Wiring Schematic Help

**Bbc.monte** · 03-06-2015

I am brand new to this site and don't know where to get info on why my 1991 tbi 350 swap into my 1984 k20 injectors arent spraying. I have spark. New ignition module and cap. Brand new airtex pump. I pulled the harness out of the donor truck still attached to the motor and spliced into the computer plugs. The fuel pump comes on with the relay as it should with the key on and cycles off but I don't hear it when it's trying to start. Was wondering if someone could point me to a wiring diagram to help.

**fastacton** · 03-06-2015

Have you verified your ignition switch wiring as described here? That's the most common problem I've seen and it needs to be ruled out before doing any other troubleshooting.

**1project2many** · 03-07-2015

Sure. Is the 350 from a 1991 pickup? 1227747 ecm?
http://www.gearhead-efi.com/Fuel-Inj...Information-42

**lionelhutz** · 03-07-2015

You have spark when cranking it, right?

**JeepsAndGuns** · 03-07-2015

What about power to the injectors?

**Bbc.monte** · 03-07-2015

i have 12 volts to red and white at the injectors with the key on. i have spark when its cranking. the fuel pump doesnt run while cranking for some reason but will cycle on and off with the stock relay. it just isnt spraying through the injectors. i still have the donor truck in the parking lot from when i pulled it. haha. its the 1227847 ecm

**Bbc.monte** · 03-07-2015

i havent measured voltage drop accurately but the truck came with apush button from the last owner and i have all of the pink and blacks that i found on schematics called for 12 volts with the key in the on position. they are hooked to the key switch and the purple and white wire (i believe, im not looking at the truck atm) that schematics said need to have voltage only when trying to start hooked to the push button.

**1project2many** · 03-07-2015

Does the ecm know the engine is cranking? Are you getting reference pulses from the distributor at the ecm? Without these pulses the ecm won't trigger the injectors and won't power the fuel pump relay during cranking.

**Bbc.monte** · 03-07-2015

Voltage to pink/black drops to 9.5 volts while cranking

**lionelhutz** · 03-07-2015

Are you setup to scan the PCM? That's how you check if you have the reference pulses.

You could also try jumping the fuel pump so it's running and then starting it. There might be a connector you can jumper power to or you could jumper the wires at the oil pressure switch. That would tell you there is most likely a problem with the distributor to PCM signalling if the injectors don't fire either.

**fastacton** · 03-07-2015

Do you have power to the injectors while cranking?

**1project2many** · 03-07-2015

Are you setup to scan the PCM? That's how you check if you have the reference pulses.

A DVOM will show voltage on the REF line during cranking if pulses are present.

**Bbc.monte** · 03-07-2015

I haven't scanned it. I hot wired the fuel pump for test purposes and have no change. Tried the noide lights. No fire on injectors. Idk how to test the pulses at my shop but like I said this exact setup without me unplugging any connectors to the motor ran in the donor truck. I removed the motor with the harness still connected to everything except the computer and the fuse block and have wired based on schematics since then. Truck runs on starting fluid no problem. Whatever tells my fuel pump to stay on and to fire the injectors is my problem as I see it. Any way to test pulse with test light, volt meter etc.?

**fastacton** · 03-08-2015

Triple check (at a minimum) that you have power to the ECM, coil and injectors with the key in the start position. If any of those aren't getting power while cranking, you'll have that problem. If it's not that, the ignition module and pickup coil would be my next areas to look at. I've seen the distributor fire the spark plugs but not give a good signal to the ECM if one of these partially fails, but not getting power during cranking is much more common.