fuel rail & regulator

[Wrench]

Got a 99 4.0L OHV that does not seem to have a fuel return line back to the tank, just a braided stainless steel line to the pressure regulator. I've searched all around the fuel rail and see no other lines coming to it. Mine also does not have an EGR system and has never been tampered with from new. Anyone else seen this setup.

 

[rwenzing]

You have a returnless fuel system that does its pressure regulation at the fuel pump instead of at the fuel rail. It doesn't need a return line like the older systems had. The part on the fuel rail that looks similar to a pressure regulator is the Fuel Pulse Damper.

2000 Ranger OHV 4.0's don't have or need EGR to meet emission standards. It's possible that your 99 doesn't either.

 

[Wrench]

Soooo, if this is a fuel pulse dampner, what is the reason for a vacuum line connected to it? Could it be that it is indeed a pressure regulator and just cuts the flow back and once the injectors have used up the excess pressure then a new lower pressure is maintained by a vacuum operated valve within the reg.
Interesting that they have done away with the EGR valve on certain engines yet the majority have them.

 

[rwenzing]

No, the fuel pressure regulation is done at the tank unit.

The Pulse Damper on the fuel rail reduces the pressure spikes in the fuel rail caused by the pulsing of the fuel injectors. The vacuum line is there only as a safety measure to contain fuel spillage if the the Pulse Damper diaphragm were ever to rupture.

An EGR system is expensive and it is included in the emission controls only when it is necessary to meet the emission standards. Interestingly, my 2003 4.0L does not have it but the otherwise similar 2002's and 2004's do.

 

[Wrench]

Could you tell me how the in-tank fuel pump regulates the fuel pressure or does it function on a constant pressure?

 

[rwenzing]

There is a pressure regulator on the intank pump assembly that dumps excess fuel from the pump directly back into the tank to maintain fuel line pressure at ~65 PSI.

 

[Wrench]

Thanks for the info on the fuel system. What's really annoying is that my factory shop manual does not discuss this system, but rather the older one with a return line and regulator on the fuel manifold. My current problem (cold engine) - starter cranks engine at normal speed but engine requires excessive cranking time before start. If I prompt the fuel pump twice before cold start the engine fires up right away so I know I have a fuel delivery problem, either pressure or volume. Engine starts fine hot. I plan on connecting a pressure guage up to the schrader valve before I change the fuel filter (changed 1700 km's ago) so I know where the baseline is. One interesting observation I made was when I filled the gas tank up, cold engine started up right away. Are the fuel pump and pressure regulator able to be replaced as seperate items?

 

[rwenzing]

Your symptoms sound like a tired pump and/or a bad check valve, both of which are part of the intank assembly. Check with a dealer but I think you have to buy the complete assembly with the pump, regulator, sending unit, etc.

 

[Wrench]

Are there any good aftermarket fuel pump assemblies available or is this strictly a dealer item?

 

[Wrench]

Update - did fuel pressure test after truck sat all night. PCM prompt roughly 3 sec's long. Zero pressure in fuel rail. First prompt gave me 25 psi. Second prompt gave me 50 psi. Fuel pressure hold test - 50 to 20 psi, 4 sec's. Replaced fuel filter and sample taken from old filter showed dark brown residue. Retest pressures. First prompt gave 30 psi, second one gave 52 psi. Start engine and pressure maintained at 67 psi. Very little pressure variation when engine rev'd. Being that this system is of the returnless type and the factory shop maual says to look for a leaking injector for the pressure loss it would appear that a check valve is not a factor or is it? Very little info in shop manual as to how this system is constructed. It would apppear that the system is failing the hold test or that the fuel pump is not building enough pressure after a 2 hr. shut down. I like the old system where all the fuel is recycled thru the fuel filter and then the excess is returned to the tank. This returnless system just cycles the unfiltered excess back to the tank thru the in-tank regulator and if it is contaminatd it just eats the fuel pump alive. Ford wins by not plumbing in the return line and letting the pump fry from minor contamination.

 

[Wrench]

Could someone tell me if there is a check valve in the fuel pump discharge or in fuel pressure regulator for the returnless system. The fuel pump can maintain good pressure while the engine is running so I don't believe the pressure regulator is at fault. I did a flow test and there is plenty of fuel flowing so I don't suspect the sock on the fuel pump inlet to be plugged and I just changed the fuel filter. This leads me to think the fuel pump itself is healthy. What is the pressure hold and time spec's for this system?

 

[rwenzing]

The only manual I have is for the 2002 Ranger but it is also mechanical returnless like your 99. The manual confirms that there is a check valve in the intank pump assembly but it doesn't say exactly where.

The spec for the 2003 Ranger (also mechanical returnless) says that the pressure should not drop more than 5 PSI during the first minute after the pump shuts off.

 

[Wrench]

Thanks for the info rwenzing. I guess the next step is to pull the in-tank fuel pump and see where the problem lies. Does this seem like the next logical step to take? As the engine will start fine with two ignition key prompts (back to back) cold and also restart quickly within 1 hr of hot shutdown that there is a leak within the tank hosing or the fuel pump check valve is shot. So which do you think is easier and more accurate to do, remove truck box to get at pump or remove fuel tank from below?

 

[rwenzing]

Thanks for the info rwenzing. I guess the next step is to pull the in-tank fuel pump and see where the problem lies. Does this seem like the next logical step to take? As the engine will start fine with two ignition key prompts (back to back) cold and also restart quickly within 1 hr of hot shutdown that there is a leak within the tank hosing or the fuel pump check valve is shot. So which do you think is easier and more accurate to do, remove truck box to get at pump or remove fuel tank from below?

My gut says that either the check valve isn't checking or the pump itself is giving up even though it can eventually get up to pressure. Either way, you will probably end up replacing the tank unit.

You can go either way to get at the tank. IMO, it is more convenient to pull the bed provided that you have a way to lift it off. 4 people can carry it but I have always used 4 motorcycle tiedowns hooked to the garage ceiling to take it off without helpers. To help prevent dents and scratches, I pad the back of the cab and the rear bumper with cardboard or floor mats.

There are six bolts in the bed (#55 Torx), three small screws at the filler neck and one electrical connector at the end of the DS frame rail.