Hey Guys -
The Volvo is back with a non-functional tach. As a reminder, it was back with me for quite a while as I reworked the fuel tank for greater capacity and also because the car wouldn't run. I ran a ground from the fuel pump relay to ground and it fired right up. I didn't realize at that point that the tach was inop (the owner didn't mention it at that time).
So today I started hunting the tach wiring from the MSD 6AL back to the EZ-EFI computer. With a lot of taking apart and standing on my head I determined that the wiring from the MSD to the computer is fine. But then another question: I know MSD's make kick-butt spark but are known to have their "issues" so I'm wondering if the MSD tach out signal has taken the proverbial dump. I'm not finding any way to test that - the Holley website had some info but it was contradictory. Any ideas out there? Before I tear into the dash again (this will be about the 97th. time) I'd like to be sure that the tach is even getting a signal. I also wondered if the car stopped running in the first place because the tach signal to the EX-EFI computer signal went out. I appreciate any input on this.
EDIT: I just found the installation instructions online and it says that it outputs a 12VDC square wave. How can I check that without a scope? Also, my DMM has a frequency function - would that tell me anything I need to know?
Dan
The Volvo is back with a non-functional tach. As a reminder, it was back with me for quite a while as I reworked the fuel tank for greater capacity and also because the car wouldn't run. I ran a ground from the fuel pump relay to ground and it fired right up. I didn't realize at that point that the tach was inop (the owner didn't mention it at that time).
So today I started hunting the tach wiring from the MSD 6AL back to the EZ-EFI computer. With a lot of taking apart and standing on my head I determined that the wiring from the MSD to the computer is fine. But then another question: I know MSD's make kick-butt spark but are known to have their "issues" so I'm wondering if the MSD tach out signal has taken the proverbial dump. I'm not finding any way to test that - the Holley website had some info but it was contradictory. Any ideas out there? Before I tear into the dash again (this will be about the 97th. time) I'd like to be sure that the tach is even getting a signal. I also wondered if the car stopped running in the first place because the tach signal to the EX-EFI computer signal went out. I appreciate any input on this.
EDIT: I just found the installation instructions online and it says that it outputs a 12VDC square wave. How can I check that without a scope? Also, my DMM has a frequency function - would that tell me anything I need to know?
Dan
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