Rear diff Service questions

[danno2944]

My fuel pressure regulator is on the back of my drivers side fuel rail as far as I know.

Yours was on the pump? I

I had a p0442 I believe that's the right pid, for small evap emissions leak, I have replaced my old cap and haven't had a code since, but we will see. Filler neck is rough which is why I got new one. Question on the fuel pressure sensor, is it prone to a bad seal or breaking causing this code?

 

[donalds]

The fpr is in the tank on the pump the fuel rail damper is on the drivers side back of the fuel rail with a vacuum line on it
Here is a pic of inside the tank and the pump arrow pointing to the fuel pressure regulator

And a link to the thread when I fixed it Is my fuel pump bad 1999 ford explorer shoc 4.0. Lots of pictures on the replacement

Repair starts a post#36 but if you want to read about all the trouble shooting start on page 1 I would but I like to read

 

[imp]

The fpr is in the tank on the pump the fuel rail damper is on the drivers side back of the fuel rail with a vacuum line on it
Here is a pic of inside the tank and the pump arrow pointing to the fuel pressure regulator.......

This is a RETURN-TYPE fuel system, right? Has two fuel lines running from the tank to the fuel rail? The "fpr" in the tank is a Fuel Pressure Relief Valve, which only functions in the event of a clog in the fuel line between pump and fuel rail, or a jammed-up Fuel Pressure Regulator, which is mounted on the fuel rail. The fpr is there to protect the pump against burn-out. The Regulator is engine vacuum-operated, contains a diaphragm and vacuum hose connection, and a small valve and seat which controls the amount of fuel flow BACK to the tank.

The later (2001 or so?) RETURNLESS system has one line only, pump to fuel rail. Tank still has pressure relief valve. Fuel rail has a Fuel Pressure AND Temperature Sensor mounted on it, which has both vacuum and electrical connections. It looks like this:

• 

It tells PCM information allowing regulation of pump speed, which controls fuel pressure, holding it constant as power demand and fuel temperature changes. In-tank relief still protects pump, allowing a limit on pressure if the FPTS fails. imp

 

[Mbrooks420]

I believe the changeover year for return/returnless is ‘99.

 

[imp]

I believe the changeover year for return/returnless is ‘99.

OUCH! imp

 

[Mbrooks420]

OUCH! imp

Lol, no need for an ouch, your post still had more info than mine.

 

[donalds]

My 99 returnless system has no sensors on the fuel rails just that vacuum controlled damper and a Schrader valve that's it

 

[imp]

My 99 returnless system has no sensors on the fuel rails just that vacuum controlled damper and a Schrader valve that's it

@donalds
So, no return line, and no wires to the "damper"? The temperature feature must have come later, as my '04 has it. Went out twice, damned if I didn't learn about it then! And that nasty back manifold bolt, beneath the "lip" on the firewall! imp

 

[mattZ]

This may be common sense for you guys but make sure you get new seals also. Annnd... Don't forget to put your lock bolt back in. I did mine and found the bolt laying on the ground after I already added the oil

 

[koda2000]

'99-'01 were return-less systems and had the fuel pressure regulator on the fuel pump assembly, in the tank. The only thing on the fuel rail is a pressure damper, which only has a vacuum line.

 

[koda2000]

This may be common sense for you guys but make sure you get new seals also. Annnd... Don't forget to put your lock bolt back in. I did mine and found the bolt laying on the ground after I already added the oil

That sucks, but I'll bet you never make that mistake again. Reminds me of when I did one of my first oil changes, forgot to put the drain plug back in and dumped 3 qts of oil into the engine before I realized it. Never made that mistake again either. We live, we learn.

 

[mattZ]

That sucks, but I'll bet you never make that mistake again. Reminds me of when I did one of my first oil changes, forgot to put the drain plug back in and dumped 3 qts of oil into the engine before I realized it. Never made that mistake again either. We live, we learn.

Oh man that sucks. Haha. Yeah I was in a rush won't do that again.

 

[imp]

'99-'01 were return-less systems and had the fuel pressure regulator on the fuel pump assembly, in the tank. The only thing on the fuel rail is a pressure damper, which only has a vacuum line.

@koda2000

I have some trouble understanding......ya know I get stuck easy! If the pressure regulator is in the tank, how can it control pressure: what tells it what to do? Unless it's electrically-controlled, which seems to be a "no".

This pressure damper as you say, it has a vacuum connection going to it? So, must have either a diaphragm acted on by the vacuum, controlling a valve, or a solenoid coil, with associated wiring, to operate a valve. I suspect it is very similar, though calibrated differently to the previous "return-type" system, was re-named "damper", which, to me, is misleading, as it in reality maintains the rail fuel pressure constant as fuel demand varies with load and speed.

