Morning folks - I've got a bit of a conundrum going with the truck and could use some thoughts. I went to go to town Friday morning and it fired, stumbled and died. After that it would just crank. Since I was sick as a dog, I didn't mess with it until this morning. I suspect that the high pressure pump has died as it is has been making some noise on start-up, but I decided to run diagnostics before throwing money at parts. I've got strong spark at the coil, fuel at rail (pressure unknown - haven't got a tester yet), high pressure pump cycles but is noisier than normal, and 3 codes that are throwing me a little.

The code are 21 - ECT out of self-test test range, 24 ACT temp sensor out of self-test range, and 85 - canister purge circuit failure.

I'm concerned that there may be more going on here than just a fuel pump issue. The ECT sensor was changed when I did the water pump a couple of months ago and everything tested fine after that install. I have inspected the harness as close as I can and do not see any rodent damage to the harness.

I'm heading out to test for injector pulses. If anyone has some ideas about the codes, let me know. If it is the computer again, this will be the 3rd computer failure since installing the 5.0L. It may be time to go to a carb...

 

I've got pulse at the injectors so I'm off to snag a fuel pressure gauge to see what I have there.

 

Codes 21 & 24 you can ignore, If you retrieved codes with the engine cold.

When you say this is the 3rd PCM, what was wrong with the other 2?

 

1st one was OEM and the capacitors went bad. 2nd failed so that ignition wasn't working. All I can get is A1 Cardone remans around here without spending a huge wad of cash and sending it in.

I thought that might be the case on 21 & 24.

 

Fuel pressure test complete...

Fuel pressure is slow to rise and maxes out at just under 40 psi while cranking. It will will slip down a little after I stop cranking, but drops back down to 30 when starting to crank and then slowly rise back up to just under 40.

At this point, I don't know if I have a plugged filter, the pump failing, or both. I really don't want to start throwing money at it until I have a good idea what's going on.

 

Since the pump has been getting louder lately, I bit the bullet and changed the pump and fuel filter out. It was pretty much a stab in the dark and while it now sounds like its trying to kick over now, it still won't fire up.

The only other weak link is the pressure regulator. There isn't any sign of fuel in the vacuum line and nothing squirts out when the pumps are on, but all that means is that the seal between fuel and vacuum is intact. The relief valve itself could have failed and is bleeding pressure off. This is the last straw - if that does nothing then the EFI is going in a box and to a shelf in my shop as soon as the weather gets above freezing.