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GMC Forum: 1996 GMC Sierra won't start?
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Old 03-15-2010, 03:43 PM
Ash Ash is offline
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Default 1996 GMC Sierra won't start?

The starter's turning over, the battery's fine, the fuel pump is kicking on, and it has at least a quarter tank of gas. I just did an oil change in January, I don't drive all that much, and I use Mobil 1 oil. I also put a gas treatment in when I did the oil change (Gumout® All-In-One®). I checked the spark pugs when I did the oil change as well, and they looked okay so I did not replace them. Any ideas as to what the problem could be would be helpful and appreciated.
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Old 03-15-2010, 03:43 PM
Jared Jared is offline
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Your either not getting fuel or fire, could be multiple things until those two things are confirmed?
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Old 03-15-2010, 03:53 PM
Molson02536 Molson02536 is offline
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Quote:
Originally Posted by Ash View Post
The starter's turning over, the battery's fine, the fuel pump is kicking on, and it has at least a quarter tank of gas. I just did an oil change in January, I don't drive all that much, and I use Mobil 1 oil. I also put a gas treatment in when I did the oil change (Gumout® All-In-One®). I checked the spark pugs when I did the oil change as well, and they looked okay so I did not replace them. Any ideas as to what the problem could be would be helpful and appreciated.
You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors.
I think each injector is on a separate driver on that one.
Check for pulse to all of them.

You may be weak on fuel pressure, Even a couple of lbs low on a cold start will cause a no start. Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. One test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.

Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel. Engine running should be 60-66 lbs pressure depending on engine load. Full pressure with return pinched off should be 75-85 or more, And if it has a fast leak down after shut off the engine you have a leak.
Post back fuel pressure readings. The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.

The other thing also you may want to check is all the electrical connection to your ignition coil and ICM which is located in the distributor cap under the rotor. It's common for condensation to from in the distributor cap from a dirty breather vent screen at the bottom of the distributor, promoting corrosion and ICM failure.

Start with the simple and see if you can get the engine running with a small spray of carb cleaner fluid in through the air intake tube to your engine, if the engine starts. Then you have a fuel delivery issue and your going to have to address that. If the engine does not start, then it's going to be an electrical problem and your going to have to address the Ignition system to find out why your engine is not starting. Keep us all posted and good luck, be glad to know your got your Sierra running 100% again soon.

Also note that there was an issue with the SCPI and a update to convert to MPI, here is a link if you think your having injector problems.

http://members.shaw.ca/betterthanyou...g%20Poppet.htm
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Old 07-13-2011, 11:35 AM
96sierra 96sierra is offline
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i have a 96 sierra with the same problem, i have replaced the plugs, wires, cap, rotor, and ignition coil but it still wont start once it gets cold. once i get it running it will start up again. the highest fuel pressure reading ive got is 60 psi. should i replace my fuel pump
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Old 07-13-2011, 12:41 PM
2001gmc 2001gmc is offline
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Thumbs up Try this.

Next time it wont start spray some pb blaster or something that will make it run down in the air intake where it goes into the motor. Just enough to see if it will hit and run for a couple seconds if it does fire up and run for a couple seconds fuel pump is faulty. Just cause you here fuel pump on turn of key don't mean nothing. I had a 2001 alero before and the fuel pump sounded normal on turn of key and my grandpa come over took off air intake and sprayed pb blaster in it and it started and ran for couple sec and he told me to replace fuel pump and it fixed my problem. Just a FYI.
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Old 07-13-2011, 03:55 PM
96sierra 96sierra is offline
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ok thanks. it hasent started in a few days without using starting fluid. after it gets warmed up i can shut it off and it will start on its own again as long i dont let it get cold. once its started it runs fine though. thanks again
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Old 07-13-2011, 08:04 PM
happy 2011 happy 2011 is offline
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hey molson you said earlyer that you need three things to make a motor run. Well you really need four things..........


Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure.

But you forget exhaust if the exhaust has no where to go a motor will not start.
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