2000 S10 fuel pump runs continuous.......?

[dans93mark]

I have a 2000 4.3 Extreme. I am preparing to check my running fuel pressure with a pressure dial kit. I understand that the fuel pump is only supposed to run for a few seconds at startup, or that you should only hear it for a few seconds. Mine runs continuous, duh, as it should,
but at over 1500 rpm it starts to break up, but the idle is fairly smooth. I haven't checked the vaccuum line on the pressure regulator yet for leaking gas or the oil pressure switch. But, I suspect the pump itself is defective. Any input here would be appreciated.

[MT-2500]

Originally Posted by dans93mark

I have a 2000 4.3 Extreme. I am preparing to check my running fuel pressure with a pressure dial kit. I understand that the fuel pump is only supposed to run for a few seconds at startup, or that you should only hear it for a few seconds. Mine runs continuous, duh, as it should,
but at over 1500 rpm it starts to break up, but the idle is fairly smooth. I haven't checked the vaccuum line on the pressure regulator yet for leaking gas or the oil pressure switch. But, I suspect the pump itself is defective. Any input here would be appreciated.

Does it keep running after the 2 second key on prime up?
If so check fuel pump relay first.

On the fuel pump go threw the full fuel pressure test and post back pressure readings.

I do not think you will find a vacuum line on the inside platinum regulator.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
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.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding 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 in system.

[MT-2500]

No oil pressure switch for fuel pump on that one.

[dans93mark]

Checked pressure on the rail with ignition on, 25 psi and fades down.
Started and running at warm up idle, 55psi and holds fairly well.
I did this before I read your reply and have already returned the pressure test dial to Autozone.
I hope these readings are an indicator or at least point to a specific. I appreciate your input

[MT-2500]

Originally Posted by dans93mark

Checked pressure on the rail with ignition on, 25 psi and fades down.
Started and running at warm up idle, 55psi and holds fairly well.
I did this before I read your reply and have already returned the pressure test dial to Autozone.
I hope these readings are an indicator or at least point to a specific. I appreciate your input

What reading you have are low or show a leak or leak down some place or clogged fuel filter or weak pump or bad pressure regulator..

You need to go threw the complete test as outlined to test pump or other stuff.

Run the complete test and pinpoint the main problem before throwing parts at it.

Post back how it goes.

[dans93mark]

First I want to take the time to thank you for your expertise. Not many mechanics out there would be as gracious as you.
The fuel pump was sporadic and intermittent, the pressure regulator as well as 2 injectors and one spider hose were on leak down.
I replaced the pump, filter, and spider w/press regulator.....perfect !
Afterwards I took a 900 mile trip, got a evap emission code, replaced the gas cap, then cruise control failed, turned out to be the Vehicle speed sensor on the tranny.
One thing, I replaced a bad waterpump (weep hole leak) and along with it a fan clutch (old one spun free) thermostat, and hoses. Now....I get a fan that seems to run too much, like a telefunkin' B-47. They say that's the nature of the beast, but it seems to be a bit too much especially when you can't hear the exhaust. Your thoughts on this.......

[MT-2500]

Originally Posted by dans93mark

First I want to take the time to thank you for your expertise. Not many mechanics out there would be as gracious as you.
The fuel pump was sporadic and intermittent, the pressure regulator as well as 2 injectors and one spider hose were on leak down.
I replaced the pump, filter, and spider w/press regulator.....perfect !
Afterwards I took a 900 mile trip, got a evap emission code, replaced the gas cap, then cruise control failed, turned out to be the Vehicle speed sensor on the tranny.
One thing, I replaced a bad waterpump (weep hole leak) and along with it a fan clutch (old one spun free) thermostat, and hoses. Now....I get a fan that seems to run too much, like a telefunkin' B-47. They say that's the nature of the beast, but it seems to be a bit too much especially when you can't hear the exhaust. Your thoughts on this.......

You are welcome.
It makes my day to be able to help people.

On the fan noise is it just with a cold engine or after it warms up?

Does fan kick in good after 195-200 degrees and the slow down when it cools back down?

[dans93mark]

Originally Posted by MT-2500

You are welcome.
It makes my day to be able to help people.

On the fan noise is it just with a cold engine or after it warms up?

Does fan kick in good after 195-200 degrees and the slow down when it cools back down?

Well, it definitely whirrs when the engine is cold thru each gear, but I noticed also today on the interstate when I had to turn off the cruise control behind a slow truck in the right lane, I decelled to 50 mph and put my foot into it to try and pass, the tach went up to about 3500 and no acceleration in speed just the fan overrevving. Eventually I was able to get back on track with the cruise control.
Then tonight, after driving it 3 hours prior and letting it sit, a little cooler outside, I didn't hear the fan once on the way back up the interstate until I started from a dead stop at the end of the exit ramp. Can't figure it....
Is it also common on these when running the a/c, for the cycling of the compressor to cause a 500 rpm drop each time it does so ?
Not sure but I think the Extreme is possessed. Or maybe my old ass is just ignorant, can't afford anything else at this point, gonna die with this one I think.......
Thanks ahead of time

[MT-2500]

Originally Posted by dans93mark

Well, it definitely whirrs when the engine is cold thru each gear, but I noticed also today on the interstate when I had to turn off the cruise control behind a slow truck in the right lane, I decelled to 50 mph and put my foot into it to try and pass, the tach went up to about 3500 and no acceleration in speed just the fan overrevving. Eventually I was able to get back on track with the cruise control.
Then tonight, after driving it 3 hours prior and letting it sit, a little cooler outside, I didn't hear the fan once on the way back up the interstate until I started from a dead stop at the end of the exit ramp. Can't figure it....
Is it also common on these when running the a/c, for the cycling of the compressor to cause a 500 rpm drop each time it does so ?
Not sure but I think the Extreme is possessed. Or maybe my old ass is just ignorant, can't afford anything else at this point, gonna die with this one I think.......
Thanks ahead of time

Fan noise cold and is good and when it is a little hot about normal.
When it does not make any noise is time to worry about it.

Ac cycle of 500 rpm drop is to much.
Scan VCM and see if IAC is controlling idle good.

[dans93mark]

Idle seems to be just fine, no codes. When I first start up at beginning of day it sputters for about 10 secs like it's gonna quit then smooths out to a purr.
I noticed today that it is breaking up under load-up hill or during any quick acceleration, and the fan runs high revs. When the motor is cold the fan usually doesn't go bezerk, when it's under load or running 190+ it revs, would a failing MAF meter or fouled TB exibit the stumbling episodes ? Still no codes.......
At your mercy here

[MT-2500]

Originally Posted by dans93mark

Idle seems to be just fine, no codes. When I first start up at beginning of day it sputters for about 10 secs like it's gonna quit then smooths out to a purr.
I noticed today that it is breaking up under load-up hill or during any quick acceleration, and the fan runs high revs. When the motor is cold the fan usually doesn't go bezerk, when it's under load or running 190+ it revs, would a failing MAF meter or fouled TB exibit the stumbling episodes ? Still no codes.......
At your mercy here

I would start with a complete fuel pressure check.
Make sure it is up to specs cold and hot and when it is acting up.
Hook up a fuel pressure gauge and watch cold start fuel pressure and watch the fuel pressure after it gets hot and or when it is acting up.
Post back fuel pressure readings.