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All right, we need help. My friend did an engine rebuild, X-Cab on shortbed frame, and wiring harness from an even different truck. Now, he goes to start it and it fires right up, but then a couple of seconds later the engine dies. If he leaves the key on with the starter engaged (great for the starter) it will keep running, but after he lets the key loose, a couple of secs later it dies. We have gone through all of the engine sensors and they seem to all be hooked up correctly. The next thought is maybe something from the body harness is shorting out when it switches from open to closed loop (or whatever) , my question is whether that is possible for something in the body harness to affect the engine. I am sort of suspicious of his TPS. He has the DOA ported newer style intake plenum and throttle body scam and a 1987 harness and had to re-wire the harness leads to the TPS since the plug is different. I dont know, we are at a loss. I told him to just hook a switch to the starter and kill the starter after it starts and leave the key in the start position, but for some reason he doesn't want to do that :confused:
 

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Do you have the AFM in place, connected to the air intake, and wiring? If not, that is your problem. The fuel pump should only run when the starter is engaged, or, the AFM senses air flow. Try shorting out the connector that forces the fuel pump to always run - or just apply 12v to the fuel pump. I'll bet it will run then... If the AFM is OK, and it runs with fuel pump getting voltage, then it is probably a problem with the "integration" relay, or the CPU.
 

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Yea, the AFM is hooked up, I checked that one for sure since I forgot to hook it up myself once (whoops) and I wanted to look like King Pimp by popping the hood, attaching the AFM and telling him to "try it now" with a smug look on my face. Oh well... the fuel pump idea is a good one, we were thinking along those lines, but we haven't tried it yet. We did swap out the computer once with a known good unit, as for the integration relay, I have no idea what you mean. But let me check the 12v to the fuel pump and go from there. Thanks dknightd.
 

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dknightd said:
The fuel pump should only run when the starter is engaged, or, the AFM senses air flow. Try shorting out the connector that forces the fuel pump to always run - or just apply 12v to the fuel pump. I'll bet it will run then... If the AFM is OK, and it runs with fuel pump getting voltage, then it is probably a problem with the "integration" relay, or the CPU.
I am doing the efi conversion and when I turn the ignition on I can here the pump running even thought I havent started it yet and after read your post was wonder if it should only run when the starter is engaged or the AFM senses air flow. After I have started it it runs rough and rich. I unplug the fuel pump and the truck idiles up and runs smooth and burns clean. It is a new fuel pump. The other problem and code that I am getting is tsp.
 

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Are you sure about the fuel pump only working once the starter is engaged? I know newer efi fuel pumps will turn on when the key is in the on position even before the starter is on.
 

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when you turn the key to on position, the fuel pump turns on to make sure the system has fuel pressure in it.when the engine is cranked the ecu pulses the injectors.

1. Spark....do you have it?
2. Fuel.....do you have it?
3. Air......do you have it?

He has the DOA ported newer style intake plenum and throttle body scam and a 1987 harness and had to re-wire the harness leads to the TPS since the plug is different
If you spark, fuel, air, you should run. Some how I think your problem was re-wiring the tps. TPS tells the computer how much fuel to mix with how much are (AFM).
 

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Lord Orange said:
when you turn the key to on position, the fuel pump turns on to make sure the system has fuel pressure in it.
No it doesn't. You're thinking of the Bosch fuel injection system, used in VW's and other cars. The Toyota EFI setup will only turn the fuel pump on under 2 conditions:

* You're cranking the starter
* The AFM on top of the airbox senses air flowing thru the airbox

Check a wiring diagram in a FSM, you'll see what I mean.

Tonichol, you didn't say what year truck the harness came from. If it's an '86+ truck, you should have a rectangular plug by the fusebox with a cap on it that says DIAGNOSTIC. Pop this cap open, take a paper clip and short the +B and Fp connectors. Now, when you turn the key to ON, the fuel pump should run. If it doesn't, then you either have a dead fuel pump, or a fault in the wiring.

You might also check your EFI relay, and the Circuit Opening Relay.
 
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