*** EDIT 3FEB2024 : THIS IS NOW FIXED. BAD IGNITION SWITCH. DETAILS IN SEQUENCE BELOW. POST#15 has the good diagnosis***

** original post starts below**

We need help. For the past 6 weeks my son and I have been struggling with a no-start condition in his 2008 F250 6.4L Powerstroke diesel. The truck has been in the family for a dozen years. We are fortunate that the initial failure was in his driveway. But there it sits while we try various things.

The symptoms are: At “key on” everything lights up as normal. The fuel pump can be heard to run. No check engine light. When the glow plug light goes off, turn the key to crank the motor and…
a) We can hear the starter solenoid click on.
b) The starter engages the ring gear and we get the noise of a short movement of the crankshaft. The movement is just momentary. Then the everything stops and we release the key. By my estimation the ring gear rotates one or a few teeth.
c) Over time, during our extended diagnosis effort we have found the motor will fire right up and run as normal at seemingly random and infrequent occasions.

What have we done so far:

a) Blame the batteries. We measure a little over 12V at the battery terminal with the truck shut off. But still… hooked up jumper cables from my truck. Then we got over 13V at the F250 battery terminals. No change in symptoms. Even so, we installed new batteries. (Thank you NAPA warranty and free replacement). None of this improved the situation.

b) Put the with new batteries on a trickle charger for a day or two. That got the battery charge up to 13.24V with the truck ignition switched off. Then the truck did start, but only once. So really no change. My son’s comment by text message was “It seems like the starter can barely get past the first compression stroke. And often it can’t do it.”

c) Blame the starter: With the idea that the starter is sick, even though the starter was less than 2 years old, we put in a new starter and solenoid unit from extremediesel. ( Surprisingly less expensive than the local auto parts store’s offerings.). After waiting for that delivery, the new starter was installed. NO IMPROVEMENT.

d) Blame faulty wiring: Looking at the wiring diagram (Attached to this post for an ’09 Superduty. I hope this is the same as our truck.), once the starter solenoid clicks it’s down to the batteries, the starter, and the electrical connection between them. New battery, new starter, that leaves wires and grounds. Some exploratory surgery pulled the main heavy gauge cable between the passenger-side battery and the starter. That showed significant darkening of the insulation at the starter end, as well as discoloration of the exposed copper. The apparent degradation of the cable bolstered our confidence that wires must be the root cause. We ordered, waited for, and installed a complete set of battery and ground cables. The replaced all the heavy gauge cables in the starter circuit. Including battery negative to the frame on both sides and ground from frame to block. It also added a second block to frame ground on the drivers side. Unfortunately, the larger tab on the starter-end did not quite fit the molded insulator on the starter. We did not spot this until after the insulator had been cracked. We put the previous starter back in and filed the tab down a bit to get a good fit. RESULTS OF ALL THIS? NO CHANGE. Several attempts to start failed. We went inside to be depressed for a bit. Then came back out and tried it a few more times. On about the third shot it fired up and ran well.

We left it run. Let it get to near normal operating temperature. Then shut it off and restarted several times. That went well, but no joy as it is clearly still sick.

Leaving it during lunch to cool down some ( 90 minutes??) and now its not starting. So no change.

Perhaps incidentally, during the last round of start attempts we heard more noise than usual with the key “on”. We found a little vacuum pump located just forward of the driver’s side hood hinge is operating continuously. We think this is the vacuum source for the 4WD autolock hubs?? Maybe we broke a vacuum connection during all this mucking about. Maybe it’s been running-on all along. We can’t be certain.

So that brings you up to date. All the components that carry full starter current have been replaced. We have not done anything with the starter relay or the PCM as we always hear the starter solenoid click “on” and the starter tries to turn the motor.

Please offer your insight and advice. (My apologies for the long post. Thank you for reading it.)

 

It sounds like bad wire, or ground. Use a test light on the starter wires, and ground while cranking. Go straight to the battery for your + - this should give you a direction to go next.

 

This is an inspired suggestion. I think what you are saying is to work through the circuit piece by piece looking for voltage to develop during attempted cranking where it should not be? And perhaps first to look at voltage across the starter during cranking. I was going check battery voltage during attempted cranking but did not as my analog voltmeter had dead batteries.

Seems the trickiest one to measure would be the ground connection from the starter case to the block. But I could look at the starter case to the block end of one of the block ground wires.

 

An incandescent test light will dim or go out if you have a connection problem. Test starter case to batt+.
test the small and big wires to batt- the circuit will need to be loaded (cranking)
one more thing test the stud, and the wire. This rules out bad connection at that point.
with a multi meter you can do a voltage drop test but since it is working, just not under load the meter will probably show perfect. The key is loaded circuit testing, and if at all possible go to the battery with the other lead.

 

To answer the other part, you are looking for voltage to drop when it shouldn't. When you find what wire is loosing voltage when loaded you will know what direction to go.

 

thank you for the detail. I am shopping for an incandescent test light now.

 

You can also use a multimeter which would be my preferred tool for voltage drop testing.

