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Surging in 96 chev pu


philrmech
03-15-2010, 06:46 PM
I have a 96 4.3 pick-up and it is surging at times.Sometimes will surge and not go faster than 60 mph then it will pick up and go normal speed.I checked the fuel pressure it shows about 50 lbs.How do you check the fuel pressure and could it be anything but a new fuel pump. it cfsi fuel system and was told it should have 60-64 psi thanks phil also has new fuel filter plugs and cap and rotor thanks phil give me some info

MT-2500
03-16-2010, 09:02 AM
I have a 96 4.3 pick-up and it is surging at times.Sometimes will surge and not go faster than 60 mph then it will pick up and go normal speed.I checked the fuel pressure it shows about 50 lbs.How do you check the fuel pressure and could it be anything but a new fuel pump. it cfsi fuel system and was told it should have 60-64 psi thanks phil also has new fuel filter plugs and cap and rotor thanks phil give me some info

Specs are 60/66 on it.

Hook a fuel pressure test gauge to test port on back on engine and tape gauge to rear view mirror or outside windshield where you can watch it going down road.

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.
Post back fuel pressure readings.

philrmech
03-16-2010, 12:04 PM
I have 54 psi at idle and running.I pinched off return line press went to 70-90 and flucuating.I have ben told this is fuel pump and also plastic spider injector.Give me some ideas thanks phil

MT-2500
03-16-2010, 12:32 PM
I have 54 psi at idle and running.I pinched off return line press went to 70-90 and flucuating.I have ben told this is fuel pump and also plastic spider injector.Give me some ideas thanks phil

Run the fuel pressure as outlined and post back all pressures.

Any fast leak down after pump shuts off?

philrmech
03-16-2010, 01:04 PM
With just cycling key off and on have 85 psi and holding with key off. any ideas phil. mechanic friend told me it was fuel pump I am a little afraid that is not it send pump will make 85 psi.Could it be in spider injector somewhere. thanks phil

MT-2500
03-16-2010, 01:25 PM
With just cycling key off and on have 85 psi and holding with key off. any ideas phil. mechanic friend told me it was fuel pump I am a little afraid that is not it send pump will make 85 psi.Could it be in spider injector somewhere. thanks phil
Are you telling us you have 85 lbs pressure key on and only 50 or little more running?
You need to do the full test.
And post back all pressure readings.
before we can help.

philrmech
03-16-2010, 02:29 PM
I have 54 psi with it running without return line pinched off either running or key off and on.I have 85 psi key on and 70-90 lbs and varying with it running. thanks phil

MT-2500
03-16-2010, 04:22 PM
I have 54 psi with it running without return line pinched off either running or key off and on.I have 85 psi key on and 70-90 lbs and varying with it running. thanks phil
Still not the full test but.
If pressure comes up to 85 or 70-90 lbs pressure with return line blocked and drops to 54 running without return line unblocked replace the fuel pressure regulator.
And retest pressure.
Also what is running on road pressures after 20-30 minutes.
Make sure pump pressure does not drop after warm up.

philrmech
03-16-2010, 06:52 PM
After your help I think it is pressure regulator.I have it all apart I took pressure regulator off and started to put new one on but there is no hose to connect to vac port on regulator is this nrmal doesnt there have to be a small hose somewhere to connect to small vac port

MT-2500
03-17-2010, 08:36 AM
After your help I think it is pressure regulator.I have it all apart I took pressure regulator off and started to put new one on but there is no hose to connect to vac port on regulator is this nrmal doesnt there have to be a small hose somewhere to connect to small vac port

They do not have a hose on them.

The regulator draws it vacum from inside intake.
Good Luck
Let us know how it goes.

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