LM7 swap won't start
04-24-2018 | 06:58 AM
#1
Thread Starter
Registered User
Joined: Apr 2018
Posts: 2
Likes: 0
LM7 swap won't start I've got an LM7 from a 1999 cable drive truck in my 71 Cutlass convertible. I paid "enginewiring" from eBay to mod my harness and tune my ECM in 2016. I just now got my engine installed/wired/plumbed this week and it won't start.
I've wired in the 12v battery (one lead from the harness and 2 relays (fuel pump and cooling fan)) as well as the 12v switched lead to the harness and 2 factory ground rings (connected to good grounding points with continuity to the negative side of battery). With key ON I get 12v on both trigger sides of the fuel pump relay, instead of one ground and one 12v to actually trigger the relay.
I tried bypassing the relay and turning the fuel pump on directly, but still got no fire. I'm wondering if my ECM isn't seeing proper ground somehow. Any thoughts??
Parts:
1999 LM7 engine/harness/ECM (harness and ECM modified by "enginewiring" from eBay
MSD fuel pump mounted to the frame at the tank
1971 Cutlass convertible (pure beauty)
I've wired in the 12v battery (one lead from the harness and 2 relays (fuel pump and cooling fan)) as well as the 12v switched lead to the harness and 2 factory ground rings (connected to good grounding points with continuity to the negative side of battery). With key ON I get 12v on both trigger sides of the fuel pump relay, instead of one ground and one 12v to actually trigger the relay.
I tried bypassing the relay and turning the fuel pump on directly, but still got no fire. I'm wondering if my ECM isn't seeing proper ground somehow. Any thoughts??
Parts:
1999 LM7 engine/harness/ECM (harness and ECM modified by "enginewiring" from eBay
MSD fuel pump mounted to the frame at the tank
1971 Cutlass convertible (pure beauty)
04-27-2018 | 08:16 AM
#3
TECH Regular
Joined: Apr 2017
Posts: 424
Likes: 41
From: Worcester, Mass
I've got an LM7 from a 1999 cable drive truck in my 71 Cutlass convertible. I paid "enginewiring" from eBay to mod my harness and tune my ECM in 2016. I just now got my engine installed/wired/plumbed this week and it won't start.
I've wired in the 12v battery (one lead from the harness and 2 relays (fuel pump and cooling fan)) as well as the 12v switched lead to the harness and 2 factory ground rings (connected to good grounding points with continuity to the negative side of battery). With key ON I get 12v on both trigger sides of the fuel pump relay, instead of one ground and one 12v to actually trigger the relay.
I tried bypassing the relay and turning the fuel pump on directly, but still got no fire. I'm wondering if my ECM isn't seeing proper ground somehow. Any thoughts??
Parts:
1999 LM7 engine/harness/ECM (harness and ECM modified by "enginewiring" from eBay
MSD fuel pump mounted to the frame at the tank
1971 Cutlass convertible (pure beauty)
I've wired in the 12v battery (one lead from the harness and 2 relays (fuel pump and cooling fan)) as well as the 12v switched lead to the harness and 2 factory ground rings (connected to good grounding points with continuity to the negative side of battery). With key ON I get 12v on both trigger sides of the fuel pump relay, instead of one ground and one 12v to actually trigger the relay.
I tried bypassing the relay and turning the fuel pump on directly, but still got no fire. I'm wondering if my ECM isn't seeing proper ground somehow. Any thoughts??
Parts:
1999 LM7 engine/harness/ECM (harness and ECM modified by "enginewiring" from eBay
MSD fuel pump mounted to the frame at the tank
1971 Cutlass convertible (pure beauty)
RobertD had a similar problem from a company on eBay that did his harness. He didn't use them by name but I'm guessing its the same one.
https://ls1tech.com/forums/conversio...bo-swap-6.html Post 108 describes what happened to him. Maybe he can shed some light on your problem. If not you'll have to either contact them or get some wiring diagrams and a multimeter and start looking everything over.