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TBI wont start HELP

Old 11-11-2018, 09:04 PM
  #1  
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TBI wont start HELP

Hi, car ran great, got home and wouldn't restart. Just turns over with no starting. I'm trying to get a friend help me check for fuel and spark. If the ignition module is bad will that keep the injectors from working?
Or will I have to disconnect the fuel line somewhere to check for fuel flow? Did the paperclip thing, but doesn't the engine have to be running to set a code? All I got were 12s. checking for spark is a lot easier...
Thanks for any assistance you can provide
Henry
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Old 11-11-2018, 11:43 PM
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Car: 1991 S10 v8 AWD
Engine: 5.7 TBI
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Re: TBI wont start HELP

Yes, I think it would cause it. I believe the cm looks for a pulse before firing injectors.
I think you are on right track, check for fuel, either behind the tb, or at the fuel filter.
I know most auto part stores will check the ignition module for you for free, dont forget to use thermal paste reinstalling the ign module.
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Old 11-12-2018, 12:10 PM
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Re: TBI wont start HELP

Originally Posted by henryd3 View Post
Hi, car ran great, got home and wouldn't restart. Just turns over with no starting. I'm trying to get a friend help me check for fuel and spark. If the ignition module is bad will that keep the injectors from working?
It can. Not guaranteed.

Originally Posted by henryd3 View Post
Or will I have to disconnect the fuel line somewhere to check for fuel flow?
You'll need to install a gauge adapter to check pressure. Checking flow is easier if you just WATCH THE INJECTOR SPRAY.

Originally Posted by henryd3 View Post
Did the paperclip thing, but doesn't the engine have to be running to set a code? All I got were 12s.
Depends on the code. Code 12 IS a code, it's telling you that there's no distributor pulses.
Originally Posted by henryd3 View Post
checking for spark is a lot easier...
IF (big IF) you have no spark and no fuel spray, you're probably looking at a failed pickup coil. It COULD be a failed ignition module (not likely) or a defective wire harness between distributor and ECM...but it's most likely the pickup coil.

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Old 11-12-2018, 12:48 PM
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Re: TBI wont start HELP

I've had my injectors get stuck on my old TBI set up. Have you tried dripping a little gas in the intake and seeing if the car would crank? In my case once it got running it would keep running. If it cranks and dies after putting some fuel in the throttle body (about a bottle cap full) then you know you have spark and can move on to fuel testing. (just make sure you are precise on pouring the gas in if you get it all over the injectors you can catch them on fire)

A few simple things to check.

When you move the key from off to run (not crank) do you hear the fuel pump kick in?
You can supply 12v to the fuel pump pin in the ALDL to manually engage the fuel pump. If you hear the fuel pump kick on with the key there is no need to test this.
Fuel pump relay, make sure it is working (most auto stores can test if you don't know how)
If the relay is good and you still don't hear the fuel pump with the ALDL fuel pump test lead jumped to 12v then its very likely the fuel pump. If you hear it with the test lead but not with the key it can be a few things.

Spark is easy enough to test, just pull a plug, rest it on metal so its grounded and watch for spark as someone cranks over the car. If you do it at night you can place it so you can see it and crank it over yourself. They also make a spark tester that is safer to use... If no spark then the ignition module in the distributor is where I would start... I had one go bad one time and the car shut off like I turned it off going down the highway. Parts store can test and they are cheap enough to replace.

Does your car have VATS (the resistor/chip in your ignition key) -- if so is the security light going off after a few seconds of the key in the run position (not the crank position).

The fuel pump fuse is in an odd place look for a little fuse holder beside the battery to make sure its not blown.
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Old 11-12-2018, 07:50 PM
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Re: TBI wont start HELP

Thank you one and all. Long strange trip but it's fixed.
First thing we did when my friend made it was find I was getting neither fuel or spark. Following Shurkey's excellent advice I pulled the distributor and we tested it while spinning by hand and compared
readings to a couple of spare distributors I got 10 years back when there were regularly 6-8 THIRD GENS at the JY and 2 or 3 TBIs just like mine. Man I miss those days!
Lower readings on the one that came out, that was a Cardone,( put in by a mechanic when I was working too much to do it myself) than the other OEMs so decided to use one of them.
Since it was out took a trip to Autozone (shudder) since they're the only ones around here with a testing machine for ignition modules, and took the one that was in the car and a couple of suspected good spares
to see how they rated. Guy who was the manager was the only guy there who "knew" how to test them said they were ALL good.
Returned home and made dumb mistake by putting the one I just took out in the other dist. and reassembled all. Still no spark or fuel . Feeling really stupid I swapped in one of the other modules and voila! the injectors were spraying fuel! Finished reassembling everything else and it started just like normal!
SO, apparently a bad module can keep you from getting both spark and fuel . Sorry about the run on sentences, buy I'm glad at least I learned something, got it fixed and answered one of my questions for myself,
and hopefully gave information that may help somebody else in the same boat
Thanks again and have fun with your cars!
Henry
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Old 11-12-2018, 08:04 PM
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Re: TBI wont start HELP

Originally Posted by henryd3 View Post
made dumb mistake by putting the one I just took out in the other dist. and reassembled all. Still no spark or fuel . Feeling really stupid I swapped in one of the other modules and voila! the injectors were spraying fuel! Finished reassembling everything else and it started just like normal!
SO, apparently a bad module can keep you from getting both spark and fuel .
Been my experience that while a module "can" kill spark and fuel, it's more typically the pickup coil.

OTOH, I've seen a couple of posts lately where it was the module at fault, so maybe I'm gonna have to revise my mental flow-chart for "no spark, no fuel".

It's entirely possible for this to be a wire-harness or ECM problem, too--but that's pretty rare.

For the record, I have VERY little faith in "off-the-car" ignition module testing.
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Old 11-12-2018, 08:09 PM
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Re: TBI wont start HELP

Het I'm sorry I misspelled your name, I'm still a bit frazzled by missteps along the way and the resulting OOOPS thoughts
I kept getting. Nothing like the smile you get when you finally get it right though.
Thanks again
Henry
Autozone IS the parts store I trust the least but I've had more accurate results there before. Have at least had another learning experience. Always
seem to have to do something dumb for that to happen sadly

Last edited by henryd3; 11-12-2018 at 08:12 PM.
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Old 12-20-2018, 11:05 AM
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Car: 1991 buick roadmaster estate wagon
Engine: 305 tbi
Re: TBI wont start HELP

I have a 91 buick roadmaster wagon there is spark and fuel, New cap, rotor, com, fuel pump and filter, starter, IAC, MAP sensor. The engine will.crank and sometimes runs. When it does run it misses a little and if I let off the pedal it dies as if the key was removed. Is there any advise? Someone told me maybe the pickup coil but how can I test or remove it seeing as it sits so far back without yanking the whole engine.
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Old 12-20-2018, 05:39 PM
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Re: TBI wont start HELP

What is the fuel pressure?
What is the cranking compression of all eight cylinders?
What is the data stream showing for coolant temperature, MAP, and RPM?
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