99 S-10 V6 losing fuel pressure
milehieagle
02-09-2008, 04:22 PM
hmmm
MT-2500
02-09-2008, 04:43 PM
60 lbs is borderline of being to low.
Specs are 60/66.
You need 64-65 lbs of fuel pressure while cranking on a cold start.
Sounds like you tested it on a good start morning.
Or flipping the key on to test primed it up more than usual.
Always check cranking pressure and engine running after pump is hot.
Block off return line and test full pump pressure.
A good strong pump will have 85-95 lbs full pressure.
And beside pressure you Ned some volume.
I have saw pump come up to 60 lbs on pressure gauge but pressure will drop when cranking because the pump does not have the volume to keep it running.
Guide lines for testing the fuel pump.
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.
Specs are 60/66.
You need 64-65 lbs of fuel pressure while cranking on a cold start.
Sounds like you tested it on a good start morning.
Or flipping the key on to test primed it up more than usual.
Always check cranking pressure and engine running after pump is hot.
Block off return line and test full pump pressure.
A good strong pump will have 85-95 lbs full pressure.
And beside pressure you Ned some volume.
I have saw pump come up to 60 lbs on pressure gauge but pressure will drop when cranking because the pump does not have the volume to keep it running.
Guide lines for testing the fuel pump.
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.
milehieagle
02-09-2008, 05:19 PM
So is the fuel line supposed to hold pressure or is it supposed to bleed off?
MT-2500
02-09-2008, 06:12 PM
So is the fuel line supposed to hold pressure or is it supposed to bleed off?
The engine cranking and running pressure that makes it start and go.
Give us what you got on that end.
A slow leak down is normal.
A fast leak down is a leak or leak back someplace.
MT
The engine cranking and running pressure that makes it start and go.
Give us what you got on that end.
A slow leak down is normal.
A fast leak down is a leak or leak back someplace.
MT
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