97 blazer runs like junk

well, good news and bad news i suppose... truck's been running progessively worse for the last month and now it barely runs. i got carried away today and checked the fuel pressure hoping the pump was finished and everything was ok. pulled off the upper plenum to check the csfi and lo and behold 5 oily poppets and 1 clean one. i wonder which one is leaking? any fixes for a leaky poppet or is it easier to replace the whole unit? thanks for any help!

Check the engine codes, the computer will point to the problem.

What was the fuel pressure?

If it is below 61-66psi with the key on and engine off, you have found your problem.

my fuel pressure was 59 psi with the key on engine off, 54 while running. i took the csfi unit off last night and brought it to my buddy's shop and cleaned it up and let it soak overnight, gonna re-assemble it today and hope that it works! i'll let you know if it's still alive later!

Fuel pressure is low. Should be around 61-66psi.

Replace the fuel filter.

If it is below 61-66psi with the key on and engine off, you have found your problem.

You should be more specific when telling people what their pressure should be. If it takes them longer than 2 seconds to check the pressure, the pump will shut off and the pressure will drop. If they don't know everything to check for, they will think they have a fuel problem when they really don't. This is according to GM spec:

When you turn the key on, the pump runs for 2 seconds. While the pump is running the pressure should be 60-66psi.

When the pump primes and shuts off (engine still off) the pressure should hold steady between 55-60psi.

With the engine running the pressure should drop 3-10psi depending on engine speed due to vacuum on the regulator.

You should be more specific when telling people what their pressure should be. If it takes them longer than 2 seconds to check the pressure, the pump will shut off and the pressure will drop. If they don't know everything to check for, they will think they have a fuel problem when they really don't. This is according to GM spec:

When you turn the key on, the pump runs for 2 seconds. While the pump is running the pressure should be 60-66psi.

When the pump primes and shuts off (engine still off) the pressure should hold steady between 55-60psi.

With the engine running the pressure should drop 3-10psi depending on engine speed due to vacuum on the regulator.

The pressure is supposed to be 61-66psi with key ON, and the engine OFF.

This is what both repair manuals and the service manual says.

We discussed this in a previous thread and the true answer is 61-66psi for a 1996+ fuel injection system.

When you test fuel pressure, you test the prime, that is why it is key on and engine off.

I said nothing wrong by doing this and if you have a problem with my advice, I can easily bring in a GM Mechanic to back what I stated.

What I posted is correct. It is taken from the GM manual. Have your mechanic friend look it up. Tell him to read it carefully. It says that during Key On, Engine Off, the fuel pressure should be 60-66PSI with the fuel pump running by using a scantool to keep the fuel pump running.

It shows 55-60PSI for Key On, Engine Off, after the fuel pump turns off from its initial prime. It states that 55-60PSI should be were the fuel pressure is once the fuel pump turns off and the system stabilizes.


So you believe that the pressure will be the same even when the pump shuts off? :grinno:

What I posted is correct. It is taken from the GM manual. Have your mechanic friend look it up. Tell him to read it carefully. It says shows that during Key On, Engine Off, the fuel pressure should be 60-66PSI with the fuel pump running by using a scantool to keep the fuel pump running.

It shows 55-60PSI for Key On, Engine Off, after the fuel pump turns off from its initial prime. It states that 55-60PSI should be were the fuel pressure is once the fuel pump turns off and the system stabilizes.


So you believe that the pressure will be the same even when the pump shuts off? :grinno:

You always test fuel pressure when the fuel pump is priming.

Why would you not check the fuel pressure when the pump is not running?

Your point is moot and you are nit-picking what I am saying and picking it apart so you can find something wrong with it when everyone knows you test the pump when it is running like everyone else here does.

If not, why would we turn the key on.

Thx.

My point was the pump only runs for 2 seconds when the key is turned on, after those 2 seconds the pressure falls below what you say is normal, if people don't know what to look for, they may think that their pressure is low.


Also they should watch the pressure after the pump shuts off, to make sure it doesn't drop immediately, which would indicate a leak.

My point was the pump only runs for 2 seconds when the key is turned on, after those 2 seconds the pressure falls below what you say is normal, if people don't know what to look for, they may think that their pressure is low.


Also they should watch the pressure after the pump shuts off, to make sure it doesn't drop immediately, which would indicate a leak.


Pressure will not drop immediately after the pump has stopped priming.

It will hold for quite a while and should only bleed down over extended periods.

If not, there is a leak in the system or the pump is poor.

:) isn't that what I just said?

It shows 55-60PSI for Key On, Engine Off, after the fuel pump turns off from its initial prime.

No , this is what you said.

You are stating after the pump shuts off the pressure will drop 5-10psi immediately.

That isn't what you quoted in your response.

To clear it up though, Yes the pressure will start to drop to immediately after the pump shuts off. After the initial drop it will hold steady at 55 - 60 psi.

For someone who is suppose to be a fluid engineer, one would think that you would know that fluid pressure drops when the pump stops.

That isn't what you quoted in your response.

To clear it up though, Yes the pressure will start to drop to immediately after the pump shuts off. After the initial drop it will hold steady at 55 - 60 psi.

For someone who is suppose to be a fluid engineer, one would think that you would know that fluid pressure drops when the pump stops.

For someone with an arrogant attitude (aka you) will note that with a fuel pressure regulator on a closed system a pressure drop will not happen as drastically as you are stating unless there is a large leak somewhere.

Drop the smartass attitude.

For someone with an arrogant attitude (aka you) will note that with a fuel pressure regulator on a closed system a pressure drop will not happen as drastically as you are stating unless there is a large leak somewhere.

Drop the smartass attitude.

I'm the one with the arrogant attitude? :rolleyes:

I'm not claiming that there will be a drastic change. 5 psi isn't a drastic change from 60 - 66psi. This isn't just me stating this, I am stating what GM says.

I don't have a smartass attitude, even if I did you don't have worry, this is my last post in this thread, my point has been made. This wasn't intended as an attack against you, it was merely an attempt to make sure people coming here for help get the right information.

For someone who is suppose to be a fluid engineer, one would think that you would know that fluid pressure drops when the pump stops.

THAT was a cheap shot and a low blow and was not warranted.

That is a remark from a smartass pulling attitude.

My opinion stands.

This was an informative post. I think my question has been answered, although I want to make sure. I have a '97 Blazer, fuel pressure is at about 45 - 50 psi when key is turned on. When started pressure is at about 50 psi. It runs fine as long as it is cool outside. When temperatures are above 85 degrees and heat builds up, it dies. I can get it to start again, but it has to turn over many times. Is it the fuel pump? What does the temperature have to do with it? It makes no difference if it has a full or 1/4 or less tank of gas.

on a lighter note, my problem has been isolated to my accel wires...apparently after i had changed every other electrical piece on the truck, i gave up and brought it to a mechanic friend of mine and he diagnosed two bad plug wires. got my wires warranteed and truck runs wicked now.