'96 K1500 - Hard to start after sitting - Fuel pump?
Mikebuild
07-12-2006, 04:37 PM
My '96 K1500, 350 Auto, 123k, has been hard to start (recently). It needs to crank for several seconds before it starts, warm or cold.
Once it starts, it runs, but seems to lunge or rev at idle (and also can hear a faint buzzing sound, like a fan motor).
Other than the above, there seems to be no other performance issues, plenty of power, normal mileage, smooth running etc.
We were guessing that the fuel may be running back into the tank when the engine is off, so I've tried stopping and starting it quickly to try and determine if this was true or not, It does restart immediatly but still takes 1/2 a crank more than normal, but alot faster than if its been sitting for a few moments. I just replaced the fuel filter, there was fuel present, but the pressure was far less than the other times I've changed the filter.
It's been suggested that its the fuel pump, what do you think.
Once it starts, it runs, but seems to lunge or rev at idle (and also can hear a faint buzzing sound, like a fan motor).
Other than the above, there seems to be no other performance issues, plenty of power, normal mileage, smooth running etc.
We were guessing that the fuel may be running back into the tank when the engine is off, so I've tried stopping and starting it quickly to try and determine if this was true or not, It does restart immediatly but still takes 1/2 a crank more than normal, but alot faster than if its been sitting for a few moments. I just replaced the fuel filter, there was fuel present, but the pressure was far less than the other times I've changed the filter.
It's been suggested that its the fuel pump, what do you think.
MT-2500
07-12-2006, 05:28 PM
My '96 K1500, 350 Auto, 123k, has been hard to start (recently). It needs to crank for several seconds before it starts, warm or cold.
Once it starts, it runs, but seems to lunge or rev at idle (and also can hear a faint buzzing sound, like a fan motor).
Other than the above, there seems to be no other performance issues, plenty of power, normal mileage, smooth running etc.
We were guessing that the fuel may be running back into the tank when the engine is off, so I've tried stopping and starting it quickly to try and determine if this was true or not, It does restart immediatly but still takes 1/2 a crank more than normal, but alot faster than if its been sitting for a few moments. I just replaced the fuel filter, there was fuel present, but the pressure was far less than the other times I've changed the filter.
It's been suggested that its the fuel pump, what do you think.
You could have several problems.\
Any codes?
How is the tune up end?
Hard to start cold.
A good fuel pressure check to start with.
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.
Do not leave home without it.
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 you have a leak.
Post back fuel pressure readings.
Once it starts, it runs, but seems to lunge or rev at idle (and also can hear a faint buzzing sound, like a fan motor).
Other than the above, there seems to be no other performance issues, plenty of power, normal mileage, smooth running etc.
We were guessing that the fuel may be running back into the tank when the engine is off, so I've tried stopping and starting it quickly to try and determine if this was true or not, It does restart immediatly but still takes 1/2 a crank more than normal, but alot faster than if its been sitting for a few moments. I just replaced the fuel filter, there was fuel present, but the pressure was far less than the other times I've changed the filter.
It's been suggested that its the fuel pump, what do you think.
You could have several problems.\
Any codes?
How is the tune up end?
Hard to start cold.
A good fuel pressure check to start with.
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.
Do not leave home without it.
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 you have a leak.
Post back fuel pressure readings.
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