My 97 Blazer is really hard to start cold...

[MissMikel]

Hi
My Blazer has been hard to start for the last couple months. When I get it started it runs like a champ and after it has warmed up it starts with out a hitch. The problem has gotten progressively worse..There are days when it wont start at all.. I relpaced my fuel filter because at one point it was not getting any fuel..that seemed to help for a few days but now same problem...Also used a can of Sea Foam in the gas tank...Could it be some kind of sensor?? Mass air flow or something?? Maybe I just need a tune up?? I don't know?!?! Please help

[MT-2500]

What engine?
Any check engine lights?

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.

[MissMikel]

I have a 4.3L V6 and yes my service engine soon light has been on for sometime...It turned off for a while after I changed my fuel filter and used the Seafoam. It came back on though. I will try to get the fuel pressure tests done soon and get back to you...Thanks for your help. Also thought I should let you know that it won't run with the air intake disconnected from the throttle body...Found this out while trying to start it with starting fluid.

[MT-2500]

Give us the fuel pressure readings and check for codes.
Post back code no.

[MissMikel]

Went and had the codes read...here they are

P0171
P0174

Let me know if you need anything else..thanx

[MT-2500]

Originally Posted by MissMikel

Went and had the codes read...here they are

P0171
P0174

Let me know if you need anything else..thanx

Codes are lean running engine right and left side.
LOW FUEL PRESSURE WILL MAKE ENGINE RUN LEAN.
We need the fuel pressure readings.

[MissMikel]

Ok Finally got the pressure tester...

When I turn the key on the pressure is at 44psi and when I TRY to start it(it won't start now), the pressure falls to between 37 and 40 psi...
Thats all I got

Thanx

[MT-2500]

Pressure is way to low.
You are not going to leave home with that low pressure.
You need 60/66 lbs of fuel pressure.
You need.
64-65 cold cranking before it will squirt injectors.
Even 60-62 will give a slow or no start.

Pinch off or block return line and then check pressure.
It should jump to 95-105 lbs of pressure if fuel pump is good and strong.
Or check direct fuel pump at fuel filter in line.

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.

[MissMikel]

I am a little confused....or maybe just a little slow...

I have a Haynes manual and it say my pressure should be betwwen 55-61psi...
( I'm still too low I know)

My engine is a 4.3L V6 with CSEFI system..

Also cant do the running tests since my car won't start...

And I don't know where the return line is...

Please forgive me I am just a dumb Girl!!!

[MT-2500]

Originally Posted by MissMikel

I am a little confused....or maybe just a little slow...

I have a Haynes manual and it say my pressure should be betwwen 55-61psi...
( I'm still too low I know)

My engine is a 4.3L V6 with CSEFI system..

Also cant do the running tests since my car won't start...

And I don't know where the return line is...

Please forgive me I am just a dumb Girl!!!

Haynes gets confused to.

The specs I posted are from mitchell On demand same as factory the repair manual.

If you can not find the smaller return line find the large in fuel line at fuel filter and check direct fuel pump pressure there.

The smaller return line can be found on fram running back to tank.

The smallest line back to tank will be the vent line do not confuse ir with the return line.
The largest pressure line runs threw the fuel filter.
Good place to start checking full pump pressure.


If you still have problems try to find a mechanical minded freind to help you.
Good Luck

[MissMikel]

Ok we tested the pressure by the fuel filter and it still is at 45-50psi....Could it be anything besides my fuel pump???

[MT-2500]

Originally Posted by MissMikel

Ok we tested the pressure by the fuel filter and it still is at 45-50psi....Could it be anything besides my fuel pump???

If you checked the pressure direct out of fuel tank/pump to fuel filter and only 45-50 it points to weak fuel pump.

But check for plenty of fuel in tank and good 12 volts to fuel pump and good ground.

If you have to replace the fuel pump only use the AC-Delco / Delphi fuel pumps.
Off brands give a lot of problems.

Let us know how it goes.
Good luck

[MissMikel]

Thanks for the help...I will let you know how it goes!!

[MT-2500]

Originally Posted by MissMikel

Thanks for the help...I will let you know how it goes!!

You are welcome and good luck.

[MissMikel]

Ok we are in the process, right now as I write this, of replacing the fuel pump..when we check the voltage going to the pump it said we are only getting 5 volts...Is that right??? or is there possibly something else going on?? My relays are working I think...what else should we check??

Please Please help....