So I have gone through all of the no start threads that I can find and I’ve learned a lot, but have not been able to resolve my issue.

I have a new to me 2000 Excursion 6.8, and shortly after we bought it in October, it began having troubles starting. It would crank but not fire. That would go on for 5ish minutes, and then finally start. My wife thinks that its worse when it’s cold, but cold is relative as it’s only been down in the lower 20’s.

I have changed the relay for the fuel pump, changed the crank position sensor, changed the cam sensor, and no fuses are blown.

I have a gauge on the fuel rail, and when it starts, I turn the key to on, and the pressure jumps to 30 - 32 psi. When I start the motor, the pressure stays at 30 psi for as long as I run it which has been 30 - 40 min. When I shut it off, the pressure drops down to 23 - 26 psi, and then climbs to 38 psi. It will over the next 2 hours drop down to 0 psi.

When it doesn’t start, I turn the key to on, and the pressure stays at 0 psi. When I crank the engine, it stays at 0 psi. Occasionally, the engine will start (roughly) and then after reaching 1000 rpm, will die off within 2 - 3 seconds. I have pressed the gas pedal after it “starts” but it does nothing to rev the engine in that scenario.

I see a lot of cranks but no start on here, with multiple culprits causing it, so I was hoping for some help narrowing this down. I feel confident that it is a failing fuel pump, but not so confident that I have pulled out my wallet to drop the tank and $350 on a fuel pump.

Any help would be appreciated. Thanks!

 

I would say fuel pump, with the 0 psi showing on no start. This is what I would do-

1-Pull the passenger kick panel and remove the connector from the bottom of the inertia switch.
2- run a wire from the battery to the connector- I think the hot line to the pump is the black/ pink, but would have to go back and look at my no start post a couple months ago to be sure.
3- turn the key to on, jumper to the hot line to the pump as described in step 2
4- listen for the pump, check fuel pressure at the rail.
5a- if there is pump ticking and pressure at the rail, test a couple more times. If it is consistent, the problem is the fuse or relay for the pump, possibly the ECU.
5b- if no ticking, no pressure, or after multiple attempts it doesn't reliably build pressure, it's the fuel pump.

by jumpering from the battery directly to the hot wire at the inertia switch plug, you are bypassing all the electrical controls to the pump and wiring directly to it. This is why you know for certain it is indeed the pump if it doesn't reliably function for this test.

After a bunch of attempts, this is the way I finally knew 100% it was the pump. Bought a new Delphi cartridge pump from Autozone, dropped the tank and replaced it into the old sending unit, cost about $100 and a day's work.

-Michael

 

Ok, well I went about that a little different so that I could check voltage ahead of the switch.

Because my problem is intermittent, I never know what reading I am going to get, and if it is going to be pure dumb luck, so I tried to start the truck, and it wouldn’t start. That usually means that it won’t start on the next 5 - 25 tries, so I pulled the harness out of the switch, and tested the Green/Yellow for voltage when I turned the key to on. Voltmeter read 11 volts for around 2 seconds, then dropped down to 6 volts. When I turn the key to crank the engine, the meter reads 9 volts.

I plugged the harness back in and tried to start the truck but it would only turn over but not fire. I unplugged the harness again, and everything repeated itself. Also, no pressure at the fuel rail from the two times I tried to start the engine with the harness plugged in.

Is it reasonable to assume that because I got voltage on the line side of the switch, that even though the truck won’t start, and the fuel pump wont run, everything up to the switch is good?

 

Maybe, but not necessarily. You tested the voltage with no load on the circuit. That can allow the voltage to appear to be normal but, when a load is applied, little to no current passes through the circuit.

It would be better to back-probe the wiring at the connector or use an insulation piercing probe to check the voltage with everything hooked up.

I like to suggest connecting a test light to the output of the inertia switch when dealing with a intermittent fuel pump symptom. The light allows for a simple visual confirmation that power is or isn't being fed to the pump circuit during the key-on priming cycle. This then enables one to half-split the circuit so as to see which direction the attention should be focused.

 

 

I'd go for a new fuel pump now.

 

Just to bring closure to this thread and hopefully help anyone else having the same issues, I thought I’d update what appears to be the solution to my problems.

I dropped the fuel tank and swapped out my fuel pump today. After I primed the lines 5 or 6 times, she started right up. The tank was not difficult to drop at all, or at least not what I was expecting. Time will tell, but I am pretty confident that the new pump is just what the doctor ordered.

Thank you guys for your help and suggestions.

 

I’m glad , you have figured it out. Best of luck.

 

Good news, how many miles on that pump?

 

 

There's a check valve in the fuel pump that's suppose to cause pressure to be maintained. If it goes (or is) bad, the pressure will leak down after the ignition is switched off.

 

 

So I checked pressure tonight at the rail, and my fuel line doesn’t even hardly pressurize when I turn the key to prime the line. The pressure goes up about 2 or 3 PSI every time I turn the key off and then back to “On”. After doing that 5 times, it was getting close to 10 PSI. I started the truck, which obviously didn’t fire right up, but did start, and after I shut it off, the pressure dropped to 0.

Is that indicative of a bad check valve on the pump? The thing that doesn’t make sense to me is why the fuel line builds pressure, albeit slowly, when I turn the key to on. And why is it building pressure so slowly? Is that because the check valve is not a total failure?

 

pickup was put on correctly? Clogged line or pickup filter?

 

It always starts now, and then runs just fine. If either was not right, I don’t think it would run without bogging down would it?