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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: ssapach on January 29, 2012, 03:54:59 pm
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I currently have a 4.3 V6 with TBI sitting in an off-road machine I'm working on. I had this setup in the Toyota pickup previously and it ran just fine. I'm trying to do a last little bit of wiring before I get it moving but I'm having issues with wiring.
I'm not sure if my wiring harness or my ECU is buggered, but something is preventing my fuel pump from running. I tested the fuel pump and it runs, so it's not a faulty pump.
What I'm wondering is if it's possible for me to swap out the TBI for a carb on this thing. The TBI was fine when it worked, but on something like this that might be subject to water and mud and sitting outside a lot, perhaps simpler is better. A carb will also greatly help me clean up wiring, as my wiring harness is much longer than needed so it sits bundled up because I really don't want to cut and splice 2 feet out of 20 separate wires.
The problem might be in my ECU, but I could get a replacement and still have a problem which would make me think it's the wiring harness next. If I have to buy a new wiring harness and ECU I might as well put a carb on it.
So, opinions.....? Should I say screw it and swap to carb? If so is it fairly simple from a TBI motor or is there some hidden trouble I will need to take care of to make it run properly with a carb?
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HI from Ralphhemi I had a friend who built a 1935 Chevy pickup hot rod with a 305 with TBI. he put a 500cfm. Holley 2 barrel on the TBI intake. Can you put a mechanical fuel on your 4.3 ? If not than an after market electric fuel pump for a carbarted engine Maybe you could use your fuel injected pump with an after market regulator With your 4.3 i think i would a 350cfm. Holley. Last year i put a electric fuel transfer pump from my 08 duramax on a 1929 model A and to reduce the pressure i installed a mopar fuel filter with a return line Ralph
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You can do away with the TBI all together and go with a straight carb. Do some research on the internet, ton's of info out there. It will do away with some of your wires and clean things up a lot.
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Its easy.. but pointless... find and fix the issue.. you will be much happier!
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worst case.. if you hate wiring ( like me), wire the pump to a toggle switch on the dash... flick it on.. runs like new... when u get home.. dont foregt to turn it off.. the noise those pumps often make... i doubt you will forget.. walking into the house and it sounds like megatron is breathing down your neck.. you know you forgot your pump
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If you add a switch, which I vote against, install a dummy light or use a relay instead.
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I did some messing around with a multimeter and it seems I have good grounds for everything and good continuity between all points. When I turn the power on I have power through the main 30A fuse in the harness, all the way into the ECU. The problem is the power coming out of the ECU to power the fuel pump relay.....there is no power for the relay at that point.
An extra switch just for the fuel pump would be easiest, however if the ECU is buggered to begin with it could possibly prevent the rest of the system from running properly, or at all for that matter.
Wreckers will have ECU's, I just need to take mine in and match it up because there is more than one style for this setup apparently.
I guess before I get excited and replace the ECU I can try a quick jumper wire to the fuel pump to see if it will start and run that way. If so, then dummy switch it is.
I did a little digging, swapping to a carb will likely cost me more at the moment.
Stuck at work for a while now, so it will all have to wait until I get back home. :-\
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Keep the TBI!!!! Pulling the tbi for a carb might sound nice but I promise you will spend the rest of your off-road days wishing you had kept that fuel injection. Keep the fuel injection!!!
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hey have u replaced anything in the distributor yet? i have had more issues with the ignition mudule and distributor on my tbi truck than anything else.
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hey have u replaced anything in the distributor yet? i have had more issues with the ignition mudule and distributor on my tbi truck than anything else.
I haven't touched anything with the distributor yet. Would something like that tell the ECM to not send power to the fuel pump?
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possibly. ive had issues kind of like yours and the culprite was the distributor.