Hard Starting when cold

Hi everyone,

I have a 1997 Blazer 4.3L Auto 4X4

I am currently having an issue when I start my blazer in the morning. I have to crank the hell out of it when it sits overnight especially if it’s below 25 degrees. I have checked the fuel pressure and it's on the low side hovering just above 60psi. Also my MAP sensor seems to be loose there is nothing holding it in. I can wiggle it up and down and side to side. Does any one know if this is normal and how it comes out? I disconnected it and it only throws a code when the motor is warm.

Any help is greatly appreciated.

You may good fuel pressure but does it hold,check and see how fast the pressure drops off when you shut it down.

You need 64-65 cold cranking fuel pressure to squirt injectors.
Fuel specs are 60/66
Make sure you gauge is right on the money.
A few lb. low can cause a no 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 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.

My no start/hard start when cold was solved with a tune-up (Plugs, wires, cap, and rotor - All AcDelco). My plugs were so worn out the gap was nearly twice the spec. Its a quick check to pull a couple plugs and inspect them.

Thanks for the replies.

I will try to check the fuel pressure tonight if it stops raining/sleeting. I will also pull a few plugs to see the condition and I will post my results. Does anyone know about the MAP sensor I'm just not sure it's supposed to be loose like that.

~Jeff

I got out last night to check the fuel pressure again; I didn't have time to pull the plugs. Here are my results

Engine off cold - 59 - 60 PSI
Leak down 3-5 minutes - 55 PSI
Running - 51 PSI

My fuel pressure tester is not long enough to tape to my window so running with no load is all I can get. I don't think I have ever changed the fuel filter I will do that this weekend along with checking the plugs. Any input on the MAP sensor question in post #1 is greatly appreciated.

Thanks,
HeavyChevy

Fuel pressure is to low.
Block off return line and /or check the full pump pressure at in line at fuel filter.
What is cold cranking pressure?

The map sensor has to have good engine vacuum.
Is it just map sensor mounting or lose or is it where map sensor taps into the engine vacuum?

Fuel pressure is to low.
Block off return line and /or check the full pump pressure at in line at fuel filter.
What is cold cranking pressure?

The map sensor has to have good engine vacuum.
Is it just map sensor mounting or lose or is it where map sensor taps into the engine vacuum?

From what I can see there is only a couple of posts that the sensor sits between on the plenum. From looking at a picture on the AutoZone web site it looks like the rubber sleeve might be worn out causing a vacuum leak. Should it be snug? It doesn’t just pull out easy but I don't think it should move around like it does. I am going to recheck the fuel pressure when I change the filter. Fingers crossed it's just clogged.

The rubber gromet will give some movement.
But if you think it is to lose drop by parts store or dealer and get a new groment.

The low fuel pressure is you main hard to start cold problem.
MT

I did some work to the Blazer Saturday. Oil change, fuel filter, and I cleaned the EGR valve. The plunger on the EGR was sticking a little now it’s very smooth. There wasn't a lot of carbon build up around the ports and I replaced the gasket with the one that has the screen. The fuel filter was very clogged I don't think it was ever replaced. I have over looked that particular piece of maintenance for years. So after putting the new filter on the fuel pressure dropped by 1 pound.:banghead: I think I am going to have to bite the bullet and put a new pump in it.

I did some work to the Blazer Saturday. Oil change, fuel filter, and I cleaned the EGR valve. The plunger on the EGR was sticking a little now it’s very smooth. There wasn't a lot of carbon build up around the ports and I replaced the gasket with the one that has the screen. The fuel filter was very clogged I don't think it was ever replaced. I have over looked that particular piece of maintenance for years. So after putting the new filter on the fuel pressure dropped by 1 pound.:banghead: I think I am going to have to bite the bullet and put a new pump in it.

Just make sure it is a weak fuel pump and not fuel pressure regulator.
Check direct pressure before replacing fuel pump.
And always go a AC-Delco/Delphi OEM type pump if you replace it.
Good luck
MT

Just make sure it is a weak fuel pump and not fuel pressure regulator.
Check direct pressure before replacing fuel pump.
And always go a AC-Delco/Delphi OEM type pump if you replace it.
Good luck
MT

I am not able to do a direct pressure test with my current tester. What type of fuel tester do you recommend?

Block off return line and see if pressure comes up.
A direct fuel pressure test can be done on the pressure line at fuel filter.
You will need some fittings to hook onto it.
Check auto parts place or a auto repair tool man for test fittings.