I have a 1999 4.3L 2 door 2wd s10 blazer.......i drove it to my kid's school, shut it off for about 5 min. and wouldn't start afterwards. The gas gage hasn't worked in years..(reads at full, less than that erratic and won't go below half). Based on my normal miliage i should have been about 60 miles before i ran out of gas, but that was what it felt like. It started for half a sec. and died. It rolls over but doesn't attempt to start. I put gas in it but I don't hear the fuel pump running with the key on or when trying to crank the engine. I've checked the fuses, and swapped relays with a diff. one..I can also feel the fuel pump relay pick up like it should and drop out about 2 sec after key to off. I checked for spark...good. and changed the spark plugs because they were overdue. I just changed the fuel pump assy/fuel sending unit. Gas gage works now. still does not start. How do I check the oil pressure sensor, the camshaft pos. sensor and which would cause the fuel pump to not start at all. I have also read about an oil pressure bypass connector in the corner of the engine compartment. I can't find it to jump from the battery to that connector. Any further help would be appreciated. One more thing I did change the connector plug at the fuel pump. For reference. the old fuel pump resistance was < 1 ohm....the new one was 28 ohms. Any suggestions?

 

Start with verifying the fuel pressure with a gauge. No need to look at any other further than that. On the newer trucks, there is no interaction between the oil pressure sending unit and the fuel pump.

Does the new pump run when the key is turned on?

 

A couple of more things.....I did change out the fuel filter as well. As a note when i went to bleed off pressure first, there was no pressure at the fuel rack gage connection or at either side of the fuel filter. The fuel filter was significantly harder to blow through than the new one...so it was due. I tried this before replacing the fuel pump...The lack of pressure along with no audible sound from fuel pump and no indication of relay problelms led to my decision to replace the fuel pump.

 

Did you miss my post above?

 

The fuel pump doesn't turn on and there is no pressure to bleed off at the gage connection after trying to start the blazer.

 

Then have you verified power to the pump?

Also, what brand of pump did you install?

 

its an airtex bought from advance......I was only getting 6 volts with the old connector when trying to start the car....while voltage to sending unit was 11. something. i didn't have small enough leads yet to check the new connector ....should have different leads tomorrow. I barely have the tank brackets in place with the bolts just started by hand so i can still check tomorrow. I wasn't getting any volts when the key was just in on. Not sure if I should have gotten voltage as the pump picks up to build up pressure in preperation to start. thanks for the quick replies by the way...i still had the screen up....without refreshing the page i didn't see your response...sorry

 

I checked the voltage at the fuel pump. With the key on, i have 0 volts. While trying to crank it it goes to 0.3 volts. when you stop cranking it stays at 0.3 volts for a couple of seconds until the relay times out. You can hear the relay click and the voltage goes back to zero. I'm seeing 5 volts across the terminals for the sending unit. I have already swapped the relay earlier.....any suggestions? I'm gonna check to see if the lines are grounded going to the pump. Would any of the sensors (crank shaft or cam) going bad cause the drop in voltage?

 

another question....where do you hook up a code reader on this year? and is it the standard connection type for recent code readers....or is it predated the standardized hook up.?...thanks btw...this has been my first thread here........and just browsing i've had almost every common issue that most blazer owners have endured...thanks for all the help guys.

 

You have a wiring problem as you are getting some voltage, but not the proper amount. Check the voltage at the relay.

Here is the wiring schematic:

Fuel pump connector view (original connector):


You want to test for the proper voltage at the terminal that corresponds with Pin 30 on the relay. This terminal should be hot at all times and is supplied with battery voltage through the ECM B fuse (20A). If you have +12V at this terminal, I would run a continuity test and measure the resistance between the terminal corresponding with pin 87 and pin B in the fuel pump connector. Also do a continuity test to ground with the relay removed. It should test open to ground (no continuity).