1997 S-10 Blazer LT 4x4 Starting problem

I have a 97 S-10 Blazer LT and for the past two weeks I have experienced problems with starting when it is cold in the morning. The fuel pump is priming and I put a pressure tester on the service port and got 44psi while cranking and when I let it set for about ten minutes it had dropped to 38psi. I have the TBI with one injector. Now it has become virtually impossible to start. If I spray throttle body cleaner in the trottle body and try, it starts just fine and it runs very well. No hesitation during acceleration or anything. It just dont want to start. I am getting no SES signals and it runs very good... if I can get it started! I do not think my injector is spraying fuel while it is cranking to start. I smell no gas during cranking. Does anyone know what the problem is? I am thinking in the distributor or whatever sensor tells the injector to fire during cranking. Can anyone help me? Thanks

If only getting 44Lbs sounds like fuel pump is probally the problem to me.

Yeah 44 is way low buddy. You want to be up at 60 at least. I'm surprised you're able to start your vehicle at all.

Does your pump prime when you turn the key to the on position? Have you changed your fuel filter lately?

Do a tune up as directed by this thread and come back if you still have problems:
http://www.automotiveforums.com/vbulletin/showthread.php?t=453370

ever replaced the fuel filter?


I have a 97 S-10 Blazer LT and for the past two weeks I have experienced problems with starting when it is cold in the morning. The fuel pump is priming and I put a pressure tester on the service port and got 44psi while cranking and when I let it set for about ten minutes it had dropped to 38psi. I have the TBI with one injector. Now it has become virtually impossible to start. If I spray throttle body cleaner in the trottle body and try, it starts just fine and it runs very well. No hesitation during acceleration or anything. It just dont want to start. I am getting no SES signals and it runs very good... if I can get it started! I do not think my injector is spraying fuel while it is cranking to start. I smell no gas during cranking. Does anyone know what the problem is? I am thinking in the distributor or whatever sensor tells the injector to fire during cranking. Can anyone help me? Thanks

If only getting 44Lbs sounds like fuel pump is probally the problem to me.I appreciate your help but I was wanting to know if you are sure about the fuel pressure needing to be around 66psi? I called the local auto parts store and was told that it should be around 42-46 psi with a bleed off of 3-4 psi. the 44psi I get is with the key on, not while the engine is cranking, but I do know that the injector isnt spraying when I crank the engine. So when I posted this question I was thinking that my fuel pressure was within specs. I have been told three different pressures. I have the Vortec 4.3 with TBI and I think it is the single injector type. I do not have the spider injection (plenum). My fuel pump is priming when I turn on the ignition and I agree, if the pressure is suppose to be around 66psi then it is my pump (which I have already purchased) but I didnt want to go through the trouble of dropping the tank if it could possibly be something else. The truck runs good once I get it started. Would it do this if the fuel pump was bad?

These are takem directly from my haynes manual..

Specs are:

TBI system - 9-13 psi, decrease 3-10 at idle.

MFI system - 41-47, decrease 3-10 at idle.

CMFI system - 58 - 64, decrease 3-10 at idle.

CSEFI system 55-61, decrease 3-10 at idle.

The fuel presssure is low. All the 96 + came with CSFI. The CSFI engines look like they are TBI. They have a throttle body on top of the engine, but they are not injected through the throttle body. They have six injectors centrally located inside the plenum (out of sight). You can't see the injectors from the outside and it has been mistaken by many to be TBI.

The Haynes manaul lists the wrong specs, the fuel pressure spec for CSFI is:

Key On Engine OFF (during the intial 2 seconds when the fuel pump is running - 60 - 66 psi

Key On Engine OFF (After the fuel pump shuts off) - 55 - 60 psi

Key On Engine running it should drop 3 - 10 psi


Just to verify that you do indeed have a CSFI, check the eighth digit on your VIN # and make sure that it is a "W".

The fuel presssure is low. All the 96 + came with CSFI. The CSFI engines look like they are TBI. They have a throttle body on top of the engine, but they are not injected through the throttle body. They have six injectors centrally located inside the plenum (out of sight). You can't see the injectors from the outside and it has been mistaken by many to be TBI.

The fuel pressure spec for CSFI is:

Key On Engine OFF (during the intial 2 seconds when the fuel pump is running - 61 - 66 psi

Key On Engine OFF (After the fuel pump shuts off) - 56 - 60 psi

Key On Engine running it should drop 3 - 10 psi


Just to verify that you do indeed have a CSFI, check the eighth digit on your VIN # and make sure that it is a "W".

Thanks for clarifying that mine is a CSFI. The eighth digit in my VIN is a "W" so I am assuming that is what you mean....I have the CSFI on my Blazer. So with that cleared up, I guess I should replace the fuel filter and recheck the pressure?, then if its still low, drop the tank and replace the fuel pump assembly? Is this the right course of action? And the last spec you gave me "key on engine running" the pressure should drop 3-10 psi from 56-60 psi, correct? Thanks for your help.

Yes, if the eighth digit is a "W", then you have CSFI.

These are the steps that I would take:

1) Make sure that the battery is good and completely charged.

2) Change the fuel filter.

3) If it's still low, I would then check the pressure at the fuel filter to rule out a faulty Fuel Pressure Regulator

4) If it is low at the filter, then I would move on to the pump.

Just wanted to a little note..... When I listed the fuel pressure spec I did it from memory and was a little off I listed 61 - 66 psi with the pump running, it should be 60 - 66 psi. And I listed 56 - 60 psi with the pump off, it should be 55 - 60 psi.

I missed your last question in your previous post:
With the engine running the pressure should be 3 - 10 psi lower than with the Key On Engine Off Pump Running (60-66)

The middle number listed (55-60) Is only to determine the integrity of the system. It should hold that pressure and not bleed down. If the pressure bleeds down it means that there is a leak in the system.

Just wanted to a little note..... When I listed the fuel pressure spec I did it from memory and was a little off I listed 61 - 66 psi with the pump running, it should be 60 - 66 psi. And I listed 56 - 60 psi with the pump off, it should be 55 - 60 psi.

I missed your last question in your previous post:
With the engine running the pressure should be 3 - 10 psi lower than with the Key On Engine Off Pump Running (60-66)

The middle number listed (55-60) Is only to determine the integrity of the system. It should hold that pressure and not bleed down. If the pressure bleeds down it means that there is a leak in the system.
thanks--I appreciate your help and advice. Guess I will be changing a fuel filter tomorrow. I'll post how it turns out. Thanks to you all.

thanks--I appreciate your help and advice. Guess I will be changing a fuel filter tomorrow. I'll post how it turns out. Thanks to you all.
Well the Blazer is back up and running. I replaced the fuel filter and tested the pressure while I had the line off the filter. It was just 46psi, so I dropped the tank and replaced the pump assembly. That fixed it. 64psi on the fuel rail service port. Starts just fine and runs very well. The job wasnt that difficult either. I have put fuel pumps in S-10 PU Trucks before and they were harder than this Blazer. Thanks for all the advice and help figuring out my problem.

Nice Job. :thumbsup:

I'm glad to hear that you got it fixed.