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intermittent starting problem 93 chevy
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captainflugel
New User
Aug 12, 2008, 8:45 PM
Post #1 of 6
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intermittent starting problem 93 chevy
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This has been a frustrating problem. Two weeks ago my truck failed to start at the auto parts store of all places. It is a 93 chevy silverado with a 5.7 engine and high miles but well maintained. Engine cranks but will not start. I spray a little starting fluid into the throttle body and it starts right up and runs fine. Next day same problem. About every 20 starts or so it does this. Usually always starts cold and usually when it is hot. Problem usually happens after the engine has been running then cools off for an hour or so and then won't start and will not start without starting fluid. I have changed the fuel filter, fuel pump, fuel pump relays, throttle position sensor, and egr valve. Have refueled a couple of times so it's not bad fuel. This has gone on now for about a month and my local shop can't find the problem and I don't know what to try next. Any one had this problem? Any ideas on where to look next?? 
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Double J
Veteran
/ Moderator
Aug 13, 2008, 12:43 PM
Post #2 of 6
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Re: intermittent starting problem 93 chevy
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One thing that came to mind....
Did you replace the fuel pump pulsator when the fuel pump was replaced?
The pulsator is the flexible connector between the fuel pump and the metal fuel line in the tank.
This will cause low/no fuel pressure/hard/no start condition....
Just a thought
Jim
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captainflugel
New User
Aug 13, 2008, 4:35 PM
Post #3 of 6
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Re: intermittent starting problem 93 chevy
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I had a shop replace the in tank fuel pump assembly and I do not know if the pulsator was replaced at that time but I will find out. Thanks for the reply.....
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DanD
Veteran
/ Moderator
Aug 14, 2008, 4:35 AM
Post #4 of 6
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Re: intermittent starting problem 93 chevy
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Maybe test for a good strong spark; a weak spark is just as bad as no spark at all. You can buy spark testers that are designed to force the coil to produce enough voltage to jump a 25K volt air gap. 25,000 volts is what is considered the minimum amount of voltage required to run the engine properly.
A 25K volt air gap is approximately a ¼” wide; so you can use a screwdriver stuck in an ignition wire, while you’re holding the driver a ¼” away from the block. Just be ready for your toes to curl, if you make a better path to ground, then the engine block. A properly functioning ignition coil can produce over 80,000 volts; so be careful.
Why I’m thinking this, is that maybe when the truck has sat for that hour or so that you mentioned; the fuel being delivered, is on the lean side for a partially cooled engine and a weak spark may not be able to fire the mixture. You give the engine a sniff of starting fluid and the truck fires. Once running the alternator brings battery voltage up full; which in turn will allow the coil to produce a stronger spark?
Dan.
Canadian "EH"
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captainflugel
New User
Aug 14, 2008, 10:16 PM
Post #5 of 6
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Re: intermittent starting problem 93 chevy
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Dan D . I hate to admit this but I did omit the fact that I also replaced the coil thinking the same thing you did but forgot to include it in the items I have changed in my original thread. Sorry. Thanks for the reply. Captainflugel
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DanD
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/ Moderator
Aug 15, 2008, 3:28 AM
Post #6 of 6
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Re: intermittent starting problem 93 chevy
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No problem but have you tested for a “good strong” spark. Yes the coil is the transformer but there are other things that can weaken a coils output. To name a few are the ignition rotor too distributor air gap being excessive or corroded, low primary voltage @ the coil, ignition module saturation time too low, ignition pick-up coil double triggering the module?
If you have checked secondary ignition output, then forget everything I just said. LOL
Time to move back to fuel supply & delivery systems.
On the times it doesn’t start, is the fuel pump being activated, what is the fuel pressure, are the injectors being pulsed? I know more questions then answers but anyone of these things or a combination of, will add up to your no start.
Dan.
Canadian "EH"
(This post was edited by DanD on Aug 15, 2008, 3:29 AM)
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