Sorry this is long, but it gives the history of the problem:
My Ranger does not start on what appears to be humid mornings. When I get home from work, it starts and runs fine. Here is a history on this and an earlier related problem.
Last year (Jul 2016) I had a problem with it missing/sputtering at 3500 rpm. In the course of troubleshooting, I replaced the fuel filter, plugs, plug wires, coil pack, and cleaned the MAF. The truck never had an error code. After a little research, I found a Tech Bulletin indicating that the Cam Positioning Sensor caused it to miss at 3500 RPM. I replaced the CAM Positioning sensor and the problem went away.

Fast forward to approx. 4 weeks ago (Sep 2017).
- Thursday-(Sep14 -afternoon) - While waiting on a friend, I shut off the truck and it would not start. After fiddling around with the fuel pump relay, the truck started. I drove it for a couple of days then left for a business trip.
- Thursday (Sep 21 -afternoon) - Upon returning from the business trip, the truck died approx. 5 minutes after starting. I restarted and it ran fine for the rest of the day.
- Friday (Sep 22 -morning) - Would not start; took alternate vehicle to work. In the afternoon truck started, no codes were present.
- Saturday (Sep 23 -morning) - Replaced the fuel pump and fuel relay. It ran great the whole day
- Sunday (Sep 24 -morning) - Would not start. Checked the fuel pressure at the fuel rail and found steady 60 psi. Checked for spark and had good spark. Inspected electrical connector going to PCM; inspected large electrical connector (drivers side of engine). The truck started and ran fine whole day.
- Monday (Sep 25 -morning) - Would not start; took alternate vehicle to work. After work, replaced the Crankshaft Position Sensor. Truck started and ran fine.
- Tuesday (26 Sep -morning) – Would not start; took alternate vehicle to work. Wait until weekend to resume troubleshooting
- Saturday (30 Sep -morning) - Truck started - took it to Firestone for analysis – They found no codes or significant findings on their computer; fixed small vacuum leak and replaced the Idle Air Control Solenoid
- Sunday (1 Oct -morning) - Would not start. Found some frayed wires for Injector #1 hidden under wire harness wrapping. Fixed bad wires. Truck ran fine the rest of the day
- Monday (2 Oct -morning) - Would not start; took alternate vehicle to work
- Tuesday (3 Oct -morning) - Would not start; took alternate vehicle to work; wait ‘til weekend to continue troubleshooting
- Friday (6 Oct -morning) – Would not start; took blow dryer to PCM connector area; truck started; removed and inspected PCM and inspected wiring harness going to PCM; no trouble found. Truck started and ran fine all day
- Saturday (7 Oct -morning) – Would not start; applied blow dryer to PCM; did not start; Pointed plow dryer at fuse box; vehicle started; inspected fuse box-no trouble found; removed and reinserted all fuses and relays; vehicle ran fine all day.
- Sunday (8 Oct -morning) – Would not start; applied blow dryer PCM – no start; applied blow dryer to fuse box – no start; Waited until later in the afternoon; vehicle started
- Monday (9 Oct -morning) – Would not start; Tried blow dryer on all locations; no start; tried blow dryer on large connector on driver’s side of engine; vehicle started

As a summary; here’s what has been replaced/checked
Fuel: Replaced Fuel pump, fuel filter, fuel pump relay and Idle Air Control solenoid; Fuel pressure at rail: 60 psi; Inertia switch checked – good; cleaned MAF
Spark: Replaced spark plugs, plug wires, coil pack, cam positioning sensor, crank positioning sensor
No OBDII Codes
NEED HELP!

 

Every time there is a problem and you disturb the given electrical connection in a given area, it appears that, cures the problem.

On my 99 3 litre, I found Ford used white lithium grease on all the connections.

I went through all of them (a big job) with lacquer thinner, small brushes and compressed are and cleaned them.

I then replaced the lithium grease with synthetic dielectric grease _ no more problems.
Just a thin smear on the cleaned terminal and plugs _ male and female.
Don't confuse this grease with a conductive type, that should not be used.

 

By "would not start" , do you me it would turn over but wouldn't fire? It seems your problem may be more temperature related to me. Have you considered the temperature sending unit that provides a signal to the PCM? Or maybe the IAT sensor? Anti-theft system? Not sure if you have it, but it can cause similar problems due to a worn key or switch. These kinds of problems can be nightmarish to solve especially when the OBDII doesn't give you a clue.

 

Thanks for the replies and suggestions. I think I may have found the problem; I'll know tomorrow morning if it's humid... I found a bad gasket on the Camshaft Position Sensor connector and potentially a bad camshaft position sensor (magnetic pickup portion of the sensor). I only replaced the mechanical portion earlier. I troubleshot with a blow dryer and a water mister. I isolated the problematic area with the blow dryer by drying an area until the truck started. I then replicated the symptom with the mister recreating the humid conditions. I replaced the connector and the camshaft position sensor magnetic pickup. I can now spray all I want and the truck still starts. I'll follow up on this post to let everyone know if it worked or not.
@ Grumpa - To answer your question, it would crank but not start. It actually started on cool dry mornings but not warm humid mornings

 

I was thinking pretty much Jeff's answer whilst reading your post, had an Alero with a fuel pump connector causing the same thing, fix was the same.


Hopefully you found the issue, kinda weird that was the cause though. Per Grumpa's question, was it even cranking when it failed?

 

Thanks for the response. Yes it has always cranked strong throughout the whole process. It started this morning, but it's not as humid, so I'll have to wait for the next really humid day to see if it's fixed