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1995 Buick Riviera 3800sc starts then dies

Tiny
SCFIERO
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  • 1995 BUICK RIVIERA
1995 Buick Riviera 6 cyl 65000 miles

My car starts up then dies out immediatly. It is a 3800 supercharged V6. I replaced the camshaft sensor (the magnet is on the gear) and the crankshaft sensor. I tested the injector wires for a pulse. When the car is turning over there is a light pulse on each injector. Once the engine starts, the pulse stops, then the engine dies and the test light pulses once. If I introduce fuel thru the air intake I can keep the engine running, but once I stop giving it fuel, the engine dies. I did check the ecm for corrosion but it looks brand new. Any help would be good.
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Wednesday, August 26th, 2009 AT 6:56 PM

12 Replies

Tiny
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Check the fuel pressure with a fuel pressure gauge could be the fuel pump -low/no pressure.
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Wednesday, August 26th, 2009 AT 7:26 PM
Tiny
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Fuel pressure is at 40psi. I did a check of the injector pulse and found that when he car is turning over I have a good pulse but once it starts the pulse stops, the car dies and then I get 1 last pulse at the end and thats it. Could it be the VATS.
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Thursday, August 27th, 2009 AT 8:44 AM
Tiny
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If I introduce fuel thru the air intake I can keep the engine running, but once I stop giving it fuel, the engine dies

If there's a problem with injectors I don't think you can continue to make it run feathering it-

Recheck your fuell pressure its suppose to be 41-47psi also do a running test
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Thursday, August 27th, 2009 AT 10:28 AM
Tiny
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The fuel pump was the first thing I replaced when this started, I also changed the fuel filter, and did complete tune up just to be sure.

I rechecked fuel pressure today w/key on got 40psi at the rail. Unfortunatly I cannot due a running test because the car only runs for a second before dieing out. After the car stops the guage stays at about 38psi. I did notice the pump kind of runs on after the car dies out. The pump sounds strong at first and then instead of just shutting off it kind of lingers and dies out slowly. Not sure if that is normal. Maybe the new pump is bad?
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Thursday, August 27th, 2009 AT 5:11 PM
Tiny
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Power the fuel pump direct from the battery and see what happens.
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Thursday, August 27th, 2009 AT 6:27 PM
Tiny
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I jumped the fuel pump at the relay and it ran a steady 40psi at the rail. It must be ok, it never even waivered. Possibly my guage is off by 1 or 2. Anyway it seems fine, and even with 40psi it should at least idle. I am not getting an injector pulse when the engine starts, this is why it dies out. Now I just need to find out why the injector pulse is stopping after the engine starts.

It has new pump, camshaft sensor, crankshaft sensor. Plugs and wires w/spark. Can dump fuel into air intake and keep vehicle running. Why are the injectors not firing once the engine starts?
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Thursday, August 27th, 2009 AT 7:35 PM
Tiny
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Could be the injector/s ground drivers in the computer
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Thursday, August 27th, 2009 AT 7:37 PM
Tiny
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I almost forgot, I even tried starting the car w/the fuel pump jumped and it still just started for a second then died out.
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Thursday, August 27th, 2009 AT 7:40 PM
Tiny
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I thought that also, I opened the computer and it looks brand new, no corrosion or abnormalities that I could SEE. Does anyone test the computer alone or is there a way to bypass or jump the injectors.
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Thursday, August 27th, 2009 AT 7:42 PM
Tiny
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If you have power on one side of the injectors and not pulsing think computer-
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Thursday, August 27th, 2009 AT 7:43 PM
Tiny
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I am using a test light. I have solid power on one side, then the other side pulses until the engine fires. At this point the pulse stops. Therefore the engine dies. Right when the engine dies out I get one last pulse on the injector but to late. I was told that the injectors all fire at start up and then once the crankshaft or camshaft sensor senses the engine running it turns it over to the pcm to keep it running. It is at this point that I think the Vehicle Anti Theft System is taking over and killing the signal to the pcm or the injectors or whatever. Does this sound about right, or should I buy a new pcm.
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Thursday, August 27th, 2009 AT 7:52 PM
Tiny
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Recheck the cam and crankshaft sensors the computer has to see their input signals before it can snchronize the injectors to include firng the coil/s. If all is good in this area-Your decision on the computer-Good Luck
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Thursday, August 27th, 2009 AT 8:01 PM

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