ok, so...has anyone figured out what this crank signal wire is for? the truck starts without it.
ok, so...has anyone figured out what this crank signal wire is for? the truck starts without it.
Some of the early code used the crank input. Later calibrations don't and the wire is unused.
You mean the wire fused at 3 amps?Originally Posted by jameslleary
That is just a signal to the ECM to tell it that the vehicle is in a starting procedure (ignition key turned to the start position).
IIRC, the ECM uses this for starting parameters, such as retarding the timing.
The man who says something is impossible, is usually interrupted by the man doing it.
Cool, thanks. I'll go ahead and hook it up. Running ASDU, dont know if it requires it or not. I dont have a PC available to me to look...Is there any way to find out which bins have air injection commands programed into them? TBI truckzs are wuite confusing in Ca.
All of the TBI squarebody trucks 87 to 91 have A.I.R., and then you get to the NBS GMT-400 TBI trucks, and sosme do have A.I.R. and some do not. what gives?
Last edited by jameslleary; 11-20-2011 at 08:41 AM.
Every 1227747 I have worked on has the crank signal wire, I beleive it has to do with fuel as well as spark when starting, I have never tried one without. I even use the crank wire on my test bench when running a rewired conversion system, next time I will try without and see if I can notice anything?
Air pumps are a crap shoot. IIRC the 7747 did and the 8747 did not. But in CA everything is differant?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
are there any differences in the wire harnesses between the 7747and the 8747, or can i just plug n play?
I think the plugs for ECM are the same. But 1227747 is $42 and used on light duty, 1228747 is $4F and used on heavy duty. Plug and play would be a crap shoot. There's a lot of differant ECMs with same plugs and most of the wiring is the same, but until you do it or compare wiring diagrams you never know.
Just looked and I don't have 1227787 wiring diagrams so if anyone has them please post up and I will do a 1227787 info thread.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Hmmm..most GMT400 half tons are the ones I se without the air pump. I will have to get an emissions sticker for one without, and show it to the ref when i get it inspected.
Posting Permissions
Reply With Quote
Bookmarks