99 Blazer no-start

[h34vy_duty]

First I'd like to say thanks up front for any help that can be provided to me.

About 9 months ago by Blazer started to run real rough and couldn't even idle without pumping the gas constantly. So, it sat in the driveway until recently when I finally cleared a space in the garage for it. So far this is what I have done.

1. Replaced battery (old one wouldn't hold a charge)
2. checked vacuum line for leaks and didn't find any
3. Tested ignition coil (no problems)
4. Pulled plug to verify cylinders are getting spark (checked out)
5. Moved to fuel system
6. Checked pressure key on engine off (60 psi, drops to zero within 5 seconds)
7. Pinched off return line checked pressure (55 psi, drops to zero within 5 seconds)
8. Replaced fuel pressure regulator checked pressure (60 psi, drops to zero within 5 seconds)

That's all I've done so far. Everything is pointing me to replacing the CPI assembly, however I really don't want to dish out the $320 for it. Have I missed something or should I just bite the bullet and buy the part?

Thanks again for your help everyone.

[MT-2500]

Originally Posted by h34vy_duty

First I'd like to say thanks up front for any help that can be provided to me.

About 9 months ago by Blazer started to run real rough and couldn't even idle without pumping the gas constantly. So, it sat in the driveway until recently when I finally cleared a space in the garage for it. So far this is what I have done.

1. Replaced battery (old one wouldn't hold a charge)
2. checked vacuum line for leaks and didn't find any
3. Tested ignition coil (no problems)
4. Pulled plug to verify cylinders are getting spark (checked out)
5. Moved to fuel system
6. Checked pressure key on engine off (60 psi, drops to zero within 5 seconds)
7. Pinched off return line checked pressure (55 psi, drops to zero within 5 seconds)
8. Replaced fuel pressure regulator checked pressure (60 psi, drops to zero within 5 seconds)

That's all I've done so far. Everything is pointing me to replacing the CPI assembly, however I really don't want to dish out the $320 for it. Have I missed something or should I just bite the bullet and buy the part?

Thanks again for your help everyone.

Fuel pump.!!!!!!!!

4.3 engine ?

Cold Engine cranking you need 65 lbs of pressure to squirt injectors.
If not and if not with return line pinched.

Check for direct fuel pressure at fuel filter.

You should have 95-105 lbs of pressure there if pump is good.
Or well over 65 lbs to hold 65 lbs on injectors.

Will it start with a shot of carb cleaner?

Guide lines for fuel pump testing.


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 85 lbs or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.