97 with fuel pump issue

[Korn1699]

Last weekend it just would crank and not fire adding fuel directly to the engine allowed it to start. I had tried swapping the relays to see if maybe that relay was bad (since they are all the same). That didn't work, but when I tried them a few hours later, all of them suddenly started working... I replaced the relay anyway since it wasn't that much to replace and to just rule it out because my starter relay had acted strange like that before too when it was going.. I didn't have any problems the next 3 days, but this morning, it wouldn't start and is doing the same thing.

I have the 4.3L, and I don't hear the pump when the key is in the run position. My fuse isn't blown. My oil pressure gauge is at 0 or almost there when it is in run, although I don't know if that is normal before the engine runs or not. I know that the sensor for that does effect the fuel pump. When I test the connections of the relay, I only get power all the time to the lower right connection, but nothing else, even when it is in run. Does anyone know what that means? Could it be the oil pressure switch? Is it ok to bypass that and test it that way to see if it is an issue with the oil pressure?

[matthew24u]

when you turn the key to the run position u will here the pump relay click on and 2 seconds or 3 later it will click again & shut off so have someone cycle the key while you listen for that at the relay. if that is working fine then go by the tank and have them cycle the key again you should here the pump run for three seconds and shut off if the relay works but pump won`t run during the time of the relays cycle the fuel pump is most likely bad. but before you pull the tank make sure you have power traveling to the pump through the power supply wire connecting to the tank. signed always stuck in diagnostics!

[Korn1699]

Ok, I think I have heard the relay click. I haven't heard much of anything from the pump though, at least when in the driver's seat. I used to be able to, but I don't now. A couple times during all the things I tried, I think I heard a click from back there, but not the pump running. I plan on trying to check the power to the pump tomorrow. I tried bypassing the oil switch today, just to see if that turned it on, but no luck there.. It looks like the power to the relay is correct too, as I was able to compare it to the 97 Jimmy that my dad drives, which is almost identical to my Blazer. Thanks for the help.

[Joe W]

I believe you are on the right track for diagnosis. I am not sure of accessibilty for the fuel pump in the Blazer, but if you are able to check voltage at the pump you can also try to apply 12 volts to the pump itself (after disconnecting all wires) using the hot to pump and ground to frame.

[Korn1699]

Thanks for the help. I ended up replacing the oil pressure switch because I didn't appear to be getting power back to the pump. It still didn't start (although was definitely getting power), so I had to take it to get a pump since I don't really have a good setup to do that here. I notice the oil pressure reading higher than it ever did since I got the Blazer last year, so maybe both died at the same time or it was just the switch and I somehow damaged the pump when I was trying to trouble shoot.. Anyway, it does work now.

[Rick Norwood]

Korn, I think you're on borrowed time. Go to Autozone and borrow a fuel pump pressure tester and check your fuel pressure. If and when you need a new fuel pump, DO NOT BUY AN AIRTEX PIECE OF CRAP PUMP. AC Delco is the only way to go. When did you last change your fuel filter?

[Korn1699]

Rick, the fuel filter was just changed within the last month. I got the fuel pump and tank replaced, and it has been fine since. I just needed the pump, but I thought that they should just replace the tank while they are in there too because with the rust around here, it would probably only be a year or two before that started to give me trouble too. I believe that neither part they put in was aftermarket.