Resolved Fuel System Troubleshooting

Dx2ry · Oct 16, 2023

First post, picked up a 2000 GT (4.6L, 90k miles, stock) this past weekend. It has been my buddies for the past 20 years and it has been sitting the past few years. I took it to get it back up and running and then start doing the fun things to it like make it no longer look like it can run the Baja 1000!

Anyway, once I got rid of the bad gas, I have been having troubles with the fuel system. Here is a summary of the issues:

Does not start - when I turn the engine over it does not start. I also can not hear the fuel pump prime either. Once I spray some starter fluid down the intake, it does start and keep running. Idle is fine although there is a slight RMP surge during the idle (up about 200RMP and then back down).
No fuel pressure at the schrader valve - I attached a fuel pressure gauge to the schrader valve and I get no readings. Even when the engine is running. Also when the gauge is off and I just press down on the schrader valve with a screwdriver, there is no fuel or pressure being released. It is dead.
Engine does not shut off when the inertia switch is activated - this is the most perplexing. I was going to change the fuel filter and hit the inertia switch to run out the fuel in the lines. The car kept running and running with no change. I finally shut it off after 15 minutes. This is by far the most perplexing issue, it does not make sense to me.
No codes thrown - zero, there is nothing being triggered by any of this in the PCM.

I am at a loss here. What do you think could be potential reasons why the car won't start off the key, but will keep running after the inertia switch is activated? All doing it with no fuel presser at the fuel schrader valve! What am I missing here? Appreciate any thoughts!

Noobz347 · Oct 16, 2023

I'm pretty sure your fuel pump is bad.

Dx2ry · Oct 18, 2023

That is definitely on the list of fixes. Going to drop the tank and replace even if it is for piece of mind since the car sat for a few years.

I am just confused why the inertia switch would not work at all.

Noobz347 · Oct 18, 2023

Dx2ry said:
That is definitely on the list of fixes. Going to drop the tank and replace even if it is for piece of mind since the car sat for a few years.

I am just confused why the inertia switch would not work at all.

It occurs to me that you're getting enough fuel to idle. I don't see where it said you tried to drive it in this condition and I didn't want to bring it up either. A few very lean pops and then you got [real] troubles.

So, my theory is that your fuel pump has bypassed internally. It's toast. If this is true, the switch means nothing. All that does is cut power to a pump that's sucking enough fuel through the internal bypass to sometimes idle.

I mean... You could confirm with a fuel pressure tester but your description of the Schrader valve makes that kinda redundant.

If it were me, I'd swap the pump and look for [stuff] in the tank while I had I had it all apart. Pay close attention to the vent line while you're in there. Change it if it looks suspicious. We've had a rash of those around here lately too.

I'm not as familiar with the returnless fuel systems as I am with the return style but your description sounds like pump. Also... when you rock the key forward before a cold start, you should be able to hear the pump prime. At least once until the system is pressurized. If you have no pressure at the Schrader valve then it should be running continuously.

Hopefully somebody more familiar will chime in.

Dx2ry · Oct 24, 2023

I replaced the pump and it starts just fine now. Fuel pressure was reading 30psi @ idle and 40 under load which looks normal based on other posts here. Cleaned the tank and it looks good, also replaced the fuel filler grommet. Everything else looked fine.

I am getting a slow tank fill at the pump. The filler neck fills up and shuts off the pump. I am guessing it is something with the vent line. Ordered a new carbon canister and vent solenoid and going to change them out. If that doesn't fix it, what else should I look for on top of the tank?

Dx2ry · Nov 11, 2023

Just to close the loop on this one.... Replacing the cannister and solinoid fixed the filler neck issue.

Thanks for the help Noobz. Appreciate it

Noobz347 · Nov 11, 2023

Have you blown through both of them to see if they are plugged/malfunctioning?

Dx2ry · Nov 11, 2023

I replaced them and there are no issues with filling the tank with gas.

Resolved Fuel System Troubleshooting

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Resolved Fuel System Troubleshooting

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