99 Chevy blazer hard staring

[ATC mechanic]

my 99 blazer gives me trouble starting when it is cold out we tested the battery and it is at 9v.Just put a tune up on it thinking that was the problem but it wasn't.It starts fine during the day its just in the morning or when it sits.you end up cranking it around 5 times before it will start. 4.3 liter V6

[MT-2500]

You need to get the battery voltage up to 13.2 volts.
Does it turn over normal or slow?
How is tune up end?
Good Ac Plugs and filters and wires and cap and rotor ?
Any check engine lights?

Fuel pressure will also give a hard start cold.
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 and fuel pressure testing guide line.
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.

[ATC mechanic]

Originally Posted by MT-2500

You need to get the battery voltage up to 13.2 volts.
Does it turn over normal or slow?
How is tune up end?
Good Ac Plugs and filters and wires and cap and rotor ?
Any check engine lights?

Fuel pressure will also give a hard start cold.
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 and fuel pressure testing guide line.
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 fuel pressure reading is 55 psi when i start it and with the engine running it is 52psi this is bad isnt it do u think it will be the fuel filter

[MT-2500]

Originally Posted by ATC mechanic

The fuel pressure reading is 55 psi when i start it and with the engine running it is 52psi this is bad isnt it do u think it will be the fuel filter

The only way to find out is to.
Do the full test as outlined.
And post back all pressure readings.

[ATC mechanic]

Originally Posted by MT-2500

The only way to find out is to.
Do the full test as outlined.
And post back all pressure readings.

fuel pressure is now at 60 i changed the fuel filter and it works now on the first try i will see if it stays that way thank you

[MT-2500]

You need 64-65 for a good cpld start.
Even a couple of lbs low willgive a hard start.
Where did you get the 60 lbs.
Starting or running at idle or under a load?
You still need to do the complete fuel pressure test to be sure it is up to par.

[Big J Olds]

Hey I dont mean to hijack this post in anyway, But this is a very recent one and I thought I'd ask you all something.

MT-2500 - I my father is having the same problems with his 2000 blazer as you mentioned about cold/hard starts and Last year we replaced the fuel pump with them crappy aftermarket ones.

Anyway...I have a fuel pressure gauge but, being that the blazer has all metal hard lines for the inlet and outlet lines. Is there a way I can test full fuel pressure at the fuel filter area? If so..how would I go about hooking up the gauge down there?

Also...last Time I checked fuel pressure on his truck it was only reading 55psi i believe. I'll check back as soon as i find more out.

Thanks again

Justin

[MT-2500]

Originally Posted by Big J Olds

Hey I dont mean to hijack this post in anyway, But this is a very recent one and I thought I'd ask you all something.

MT-2500 - I my father is having the same problems with his 2000 blazer as you mentioned about cold/hard starts and Last year we replaced the fuel pump with them crappy aftermarket ones.

Anyway...I have a fuel pressure gauge but, being that the blazer has all metal hard lines for the inlet and outlet lines. Is there a way I can test full fuel pressure at the fuel filter area? If so..how would I go about hooking up the gauge down there?

Also...last Time I checked fuel pressure on his truck it was only reading 55psi i believe. I'll check back as soon as i find more out.

Thanks again

Justin

55 is way to low.
You need 64-65 for a good cold start to squirt injectors.

On direct fuel pressure you can check it by hooking onto the in line at fuel filter.
Remove it from filter and couple the gauge on the end of it.
Full prsssure should be 95 or more.
But only run it at full pressure just long enought to test.
Good Luck
May require

[ATC mechanic]

Originally Posted by ATC mechanic

fuel pressure is now at 60 i changed the fuel filter and it works now on the first try i will see if it stays that way thank you

well i ended up replacing the tps that was bad it doesnt take 8 cranks anymoe now it takes 2 i would really like it to start right away the fuel pressure is 52 at start up and 55 at idle going up a hill it reaches 59 i know that still isnt good for this year i have a fuel pump should i just put that in

[MT-2500]

Originally Posted by ATC mechanic

well i ended up replacing the tps that was bad it doesnt take 8 cranks anymoe now it takes 2 i would really like it to start right away the fuel pressure is 52 at start up and 55 at idle going up a hill it reaches 59 i know that still isnt good for this year i have a fuel pump should i just put that in

Before throwing parts at it run the test.

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 and fuel pressure testing guide line.
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.

[Big J Olds]

Ok...I did the full pressure test. Pressure did NOT go over 65psi.

Try it again just to make sure i wasnt reading it wrong...same thing 65psi.

So With that in mind...I'm safe to say the pump is bad correct?

Here are all the pressure readings i gathered just to help you.


Full pressure - 65
pressure at the schrader valve - 55-58
Pressure while cranking but NOT runing - drops from 55-58 to 40 for a split second, then went back up to 50...Still did not start.
Pressure while running is 54-56psi.

[MT-2500]

Your pressure is low.
The pump should run 95 to 105 lbs full pressure.

Always replace with a AC Delco/Delphi feul pump.

Airtex and other after market pumps are junk.
Good luck