Return to Returnless engine differences...

[wadespencer99]

I'm putting an (originally) return style engine in a returnless car. I know most of the major differences (wiring harnesses, fuel rail, LIM, knock sensor), but I have some questions....

EGR?
DPFE?
IACV?
O2 Sensors?

I know there are additional differences with between the 99/00 and 01/02 engines (valve cover, timing cover, coil pack, plug wires, etc), but the car is a 2000, and the new engine is a 99, so those are not problems.

Thanks!!

[deliveryguy]

I have heard of the term "returnless" but I never knew what it meant - I just did a quick google search and now I know! Found this:

AutoSpeed Article

Not sure if it would help - this is returnless => returned. I'm gonna read up on it for kicks.

[wadespencer99]

No, that doesn't help

Basically I'm converting a return style engine to go in a returnless style car and need to know exactly which components need to be changed, other than the ones that are obvious.



To sum up the difference for you, return style cars have two fuel lines coming out of the fuel rail. One line obviously carries fuel to the rail from the fuel pump, the other line returns the excess fuel to the tank. ReturnLESS cars only have one fuel line, it carries fuel from the pump to the fuel rail. The ECU varies the voltage to the fuel pump so there is no excess fuel.

Early 99 Cougars with a build date before 05/xx/99 are return style. Any Cougar built after that, including all 2000, 2001, and 2002 cars are returnless.

For more info on what visual differences there are between return and returnless cars, view this thread:

return or returnless fuel rail?

[nadthomas]

I put a returnless engine in my return style cougar, and I the logic I used was when in doubt go with what came on the car, not what came on the engine. Internally the engines are essentially the same, so the engine is not going to know what sensor you are using, but your computer sure will. I would say that the DPFE and IACV would be the same, not sure about the EGR, and I believe the O2's actually have a different type of connector so those simply will not plug into the harness. Also you could always call a parts store or Ford and see if there is a different part number between the parts that you are unsure of.

For the most part the only things that need swapped over are the obvious parts, and if I recall correctly there was one sensor on the backside of the block that was not on my returnless engine, but was on my return and need plugged into the wiring harness. So I had to take out one of the plugs in the engine and pop in the sensor, I have no idea what the sensor was, but since you are going the other way you could just ignore the sensor that is in the block and not plug it in since you should not have that connector on your harness. If you want to remove it you will need to get something to plug it.

[wadespencer99]

I did check the DPFE at advanced, trying to see if I could swipe the one from the donor engine to try on my own car, and they APPEAR to be the same. Advanced listed a different one for 01/02 cars. I hate the jackass that works at the Ford parts counter, so I'd like to avoid calling them.

I can just pull the EGR and everything from the old engine if need be, just trying to make less work tomorrow

Thanks for the heads up on the 02s. I'll change those.

[deliveryguy]

Thanks for that Wade - Now I'm trying to figure out what the advantage would be. Wouldn't a returnless setup be tougher to maintain? Everything I know about this is what google just taught me, but I'm under the impression that tuning, filtering, efficiency, and general maintenance is more of a hassle on a returnless system.

[jaged]

i have returnless injectors/harness with a return fuel rail in the 3L and it works fine.

if you swap out all the wiring and fuel rail from the old to the new there shouldnt be any problems

[nadthomas]

Originally Posted by jaged

i have returnless injectors/harness with a return fuel rail in the 3L and it works fine.

if you swap out all the wiring and fuel rail from the old to the new there shouldnt be any problems

Yeah, but I would bet that something had to be done with your computer to make that all work right. Like I said I know for certain the return harness had one more sensor then the returnless. The computer is not going to be happy and should through a CEL if all of a sudden a sensor was missing.

[jaged]

true, it was switched over on the chip

[brapple]

Originally Posted by nadthomas

Yeah, but I would bet that something had to be done with your computer to make that all work right. Like I said I know for certain the return harness had one more sensor then the returnless. The computer is not going to be happy and should through a CEL if all of a sudden a sensor was missing.

maybe, maybe not ... example: my 99 contour doesn't have a knock sensor. I am using a SVT PCM and I have not gotten a CEL for the knock sensor.

as for the fuel injectors they don't know what fuel system they belong to. All they need is the correct harness connector. So you can use returnless injectors in a return system but you will have to splice the wire connectors also.

differences:

the returnless engines are slightly less in displacment and the compression was bumped alittle. I know this is true for the SVTs so I would assume the same is done for the non-SVT's.

O2 sensors. the return fuel systems have a square connectors on the upstream sensors and round on the downstream sensors. I believe that all returnless cars (and 2k and on based on 3L I have seen) all have round connectors for the O2 sensors. The upstream are green and the downstream are blue.

As for the dpfe, I believe they are all the same. we have used 3L ones on engine swaps we have done.

The egr valves should all be the same, don't know if the cougar egr tube is different or not.

bottom line use everything that came in the car and just use the mechanicals of the engine you want to swap it. this should avoid any possible issues with differences.