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weird tbi problems

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MuddinK5

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1988 blazer 350 tbi. the other day i started my blazer with no problems, yesterday i went to start it and there is no fuel from the injectors (no injector pulse) :crazy:. i have searched and found plenty of useful info on this topic but i have a few different variables. for 1 my fuel pump is straight wired and turns on and off with a toggle switch (like that whe i bought it), 2 i have no oil pressure sensor hooked up or o2 sensor (like that when i bought it) i was going to fix those things but i figured if it aint broke dont fix it :wink1: any clue on what this could be? oh yea and i am getting spark. just thought id get you guys opinions befor i started messing around with anything. thanks
 
First thing I'd be checking would be the fuse that powers the injectors. You can check it by probing the hot side of each injector to make sure they have battery voltage between them and ground with the key on. If there is voltage there, your fuse is ok. If there is no voltage, then you have a blown fuse somewhere.

Since the ECM provides the grounding for the injectors to actuate them, you will need to make a noid light to make sure that the injector drivers in the ECM are doing their thing. To make a noid light, take a 168 or 194 bulb from one of your fender marker lights and hook it up in place of the injector. Have a friend crank your truck to make sure that the light bulb flashes. It will flash dimly, but noticeably.

If the noid light does flash, then either both your injectors have failed electrically (not likely to happen at the same time), they are clogged off, your fuel pump has failed and is no longer supplying fuel to them, or your fuel pressure regulator has failed and you have insufficient fuel pressure.

If the noid light does not flash, then you need to have your ignition module tested. Since you do have spark, I am going to suspect that you have a fuel pressure / injector problem rather than an electrical problem, and that you will likely find your noid light flashes.

You may want to hook up a fuel pressure gauge inline with your supply line on the injector pod to help with investigating the problem. The fuel lines themselves use the Saginaw o-ring fittings, but they do not thread directly into the injector pod. Between the lines and the pod is an adapter with pipe thread on one side, and the Saginaw fitting on the other side. To install a fuel pressure gauge, just remove the adapter and install a T fitting between them, and thread a fuel gauge into the top of the T. You should have approx 12 - 15 PSI of fuel pressure displayed on the inlet (driver's side of the injector pod)
 
ok thanks for that info Russ, i should be able to get to do some work on it today and ill try everything you've mentioned hopefully ill git-R-running lol if not :weld::grind::hack: and it'll be carbureted :haha:naw just kidding. ill report back on how this goes. thanks!
 
Russell said:
You may want to hook up a fuel pressure gauge inline with your supply line on the injector pod to help with investigating the problem. The fuel lines themselves use the Saginaw o-ring fittings, but they do not thread directly into the injector pod. Between the lines and the pod is an adapter with pipe thread on one side, and the Saginaw fitting on the other side. To install a fuel pressure gauge, just remove the adapter and install a T fitting between them, and thread a fuel gauge into the top of the T. You should have approx 12 - 15 PSI of fuel pressure displayed on the inlet (driver's side of the injector pod)
Click to expand...

This is incorrect info. The TBI fuel fittings are 14mm x 1.5 and 16mm x 1.5 where they thread into the injector pod. The fittings seal on a teflon gasket not the threads.
 
Sorry about that! I was always under the impression that those were pipe threads back there.

Thanks for the save there Scott!
 
Russell said:
Sorry about that! I was always under the impression that those were pipe threads back there.

Thanks for the save there Scott!
Click to expand...

No problem, would just hate to see the guy screw up an injector pod trying to thread a NPT fitting in there.
 
thanks for the help every1. i finally got it running. i decided to just go rent some noid lights from oriely's auto parts so i pulled the module and took it with me so it could be tested to just in case. well i got there and they tested it and it was good so they said mayb my pickup in the dizzy was bad so i got 1 of those, along with some dielectric grease in a lil packet for the back of the module because it was pretty dry, well got home and couldnt figure how to get the pickup coil thing out of the dizzy :doah: so i said forget it i threw the electric grease on the back of the module, bolted everything back together and ill be damd the truck cranked up :eek1: i couldnt believe it i didnt even do anything except the grease lol. i gotta get the timing right because its off a lil bit. thanks for the help anyways yall :bow:
 
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