Silly Questions

[lakedrifter]

Last silly question for the day. lol

With regaurds to Throtle Position Sensors I have notice a difference in connectors between 89' and 92'. The 89' has a smaller round 3 pin connector and the 92' has a larger flat 3 pin connector. Other than that, they should still function the same correct?

[fastacton]

It's actually the reverse. They went to the smaller round connector (metripack) in '90, I believe. They both work the same and use the same wire colors, but they don't bolt up to the same throttle bodies.

[lakedrifter]

Hmmmm. that is highly interesting. I'm going to have to check the the wiring harness donor in the junkyard this weekend. Maybe it wasn't a 92.

[Fast355]

ASDU is normally recommended as a starter for a 5.7/700R4 application when using the '7747. It's the most mature of the factory tunes.

I don't use ASDU in Van applications. A van runs better with an OEM van calibration.

[buddrow]

If you watch the knock counts and adjust spark as necessary the ASDU is a very capable bin in most applications from my experience, it is at least a good starter.

[Fast355]

If you watch the knock counts and adjust spark as necessary the ASDU is a very capable bin in most applications from my experience, it is at least a good starter.

I prefer ARJT or AYUB for a van or a 1992 AWLD. All run better than ASDU ever thought about. I am not an ASDU fan at all as it was setup for a 2.73 geared truck.

[lakedrifter]

yeah someone already pulled the one g20 ecm that would have worked the easiest.

[lakedrifter]

Ok, back to silly questions:) I hope I dont seem nagging to anyone.

While disecting all the diagrams trying to make it easier on myself. I find myself pondering on these. Everything else I have pretty straight.

1) What is an Electronic Air Control Valve (1227747, Pin C2)? I know what an IAC is but when I search to familiarize myself with the EAC, Im always lead back to the TBI and the IAC.

2) What are the most common locations to pick up the ECM fuse block terminations (ECM B and ECM/IGN). If its just Battery and Ignition circuits I can manage that but is there a better, cleaner, easier solution?

[fastacton]

1) is for applications that have air injection (smog pump). Most applications that I've dealt with don't even have it, I think I see it on about one out of 5 harnesses.

2) the fused power wires are normally ignition hot (pink/black for ECM and red for injectors, near ECM connectors), the battery power comes in off a fusable link (orange wire near fuel pump relay). If you're running a DRAC/VSSB or heated O2 sensor, they will have their own ignition hot wires as well.

[lakedrifter]

Ok, maybe I wasn't so clear on the Fuel system lol. Found a good video though.

I was missing the Secondary FP fail over from Oil Pressure Sensor, FP test port and Fuel Cycler Module:)

Now I get most of it...

Circuit assets identified
Fuel Pump Relay: Check
Fuel Cycler Module: Check
Fuel Test port: Check
Oil Pressure Switch: Check
Fuel Pump: Check
ECM pins: A1 and B2

Orange is the "Hot in Run" feed to the FP Relay and the Oil pressure switch. The ECM B2 is signal to the FP relays switch side (requires a crank signal?) to activate the FP in Run.

GM integrated a secondary fail over - If no power from relay to fuel pump the oil pressure switch will engage the Fuel pump via hydraulic switch at 4lbs causing the fuel pump to run.

The last piece I don’t get is Fuel Cycle Module, is this the “Key On” 2 second FP primer shot? It is pin A1 of the ECM.

Side note - Extremely long cranking times is an indicator of a possible bad fuel pump relay.

[lakedrifter]

I stumbled across an issue today. Can someone tell me the difference between a 3 wire esc and a 4 wire esc?

Dark Blue - Knock
Black- ECM
Brown - Ground

Yellow/red - ?
Red/Black - ?
Brown - Ground?
Blue - Knock?

[fastacton]

I haven't seen a 3 wire ESC for '7747 style ECM use. Here's the colors I see most often and where they go (not in any particular order):

pink/blk - key on +12v
yellow/red - to ECM
brown - ground
blue - knock sensor

[Fast355]

I stumbled across an issue today. Can someone tell me the difference between a 3 wire esc and a 4 wire esc?

Dark Blue - Knock
Black- ECM
Brown - Ground

Yellow/red - ?
Red/Black - ?
Brown - Ground?
Blue - Knock?

Don't recall mine having a 3-wire.

I may have the Brown and Black swapped. Been way too long since I messed with it to bypass it during my 7427 swap.

Dk Blue = Knock
Black = ECM
Brown = Ground
Pink/Blk = +12 VDC Keyed

[lakedrifter]

I'm hoping all my issues are resolved today. I love junkyards.

I stumbled across fresh meat today. 1990 G20 vin K. ECM and wiring harness are all intact:). I grabbed the ECM today and will be going back tomorrow for the rest. I had some obligations this afternoon.

1227747 with the correct Chip

[1project2many]

The last piece I don’t get is Fuel Cycle Module, is this the “Key On” 2 second FP primer shot? It is pin A1 of the ECM.

You're finding terms that GM doesn't generally use. I believe this refers to the "hot fuel handling module" used on some trucks to circulate fuel for up to 20 seconds. Old GM literature said the module could circulate fuel after the key was shut off but folks on the net seem to believe it simply extends the pump prime time. Either way it's not found on most trucks.

GM integrated a secondary fail over - If no power from relay to fuel pump the oil pressure switch will engage the Fuel pump via hydraulic switch at 4lbs causing the fuel pump to run.

Although pump relay failures were rare with these systems, often the only clue to a bad relay was extended crank times after a long "off" period.

I also don't remember a KS module which did not require external power (i.e. 3 wire). Do you have a link to the diagram or information you are referencing?