Ok, here we go , I have had 3 vehicles go out on me this week. Some luck huh? My F250 motor spun a bearing and lost oil pressure so I bought a newer f250 just to have it go dead on me 3 days later. With the help from these guys in the forum , we narrowed it down to the gpcm. Thanks guys. Now today my wife breaks down in the expedition. You can't imagine how much work I have missed. Lol. So I have been noticing the truck stalls for a moment and then picks back up every once in a blue moon. Here lately it has become it seems a little more often. We replaced the fuel pump from autozone 2 years ago. When I arrived to her broke down , I got in the truck and couldn't start the it. So thinking it was fuel related, I turned the ignition on without cranking several times to make the pump engage enough to push fuel up the line. Low and behold it fires up and runs about half a mile. Meanwhile I notice pressing the gas peddle to accelerate makes the truck stall more so I let off the gas and tap it randomly to get the rpms back up. It didn't work long. Every time I filled the rail by engaging the pump manually with the ignition it would start and idle fine. Soon as I hit the gas it would stall out. I ended up pushing them home the rest of the way. I'm going to check for codes in a few minutes as I just walked in the door from work. My boss is very upset with me even though I don't think he believes 3 trucks went out this week so I'm trying to make it up. So I will be working late hours on this in the evenings. I tried researching around , but only thing I have found is the throttle position sensor or something. Any way to test it with a multitester or any thoughts what this could be. I would hate to drop the tank to get to the fuel pump, but knowing autozone has crap parts, I'm thinking it could be the fuel pump purchased 2 years ago. But , when the pump went out then it did not even let me manually fill the line by turning the ignition on several times before cranking. One more thing, and this could be unrelated. I did notice a sound coming from the truck every now and then , like a super duper wind tunnel fan blowing air force under the hood. But it was not very often. I appreciate any and all advice as I'm about ready to pull out all my hair that's left!

 

Nate,

Autozone may have a fuel pressure test gauge that you can borrow. If not, they do sell them. The fuel rail will have a Schreader type valve on it that looks like a tire inflation stem. You can screw on the pressure gauge then look at the pressure reading during the different phases of what your experiencing to see if pressure is dropping off. It could be the pump or debris clogging the in-tank screen if the pressure is not stable.

 

You're the man. I'm headed there now before they close.

 

Just remember your dealing with pressurized gasoline. So wait a few minutes after shutting off the motor, but expect that there still will be fuel that will spray when hooking up the gauge. Then restart the vehicle! And check for leaks. You've had enough adventures for the week.

 

I feel like a puppy tagging along. If one of the auto parts stores don't
have one that "lend" then if you have a Harbor Fright they do have a fair kit.
One other place just came to mind. Regular rental outlets might also have a kit.

Autozone or one of the big chain stores would be the best bet because they
"loan" and then when you bring it back you get your money back.

Good luck.



Sean <BR>

6.0L Tech Folder

 

Fuel tester will have to wait till I can get one from another store. There's was lent out. Also I went ahead and change out the maf sensor, we can rule that out. I'm leaning g to ftp server sensor or emc. Maybe. I plugged in my odb earlier and got P1450, P0174, P0175

 

So I'm getting 0 on the meter when engaging the fuel pump. At idle I was getting 28 and the same at the 2000rpms. It stays at 2000 rpms for roughly 10 seconds and then started something similar to a tale pipe backfire in the air filter chamber. So I had her let off the gas and then when we tried the gas again you would have to tap it like to get it to rpms back up or it would try to drop off . It was creating like a back pressure on the gage.

 

I also bought a vacuum tester while I was there and got 19 to 20 on the vacuum while at idle. Definately worth the investment if you plan to maintain your own vehicles. Boy have I been getting educated! Thanks Toomany!

 

I'm am so deliriously tired , I appoligise , it was the vacuum that was dropping off not the fuel, the fuel stayed at 28 when idle and 0 when engaging the fuel pump. The vacuum dropping and then having like back pressure or something. I'm so tired guys . I appoligise.

 

I forgot to add it was getting realy bad gas mileage there at the end before the break down.

 

Ok new test this morning. Fuel checks out at 8 priming then around 30 cranked. Vacume read around 20 and would drop to 0 when pressing the gas. The truck ran fine for around 6 minutes. I could gas it and it was fine I could hold it at 2000rpm and fine. After 6 minutes it started to act up again.

 

Vacuum dropping when hitting the throttle is normal as long as it rebounds.


When the engine acts up is there any change in the vacuum or fuel pressure?

 

No just a popping in the air filter area, but I changed the maf sensor.

 

Nate: you have changed the fuel filter already? Any chance this started shortly after getting fuel?

The fuel pump is an integrated unit and depends on fuel to cool itself -- that's why we don't run ours below 1/4 tank. In the unit is the tank level and a check valve that is supposed to hold system pressure with engine off. If the check valve starts to go bad first symptom will be longer crank times after sitting a couple days, then just a day, then any time you try to start. You can leave your gauge hooked up over night to see what the reading is on shutdown versus the next morning.

If the check valve completely fails, it will have trouble maintaining fuel pressure at all.

But bad gas and/or a clogged fuel filter will cause issues like you're seeing...

We replaced our fuel pump twice: 1st was under warranty and that was the level reading going wack-o, that's when the mechanic at Ford said not to run it below 1/4 tank (this is common to many vehicles with in-tank pumps btw).

Second replacement was the check valve failing. We took it to a mechanic and his bad luck: he got a bad fuel pump NEW from Ford -- had to do the job twice, bummer. BTW: anytime you change that pump you are supposed to put a new fuel filter on...

How many miles on your Expy? Good luck....

 

And another thought, not fuel related: have you tried pulling codes? When is the last time you've changed plugs and COPs/boots?