2000 4.0 SOHC just quit while driving on the highway

[aveteam]

They will run and idle with as little as 42-45 psi! I have seen it. But put it under load and it cannot keep up.
The pump can supply good pressure until it gets hot and then start to drop off
That is why these issues can be hard to diagnose
The gauge does not lie!
Best time to test rail pressure is when the truck is acting up, if course

The older trucks with return style fuel rails, the pumps seemed to either work or not. Pressure on those is 36-42 psi

The returnless rail trucks (98+) the pumps seem to run forever, but when they get to 120-160k likes they begin to get weak
Truck will still start idle run most places
And then it slowly gets worse until the poor thing completely qu

I do have Forscan and an OBDLink EX so I'll definitely give that a try.

I went ahead and hooked up my OBDLink, but I didn't find any monitors in Forscan for fuel pressure directly. I did find one for fuel pump status (FP) and fuel pump monitor (FPM) and they only showed "on" when the key was turned to START. When I turned it back to run, they both went to off. I don't know a lot about how this is supposed to work, but common sense says that both those should be ON unless the key is off, right?
When there's daylight tomorrow I'll check for voltage at the fuel pump connector.

 

[C420sailor]

I’ve yet to find an Explorer that provides fuel pressure info to OBD/Forscan

 

[410Fortune]

Fuel pressure sensors did not get fitted to the sohc until 05-06

 

[aveteam]

Fuel pressure sensors did not get fitted to the sohc until 05-06

I was wondering about that, I didn't find a monitor for fuel pressure per se. It looks like the pump is running according to Forscan, but goes off as soon as the key is turned from START.

 

[410Fortune]

The pcm primes the pump each time the key is turned to run
The pcm will turn the pump on full time once the truck starts

 

[aveteam]

So, quick update. The pressure gauge kit arrived, but apparently they've never seen a Schrader valve, there wasn't an adapter for it. So I did what any shade-tree mechanic would do, I adapted it. I got a clip on air chuck, cut off the fitting they had on the hose on the gauge, and installed it. Zero pressure, even with the core of the Schrader valve removed. Very little fuel came out when I unhooked everything, so I can't see there being anything close to 68 psi there.
Next is to see if there is voltage at the fuel pump connector, which I suspect there is because you can hear the pump run for a few seconds when you turn the key on.

 

[donalds]

Fuel pressure sensors did not get fitted to the sohc until 05-06

Our 04 has one and you can see a few pids in forscan

 

[gatzdon]

So, quick update. The pressure gauge kit arrived, but apparently they've never seen a Schrader valve, there wasn't an adapter for it. So I did what any shade-tree mechanic would do, I adapted it. I got a clip on air chuck, cut off the fitting they had on the hose on the gauge, and installed it. Zero pressure, even with the core of the Schrader valve removed. Very little fuel came out when I unhooked everything, so I can't see there being anything close to 68 psi there.
Next is to see if there is voltage at the fuel pump connector, which I suspect there is because you can hear the pump run for a few seconds when you turn the key on.

Thanks for the update. Having replaced a fuel pump once, it's not that hard to drop the fuel tank and change it (unless you have so much corrosion you are afraid you will snap off bolt heads).

I went back through your posts and I may have missed it, but I don't think you said that you changed the fuel filter. Make sure you change that before tearing too much else apart.

 

[aveteam]

Thanks for the update. Having replaced a fuel pump once, it's not that hard to drop the fuel tank and change it (unless you have so much corrosion you are afraid you will snap off bolt heads).

I went back through your posts and I may have missed it, but I don't think you said that you changed the fuel filter. Make sure you change that before tearing too much else apart.

correct, I haven't replaced the filter yet- I'll do that before anything else. Looks like I'll need a tool to get the fuel line off.

 

[aveteam]

Ok, another update. I replaced the fuel filter and no change. Still tries to run, if it does run it's only for a second or two then it stumbles and dies. As a quick test I removed the core from the Schrader valve, hooked a piece of fuel line to it and ran it to a jug. When the key is on, it will prime and put out a teaspoon or so of fuel then stop- no continuous flow. I didn't try to start it but it looks like the pump is at least running enough to prime the system.

 

[Pete Deering]

I went ahead and hooked up my OBDLink, but I didn't find any monitors in Forscan for fuel pressure directly. I did find one for fuel pump status (FP) and fuel pump monitor (FPM) and they only showed "on" when the key was turned to START. When I turned it back to run, they both went to off. I don't know a lot about how this is supposed to work, but common sense says that both those should be ON unless the key is off, right?
When there's daylight tomorrow I'll check for voltage at the fuel pump connector.

The fuel pump runs for about 30 sec, when the key is turn to the on position. Too Prime the fuel line. You should hear the pump turn on.

 

[aveteam]

The fuel pump runs for about 30 sec, when the key is turn to the in position. Too Prime the fuel line. You should hear the pump turn on.

You can hear it run but it only runs for a couple seconds.

 

[Mbrooks420]

Definitely won’t run for 30 seconds. Get a pressure tester, that’s the only way to rule it out.

 

[Pete Deering]

Th

You can hear it run but it only runs for a couple seconds.

that normal

 

[wollimann]

Maybe the fuelpump is still ok and you hear it, but in many times the the rubber hose between pump an fuel line is
porose and leaking. So the pressure is lost before it goes to the fuel rail.

 

[aveteam]

Thanks all. At this point I've done all the easy stuff so it looks like I'm just going to have to drain the tank and drop it and replace the fuel pump. It has a new fuel filter and I've pretty much ruled out the crank position sensor using Forscan. I've hooked up a pressure gauge and no pressure, at least not enough to move the needle.

 

[wollimann]

Last year i have to change the fuel pump,
ordered this one from Summit.

Bosch Automotive 66085 Bosch Electric Fuel Pumps | Summit Racing

Free Shipping - Bosch Electric Fuel Pumps with qualifying orders of $109. Shop Fuel Pumps at Summit Racing.

www.summitracing.com

The pump is clearly a little bit louder at startup,
while driving you didn't hear it.

You must not drop the tank if you prefer this method (not my Explorer).

A lttle pain to loosen the fuel line quick connect, lowering the tank for about 25 cm with wheel off.
So you have enough space to use the quick disconnect tool.
Tank strap sometimes is very corroded, tank bolts should come off a litte bit easyer.
The fuel filler neck could be corroded too, rust particles could clogg the intank filter.

Rust all over...

good luck and kind regards

Wolfgang

 

[aveteam]

Quick update-
Thanks all for your help and suggestions, I was finally able to drop the tank and replace the fuel pump with the help of my father in law. The fuel pump was the problem- as soon as we hooked everything back up, it fired right up. 'Ol Blue is back on the road!

 

[410Fortune]

Well done!