FIXED! 2000 F350 Super Duty 6.8L V10 Gas Crank/No Start, Fuel Pump Runs Constantly - NOT PCM
#1
07-20-2018, 08:34 AM
FIXED! 2000 F350 Super Duty 6.8L V10 Gas Crank/No Start, Fuel Pump Runs Constantly - NOT PCM
Okay guys, wanted to share this as a separate post and hopefully it helps someone having these issues.
Brief history: 2000 F350 Super Duty 6.8L V10 gas engine. Crank/No Start. Fuel pump runs constantly with key on/engine off (KOEO). Fuel pump relay (located behind the dash in case anyone is looking for it - pull your radio, look through the hole and down - there are 3 relays there, blinker, fuel pump and another one) clicks with key on/engine off and clicks like crazy when cranking.
If you research this problem on this forum and the internet, 99% of the conclusion is that you need a new PCM. While this may be true some of the time or even a high percentage of the time, it's not every time. I replaced my PCM and you can imagine my disappointment when I had the exact same issues described above. I even contacted the people I bought my PCM from because you can also find lots of internet stories about getting bad PCM after bad PCM.
So out of desperation, I started checking relays and fuses again. I had visually inspected all these once already and had applied 12V to the relays to hear the click, but thought maybe I missed something. Fuse #5 under the hood is "Electronic Engine Controls. 20A* (Gasoline only) PCM, Fuel Pump Relay Coil, Mass Air Flow Sensor, Fuel Injectors." This fuse looked good visually. It tested bad with a multimeter. Under a magnifying glass, you could see the break way, way low and it wasn't discolored. Put a new one in and the truck fired right up and is running like a beast.
I have another post here about my helper shorting two pins on the MAF sensor trying to pin it out. I can only assume this is what blew the fuse as everything is still good.
So check fuses with a multimeter if something has you stumped, it could definitely be that. And don't believe everything you read, because I fell for the "if your fuel pump runs all the time with the key on, but it doesn't run when you disconnect the PCM, the PCM is bad." Not every time guys, not every time. Hope this helps someone.
Brief history: 2000 F350 Super Duty 6.8L V10 gas engine. Crank/No Start. Fuel pump runs constantly with key on/engine off (KOEO). Fuel pump relay (located behind the dash in case anyone is looking for it - pull your radio, look through the hole and down - there are 3 relays there, blinker, fuel pump and another one) clicks with key on/engine off and clicks like crazy when cranking.
If you research this problem on this forum and the internet, 99% of the conclusion is that you need a new PCM. While this may be true some of the time or even a high percentage of the time, it's not every time. I replaced my PCM and you can imagine my disappointment when I had the exact same issues described above. I even contacted the people I bought my PCM from because you can also find lots of internet stories about getting bad PCM after bad PCM.
So out of desperation, I started checking relays and fuses again. I had visually inspected all these once already and had applied 12V to the relays to hear the click, but thought maybe I missed something. Fuse #5 under the hood is "Electronic Engine Controls. 20A* (Gasoline only) PCM, Fuel Pump Relay Coil, Mass Air Flow Sensor, Fuel Injectors." This fuse looked good visually. It tested bad with a multimeter. Under a magnifying glass, you could see the break way, way low and it wasn't discolored. Put a new one in and the truck fired right up and is running like a beast.
I have another post here about my helper shorting two pins on the MAF sensor trying to pin it out. I can only assume this is what blew the fuse as everything is still good.
So check fuses with a multimeter if something has you stumped, it could definitely be that. And don't believe everything you read, because I fell for the "if your fuel pump runs all the time with the key on, but it doesn't run when you disconnect the PCM, the PCM is bad." Not every time guys, not every time. Hope this helps someone.
#2
07-22-2018, 09:10 AM
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Brady9892
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03-18-2019 07:09 PM