73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 1979C20 on April 14, 2014, 12:47:31 am
-
89 V2500 Burb TBI 350 crate motor. Ive been having an issue recently, and very randomly. It started 4 nights ago, I was driving home from the lake and I got a mike from my house and my truck shuts off while driving down the road at 45. I pull over, pop the hood and pull the air cleaner off. I remote start my truck to watch the engine and the injectors are not spraying fuel. I check fuel pressure from the pump all the way to the throttle body and out the return line, nice strong pressure throughout. I have a 2 month old fuel pump, I rebuilt the TBI 2 1/2 months ago. The computer is about 2 years old. I checked all of my fuses and fusible links, all good. After sitting on the side of the road for 20 minutes, my buddy rolls up to help and my truck starts up with no issue before he even gets out of his truck. Not sure whats going on here or what to check
-
Check the control wiring plugs on your distributor. The one with 4 prongs connects the ignition module to the ECM. The ECM needs to see a pulsed signal from the modulator before it will operate the injectors. Also, if the module is bad there will be no spark at the plugs anyway.
Along with a power supply input from the battery, the ECM needs to see 2 things before it will allow the injectors to open and allow fuel into the throttle body. One of the following two permissives must be met at all times:
1. A crank signal (from the starter solenoid) that an attempt is being made to start the engine. This is only needed until the ignition system fires up - after that it goes away because you release the ignition switch from the START position and the solenoid is de-energized.
2. After the crank signal drops out, the pulsed signal from the distributor module takes it's place. As long as the ECM senses an operational ignition system it will permit injector function.
It is often possible to start the engine without a crank signal because the ignition system will fire up and provide the input to the ECM even without fuel.
But, as you can see, the opposite is not true. If the distributor module is not firing the plugs, the engine won't fire up regardless of whether you have fuel flow or not.
Bottom line - you can probably start an engine without a crank signal, but not without a functioning module due to the accompanying lack of spark in the ignition secondary (i.e at the plugs).
As a test, just pull and ground a spark plug and observe whether you get an arc across the electrodes. No matter what ever else, no spark = no start.
-
I forgot to mention, I had spark. This has also happened 3-4 since this initial breakdown but, it started right back up no problem. I saw the TBI troubleshooting page in the technical section and I know what to test now if it happens again and wont start.
-
Found the problem. The plugs that go into the top of my ignition coil were loose because the clips broke. Lost spark, computer saw no spark and shut off injectors.