to check from the starter relay onward or the systems at play in getting the truck to turn over?

All help is most appreciated.

 

[BrooklynBay]

The brushes in the starter might be going bad. The starter might still be under the warranty.

 

[brinkster]

Always a possibility but with the starter replaced 06/2018 (and I believe the one I removed was the original factory one) and the starter spinning if you jumper the two larger terminals on the starter/solenoid, I don't think that's the issue. Plus not sure where the fuse box being hot is related to the brushes in the starter. Thank you for the reply. Any other thoughts?

 

[BrooklynBay]

A failing starter will require more current than usual to crank. Check all of the terminals on the distribution box, battery, grounds, and feed wiring to the starter for corrosion. Use an antioxidant cream.

 

[brinkster]

Correct. All lines from the battery to the starter and to the fuse distribution box look clean for a truck with 179k miles on it. One other piece of information, the truck becomes more reliable in the winter months and I would think that the cold would make it harder for the truck to start if the power to the starter was being hindered by corroded wires or weakened connections.

 

[Explorer_PL]

A friend of mine who is an Acura tech, had something somewhat similar.
One of the cars he was working on would lose power to the dashboard and gauges. After a long troubleshooting, it came to 1 pin in the main harness connector. Somehow, the female end of the connector would shrink from the cold and "close" and seal better on the male pin, but when hot it would open up and lose the connection.
Maybe something similar is going on with your car ?

 

[brinkster]

Quite possibly ... wondering whats in that area around the fuse box that would respond to a temp change like that. Still searching for wiring diagrams to help trace the flow from switch to fuse box to relay to starter.

 

[Drewmcg]

Maybe I missed it -- but did you try simply replacing the starter relay? Under $10 from RockAuto....

 

[brinkster]

When it stopped responding to the cold air, to get it back to running with the cold air, I replaced the starter relay. It had a residue coming out from one of the pins. The next item I have ordered to replace is the start diode as that is where I spray the cold air to get it to start. This is repeatable without fail ... or until the starter relay went bad. I have not heard of diodes going bad unless under a lot of stress.

 

[Drewmcg]

Is the diode on the starter? If not, where?

 

[brinkster]

It's located in the junction/fuse/relay box under the hood in front of the driver. I found an image of the junction box for the 2008 Ford Explorer.

 

[Drewmcg]

Thanks. Let us know if the new starter diode fixes the problem.

 

[08Ex]

I think you have an electrical resistance issues which increases with temp. Check your grounds.

 

[brinkster]

The grounds appear to be in place but with out a wiring diagram, I cannot be sure to have checked all of them. The diode arrived today. I may take several days as we don't drive alot to see if the diode helped. Still looking for wiring diagrams as I would like to trace the wires pre and post the diode and relay.

 

[brinkster]

Okay ... so finally had a good day running around making about 8 stops. Car started without issue however, after the last stop, accelerating onto the highway, the engine light came one and the wrench light came on. Heard a thump and the engine went to idle. Coasted into a shopping center and pulled the codes. Codes thrown: P0402 for EGR, P2104 forced idle, P0600 Serial Communications Link - tied into the PCM.. All appear under PCM related codes thrown. Left the truck sit till the next day when I could go get it and the wrench light was off and the only code active was the P0402. Was able to drive the truck home. Thinking I have a short related to the EGR that is tied into the PCM somehow. Still looking for a wiring diagram. Going to have time to work on it this evening as I start to trace wiring in and around the EGR looking for broken wires.