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1999 flatbed dually with a no start vortec
06-02-2014, 10:49 AM
Post: #1
1999 flatbed dually with a no start vortec
I have a 1999 chevy 3500 flatbed dually with the 350 vortec motor and it died while driving it down the freeway. My fuel pump was making a loud whining noise and had been for a while so I started by changing it and the fuel filter, no start. The "service engine soon" light was on so we got a scan tool and it gave a crank position sensor fault, so we changed that, no start. We then moved on the the fuel pressure regulator, cleaned the injectors, the oil pressure sensor, still no start. Now it will crank over as soon as the cables are put on it (as you can imagine, the battery is pretty tired) although there is no key in the ignition!
Is this truck haunted? Can anyone shed some light on this situation?
We are going to check to make sure it has good compression but need to figure out this starter thing first.
Any help would be appreciated.[/b]
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06-02-2014, 09:55 PM
Post: #2
RE: 1999 flatbed dually with a no start vortec
Lets start from the beginning when you changed the fuel pump did you look at the fuel pump fuse... I once changed the fuel pump because I didnt hear the pump come on and tried to start it but then come to find out that the fuse had blown replaced that fuse and the damn truck fired right up
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06-02-2014, 10:41 PM (This post was last modified: 06-02-2014 10:43 PM by Rupe.)
Post: #3
RE: 1999 flatbed dually with a no start vortec
Getting back to your phantom cranking.... good chance the weak battery has caused a high curent draw condition and possibly welded the starter solenoid contacts. You can try giving it a good smack with a hammer and see if that helps but I strongly suggest you find a good loaner battery to finish your diagnosis. It's hard to do voltage checks when you don't know what your voltage is or how many volts drop across a loaded circuit when the battery can't supply 12 volts. Once you get that far see if you have spark and fuel, or which one is missing. Obviously you will need a known good battery to do a compression test if you feel that is the problem.

BTW, a weak battery can also cause slow cranking, which can cause the thing not to fire up even if you do have spark and fuel. The bottom line in this case may be a flooded engine. Pulling the plugs may give you a clue.... and of course the plugs may be old and tired as well.

Oh, a couple more pointers...

While the fuel pump gets both the ground and a hot from the wiring harness plug, if you follow that harness forward there's usually a ground wire to the chassis that breaks out of the harness. Sometimes that gets disturbed when you are working so worth a check for rust / cruddy connection if you find the pump is not in the picture. As mentioned above, also check the fuse, and additionally try swapping the fuel pump relay for another in the relay block. Read the diagram in the relay cover and I think you will find the AC relay is the same part number.

Edited to add: There are 3 fuses that can cause your problem. They are marked ECM1 ECM2 and Fuel Pump.
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