96 S-10 Blazer runs fine won't start

96 S-10 Blazer runs fine won't start Have to use starting fluid every time to start ,brought it to two shops and no one can figure it out ,good fule pressure , and full tune up ,Help Please

Without checking wiring diagram, the first thought may be oil sending not working properly. Keeping it from priming up when key turn on.

Or weak fuel pump. Define good pressure.. Could also be weak spark.

Without checking wiring diagram, the first thought may be oil sending not working properly. Keeping it from priming up when key turn on.

On these vehicles the oil pressure switch isn't used for the initial prime. It is wired in parallel with the relay. When the key is turned on the PCM commands the fuel pump on for 2 seconds through the relay. The oil pressure switch serves more as a redundant system on these vehicles, in case the relay fails the switch will close and supply power to the pump when the oil pressure reaches 4 psi. The 4 psi would be achieved after an extended crank time or the use of starting fluid.

I betting on low fuel pressure. Most mechanics don't know how much pressure it takes to actually run these things. If your battery is weak or your pump is not operating within spec., the voltage will drop enough while starting to not allow the pump to achieve the proper pressure.

The first thing to do is make sure your battery is fully charged.

When you turn the key on, (engine off) the pump runs for 2 seconds. While the pump is running the pressure should be 60-66psi. If the pump doesn't come on when you turn the key on, check the fuel pump relay.

When the pump primes and shuts off (engine still off) the pressure should hold steady between 55-60psi.

With the engine running the pressure should drop 3-10psi depending on engine speed due to vacuum on the regulator.

Thanks guys, have a weak battey but thought it was from trying to start it all the time ,going to get a battery Monday and ask the mechanic what fule pressure was . Again thanks for your replies I'll let you know how it turned out.

i had the same problem checked fuel pressure and was good. this got the best of me for 2 to 3 months. would crank and crank and not start, but some days it would start great like there was never a problem. everyone on here kept saying fuel pump is bad. i disagreed over and over because that is the first thing this board points to for some reason.

but bud it ended up being the crank sensor. replaced it and not a problem since. crank sensor will cause more problems than you think. its a bummer its not a checkable sensor at a autozone or somewhere.

also make sure you reset computer by disconnecting battery for a few after any sensor replacment, that almost got me after i replaced this sensor also.

What is the fuel pressure.

And stop starting it with starting fluid, that is murder on the cylinder rings and will overheat the pistons.

Had fuel pressure check yesterday ,Was 40 PSI at prime giong to replace pump today ,just like to say thanks to everyone how helped ,it's good to know there is someone to help when you need it.
Thanks, Chaka234

Definatly low fuel pressure, 40 won't kick open the poppet. Needs to be at the very least 60 at prime.

You took it to 3 mechanics and they couldn't figure that out? I wouldn't let them work on my car again, that's for sure.

While you're at it, change out your fuel filter. Less hassle down the road.

If the new pump doesn't help, you know the fuel pressure regulator is shot.

i had the same problem checked fuel pressure and was good. this got the best of me for 2 to 3 months. would crank and crank and not start, but some days it would start great like there was never a problem. everyone on here kept saying fuel pump is bad. i disagreed over and over because that is the first thing this board points to for some reason.

but bud it ended up being the crank sensor. replaced it and not a problem since. crank sensor will cause more problems than you think. its a bummer its not a checkable sensor at a autozone or somewhere.

also make sure you reset computer by disconnecting battery for a few after any sensor replacment, that almost got me after i replaced this sensor also.
I am having the similar problem, on and off, some days it fires in the first try, sometimes it just crank and crank and wont start, this morning, it cranked OK, after a couple of cranking, it almost started, but did not. I see no Service Engin Soon light.

This is my second car, so I just keep trying whenever, it will start OK after a day or two. Then it will be good for a few weeks, then won't start asgin.

What and where is the crank sensor?

Thanks for any help. Oh, mine is 91 Olds Bravada 4.3 TBI.