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Hi all. New to the forum. Had to join because of all the expertise that is available on this site. There are some really amazing people here. I have a 2001 Excursion XLT, V10, with 150,000 miles on it. It cranks fine, but will not start most of the time. When it does start, it idles and accelerates fine.The PATS seems to be operating good judging from the THEFT light operation. I've checked the fuel pump relay and its good, The fuel shutoff switch is good. Fuses are good. I checked voltage at the fuel shutoff switch, on the green and yellow wire which is supposed to supply power to the switch from the PCM, but am not getting any voltage. I don't want to mess with the fuel pump itself until I am getting proper voltage to it, and it looks like my problem is no voltage into the shut off switch, so no voltage out to the pump. From research, the PCM relay can be at various locations depending on the year. I can't find it to check it. Anybody know where the PCM relay and the PCM itself is located on a 2001 V10 Excursion? Also, if anyone has any other troubleshooting suggestions I would greatly appreciate hearing them. This is getting a little frustrating!
a. Verify PCM is applying ground to the LB/OG wire for 2-3 seconds at ignition power-on.
b. Verify relay operates (clicks).
c. Swap with the adjacent relay.
It's going to be a lot more difficult to diagnose without a scanner. I'll bet that PCM is choc full of interesting info. Every time it fails to start it throws a code.
It's going to be a lot more difficult to diagnose without a scanner. I'll bet that PCM is choc full of interesting info. Every time it fails to start it throws a code.
There is no need for a "scanner" to diagnose a fuel pump that doesn't work. Totally useless for this job.
All that is needed is some careful observations along, perhaps, a test lamp or multimeter.
Okay I didn't say you needed it. The schematic will tell what the circuit looks like. It wont give you a description of how it works. Especially with this statement from the OP. "When it does start, it idles and accelerates fine". When my fuel pomp went out it manifested the trouble under certain conditions. Under heavy load with between 1/4 and 1/2 tank of fuel. When i finally replaced it I noticed significant improvement in performance under all conditions. A clue was the PCM throwing lean codes when the trouble appeared. I'm just trying to help. Having a scanner is good idea with any of these modern trucks. Particularly OBDII.
First off, thanks for all the info, especially the schematics. Here's where I'm at now. Checked fuse 112, good. Swapped relays, good. To verify PCM applying ground to LB/OG wire, I pulled the fuel pump relay, and connected Ohm meter from relay connection socket 2 in the battery junction box to ground. When I turn on the ignition switch to run, I get a constant reading of 9.66k ohms, so not good, as it should ground for 2-3 seconds, no? Then I checked voltage at the DG/YE wire at the connector for the fuel shut off switch, and when I turn the ignition to run, I get 12v for a about a second, and then the voltage drops to 6v, and stays constant at 6v. Any comments will be greatly appreciated.
When I turn on the ignition switch to run, I get a constant reading of 9.66k ohms, so not good, as it should ground for 2-3 seconds, no?
Don't do that, applying an ohmmeter to a powered circuit is usually a good way to let the magic smoke out of the meter. It will also cause confusing readings that are useless...
Then I checked voltage at the DG/YE wire at the connector for the fuel shut off switch, and when I turn the ignition to run, I get 12v for a about a second, and then the voltage drops to 6v, and stays constant at 6v.
Good although it's usually 2-3 seconds but software is in control of the exact interval. That is a nromal observation of a system that is working correctly up to that point.
Verify the inertia switch is not tripped or "open".
Disconnect the inertia switch and see if you can inject power to the PK/BK wire. In a functioning system, that should turn the fuel pump on.
Success. She is running great, much stronger than before. The inertia switch checked good, so about the only thing left was the fuel pump itself. After several hours of work and saying some impolite things, I replaced the fuel pump, and since the tank was dropped, also replaced the fuel tank pressure senor, as with my luck it would go out next and I would end up having to drop the tank again. While not to difficult, it's not something I want to do again any time soon. Many thanks to Project SHO89 and bluovl for the advice.
Success. She is running great, much stronger than before. The inertia switch checked good, so about the only thing left was the fuel pump itself. After several hours of work and saying some impolite things, I replaced the fuel pump, and since the tank was dropped, also replaced the fuel tank pressure senor, as with my luck it would go out next and I would end up having to drop the tank again. While not to difficult, it's not something I want to do again any time soon. Many thanks to Project SHO89 and bluovl for the advice.
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