 

Yes you can I didn't word that the best if you're using a multimeter you need to load the circuit. With something like the starter you always need to load the circuit, a test light isn't enough load.
I just generally prefer a test light until I need to go multimeter. If you prefer multimeter I would suggest clamp and back probe leads, it's easy to get a bad connection holding them on something.

 

I believe I understand. Now it will have to sit for a week or so, until after the Holiday.

 

Back at it. Armed with an incandescent test light. We set up to measure voltage during attempted starting/cranking at the main starter motor 12V stud, as well as the stud for the starter solenoid. Unplugged the little vacuum pump so it does not run. (Recall, we have a leak in the vacuum lines to the 4WD hubs.) Key ON, ignition ON, wait for the glow plug indicator to go out. Hit the starter and it fired right up as normal. Repeat and it started a second time. Well, against reason we plug the vacuum pump back in. Then it failed to start, but we didn’t have the test light in place. Leave the vacuum pump plugged in and try with the test light. Then it starts up just fine.

After repeated attempts, we never got the truck to misbehave with the test light in place. Qualitatively, perhaps one fourth of the start attempts failed.

All of this built confidence that the high-current circuits are just fine. We began looking at the starter relay in the battery junction box (BJB). Pulled the relay out and it passed a visual inspection. We swapped the relay with its neighbor of the same part number. NO CHANGE.

To further verify the high current circuits, we unplugged the wire from the starter relay to the starter solenoid at a connector located next to the passenger-side battery. This is C139 in the brown wire of the circuit diagram I put in the first post of the thread. With key ON, touching and holding the male connector to the nearby BATT+ terminal, the starter spins up and the motor starts like a champ.

This leaves us looking hard at the Power Control Module (PCM) and the BJB.

The truck seems to be equipped with On Touch Ignition System (OTIS). At the moment my understanding of this is limited. The basic function seems to be that the driver initiates a start sequence by turning the key to START. Once initiated the OTIS takes over and keeps starter spinning until the motor starts. Once the motor starts OTIS shuts the starter off. The whole thing is starting to smell like the OTIS system is shutting the starter down before to motor fires.

We need to isolate it further as PCM, BJB, or something else? Any input/suggestions/advice on next steps is welcome.

Recall that the truck is a 2008 F-250 Powerstroke Diesel, Crew Cab, King Ranch.

 

This is concerning, as at first I thought you might have a hydrolocked engine - but then you mentioned it WILL sometimes start.

However, since it seems to start EVERY time a test light is hooked up, but NOT when it is disconnected...I would be inspecting wiring. This sounds like a bad connection or a flat-out short somewhere in the starter circuit, that by adding the test light allows enough current to flow to allow the truck to start. Where that short/bad connection would be, I don't have a clue.

 

To test, simply continue to hold the ignition switch in the START position instead of releasing it and letting OTIS take charge. While the ignition switch is in the START position, OTIS is effectively bypassed.

 

Maybe swap relays.
to me this sounds like a bad connection, starter circuit works until it gets a real load resistance makes it lose power.

 

we have to include that it starts well when the wire to the starter solenoid is jumped straight on to the battery. I think that pretty much settles the starter circuit as healthy and the put the onus on the real;ays and their controls circuits.

 

We’re back with preliminary good news!

After painstakingly inspecting all the wiring for rodent damage or abrasion and deciphering the wiring diagrams we were able to locate on the internet, we still had a truck that most often would crank when the key was turned to START, but only for a moment. Maybe half a second.

We did find that disconnecting the BN-GN (see ckt diagram near top of this thread) wire that runs from the battery junction box to the solenoid on the starter, then putting the KEY to RUN and holding the BN-GN wire to +12V battery terminal would always start the motor.

However, too many components are involved in the starter circuit to enable simple diagnostic efforts. The starting circuit involves:

CDIM (Circuit Deactivation Ignition Module)
IGNITION SWITCH
OTIS DIODE (One Touch Ignition Sytem)
PCM (Power Control Module)
BATTERY JUNCTION BOX (BJB)
STARTER MOTOR and SOLENOID
SMART JUNCTION BOX (SJB)

All of this was complicated by the fact that circuit diagram we had, post above, was WRONG.

We knew that OTIS was implicated in the problem but couldn’t figure out how.

Eventually we got smart and began proper diagnostic methods. To do this we:

1) Got a monthly DIY subscription to IDENTIFIX

2) upgraded our OBDLink adapter to the newest Blue Tooth version

3) Updated FORSCAN to get all the body and engine proprietary system codes.



FORSCAN had a bunch of codes set. Mostly related to effects of our DVM measurements throughout the truck. We cleared all of these. None of the codes gave us the diagnostic answer.

Then, we (my son, really) worked through the systematic FORD diagnostic routines within IDENTIFIX. Some of these involved using FORSCAN to run a built-in FORD diagnostic test. Other were DVM measurements while in START or RUN.

I won’t go into the details. We followed the FORD procedure in IDENTIFIX. 4 or 5 hours of careful measurements and….

BAD IGNITION SWITCH

FYI: for you OTIS aficionados. Three things will make OTIS stop cranking the engine.

1) the engine starts

2) The PCM times out (does not get signals indication the engine is running)

3) The ignition switch senses OFF

That is where we are at. I’ll up date when we put in a new switch.