The problem finally showed up
Senior Member
Joined: Jul 2012
Posts: 9,003
From: C-Town
3.7 Engine swap COMPLETE!!!
3.5 to 3.7 swap...
1) MUST use 3.7 from 07 model truck NO OTHER WILL WORK.
2) MUST swap fuel rails from the 3.5 TO the 3.7. Why? Because the 3.5 use's a return style fuel rail, the 3.7 use's a returnless fuel rail. I also swapped out the fuel injectors sense they were newer.
3) MUST swap over the EGR block off plate. The newer engine use's a egr, our older engine's did NOT.
4) MUST use your older 3.5 harness! The newer one has wire's ran for the egr valve, as well as some connector's I DID NOT see on there for my engine. MAYBE you could get away with useing it, But I highly doubt it.
5) IF you have a factory Block heater....YOU WILL NOT have it anymore..lol. The new 07 engine does NOT have a hook up for it. So be prepared for that.
6) There Are TWO O2 sensor's on the 3.7 mani...the 3.5 only has 1!!! SO, what do you do? lol I hooked up teh rear o2 sensor from the back of teh truck like it was stock. then i hooked up the FIRST o2 sensor closer to the engine...it works great. Then i just left the last o2 sensor just in case, and tied up the wire. But this is just another of those things I could not find anywhere on here..
7) The 3.5 ECM will run the 3.7 just fine. No need to swap it for the 3.7 ecm. Well, at least for me that is.
3.5 to 3.7 swap...
1) MUST use 3.7 from 07 model truck NO OTHER WILL WORK.
2) MUST swap fuel rails from the 3.5 TO the 3.7. Why? Because the 3.5 use's a return style fuel rail, the 3.7 use's a returnless fuel rail. I also swapped out the fuel injectors sense they were newer.
3) MUST swap over the EGR block off plate. The newer engine use's a egr, our older engine's did NOT.
4) MUST use your older 3.5 harness! The newer one has wire's ran for the egr valve, as well as some connector's I DID NOT see on there for my engine. MAYBE you could get away with useing it, But I highly doubt it.
5) IF you have a factory Block heater....YOU WILL NOT have it anymore..lol. The new 07 engine does NOT have a hook up for it. So be prepared for that.
6) There Are TWO O2 sensor's on the 3.7 mani...the 3.5 only has 1!!! SO, what do you do? lol I hooked up teh rear o2 sensor from the back of teh truck like it was stock. then i hooked up the FIRST o2 sensor closer to the engine...it works great. Then i just left the last o2 sensor just in case, and tied up the wire. But this is just another of those things I could not find anywhere on here..
7) The 3.5 ECM will run the 3.7 just fine. No need to swap it for the 3.7 ecm. Well, at least for me that is.
Thread Starter
|
Member
Joined: Jan 2022
Posts: 45
From: Alberta
I'm still not convinced this swap is gonna be as straight forward as it sounds. I got my motor a little late, yesterday. And I know forsure the harness is different at the junction box, so I can verify that the harness will not work. I almost jumped the gun and got a ecm from a 07 hummer, but at the very least its gonna need a tune I figure. But I will keep adding info as I go along on this adventure seeing is I have came so far lol
Thread Starter
|
Member
Joined: Jan 2022
Posts: 45
From: Alberta
Good morning everyone, it has been a while but I figured I would chime in. The 2007 3.7 that I installed in my 2006 Hummer H3 3.5 (originally) has been excellent. I did not have to tune it or anything along those lines. It has been running very well and no more issues since the swap. So if anyone wants to do that swap it is very easy straight forward. Have a good day everyone and if anyone needs some 3.5 engine parts I do still have quite a few new ones lol.
Junior Member
Joined: Apr 2023
Posts: 9
Hey guys. Just rebuilt my 08 3.7 with the block and crank from an 07 3.7. Running into issues with sputtering and acting like it wants to stall. After initial startup it threw the P0014 code. Changed the cam actuator and still didn’t help. Mechanic checked time and just retorqued the CK bolt, and nothing. Still acting the same. I know the machine shop that did the rebuild used my old cam sprocket, so we haven’t changed that yet but we are swapping cylinder heads next week to see if that changes anything (the machine shop had an extra 3.7 laying around). My mechanic and myself are at a loss here on what to do next.
Senior Member
Joined: Jan 2023
Posts: 133
3.7 Engine swap COMPLETE!!!
3.5 to 3.7 swap...
1) MUST use 3.7 from 07 model truck NO OTHER WILL WORK.
2) MUST swap fuel rails from the 3.5 TO the 3.7. Why? Because the 3.5 use's a return style fuel rail, the 3.7 use's a returnless fuel rail. I also swapped out the fuel injectors sense they were newer.
3) MUST swap over the EGR block off plate. The newer engine use's a egr, our older engine's did NOT.
4) MUST use your older 3.5 harness! The newer one has wire's ran for the egr valve, as well as some connector's I DID NOT see on there for my engine. MAYBE you could get away with useing it, But I highly doubt it.
5) IF you have a factory Block heater....YOU WILL NOT have it anymore..lol. The new 07 engine does NOT have a hook up for it. So be prepared for that.
6) There Are TWO O2 sensor's on the 3.7 mani...the 3.5 only has 1!!! SO, what do you do? lol I hooked up teh rear o2 sensor from the back of teh truck like it was stock. then i hooked up the FIRST o2 sensor closer to the engine...it works great. Then i just left the last o2 sensor just in case, and tied up the wire. But this is just another of those things I could not find anywhere on here..
7) The 3.5 ECM will run the 3.7 just fine. No need to swap it for the 3.7 ecm. Well, at least for me that is.
3.5 to 3.7 swap...
1) MUST use 3.7 from 07 model truck NO OTHER WILL WORK.
2) MUST swap fuel rails from the 3.5 TO the 3.7. Why? Because the 3.5 use's a return style fuel rail, the 3.7 use's a returnless fuel rail. I also swapped out the fuel injectors sense they were newer.
3) MUST swap over the EGR block off plate. The newer engine use's a egr, our older engine's did NOT.
4) MUST use your older 3.5 harness! The newer one has wire's ran for the egr valve, as well as some connector's I DID NOT see on there for my engine. MAYBE you could get away with useing it, But I highly doubt it.
5) IF you have a factory Block heater....YOU WILL NOT have it anymore..lol. The new 07 engine does NOT have a hook up for it. So be prepared for that.
6) There Are TWO O2 sensor's on the 3.7 mani...the 3.5 only has 1!!! SO, what do you do? lol I hooked up teh rear o2 sensor from the back of teh truck like it was stock. then i hooked up the FIRST o2 sensor closer to the engine...it works great. Then i just left the last o2 sensor just in case, and tied up the wire. But this is just another of those things I could not find anywhere on here..
7) The 3.5 ECM will run the 3.7 just fine. No need to swap it for the 3.7 ecm. Well, at least for me that is.