99 Tahoe hard to start after sitting

[Dougalass]

OK I have 99 tahoe 5.7 that is very hard to start after sitting more than a few hours. Replaced the fuel filter today. Started up but same symptoms a few hours later. Replaced the fuel pump last year and I hear the pump turn on. There is also pressure at the needle going in to the intake. Trying some serious fuel injector cleaner now. Anybody have any ideas?

[MT-2500]

You need to check the cold cranking and running fuel pressure with a fuel pressure gauge.
Post back readings.
You need 65 lbs of cold cranking fuel pressure.
If fuel pressure is lower it will not squirt injectors when cold.
MT

[Dougalass]

It's 60 I heard if it is at least 60 thats alright.

[MT-2500]

Is that 60 running or 60 cold cranking pressure?
Specs are 60/66
60 lbs is low on cold cranking .
You need 65 on cold cranking for the injector to squirt.
MT

[2000CAYukon]

Since it is hard to start after sitting for a while, what does the fuel pressure do after you shut off the engine? If the pressure drops down to 0, you have a leaking fuel pressure regulator, a leaking injector or a bad check valve in the fuel pump.

//2000CAYukon

[Dougalass]

Yea the pressure drops quite a bit after I shut it down. I'm going to replace the regulator. Thanks for the input.

[MT-2500]

I would run a fuel pressure test.
The regulator contrals press ure but you need a fuel pump capable of full pressure and fuel volumn for regulator to be able to control it.
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.
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.
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.

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.

MT

[Dougalass]

Turned out to be a defective fuel pump from the manufacturer. I only had 11K miles on the new pump. The company replaced the pump for free but still have to pay for the labor. Thanks for all your posts.

[MT-2500]

Originally Posted by Dougalass

Turned out to be a defective fuel pump from the manufacturer. I only had 11K miles on the new pump. The company replaced the pump for free but still have to pay for the labor. Thanks for all your posts.

You are welcome.
What brand was it?
Good luck with the pump and getting a labor claim.
If the replacement doe not check out on pressure or hold up make the exchange it for a good AC-Delco/Delphi fuel pump.
MT

[Dougalass]

I'll find out. It drives me crazy because its really not that hard to do but they both went with full tanks of gas and the thought of siphoning almost 30 gallons out isn't fun. Timing couldn't have been better because I drive cross country next weekend.

[Dougalass]

They put in a carter fuel pump this time. It's amazing how much quieter this pump is compared to the last one. Truck works fine now.