Semantics, then. @shucker1 What do you think of all this?? imp

 

[danno2944]

That sucks, but I'll bet you never make that mistake again. Reminds me of when I did one of my first oil changes, forgot to put the drain plug back in and dumped 3 qts of oil into the engine before I realized it. Never made that mistake again either. We live, we learn.

Lol, I have left the filler cap off after changing oil, only lost a quart before I.noticed most of it went on the hood liner...

@koda2000

I have some trouble understanding......ya know I get stuck easy! If the pressure regulator is in the tank, how can it control pressure: what tells it what to do? Unless it's electrically-controlled, which seems to be a "no".

This pressure damper as you say, it has a vacuum connection going to it? So, must have either a diaphragm acted on by the vacuum, controlling a valve, or a solenoid coil, with associated wiring, to operate a valve. I suspect it is very similar, though calibrated differently to the previous "return-type" system, was re-named "damper", which, to me, is misleading, as it in reality maintains the rail fuel pressure constant as fuel demand varies with load and speed.

Semantics, then. @shucker1 What do you think of all this?? imp

It Sounds logical to me, but I'm no expert.

I know the "pressure damper" has a vacuum line and has a diaphragm inside and it is attached to the fuel rail, that's it, no wires. The fuel pressure sensor is on the tank.

 

[1998Exp]

Well, one has to wonder how those "new" (to me, owner of a 20 year old MY98) systems work. The old wisdom was to regulate the fuel pressure against the manifold pressure, because that's where the fuel is going. This required a manifold-vacuum controlled regulator. If the pressure regulation is absolute, something has to account for the manifold pressure. It's entirely possible that the pulse duration calculation takes that into account, but I wish someone in the know would chime in...

 

[donalds]

The way I understand it the fpr is on the pump sending unit it allows the rail pressure no more any extra and it dumps the extra fuel back into the tank

The damper just smooths out the pressure spikes when the injector s fire off

If you hook up a fuel pressure gauge and look at the needle it Is almost still it moves every time a injector opens looks like a bouncing needle very little bounce
If you unplug the damper it bounces much more
The damper smoothed out the pulses caused by the injector s

 

[david4451]

The fuel pressure regulator is constantly flowing the fuel back into tank, as you can imagine the fuel pump can supply much more fuel than the engine could use.

The fuel pump works continuously and the fuel pressure regulator opens at a constant pressue between 65 to 70 plus psi on return less set up. My ST is 72 psi and stays constant.

 

[J_C]

Don't the original ball joints use plastic bearings in them? That's typical for sealed-for-life BJs. IF so, I doubt they're going to be squeaking before they've completely disintegrated the bushing inside and if that has happened you should see play with the usual prying-test.

Anyway I would sooner suspect the sway bar bushings and would spray some soapy water on them, them immediately drive to see if the squeak goes away. If the noise is still present, next spray the control arm bushings and test drive again.

As far as using WD-40 to test the BJs, you can get lithium spray grease in a can instead, that uses an included straw, that comes out like water and thickens as the propellant evaporates away. Rather than diluting any grease that might remain, it will replenish the BJ grease some. Very handy stuff, useful for hinges 'n latches 'n such too.

 

[shucker1]

The way I understand it the fpr is on the pump sending unit it allows the rail pressure no more any extra and it dumps the extra fuel back into the tank

The damper just smooths out the pressure spikes when the injector s fire off

Perfect explanation by @donalds

During acceleration or heavy load your intake manifold pressure will change as well as the injector pulse rate (As function of speed) and injector pulse duration will change (As a function of load). The control line connected to the damper in turn changes the dampening force required.

We have been using the same type system on the big bore units since the 70's. However we are dealing with natural gas as fuel rather than a liquid fuel.

To reduce emissions we use a "Jet Cell" (A Pre-combustion Chamber if you will") fuel flow to the "Jet Cell" is biased off of Air Manifold Pressure.

More Load, More Air = Higher Jet Cell Pressure.

 

[koda2000]

The way I understand it, In the return-less fuel system the fuel pump makes a constant pressure of around 65-70 PSI. The FPR in the tank (which is located right above the fuel pump) returns anything above that pressure right back into the fuel tank. Hence the fuel pressure at the rail remains close to a constant pressure and the PCM regulates fuel injector pulse rate and width based on feedback from various sensors (like the O2's, MAF, air temp, coolant temp). The damper on the fuel rail buffers the fuel pressure as needed based on engine vacuum.

The FPR in the tank is strictly a mechanical device, which uses a spring to route excess pressure back to the fuel tank. The in-tank FPR is a simple, reliable device which rarely fails. If it does fail it's typically because its plastic housing cracks. Other than the fuel pump itself the most common fuel pressure problems are due to splits in the in-tank submersible fuel lines.