unusual starting problem

[Taharaman]

I have a 2002 Explorer. Has a starting problem. Intemittent. So mechanic changed security box, Ford also said change battery & reprogram keys. Done. Here is where it's weird. It still has a starting problem, but only when it has sat in the sun for about 3 - 4 hours. Literally. Starts fine first thing in the morning, and 2 hours after sunset through the night. the only variable is the ambient air temp in the engine compartment, and only after sitting in the sunlight. I drove it last evening for about 5 miles, turned it off and went shopping for 20 mins. Came out and it started right up. Today, around 12:30 PM it would not start after sun had been direct on the engine compartment for about 1 1/4 hrs.

Help

 

[matt0248]

What does it do when it does not start? Does it crank? Does it start and stall right away?

 

[Taharaman]

It does nothing. No clicks, no noises of any kind. I just started it. Instantly. No hesitation, no problem of any kind. Ran it for 2 minutes. I am taking my other car to work now. Will be back home around 11 to change clothes. Will check here then, and also see if it still starts.

 

[AviatorSport]

It does nothing. No clicks, no noises of any kind. I just started it. Instantly. No hesitation, no problem of any kind. Ran it for 2 minutes. I am taking my other car to work now. Will be back home around 11 to change clothes. Will check here then, and also see if it still starts.

Do the instrument cluster lights illuminate and odometer goes blank when the key is switched to the start position?

yes/no?

(no)check ignition switch circuits- suspect ignition switch
(yes) does the theft light prove out(not flashing fast)?

yes/no?

(no)suspect PATS transceiver (ring around ignition switch)
(yes)suspect transmission range sensor or starter

It would help a ton if you can have it scanned for codes stored in memory

Also are both keys OEM Ford?

 

[sethmorgan]

Bad/intermittent ground?

 

[Taharaman]

Sorry it took so long to reply. Been too busy with other things. Instrument cluster "lights" normally. Ignition functions normally 18 hrs a day. Seems fine all the time. If the PATS transceiver is the security device, it was replaced, keys are OEM annd reprogrammed, brand new battery. There are NO codes in the memory.
The one thing it seems to be related to is AMBIENT air temperature and sitting in the sun. I drove it for about 50 miles intermittently one day in the mrning. Stopped and started 6 times with 10 to 45 minutes between stops and starts. Parked it at 11:30 AM. Went to start it at 3:30 PM. No cranking. Ambient air temp was aobut 95. An hour after sunset tried again, started right up. It's at a mechaniox today. Will try starting at 4 PM after sitting in what is supposed to be a 90 deg. day here in Los Angeles. We'll see. I will post results this evening.

 

[sethmorgan]

I wonder if there's some issue with sunload sensor on top of the dash. Since you said it only happens in the sunlight, and the sunload sensor feeds info to the PCM.

If you have a really bright halogen spotlight or similar, see if you can reproduce the problem at night after shining the light on the sensor for a few minutes.

Or pop the cover off and unplug it. The cable runs from the sensor to the driver's side, and has a connector at the sensor and another near the driver's side.

 

[matt0248]

I remember having a similar problem with a 2002 Sable. The only way I was able to trace the problem was to connect a DVOM to the small wire on the starter, let the car sit in the sun all day and try to start it. After every no start attempt, I was able to move my meter to a different component (using wiring diagrams) and try again. What I eventually found was a very small wire into a terminal block under the dash was almost completely broken out from the pin in the connector. When it was hot in the car it would not make good enough contact to allow the car to start. FYI, this car did not crank when it was a no start, there was no power on the wire to the starter solenoid on the starter, so I was able to trace it backwards. I can't exactly remember what the wire did to cause the starter to not work, it may have been a wire for the security system or something. It took a long time to find it. After it was fixed, that car never came back to the shop.

 

[BobWiersema]

The PATS system wont do that. Next time it refuses to start, try it in neutral. If that does nothing, see if you can start it by jumping the starter solenoid. Also the heat issue sounds like a bad cable.

 

[swetrid]

V8 or V6? If its a V8 it could be the wiring rubbed through at the oil filter shield.

 

[Taharaman]

learned something new

Wow, I learned something new today. I have never heard of a "sunload sensor". sounds easy enough to disconnect. It it proves to be the problem, is it necessary to replace?

Tried it in neutral, no difference. but did not try jumping the starter solenoid.

I have checked all the major cables and grounds (disconnect, clean and retighten). All appear to be good.

I hope I do not have to go the route of attaching a VOM to all those small wires, but, if it comes down to that.......

It has now taken on some urgency since this vehicle is equipped with lights and siren. It is part of a small fleet of emergency response vehicles belonging to a totally volunteer (not a single paid employee) non-profit (very) emergency medical organization. I need to know that when I respond with it to an emeergency, I will be able to restart it to drive away. It would be very embarrassing to be stuck somewhere.

thanks guys. It looks like I have my work cut out for me this weekend.

 

[Taharaman]

I am not sure if it is 6 or 8. Have to look when I pick it up from the shop.

 

[sethmorgan]

Wow, I learned something new today. I have never heard of a "sunload sensor". sounds easy enough to disconnect. It it proves to be the problem, is it necessary to replace?

See if you can reproduce it at night with a spotlight first. If it is the cause of the problem, disconnecting it might be the solution. Are you having any issues with the Autolamp feature? This is the only feature I know of for certain that uses the sensor.

 

[Taharaman]

This Explorer does not have an AutoLamp feature. Headlamps are manual only. I wish it had auto headlights. So I guess I am pursuing other avenues. the weather here is now too cool and overcast to be able to reproduce the problem. I will however continue to check and recheck wiring possibilities, which seem to make the most sense. And, btw, it is 6 cyl.