OK. Let me give you some background. This truck has been a daily driver for a while. Last weekend I tried to start it, and it would only turn over. Then randomly after about 20 times. it starts, and runs perfectly fine, and started fine several times after that. Now after sitting for about 5 days I am having the same problem, and it will only start if starting fluid is sprayed into it. I am assuming it is the fuel pump, but would like to know if there is a way to confirm that ,and then maybe a walk through or a link to a walkthrough on fuel pump removal/installation.
1999 GMC Sonoma only starts when Starting Fluid sprayed
- Thread starter pdt2326
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- fuel pump gmc sonoma starting
Molson02536
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Start with checking your fuel pressure at the shredder valve located on the fuel line by the distributor on the drivers side. You should get a reading of 62-65 psi (ignition on engine not running) and will drop 5 psi when the engine is running.
Anything less the 62 psi will give you hard starts or no start at all from a weak or bad fuel sending unit. Before you replace the sending unit, inspect the ground wire from the harness in top of the tank to the frame. The ground wire corrode at the frame and the bad ground will cause the pump to be weak and you get low psi.
Once you have confirmed that the sending unit is bad and needs to be replaced, there are 2 ways you can replace it.
You can find a few friends to help you lift the bed off the frame after you have disconnected a few bolts and undo the light harness and gas filler tube to gain access to the top of the gas tank to replace the fuel sending unit.
The other way is to raise the truck to drop the tank to get to the top of the gas tank. Once you have secured the truck off the ground enough so you can drop the tank to slid it away from under the truck. Place a jack under the tank and undo the tank straps, but spray the bolts down with good penetrating oil the night before you get started.
Once you have the jack under the gas tank holding the tank up, gas filler tube and straps taken off. SLOWLY lower the tank enough so you can get your hands on top of the tank to disconnect the fuel lines and wire harness. Once that is done, lower the gas tank to the ground and slide it away so you can remove the sending unit.
The sending unit is locked down on to the gas tank by a C ring that will need to be sprayed with penetrating oil again from corrosion, so don't be surprised that the gas tank will be corroded also depending where you live and it may be better to just replace the gas tank and sending unit at the same time.
To reinstall is in reverse and replace the fuel filter after running the engine about an hour to ensure that any dirt that may have gotten in to the tank is caught in the filter and will need to be replaced.
Good luck and make sure you connect the sending unit new wire harness that comes with the new fuel sending unit correctly, reversing the pumps wires will not pump the fuel, but will still work in the opposite.
Hope this helps and stay safe
Molson02536
Molson02536
New member
My mad, from what you have described, you have a 2.2 liter. The Schrader valve is going to be on the passenger side and should have a green cap on top of it labeled fuel.
Hope this helps.
Molson02536