Calling the TBI Experts,,,,

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   The ignition module in the distributor triggers the injectors. Seen many fail. 

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Thad in AR. Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Arkansas Points: 9731	Post Options Post Reply Quote Thad in AR. Report Post Thanks(0) Quote Reply Posted: 23 Jun 2023 at 5:49am
	The ignition module in the distributor triggers the injectors. Seen many fail.

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8070nc Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 21 Mar 2019 Location: North Carolina Points: 722	Post Options Post Reply Quote 8070nc Report Post Thanks(0) Quote Reply Posted: 23 Jun 2023 at 4:48am
	I know this is uneeded informatuon but I have a 1988 3500 4 door that was originally a air force rescue vehicle. 454 np 205 cast irn transfer case Dana 80 rear dana 60 front. Its geared 4.56 Came with a turbo 400 I change it to a4l80e because with the turbo 400 it was turning 3000 at 55 mph. It willbe the last thing to leave my place
	1984 80780 1957 D14 DES 300 with 25000 engine 616 tractor

Dirt Farmer Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Access Joined: 15 Sep 2020 Location: Illinois Points: 473	Post Options Post Reply Quote Dirt Farmer Report Post Thanks(0) Quote Reply Posted: 23 Jun 2023 at 12:11am
	It may never run again Joe, better just send it my way and leave those worrys behind, kinda partial to them square bodies. Not that it matters for this but is it 4wd? Ok joking aside, the fuel pump is in the tank on that model with fuel injection. First confirm that there is gas in the tank, dont trust the gage. If you turn the key in run position you should hear the pump running if not take off the gas cap and listen. If you dont hear anything first check the fuse box for a blown fuse or relay, if all checks ok there then tap on the bottom of the fuel tank with a board or rubber mallet and see if that frees the pump up. That trick only works once or twice to get you home then its replace the pump time. To replace the pump if the tank is less than quarter full I pull the tank, if its more I lift off the bed and reguardless DO NOT use drop lights with glass bulbs when removing the fuel tank. One wrong splash and not good results. A truck of that era probably needs the whole sending unit replaced as the lines may be brittle from rust if you have to take it apart anyway. Just be careful and if you give up on it and throw in the towel I may be up for a road trip with my trailer. Keep us posted and include a photo. Dave and I must have read this at the same time but hes faster than me and knows his stuff Edited by Dirt Farmer - 23 Jun 2023 at 12:18am

DaveKamp Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 6124	Post Options Post Reply Quote DaveKamp Report Post Thanks(0) Quote Reply Posted: 22 Jun 2023 at 11:42pm
	You're certainly not getting fuel flow. The throttle body unit was made by Rochester for GM, and it's referred to as the TBI 220, and will probably have a pair of 45lb/hr injectors. The fuel pump needs to develop around 15psi for this IIRC, and there's usually NOT a fuel pump on the block. The TBI-220 has a pressure regulator and a fuel return line that sends unneeded excess back. The ECM that runs this system is referred to by four digits of it's model, it SHOULD be a 7747 controller, uses an EPROM chip with all the mappings. The fuel pump is PULSED by the ECM, so it is possible that your TBI and injectors are fine, and you're just not getting a power signal. USUALLY the 7747's FUEL PUMP output drives a fuel pump RELAY... and you'll know it's working when you turn the key on and hear the pump run for about 4 seconds or so. You can pull the high side line off the TBI-220, place it over a bucket, and cycle the key several times which will clear out the old gasoline... but after you've done that, connect it back up. The startup process should pressurize the system and trigger the injectors a couple times. This clears any air bubbles and 'primes' the engine for a cold-start. Once you're cranking, if the 7747 isn't getting an IGNITION pulse, you won't get an injector pulse, so check the electrical trigger from the ignition to the ECM... if that's disconnected or bad, you won't get injectors firing in the TBI during cranking.
	Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.

desertjoe Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 23 Sep 2013 Location: New mexico Points: 13769	Post Options Post Reply Quote desertjoe Report Post Thanks(0) Quote Reply Posted: 22 Jun 2023 at 11:33pm
	OK, I bought a 1988 GMC 3500 with the 454 engine and Turbo 400 couple of weeks ago and finally drug it under my work area,, Suppossedly it was "Running When Parked" but the owner tol;d my brother that the 454 was in great running shape The engine has a Throttle Body on it and I'm assuming it does have the HP pump in the tank,,,?The engine will start and run when you prime it but will stop soon as the fuel is burned in the TBI,,,, SO many hoses in the way to tell if there is a manual fuel pump on block,,,,?? Any suggestions out there before I start dismantling?