It doesn't have anything to do with the fuel bowl heater actually coming on. The heater is on the same circuit that powers part of the PCM. On a few occasions we've read about a partially shorted heater, or connection, or something else still not understood was causing a disruption of power in that circuit (dead PCM) without blowing the fuse like it typically does. When they unplugged the heater, the problem went away.

It's a cheap and easy test.

 

Awesome. I'll give it a shot. Looking through the trusty "Diesel Engine Repair Manual" now.

 

Since removing power from the under dash fuse box by pulling fuse 22 underhood seems to clear the problem (at least temporarily) I would try pulling and replacing the under dash fuses one at a time. Hopefully this would narrow the problem down to a single circuit that needs to be de-powered for the truck to start. Actually instead of one at a time do half of them at once. If truck starts it's one of those circuits. If it doesn't start try pulling and replacing the other half. Then just pull and replace half the fuses in the half that got the truck to start. You will quickly get down to just a couple of fuses.

 

I tried pulling every fuse individually, attempting a re-start after each one, and the only fuse that allowed the WTS light to operate normally (thus the truck actually starting) was #22.

For clarification, I'm just using the WTS as an indicator of normal operations (ie. if the WTS light extinguishes immediately, or if it stays illuminated for the appropriate amount of time). I'm not convinced that the issue is isolated to the WTS circuit, but when I attempt to start the truck, that's my only instrumentation that tells me if the truck is going to start, or if it will just crank all day and not start.

Next, is to look into the fuel heater correlation. I'll start by simply disconnecting the fuel heater. I haven't dug into it yet, but from what I can tell, it looks like there is just a single connection to the fuel heater. Hopefully it's located outside of the fuel filter bowl assembly. I'll find out this afternoon.

 

It is right on the back of the fuel bowl. One connector there and fairly easy to get too.

 

I found it no problem, right where the book indicated. I did unplug it, although the connection didn't look that great in the first place. It wasn't quite seated, and the connector clip was not engaged. Regardless, I completely removed the connection for the fuel bowl heater. Truck started right up, but at a second attempt to start the truck, she didn't fire. So I was back to pulling #22 fuse to get me back on the road.

 

that fuse 22 under the hood has brake pedal psi sw, brake position sw, instrument cluster, pcm, gem, flasher horn relay,cigar lighter, data linc connector, glove, engine, map and vanity lights on it. It also powers the the interior lamp relay & battery saver relay. In the instrument cluster it is powering the keep alive memory

Fuse 15 in the cab powers up the gem pcm and instrument cluster and the brake position switch part that controls the shifter interlock. So when it goes crazy and will not start, see if it will come out of gear. If it does power is good to it through fuse 15.



The Glow Plug (GP) light signal controls the WAIT TO START indicator light located on the instrument panel. When the light goes off, the engine is ready to be started. As a bulb check, the light comes on every time a key on reset occurs, even though the glow plug system is not commanded on. On-time normally varies between 1 and 10 seconds. WAIT TO START light on-time is independent of glow plug relay on-time because the glow plugs may stay on to improve performance until engine reaches operating temperature. =short light no commands

An open circuit in the glow plug light wiring will result in an inoperative glow plug light. A short circuit will result in a glow plug light always ON condition


You may have misreading oil temp switch causing it to not to engage GP system. It may be too that you are rebooting part of pcm and that is why it cranks.

 

The diesel fuel heater was INOP, confirmed by a bench test, so I replaced it with a Dorman PN 904-210. During reassembly, I sheared the FPR threads when snugging down the fuel line. Awesome.

So I began digging deeper into this project, and decided to couple this with my quest to terminate all oil / diesel leaks on this engine. How can I identify what's leaking if everything is covered in oil / fuel?

Bob at Diesel O Rings was a great help. He even offered a replacement FPR, made from billet aluminum. I ordered the master o-ring kit as well, which included all the associated fuel bowl and HPOP O-rings. Quite a job, considering I started all of this simply to troubleshoot the no-start issue.

So far, so good. The engine has never started easier, and everything is cleaned up. I'll report back to see if in-fact this solved my no-start issue.

Thanks for all of the help.

 

I hope you've already solved your problem this morning, but that BSR was the first thing I read that popped a red flag in my head. If the problem re-occurs, I'd be very curious of what this does.

 

Well, back to square one. The truck displayed the same no-start symptoms identified above. I got back on the road by pulling the #22 fuse...

I forget to check to see if the truck would shift out of gear or not. I'll investigate the Battery Saver Relay (BSR). First, I have to find it. Is that in the main junction box under the hood?

 

Anybody know where I can find the Battery Saver Relay on my '01 F250 7.3? From what I can tell, it is relay #2 under the steering column fuse box, but the owner's manual indicates that slot is not used.

Anyone?

 

According to Ford, the BSR is integral to the GEM. GEM replacement would be required for a failed BSR.