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I have a 95 Silverado 1500 5.0 liter v8. it wont start unless I spray carb spray into the intake. after that it runs fine, and will start if it hasn’t been sitting long. but I have to spray the fluid in every morning in order to start it. I replaced the fuel filter hoping to solve the problem but it still persists. any info would be appreciated.
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First, you will need to scan for fault codes in your OBD 1 system. If you have a scanner that supplies data, check the coolant temp value to see if it’s close to the ambient temperature. Have the battery and starter checked to be sure they are up to the task. A tired battery or a starter that draws too much current won’t supply enough power to the ignition system and fuel pump to start the engine.
Next thing is to connect a fuel pressure gauge to make sure it’s building enough fuel pressure to fire the engine. (I suspect that’s where your problem is)
Check the spark plugs and Ignition spark output to be sure there is a HOT enough spark to fire gasoline at startup.
Check Erics NO start video . It may help you perform some basic testing.
I would suspect a bad fuel pump. try this test ( before using carb cleaner ) when the truck has sat for a while –
Turn key to on but not cranking for 3 seconds. turn to off. immediately turn to start again and after 3 seconds turn off. repeat this 3 times then immediately try to start truck. if it now fires up you probably have bad drain back valve in the fuel pump.
Belive it or not I ran into the exact same problem about 5 years ago at the shop.
Crazy as it seems it was an ignition module. The run part of it worked beautifully, but the internal start bypass had burned out and would not fire the coil until the run part had gone hot.
[quote=”619DioFan” post=75327]I would suspect a bad fuel pump. try this test ( before using carb cleaner ) when the truck has sat for a while –
Turn key to on but not cranking for 3 seconds. turn to off. immediately turn to start again and after 3 seconds turn off. repeat this 3 times then immediately try to start truck. if it now fires up you probably have bad drain back valve in the fuel pump.[/quote]
I was going to suggest this very thing. Here’s a video showing what’s inside a fuel pump.
[quote=”Raistian77″ post=75328]Belive it or not I ran into the exact same problem about 5 years ago at the shop.
Crazy as it seems it was an ignition module. The run part of it worked beautifully, but the internal start bypass had burned out and would not fire the coil until the run part had gone hot.[/quote]
Interesting theory. Does the ignition module help dictate the fuel delivery? I only ask because he says that he can get it started if he sprays carb cleaner in the intake. That lead me to believe it was a fuel delivery issue.
[quote=”EricTheCarGuy” post=75808][quote=”Raistian77″ post=75328]Belive it or not I ran into the exact same problem about 5 years ago at the shop.
Crazy as it seems it was an ignition module. The run part of it worked beautifully, but the internal start bypass had burned out and would not fire the coil until the run part had gone hot.[/quote]
Interesting theory. Does the ignition module help dictate the fuel delivery? I only ask because he says that he can get it started if he sprays carb cleaner in the intake. That lead me to believe it was a fuel delivery issue.[/quote]
In that model, yes. The ignition module sends pulses to the ecm to signal the ecm to fire the throttle body injectors. There are 4 wires going from the ignition module to the ECM, IC output: which causes the module to retard timing, Ground reference, The set timing lead or bypass (the wire you ground to set base timing on that system) and reference high: this wire tells the pcm when to fire the injectors. When you crank the engine the PCM grounds the bypass wire changing the timing and injection pulses during start. The module we had failed to send the injection pulses when the bypass wire was grounded (the start portion was bad shorting out when the bypass wire was grounded) if you sprayed a fuel source into the throttle body the engine would start, you would let go of the key and the bypass wire would unground, unshorting the injection signal and allowing the injectors to pulse.
Oh, they way I confirmed it was the truck would stall and the injectors would quit firing if you grounded the set timing lead.
[quote=”Raistian77″ post=76009][quote=”EricTheCarGuy” post=75808][quote=”Raistian77″ post=75328]Belive it or not I ran into the exact same problem about 5 years ago at the shop.
Crazy as it seems it was an ignition module. The run part of it worked beautifully, but the internal start bypass had burned out and would not fire the coil until the run part had gone hot.[/quote]
Interesting theory. Does the ignition module help dictate the fuel delivery? I only ask because he says that he can get it started if he sprays carb cleaner in the intake. That lead me to believe it was a fuel delivery issue.[/quote]
In that model, yes. The ignition module sends pulses to the ecm to signal the ecm to fire the throttle body injectors. There are 4 wires going from the ignition module to the ECM, IC output: which causes the module to retard timing, Ground reference, The set timing lead or bypass (the wire you ground to set base timing on that system) and reference high: this wire tells the pcm when to fire the injectors. When you crank the engine the PCM grounds the bypass wire changing the timing and injection pulses during start. The module we had failed to send the injection pulses when the bypass wire was grounded (the start portion was bad shorting out when the bypass wire was grounded) if you sprayed a fuel source into the throttle body the engine would start, you would let go of the key and the bypass wire would unground, unshorting the injection signal and allowing the injectors to pulse.[/quote]
Excellent info! Thank you!
Any word from the original poster to see if this worked?
I have tried these solutions and I am still having the problems. there are not any dtc’s either. I am going to try to bypass the cts and put it into cold start mode to see if that will help.
thanks for all the ideas
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