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Old 10-23-2007, 07:44 PM   #1 (permalink)
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Another TBI Need Help Thread...

I am in the process of converting an '85 4.3 carb motor to TBI. Have a harness off a 350 and TB off a 4.3, I have everything swapped over and hooked up. I cannot get my injectors to fire. I have the schematics on the wiring and have check all grounds and have power going to both hot injector wires, but they don't fire. The coil is working I can get it to run off ether but injectors aren't working. I don't think its injectors being bad since both are not working but I don't know. Fuel pump is good and working.
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Old 10-24-2007, 07:28 AM   #2 (permalink)
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Engine ground hooked up?
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Old 10-24-2007, 07:53 AM   #3 (permalink)
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read this it might help
http://www.pirate4x4.com/forum/showt...ght=tbi+wiring
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Old 10-24-2007, 09:41 AM   #4 (permalink)
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Engine ground hooked up?
Yes grounds are all there. Got the injectors to fire but it wont crank, can crank it with ether and it will stay running and has throttle response but wont start without ether.
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Old 10-24-2007, 06:31 PM   #5 (permalink)
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Don't know what all you have swapped in this process, but is the fuel pump putting out the pressure the injectors require to pop off properly? I only ask this because i was taught you can't run an engine off ether alone, it has to have a little gas (or diesel) to run. Sounds like a fuel pressure problem.
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Old 10-24-2007, 06:43 PM   #6 (permalink)
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To correct myself before i get busted, diesel injectors rely on pressure alone to fire, yours are opened by electricity but if the fuel pump is from the carburetor the gas is dripping out instead of spraying a mist which is crucial in a TBI to get the right air/fuel mix through the maifold to all the cylinders.
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Old 10-24-2007, 06:45 PM   #7 (permalink)
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What distributor did you use? The distributor signals the injectors to pulse
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Old 10-24-2007, 07:02 PM   #8 (permalink)
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Quote:
Originally Posted by KWTMECH View Post
What distributor did you use? The distributor signals the injectors to pulse
+1.

There is also a wire that goes to the starter to tell the ecm that the engine is cranking.
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Old 10-24-2007, 08:44 PM   #9 (permalink)
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The C8 crank signal wire is not required to start the engine.
It is used to adjust the parameters during cranking.

Start by ensuring you have 12V to the injectors and the ECM while you are cranking.

It sounds like you tried to wire the injection system straight to the stock wiring and are not using relays to power the system.
The old 12V wire going to the coil should only be used to energize the relays...meaning more then one relay.....

If you haven't been to the link in my sig yet then start there in the injection forum and the FAQ's.
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Old 10-24-2007, 10:59 PM   #10 (permalink)
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Check the oil pressure switch.
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Old 10-25-2007, 07:14 AM   #11 (permalink)
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Also make sure you review the parts required FAQ.
You need the ecm to match the engine.
Both removeable chips in the ECM are different between the 6 and the 8's.
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Old 10-25-2007, 07:28 PM   #12 (permalink)
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Quote:
Originally Posted by hardline04 View Post
I am in the process of converting an '85 4.3 carb motor to TBI. Have a harness off a 350 and TB off a 4.3, I have everything swapped over and hooked up. I cannot get my injectors to fire. I have the schematics on the wiring and have check all grounds and have power going to both hot injector wires, but they don't fire. The coil is working I can get it to run off ether but injectors aren't working. I don't think its injectors being bad since both are not working but I don't know. Fuel pump is good and working.
What is the ECM service number? Is it from the 4.3 or the 350?

If you have no luck with this, take a look at our aftermarket wire harness:

http://www.affordable-fuel-injection...ng-harness.htm

It is a lot easier to install than a factory harness, and includes all of the relays that you need. You may also want to get a custom chip as well. We specialize in building custom wire harness and chips for engine transplants such as yours.
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Old 10-26-2007, 03:26 PM   #13 (permalink)
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Yes grounds are all there. Got the injectors to fire but it wont crank, can crank it with ether and it will stay running and has throttle response but wont start without ether.
Check to make sure the computer is getting power while cranking. I suspect you hooked it to one of the power leads that is not energized while cranking, but is while the key is in the on position.

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