Electrical Howell EFI - No RPM Signal

[John Casey]

For those who had RPM signal problems at the ECU, were they caused by a grounding issue?

My situation is as follows:

AMC 258 i6 / 4.2l with Davis DUI
Engine cranked, but didn't start.
Tested spark, but no fuel after prime when cranking.
WinALDL revealed no rpm signal.
Talked to Troy at Howell, did the 3 x tac tests, and got the pump to run and injectors to click indicating a ingition or filter problem
Replaced the DUI module with OEM GM unit, no change
Replaced the tact filter and ECU with new ones from Howell, no change.
Read about voltage issue when the difference from neg batt post to engine is > .2v when cranking.
I was showing .39

I got it down to .3 by:
12ga wire from Howell harness grd bolt on the intake, to firewall on a mast cylinder bracket bolt.
Batt neg to same firewall bolt.
Instrument grd bus to other side of firewall to that same bolt.
2 X OEM grd on headlight harness to a different firewall bolt
Other side of instrument panel grd to engine block.

Still no rpm signal

I only have one OEM grounding strap that goes from the top of the driver side engine mount, around to the underside of the same mount.

I'm off to find a bunch of tinned copper straps tomorrow to go batt grd to engine, engine to frame, frame to tub.

At this point, I don't know what else it could be.

Any thoughts?

 

[Belizean]

Bad grounds ( rust ) are just about as bad as no ground. I have a Holley sniper so no real help on Howell. But I keep learning about it. Latest is you need a well charged battery. Having over 12 volts was fine starting up, but it would just die from LV, but would crank back up. Just something to keep in mind. Thinking i have about 4 ground straps.