Help, I have a second generation blazer(98) and my pump will not start up at all. I cannot believe it is burned out as the vehicle ran fine until I shut it off. It was running continuous, however in recent months.
Someone mentioned that the oil pressure sending unit shares the same circuit as a safety shut down feature in case of an accident. I would love to disable this feature!! I cannot find the oil pressure sensor on the 4.3 v6 for love nor money, even on wrecks in the junkyard that have no fenders.

Then there is the problem of not being able to find a fuel pump fuse anywhere. I have reversed the horn relay (under the hood fuse box) for the fuel pump relay which is identical. The horn works either way but the pump does not.
I have bypassed a rusty looking ground strap connection but still the pump will not run. What can I do??

Thanks,
Ken S.

 

I have a 98 and I dont have a fuel pump fuse either but if you look just out side the fuse box under the hood you might see a fuse just wired in right there if you do then tihs is what has happened the car dealership you bought the car for use to have on it what they call a black box which meens they could shut it off by the fuel pump if someone didnt make there payment. But if you dont have a fuse just sitting there thin look for a small black box on the left side ( if your sitting in the truck) with six wires going in to it and this could be the culprite or it could just be that the fuel pump has gone out completely.

 

Daddysblazer - Are you serious about the "You didnt pay so we turn your truck off box"?
Sounds like something out of the movies.

I would grab a meter and check for power at the fuel pump harness on top of the tank. Thats where it matters. (If there is power then forget looking for the fuse.) If there is power there and you dont have fuel pressure, you need to drop the tank and replace the pump. Pumps doing always die a slow agonizing death. Sometimes they run fine and then the next time they dont. Ive seen brushes worn out where they barely make contact on the commutator. Thats when you can smack the bottom of the tank and they make contact again.

Im curious why you would want to disable the oil pressure switch or more importantly the the inertial switch! They are safety devices! Imagine a collision where you are trapped in the vehicle. The fuel pump doesnt shut off but keep pumping fuel all over the smashed engine compartment where the wiring and everything else in crushed!

Not a good place to be!

 

You could do what this guy did..
https://blazerforum.com/forum/1st-ge...el-pump-62497/

Known facts some splices are problematical

 

I agree i wouldn't wanna do that or be there .

 

Oh yea, forgot to mention. The oil pressure sender is under the distributor.

 

Thanks guys for your input. Still, I just cannot believe that GM did not incorporate a fuse someplace. I suspect the pump is hatched but it is not rotating either way and must be either drawing a lot of power or none at all.
I just cannot get the middle line off the pump(plastic fitting) which is a different style than the other two.
It(fuel pump) is coming out and i am mostly there already. I could do the meter thing now just to determine whether the integrated circuit control regulator is working or not. It is tied in with my cruise control(something else I don't need or use). If replacing, do I remove the large attached tube from the box or at the throttle body??

As far as the safety oil pressure thing goes, I would love to know if my wonky oil pressure gauge is telling me that the safety feature is what is causing the problem now. Nobody has ever been able to find this oil pressure sensor unit on a blazer engine for the purpose of replacement, diagnosis or whatever.

These vehicles have far too much complicated wiring on them. Perhaps GM should have stuck with a mechanical fuel pump system and fuses instead of expensive black boxes full of circuitry.

 

Yes im very serious about this because (you know what im going to say something i might regret) why dont you just post your own opinion and keep my name out of it. Apparently you havent bought a new car in a while smart pants my wife has a car we got from gerald jones mazda that has that very item on it

 

Good Morning.
I dont have access to any of my blazers right now to look. I have a 97, 98, had a 99 and a 00. I assure you, there is a fuse someplace, just cant remember if its under the hood or in the dash.

Cruise control has no connection to the operation of the fuel pump.
Oil pressure sender is located under the distributor. Are you getting weird oil pressure readings? This may be something to look into if it is! If the oil sender is bad it could prevent the truck from running. That is why I suggested you check for power first.

I am not upset at all to see mechanical pumps go away. When they failed they could spew fuel all over the engine. Since they were not submerged in the fuel tank, they were prone to vapor lock and if you had run out of fuel, you had to crank the engine for ever to reprime the pump. The fuel pump design we were all used too could never create the pressures required to supply fuel injection. 7 psi was only enough to supply a carb. Carbs are fine, crud and required adjustments that most people couldnt perform. Modern fuel injection is constantly adjusting itself. This results in better economy, more power, easier starting ect.

If you find a schematic for your truck, follow the circuit for the fuel pump. The circuit is actually very simple.

Good luck with everything!

 

That is false!!


I assure you that the truck WILL crank up and drive just like normal even if the oil pressure sending unit is unplugged, inoperable, or even removed from the truck.

Don't believe me?
You say you have 4 Blazers, go unplug it and see what happens.

Think about it for a second, if it really did cut power to the fuel pump on low pressure you would have people cruising down the highway and if they are a quart or two low, it would just kill power steering and brakes, sounds very dangerous doesn't it.....

OP, I hope you find you're problem, but the oil pressure sending unit is not it.