Wiring Schematic Help

[Bbc.monte]

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]

Have you verified your ignition switch wiring as described here? (http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3514-Over-my-head-with-a-73-Landcruiser-350-TH-350-TBI-Conversion&p=42914&viewfull=1#post42914) That's the most common problem I've seen and it needs to be ruled out before doing any other troubleshooting.

[1project2many]

Sure. Is the 350 from a 1991 pickup? 1227747 ecm?
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42

[lionelhutz]

You have spark when cranking it, right?

[JeepsAndGuns]

What about power to the injectors?

[Bbc.monte]

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]

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]

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]

Voltage to pink/black drops to 9.5 volts while cranking

[lionelhutz]

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]

Do you have power to the injectors while cranking?

[1project2many]

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]

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]

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.

[lionelhutz]

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

So put a voltmeter between PCM pin D4 and ground and look for a voltage while cranking?

[1project2many]

Triple check (at a minimum) that you have power to the ECM, coil and injectors with the key in the start position.
This is a good idea. It starts on ether so the coil *should* have power in crank, but it's still worth the time to ensure solid power to the ecm.


So put a voltmeter between PCM pin D4 and ground and look for a voltage while cranking?
Yes. A voltmeter between D4 and the black/red wire from the module (often called REF LOW) should show voltage during cranking. I've also seen modules fail in a way that they deliver spark but won't send the reference pulses.

[Bbc.monte]

I feel dumb but I have to share in case someone else runs into it but I noticed my distributor wobbling while cranking. Probably from the cherry picker I used. I didn't notice it before but I replaced the whole distributor and it fired up first try. Thanks for the help everyone.

[1project2many]

No problem. Have any pics to post in trade?

[fastacton]

I'm glad you found the problem. Sometimes the obvious stuff is very easy to overlook.

[1project2many]

BTW, don't feel dumb. Years ago doing an engine swap at the dealership I got the ignition module and IAC connectors swapped then spent over an hour trying to figure out why the engine wouldn't start. I had it in my head that I had the connectors right so I kept skipping over the problem even though it was pretty obvious.

[Bbc.monte]

I'm happy with the way it runs and better than that so does my old lady. The previous owner must've removed the Tstat so I have to go pick one up. Stock is 195 and I've read people with mild build motors run 160 so I was thinking to run a 180? I'll try to post some pics. I still have to run the wires into the cab and what not. But it runs and drives pretty nice.

[Bbc.monte]

http://www.gearhead-efi.com/Fuel-Injection/webkit-fake-url://246c54c0-9615-4ade-8c1a-03bebd117e67/imagejpeg

[Bbc.monte]

8599

[1project2many]

180 is ok if you're in a warmer area or most of your drives are longer. 195 won't take away much power. Don't go below 180 though. The ecm won't go into closed loop at that temp.

It warms my heart to see old trucks kept alive with EFI swaps.

[Bbc.monte]

I love these k series trucks. That's my girls truck. Sits on 33s with the sm465. Little sound system. Long bed. Mine is an 84 k10 old diesel truck I swapped a 454 into with th400 on 39.5 boggers. Locker front posi rear. My dad had an old 80s truck and I fell in love early. Haha

[Bbc.monte]

So we drove it around town and it runs awesome on our few mile trips. Then it died in a drive thru, let it sit and it started right up after about 45 mins. Ran great until I got it home 5 miles later and now it fires randomly based on my timing light. The coil is firing consistently but it randomly fires to the plugs. I don't believe it's overheating because I can still stick my finger in the radiator (definitely warm but not scalding hot) and I see the water flowing through the radiator. For information I still have the computer in the engine compartment until I know that I have this thing running properly. Any suggestions?

[Bbc.monte]

Which was another question, my stock gauge is the same temp range as the one that was in the donor truck. Can I use the temp gauge with the green wire on the drivers side of the motor in the head?

[Bbc.monte]

And I was wondering if anyone had the schematic for the obd1 port so I van wire it up along with the idiot light.

[Bbc.monte]

I'm having trouble getting the right vss to mechanical speedo adapter. My ecm runs 2k ppm while every adapter I can find runs 8k ppm. Jags that run has the right adapter but isn't selling them for another month. Any way to flash my ecan to read 8k or maybe a resistor or something? It keeps dying on short trips.

[Bbc.monte]

Or can I just run a ecm from a truck that had the 8k vss?

[fastacton]

I don't think there's a TBI truck ECM that uses an 8k signal. I just got my notification on the Jags that Run backorder and spent a good bit of time trying to find someone else that has something available, but no luck. I wish I knew who actually builds them.

[Bbc.monte]

I called them and they said their manufacturer stopped production but they are starting to make them in house. Supposedly from my research, 8k ppm is after 1993.

[lionelhutz]

I don't think any GM used 8k ppm into a PCM. They basically went from 2k or 4k to the reluctor ring with 40 counts per driveshaft rotation which comes out to around 100k ppm give or take depending on the gear ratio. I also believe all the sensors > 2kppm are an AC signal while the 2k ppm sensors are a DC signal.

I have a home made one that not using anymore. I could share the circuit if there is any interest. I just drilled holes in the gear for a couple of small cylindrical magnets and used a hall effect sensor to detect when they pass by.