Swapping engines need advice

[bmx2guy]

I have a 98 Explorer with a bad motor(4.0 sohc) and I found a 2002 motor with 59000 mi. everything looks the same except my old fuel system uses a separate line to each fuel rail and the newer motor uses one line in then splits at the rail. Can I just plug one of the lines? Is there any other differences I need to know about.

Thanks
Bob

 

[CDW6212R]

Not knowing the differences I'd suggest keeping as much of the 98 unique parts, meaning the fuel rail since you mention it. I'd think that the intake would also be different, I'd expect that you have to change one or both of those.

The PCM can likely handle any minor differences like the intake or camshafts. But really all you should need to worry about is getting the same sensor signals needed for the 98 PCM. Concentrate on what differences there are with the wiring connectors, and sensors.

The pre 1999 trucks(your 98) have return type fuel systems, you must use the 1998 fuel injectors, fuel rail, and fuel pump. So plan to swap out the 2002 rails and injectors to start with. Good luck,

 

[bmx2guy]

Yes I see what you mean the fuel rail is tied together in the back so as to form the fuel loop. I hope the harness is the same! If not I could switch them out.

 

[n0xdw]

I would use your original harness, it will probably be easier. The 99 up injectors use higher fuel pressure so like Don said plan to use all of your 98 stuff for on top of the engine.

 

[Gannz]

Do you guys know just how much of a difference there is between the two injectors? I just finished a '98 to '03 swap and I used the injectors from the '03. I thought they changed in '04 to 24 lbs. (from 19 lbs.).

Mine was out of tune a little when it first fired up but it fluctuated for five seconds or so between 500 and 1500 rpm and then it seemed to tuned itself in.

I'm going to change them back of course but there can't be that much of a difference between the two injectors. I noticed that it idles well (about 800) when first started. If I start it up and let it sit it will idle at 800 forever but after you give it some gas and let it go back to idle it's a little low (about 550). Everything seemed fine when on the road but, looking back, I did notice some hesitation w/ the a/c running.

Guess I get to tear back into her...

 

[CDW6212R]

The fuel systems changed in all Fords in 1999, to the returnless style. The fuel pressure changed from about 35psi to 62+psi. The injectors were purposely made differently, the wiring connectors are different.

The later fuel injectors will flow more fuel given the higher pressure, and they are likely a smaller injector due to that. The PSI difference makes comparing them useless, apples/oranges.

Either system should not be used with the other type of fuel injectors or fuel pumps. You could swap a bunch of parts to gain what should be potentially better efficiency with the 99+ parts. But that isn't worth the trouble for the almost insignificant difference.

"...I just finished a '98 to '03 swap and I used the injectors from the '03..."
If you used the later injectors, what wiring did you use, the 98 connectors will not plug in? You should swap the 98 injectors and wiring back onto the 03 engine, I assume you still have the 98 fuel pump? The PCM's are very smart, that is the only reason that it actually runs. An EECIV PCM would not begin to operate an engine with unmatched injectors/MAF/fuel pressure, etc. Good luck,

 

[bmx2guy]

You have to use the 98 engine harness it is different, so I will swap the intake and injectors to the new motor and deal with swapping any sensors if they come up different too.

 

[CDW6212R]

Once you begin to look for and find the differences, it falls in place. You will get it right, I hope you take some pictures and post some here. A lot of people will be making the swap to later engines ongoing. Regards,

 

[Gannz]

If you used the later injectors, what wiring did you use, the 98 connectors will not plug in? You should swap the 98 injectors and wiring back onto the 03 engine, I assume you still have the 98 fuel pump? The PCM's are very smart, that is the only reason that it actually runs. An EECIV PCM would not begin to operate an engine with unmatched injectors/MAF/fuel pressure, etc. Good luck,

I used the 98 wiring. The outside of the connector is a little beefier and nicer on the 03 but the fit is exactly the same. I know b/c I broke off one of the tabs on the 98 connector and I had to swap one out from the 03. Even the color coding is the same.

The injectors are the same exact size (miked them before installation). I believe you that they're running a different pressure but everything else is the same.

Yes, still have the 98 fuel pump.

 

[Gannz]

You have to use the 98 engine harness it is different, so I will swap the intake and injectors to the new motor and deal with swapping any sensors if they come up different too.

I just did this swap and worked around all the issues you're about to face. It's not hard but this will probably save you some time if you know what to look for going in...

http://www.explorerforum.com/forums/showthread.php?t=191529

I'll post some pics also.

 

[CDW6212R]

Very good, my friend was the first I heard of with the injector issue when he needed one for his 99 302 Explorer. Parts stores at the time were selling him the 98 injectors. It would make sense to try the 98 injectors even if they did appear the same. The 99+ parts should be different functionally at least. Good luck,

 

[explorerjim]

How did this end up? Did you end up using the 98 wiring and 98 injectors? I'm trying to put a 99 sohc in a 97 explorer and I'm confused on what I have to move from the 97 to the 99 engine. Help! I thought I understood this but now I'm not sure.

 

[CDW6212R]

How did this end up? Did you end up using the 98 wiring and 98 injectors? I'm trying to put a 99 sohc in a 97 explorer and I'm confused on what I have to move from the 97 to the 99 engine. Help! I thought I understood this but now I'm not sure.

If both engines are SOHC V6's, then use the 97 fuel rails/injectors, as well as the 97 PCM. The rest of the parts should be basically the same, most other extra parts will be spares. Regards,

 

[explorerjim]

Thanks for the info CDW6212R. I'm not a mechanic by trade but love pretending I am. I've switched the fuel rail and injectors over . I'm assuming I need to transfer the 97 vacuum array? to the 99. Hope I can find all the right spots for them. Not much of a diagram to go by under the hood but it should be fun trying! Is it necessary to get a new o-ring kit for the injectors?

Old engine is almost out. Kind of exciting at this point. I always wonder if it will start or if I will have more issues.

Thanks again

 

[CDW6212R]

The o-rings on the injectors usually don't need replacement. Look at them each closely, if any are damaged then replace them. Those are special fuel type o-rings, so check them early on so that you can locate others if needed. Basically you want everything to be as it was on the original engine. Pictures taken beforehand make it easier to swap parts. Good luck,