I have a 1998 4x4 blazer with 4.3 engine. We just put new gas tank and fuel pump on it and it ran for a couple of days then sat for the weekend. Came home and tried to start it and it acts like it`s not getting fuel. Replaced the filter and still no go. It will start if you put gas in the throttle body but will quit as soon as it uses up that fuel. Gas is getting to the pressure release valve. What is between that and the throttle body that might be stopping the flow of fuel??

 

Fuel pressure regulator, and spider injection. Check the pressure at the relief valve using a fuel pressure tester.

What brand pump did you use? If it was anything other than ACdelco or Delphi you're probably going to be replacing it again. The problem with other brands is the pump itself is "universal" and may only produce 54-56 psi...which under certain circumstances WILL be enough to start/run the vehicle. But they are sensitive to pressure and like to see 60+ psi to run properly

 

O.K. everyone says pressure should be at least around 60 psi but my book says it should be 9-13 psi. for the TBI system which is what MY truck has. The book shows those higher readings for the MFI ,CMFI and the CSEFI systems.

 

If you are working on a 1998 truck as you stated in the original post, you DO NOT have a TBI engine, but rather, the newer CMFI (aka CSEFI, SCFI, etc) engine.

 

Well it's definitly a 1998. I have the oringinal owners manual complete with window sticker. It was "born" in aug. 1997 but is a '98 model. My husband who is NOT a "professional "mechanic but has always worked on his own cars (his father WAS a mechanic) says it's definetly a throttle body. Now we are talking about a truck that for some reason had a 19 gal. gas tank that was only used on a few trucks for some reason. Do you think for some reason the fuel system could be an oddball setup too? The VIN is 1GNDT13W1W2109117. I know when getting the fuel pump they had to know the vin to get the right pump. When we got the first pump we gave them" '98 blazer 4x4 4-door, 4.3" and it wasn't right and they said what's the vin. we told them and they said OOOOO that's a different one!

 

That engine does have a Throttle Body (TB), but not Throttle Body Injection (TBI) Your TB is basically a pivoting plate to control airflow. The fuel is injected by means of 6 injectors centrally located and squirting fuel directly into each intake port through hoses and nozzles (affectionately called Spider Injection). Fuel Pressure for TBI is relatively low (9-13psi ?) but for SCFI the system requires 55-60+ psi.

 

There was only one fuel injection system in '98 and that is the SCFI (sequential central fuel injection) which could also be called CMFI (central multiport fuel injection) or CSEFI (central sequential electronic fuel injection).

For it to be TBI (throttle body injection), the injectors would have to be in the throttle body. If you and/or your husband were to pull off the plastic intake piping that is attached to the top of the throttle body, you would see that there are no fuel lines or injectors to/in the throttle body.

The tank size does matter when sourcing a fuel pump, but that is the only variable.

 

Yep, Just throttle body not TBI. Thanks, didn't know there was a difference. Figured if there was a throttle body that that would be the injection system. Appreciate the insight. Now gotta find someone with a pressure gauge to check that. Now, just to skip ahead, IF the pressure is o.k. what would be the next thing to check that could be the problem? OR is that the only possible answer.

 

Till you get that FP gauge:

Can you hear the pump at key-on? Should run two seconds when you turn ign key on.
if not:
Swap the relay with one next to it. Will be numbered identically

if no change -
find 2-4 foot 2x4. smack tank with it flat just after key-on {takes 2 people, natch}

With Multi meter probing fuse block {will need to carefully raise relay enough to get to pins, maybe remove adjacent relay} check pin 87 for 12v for 2 sec, at key on. if good then remove batt neg terminal and check pin 87 for less than 6 ohms

Pin 87 is right side and closest from over the fender, pin 30 is rt side toward engine. IOW the relay is shown as from the fuse block looking up.

Also if the FP connector was square, 2x2 pins, rather than flat.. 4 in a row.. good chance that is your problem. Why they changed it.

 

Nowhere in the original post does it say TBI. I'd say the op just assumed gas came from there since that's where they poured fuel to get it to run.

No need to nitpick crap to death.