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so i am fixing a 94 chevy 3500 350 tbi for a friend, it only runs on starting fluid, i looked around and found a crimped fuel line, i replaced the fuel lines and fuel filter, but it still wont run unless on starting fluid, any ideas?, thanks
 

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Start with the basics: supply, power, ground, filters. most people make the mistake when trouble shooting, of thinking everything is good and go right to what they perceive as the problem.
 

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Fuel problems, as suspected.
Been a while since I owned a TBI, but recall the ignition module regulates the pulsing of the TBI.

If you never get the power to the injectors or ground they don't open.
A 'noid' light will see if you have power and ground at the injector harness.
 

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OK, a quick look at the wiring diagram.

You should have power at the injectors with the key on, the ECM grounds the injectors to open them.

I believe the ignition module via pulses to the ECM tells the computer you are cranking and to open the injectors.

Start with do you have 12V at the injectors with the key on, then a noid light to see if the ECM is pulsating the injectors, then ignition module to see if it is sending signals to the ECM.
 

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ugh, forgot the attach

Well it won't attach...page down.
 

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If you're going to own and/or work on a fuel injected vehicle, owning a fuel pressure test setup and a set of Noids is nearly a necessity. At the very least they're a huge boon to quickly and easily trouble shooting a "No-start" situation.

Nobody wants to pay 40+ bucks for Noids, and it's aggravating that they cost that much 'cause there's nothing to them. If you don't want to buy them, it's really easy to make them out of some very inexpensive 12 volt LED lights. A couple bucks...
Note: It must be LED lights for this, as incandescent bulbs won't work, and correct polarity connections on the LED is a must or they won't work either.

That's what you really need here. It sounds like it's either dirty/stuck injectors, or an injector electrical problem. Noids will tell you which in 5 seconds.

You can pop those injectors out the top of the TBI to clean them by removing the top cover without even removing the TBI unit from the engine if desired.

ADD:
Once you get them out, they're pretty easy to test. Take a 9 volt battery, and quickly touch it to the injector terminals on and off. (Polarity doesn't matter.) If they "click", they are working/opening. You might even be able to test them that way in place by pulling the connector off. They might be hard to hear that way, but maybe if it's quiet. Note: Only do quick, momentary connections with the battery.

Vettepilot
 

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I am kind of surprised that didn't get a response. I didn't mean to shut down the thread.

I wonder how he's done with his problem? It's always good to post follow ups and solutions for the benefit of others, and just general interest/curiosity.

Vettepilot
 

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Even with very little fuel pressure, you should still get something from the injectors if they pulse..even if its a dribble. But I do agree, fuel press gauges/testers are highly valuable. Many poor performing engines (idle/drivability etc) can be traced to lackluster F.P.....some systems are more sensitive to low F.P vs others.
 

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If you are getting a decent fuel flow, the pressure is likely sufficient on a TBI setup, as it's a low pressure system. They only run around 9 to 12 lbs. stock. It's a bummer that GM didn't make it very easy to check fuel pressure on the TBI systems like it is on the TPI systems, but if you're going to keep the vehicle, it's very much worth it to buy the test fitting and install it. I just install them and leave them in place permanently, like GM should have done.

Actually, more important in your case, is the Noids. Since you're getting fuel supplied to the injectors, I would say it's either clogged injectors or else the injectors not getting triggered electrically. Instead of chasing all the things one by one that could cause the injectors to not get triggered, Noids should be used first to see if that's in fact happening.

I recently had a TBI "No-Start" issue on a TBI truck. It had some old fuel in the tank, plus sat without running for 4 months in very hot temperatures. Turns out the injectors themselves were thoroughly clogged, yet it had run perfectly 4 months earlier. I cleaned them myself, and now it runs great again.

FUEL INJECTION NO START:

1. See if it will run on starting fluid. If not, trouble shoot "no spark".
2. Runs on start fluid: Test fuel pressure and use Noids.
- A. No fuel pressure--> Filter, pump, etc.
- B. No Noid signal--> Trouble shoot electronics.

This simple procedure prevents a ton of "what if" and "maybe" trouble-shooting time and tail chasing...

"If it's got spark, right amount of fuel, and compression all at the right time, it WILL run." Thats just a law of physics and not magic.

Vettepilot
 
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