Starting problems

Hey there, new to the web site. Glad I found it. I am having problems with my Blazer. It wont start. It cranks but doesnt start. I removed the fuel pump and tested it. Seemed ok. Reinstalled it replaced the fuel filter and it started right up. Went to start it the next morning and wouldnt start. I checked voltage at the pump and am getting nothing with the key in the on position. All fuses and relays seem to be ok but the manual says if Im having problems troubleshooting the fuel pump circuit to check the oil pressure switch. But it doesnt tell me where the heck that switch is located. Can anyone tell me where it is? I have the 4.3 liter V-6. Thanks in advance for any help. Please respond soon. My wife is without our main vehicle.

Are you hearing the pump priming when you put it to the first position before start.

You shoul dhear it prime for 2 seconds.

No it is not getting any voltage. After I put it back together the first time I did hear it and it started right up, but this morning my wife went to start it and it did the same thing it did before. When I pulled the connector off the pump I found that I dont have any voltage on the plug no matter what position the key is in.

No it is not getting any voltage. After I put it back together the first time I did hear it and it started right up, but this morning my wife went to start it and it did the same thing it did before. When I pulled the connector off the pump I found that I dont have any voltage on the plug no matter what position the key is in.

I would check the grounds and maybe replace the relay.

My most recent findings are that I have a trouble code P0452 Fuel tank pressure sensor low voltage. Is that the second connector on top of the fuel pump? Also I am still trying to locate the oil pressure switch. I have no voltage to my pump. If I hook it directly to a 12VOLT source it runs fine. I am trying to trouble shoot the fuel pump circuit. All fuses are good and as far as I can tell my fuel pump relay is ok, I tried switching it with an identical relay that I know is good. Any help?

When you turn your key to the on position. does all your indicator lights light up? Oil, ABS, Volts, ect. If not, Then I would say that your ignition switch is bad.

Yes all the lights light up. When I put my meter on the fuel pump relay with the key off I read nothing but when I turn the key on I get 12volts on the relay but it doesnt make it to the fuel pump. Im not sure where im losing it. The wiring diagram in my repair manual tells me the routing but following that through the engine bay and then under the vehicle will be a chore. Im sure you know that.

My most recent update. I checked and triple checked the fuses and relays. All are good. What I do seem to have though is this. I took the relay out and applied voltage across the terminal under the relay coming from the fuse block to the terminal going to the fuel pump. I had 12 volts at the pump. I then put my meter across the terminals at the fuel pump and put the relay in. I turned the ignition to on and watched the meter. It went to 7 volts very briefly. Not enough voltage or even long enough for the fuel pump to prime the system. When I turn the switch off the voltage goes to 11 volts briefly. Its not the relay, as I tested that relay and tried other identical relays in place of it. What do you guys think? Im thinking a worn ignition switch or something in that area of the system.

Check the relay connecting socket. You mite have a loose connectior or wire behind. With the relay in and the ignition on. Test your voltage from behind the relay socket. Input and output.

When you applied voltage to the relay and you had 12 volts at the pump did you hear it turn on to prime the system? If not i would try a new pump. I've been told by a couple mechanics that at least for my truck (I have a 93 full size blazer) the fuel pump is notorius for going bad i dont know if this would be true for yours but its worth a shot.

Yeah the fuel pump would be the next step. Im just trying to leave that for last chance since a new one is $266. I checked voltages at the relay and under the relay I can get 12 volts at the relay but it just doesnt make it back to the pump. The most ive been able to get at the pump is 10 volts but not for the expected 2 seconds for priming. Im not sure, I might just have to put it back together and take it to a repair shop. UUgh!

I got the truck running. I found that I had 10 volts to the pump but after charging my battery I got 12volts. Why would the battery be strong enough to crank the engine or just about anything else besides primming the pump? Does anyone know? Also Im getting a code P0452 EVAP fuel tank pressure sensor low input. Where is that sensor located? Is it in the charcoal canister?

So after charging the battery is only putting out 12 volts?

It shoudl be putting out 12.8-13.5 volts fully charged.

How old is the battery?

So after charging the battery is only putting out 12 volts?

It shoudl be putting out 12.8-13.5 volts fully charged.

How old is the battery?
No Im not saying that Im getting 12 volts at the battery. Im getting 12 volts on the fuel pump connector.