Explorer returnless fuel, what year?

I'm picking up a complete 1998 ford explorer engine this weekend. I read in a couple of CB posts that 98 explorers have the returnless fuel design, while on fordfuelinjection.com Ryan states that explorers after 1999 1/2 have the returnless system. What gives?, I think Ryan may be correct, thanks for any input, Marco.

There was a hybrid fuel system in some of the Explorers, where the FP regulator was back inside the tank and returned the extra fuel before it left the tank. Unfortunately the fuel rails on the engine still have only 1 high pressure input and no regulator.

My 98 has a return line. The 2000 I'm putting in my 70 is returnless. Returnless really simplifies the installation and works well. Not compatible with the older PCMs such as the mustangs that are commonly used in the retrofits. The injectors are different and run at higher pressure. As stated the regulator is in the tank. I think the transition was about 98-99.

http://classicbroncos.com/forums/showpost.php?p=1336399&postcount=108

i've never been a fan of returnless systems. i'm sure it'd be fine in a bronco but there's always going to be a lag from when the computer wants more pressure to when it actually shows up.

The 5.0 Explorer returnless system doesn't demand fuel pressure. The regulator is in the tank and maintains a constant pressure in the rail. Some of the other engines use a fuel pump controller and a variable speed pump. Can't really speak for those systems but the returnless 5.0 system is simple and works well.

The retrunless also adds a pulse damper to the fuel rail. It is the thing that looks like a fuel pressure regulator but isn't. What it does is act as an accumulater so when an injector fires the whole mass of the fuel in the fuel line doesn't have to start moving. Also when the injector stops it acts as a bumper so the fuel pressure doesn't hammer the system.

Why returnless? There is a little cost savings in only running 1 fuel line, also less potential for leaks. But the biggy is emissions. A return style dumps hot fuel back into the tank. That wants to vent as vapor. If you keep the tank cooler it is easier to control evaporative emissions. We did a lot of testing of this stuff back in that time frame.

Now there are a few tricks you can do. Mustang EFI systems need a constant delta of fuel pressure. That is the pressure on the fuel side of the injector is constant to the air pressure inside the manifold. Thus the vacuum controlled fuel pressure regulator. The newest computer programming avoids this by programming around it. So how do you run an old style fuel control system on a modern fuel rail? MSD-2222 is a low cost generic stand alone fuel pressure regulator. Has the vacuum nipple to maintain that constant pressure differntial just like the mustnag EFI expects to be there. I did this on my 5.0 stroker Ranger years ago. I put the regulator by the hood hinge. Supply line ran to the returnless fuel rail. where the line went from the body to the engine I put in a T-fitting. Ran a line from the T-fitting to the inlet to the regulator and hooked up the return as well. routed a vacuum line and that was it. Remember that the EFI regulators don't limit fuel going into the fuel rail but are a pressure relief valve. As the fuel pressure reaches the target pressure (modified by the vacuum) the regulator then vents excess pressure as the return line. In theory you could even mount the regulator back at the tank or even in the tank. The trouble with that theory is the vacuum signal gets buffered by the long vacuum line. So the regulator should spend its life under the hood so the vacuum signal can be as accurate as possible.

Dave said:

The 5.0 Explorer returnless system doesn't demand fuel pressure. The regulator is in the tank and maintains a constant pressure in the rail. Some of the other engines use a fuel pump controller and a variable speed pump. Can't really speak for those systems but the returnless 5.0 system is simple and works well.

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my experience with them is from an 03 cobra that uses a fuel pump driver module, fuel rail pressure sensor, and variable speed pump. it sounds like the explorer setup works alright... the cobra setup has some flaws.

Broncobowsher said:

The retrunless also adds a pulse damper to the fuel rail. It is the thing that looks like a fuel pressure regulator but isn't.

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Some return-style systems have a pulse damper, too. It was stock in '94-96 and retrofitted to '92-3 by this TSB:

Broncobowsher said:

So how do you run an old style fuel control system on a modern fuel rail? MSD-2222 is a low cost generic stand alone fuel pressure regulator. Has the vacuum nipple to maintain that constant pressure differntial just like the mustnag EFI expects to be there. I did this on my 5.0 stroker Ranger years ago. I put the regulator by the hood hinge. Supply line ran to the returnless fuel rail. where the line went from the body to the engine I put in a T-fitting. Ran a line from the T-fitting to the inlet to the regulator and hooked up the return as well. routed a vacuum line and that was it. Remember that the EFI regulators don't limit fuel going into the fuel rail but are a pressure relief valve. As the fuel pressure reaches the target pressure (modified by the vacuum) the regulator then vents excess pressure as the return line. In theory you could even mount the regulator back at the tank or even in the tank. The trouble with that theory is the vacuum signal gets buffered by the long vacuum line. So the regulator should spend its life under the hood so the vacuum signal can be as accurate as possible.

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Broncobowsher --- any chance you might have some pics to illustrate what you have explained above. I am in the never-ending process of converting to EFI and would love to avoid doing the return line. Didn't realize it might be a possibility until I just saw what you wrote.

I don't any good photos of it out of the truck, nor do I really have many good shots in the truck. Here are the two engine compartment photo I could find. Will try and walk you through it.

Supply and return lines come off the frame and can be seen between the power steering resivior and cruise control can. The cleaner rubber lines going by the washer bottle are fuel lines.

Supply can be seen going into some brass fittings above the cruise control can in the extreme corner of the engine compartment. The feed from the tank is the denter, right to the regulator left goes above the brake booster and to the fuel rail.

Between the brass T-fitting and the cruise control is the fuel pressure regulator. you can see the vacuum reference line going to it. The return runs parallel to the feed and back to the factory fuel lines mentioned above.

Broncobowsher said:

I don't any good photos of it out of the truck, nor do I really have many good shots in the truck. Here are the two engine compartment photo I could find. Will try and walk you through it.

Supply and return lines come off the frame and can be seen between the power steering resivior and cruise control can. The cleaner rubber lines going by the washer bottle are fuel lines.

Supply can be seen going into some brass fittings above the cruise control can in the extreme corner of the engine compartment. The feed from the tank is the denter, right to the regulator left goes above the brake booster and to the fuel rail.

Between the brass T-fitting and the cruise control is the fuel pressure regulator. you can see the vacuum reference line going to it. The return runs parallel to the feed and back to the factory fuel lines mentioned above.

Click to expand...

Thanks for the pics and explanation. I am debating on going this route or just doing the return line. The only reason I am trying to avoid the return line is due to needing to tap into the tank at some point. Not only are my welding skills sub-par...I've had bad experiences with welding anywhere near fuel areas...gets me nervous thinking about it. I'm gonna have to figure this one out soon enough though.