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1993 Engine Running Rough and No Power

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Old 07-19-2012, 02:56 PM   #1
73737373
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Default 1993 Engine Running Rough and No Power

1993 LT1, 6 speed manual. No engine mods other than K and N Filter.
112K miles. Regular maintenance, never abused.

Started and drove great one day. Started it up an hour later and was running rough. Shifted into 1st gear and car would almost stall as I let out the clutch before I could get it to move. That's as far as I got driving it for fear of it quitting on me somewhere other than my driveway. Waited a couple days and tried again, same symptoms.

Plugs/wires done w/in the past year. New opti less than 60 days ago. New fuel pump/filter about 5 years ago.

My mechanic suggested a fuel starvation problem attributing it to a small piece of hose in the tank between the pump and the fuel line that will deteriorate and fuel will escape thru holes/cracks. There was also a very low, but noticeable whine coming from the rear of the car for a few days before this happened. The whine was not movement related...sometimes would make the noise, even when the car was stopped.

Like I said, was running as strong and smoothly as it ever had after the new opti.
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Old 07-19-2012, 03:12 PM   #2
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I think you might trust the mechanic on this but to save time/money put a pressure gage on and see how much fuel pressure you have. With the whine you had in the back it sure could be the pump.
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Old 07-19-2012, 03:14 PM   #3
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Concur, that was the 1st thing I was going to check.

Off the top of your head, how hard is to change a fuel pump in a C4? Do you have to drop the tank or is the pump accessable some other way?
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Old 07-19-2012, 04:15 PM   #4
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Quote:
Originally Posted by 73737373 View Post
Concur, that was the 1st thing I was going to check.

Off the top of your head, how hard is to change a fuel pump in a C4? Do you have to drop the tank or is the pump accessable some other way?
Do a search. I'm pretty sure I've read that you take out the inner shield around the gas cap and you can get it out right through the filler door. Just be careful not to drop any crap in the hole. With my Fords I just buy a new float/pump assy. I'm too lazy to just swap out the pump.
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Old 07-19-2012, 04:17 PM   #5
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That's what the mechanic said, but he wasn't certain. Hey, this may be easier than I 1st thought. Wouldn't that be a novelty on a Corvette?
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Old 07-19-2012, 05:34 PM   #6
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That's what the mechanic said, but he wasn't certain. Hey, this may be easier than I 1st thought. Wouldn't that be a novelty on a Corvette?
I'm thinking it's pretty bad when a fuel pump is easier to change than an outer tail light bulb.
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Old 07-19-2012, 05:42 PM   #7
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And they're only about $50, too. This is almost too good to be true. Watch...my fuel pump will be fine. It will some other PITA repair that needs to be done.
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Old 07-20-2012, 07:54 PM   #8
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The Fuel pump can be changed from the top. Not the most enjoyable job in the world, but not too too bad. As others said - check the fuel pressure with the car running first.

With a whine from the back being noticed - I'd think fuel pump pressure first, but Remember - just becuase the opti is quite new - doesn't mean it isn't bad.
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Old 07-27-2012, 05:11 PM   #9
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I went ahead and replaced the fuel pump, if for no other reason than to get rid of the whine and hoping it would solve my problem. It did not...exact same symptoms as before.

I'll check the filter.
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Old 07-27-2012, 11:50 PM   #10
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I haven't heard a 90's GM fuel pump that DOESN'T whine. That is normal for them.

Since it presents the symptoms easily.
Your going to have to diagnose the issue or just keep throwing parts at it.

Let it idle (if it will).
Check spark with spark tester at plugs and off the coil wire. I like inline checkers.

Check the following:
Fuel Pressure
Injectors (feel for firing on all)

Start with that. No codes I assume?
Scan the ECM for data and see if it is within specs. if possible.
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Old 07-30-2012, 09:28 AM   #11
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Thanks.
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Old 07-30-2012, 11:50 PM   #12
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For the cost of that fuel pump and a few more dollars you can get a shop manual that will have all kinds of trouble shooting diagnostic tests you can perform to determine the problem. If this thread goes like so many others you will be told to replace the opti, fuel injectors, plugs, wires, fuel filter, fuel pump, fuel pressure regulator, catalytic converter, fuel cap, ECM, wiper blades and sprinkle Rhode Island Red chicken blood on the starter. That money will buy a dozen manuals.
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Old 07-31-2012, 09:14 AM   #13
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I have one. Maybe a good idea if I opened it and read it.
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