Question about 1996 GMC Sonoma
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Posted on Jan 02, 2017
These trucks are plagued with weak fuel pumps and need a high amount of pressure to start...especially in coder weather.
Remove the air intake on front of engine, it is the rubber tube that is around 5 inches in diameter, be careful as there is a sensor attached on the underside. Squirt some starting fluid into the intake and try starting it right away. If it starts or even acts like it is going to start, you are having a fuel problem.
If you did see a difference by doing the above, then you need to test the fuel pressure with a gauge. The fuel pressure test gauge can be bought for very cheap (around $20) from your local auto parts store. It hooks up to the fuel rail test port on the drivers side of the engine. The test port looks like an overgrown air inlet that you would use to put air in a tire. It should have a plastic cover that you unscrew.
Once the gauge is hooked up, turn the key to prime your fuel pump...do not crank the engine. Look at the gauge to see if you are at least to 56psi, closer to 60 is more desirable. Also take notice if the fuel pressure is dropping, it should stay steady. If it is slowly dropping, then you need to take a look at your hoses from the fuel pump to this point.
If it is steady and within the required psi, then you are looking at a problem within the plenum. The plenum is the aluminum colored cover that is on top of the engine, under your black plastic Vortec label. inside the plenum you will find what is referred to as the "spider assembly". The spider assembly houses the fuel pressure regulator, injector and propet nozzle hoses (6 hoses). A common failure of this unit is the hoses leading to it that supply fuel, they are known to leak. You can easily see if it is leaking by looking for "wash marks". Wash marks are where fuel has leaked and cleaned the inside of the plenum in spots. If this is your case, buy a rebuild kit for the hoses. There is also the possibility of your fuel pressure regulator acting up. This part can be bought separatly from the whole spider assembly, even though you will be told otherwise. I have had to buy it online.
If your psi was not within par, you more than likely have a weak or bad fuel pump. But before going through the fun of replacing it, I would first check to see if the ground for the pump is making a good connection. The ground comes right out of the top of the fuel tank and connects to the rear bumper, it is a tight fit and may not be the easiest to access it. Unbolt it fromt he bumper and take soem sand paper to remove any rust on both the bumper and the wire connection. Put it back together and test your fuel pressure again.
If no change, then you are looking at replacing the fuel pump. You will need a basic socket set, screw drivers, jack, tire iron, hammer and basic wrench set. If you have access to air tools, it really helps with removing the gas tank. Use the jack to not let the tank fall and to lower it down so you can disconnect the hoses going into the fuel tank. Once tank is removed, use the screw driver and hammer to spin the retaining plate around. CAREFULLY remove the fuel pump, DO NOT bend the float arm, if you do, your gas gauge will not display correctly. Pull the fuel pimp out of the assembly and put your new one into it. Do not forget to install the filter that goes on the bottom of it. Once you have that done, put it all back together. Make sure that the hoses to pump are snug, you do not want an air leak. Also make sure that the ground is clean and snug.
Once it is all back together, your psi should be within an acceptable range.
Almost forgot, change your fuel filter while under the truck. Also, when you buy a replacement fuel pump, make sure it is the high output (there are 2 different fuel pumps for this truck) and do not skimp on price. I have seen cheap pumps burn out in under a year. If you can, buy an OEM pump. Copy down your VIN number and take it with you when buying the pump, you will be asked if you have a W or Z vin.
Buying a repair manual for this truck is worth it. Nice truck overall, the egine has the same horse power as the 305 did for that year. You can beat it, abuse it, neglect it and it still runs fine for a long time.
Posted on Oct 20, 2009
did you do a fuel pressure test? if you havent do it its cheep an at least you can elimanate that. if thats not an issue, then there is only two other things crank sensor, and if there is one cam sensor.
Posted on Feb 02, 2009
I have the same problem and have trouble codes 35 and 36. I found out that there is a computer module that needs replaced as it sits low in a valley and gets hot and seperates. I am reseaching about the a/m fix that installs the new module away from heat.
Posted on Mar 12, 2009
u may want 2 check with a dealer gmc dealer but u may have 2 fuel filters on your jimmy poss. an in-line filter runs down the pass. side or driver side not all cars are the same
Posted on Apr 25, 2009
i think if you checked the sparking plugs and map sensors then check your distributer its maybe not delivering the current nedded to perform the spark to some of the cylinders
Posted on May 30, 2009
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