2004 Expy, Crank, No Start. No fuel pressure. Internal Relay seems fine. Inertia switch not tripped. Help!

2004 Expy 5.4L V8 Triton, former State Police transport vehicle, owned a couple months.

I bought this a couple months ago. It's a former police vehicle. I have been going over the wiring for days. Currently stuck in a city parking lot near my work.

I pulled into a gas station one morning for coffee and smokes, and when I went to fire up the beast, she cranked with no turn over. The truck ran fine until this happened. No stalls, no stuttering, no apparent loss of power.

My OBDII scanner can't connect to the vehicle, getting stuck waiting for the vehicle to respond, which it never does. The instrument panel self diagnosis test shows one DTC code, d262. I don't know if it is related, but apparently there's a communication failure with one or more modules somewhere. I can confirm that I have never been able to connect my OBDII scanner, having tried it right after buying the vehicle.


I have tested power going into, and coming out of, the internal fuel pump relay. Both sides show a short period of aboitut 12v, dropping to 6.5 or so after a couple seconds. Thinking it may still be the relay, I bypassed it, connecting the fuel pump to a hot fuse and it still would not turn over. I put a second battery in parallel while bypassing the relay, thinking the battery didn't have enough muscle to energize the pump. No luck.


I really REALLY don't want to drop the tank and swap out the fuel pump, but apart from verifying the inertia switch is functional, I'm running out of options. Fuses 31, 32, and 33 show 12v across both sides, 9 as well, and 28 shows 12v when the ignition is in the ON position.

I am holding out hope that a rodent simply chewed a wire, and that I won't have to spend 3 or 4 hours dropping the tank and replacing the pump. I fear that if I do, and it still won't start, I'll go insane.


What else can I do? Mechanics can't see me for at least a month, and I need this running ASAP. I'm open to any suggestions or words of encouragement. I know these old cops cars can be electrical nightmares, and there are plenty of loose cut wires that used to power all those cool toys. So, I'm hoping it's electrical, and not the pump.


Help!

No, my anti-theft light does not rapidly flash. Factory keys. Security light turns off after a second when ignition is on. I wait for it to go off, crank her again, no start.

Wish I could help you with the electronics, but if you can't get it working, any chance I could buy the skid plates off ya? I think the police version came with a few different skid plates, do you still have any on your expy?

Check the top right relay in the fusebox ( the PCM relay...) for any signs of melting. Swap it with one of the other relays (there's two more on the top row...). Check the harness and all harness plugs going into the PCM there on the firewall. Look for any loose wires that might've been pulled loose from the connection plugs over the years. Especially the red ones that provide power to the unit. Being a former police vehicle look for any splices in the wiring. Not communicating with the OBD port suggests that.






.

I actually did check that relay, and swapped it out for another. No luck.

I heard a mouse in the engine compartment last night, chewing something. There's also a rather fresh mouse corpse near the belts. I don't see any obvious shorts or open circuits, but I'm going to go over everything with a fine-toothed comb when I have time.

I don't think the dtc error is related. Even when it ran, I was unable to access OBDII codes. There likely is some wiring shenangigans, but I'm almost certain it's not causing this no start condition.

I thought I heard a mouse the morning the truck died, and it's been gnawing at me ever since, pun intended. Hearing it again last night, and seeing the fresh corpse, galvinizes that hunch. It was odd that the pump would just stop suddenly with no prior symptoms. Usually there is some hint, loss of power, stalling, etc. This seemed very much like a short or open circuit, and I believe that is exactly what it is. Now I just have to find it.

I had a similar problem on a Nissan, battery leaked enough to corrode into fuse link wires attached to positive terminal. Sometimes 12V, sometimes not enough volts to power either the ecu or a smart relay/ fuse distribution unit. Dealer replaced both. Eventually they replaced the corroded wiring assembly & voila, all was well. Check all wire ends & terminals coming off battery very carefully for any signs of corrosion. If is the rodent thing, best of good luck cuz that's completely random.

EngineerMike said:

Check all wire ends & terminals coming off battery very carefully for any signs of corrosion.

Click to expand...

@Xooxer To do this you can do a VOLTAGE DROP TEST

My '06 had a fuel pump control module located on the left rear frame rail near the tank and wheel kick-up. They are subject to corrosion / failure. I presume yours, also 2 gen, has the same. You might want to check that out before you drop the tank.