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95 Blazer Vortec starting problem.

I can not get my 95 Blazer Vortec to start. Before it would not start it would not stay running if you push the throttle past 50%. It would act like it was not getting fuel. I have heard the Injection system was notorious for going out. But I also heard of people replaceing them and still had the problem. What I dont know is if they replaced the fuel pressure regulator. I do know I am at my wits end with this. I have replaced Cam Shaft Sensor. Throtle position sensor, The Ignition Module, and done a complet tune up. throwing money at it is not an option. I need an answer.

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1995 Vortec 4.6L V-6 requires at LEAST 60 PSI before start. A new tank pump will pressurize the system within a second up to 62~65 PSI just before start. After engine start and it settles into idle, fuel pressure may drop to about 55~57 PSI, less than 50 PSI at idle will tend to make engine stumble and stall. Low pressure too @ start can cause hard starting, no starting at all.

Fuel regulator having gone bad will give one the distinct odor of raw gasoline near the engine and nose of the vehicle. It tends to spray fuel all inside the intake plenum too, draining into oil, thinning it dangerously. Easiest way to check for fuel regulator or fuel lines/injector poppet tube leaks is to pull the Vortec name plate off the top of the engine - you'll need a No. 35 Torx to get it off. Under that is a round plastic part with a clip and wire leads going to it, this is your upper intake manifold tuning valve. Removal of that valve and looking inside the plenum with a small flashlight will tell the truth.

A strong odor of gasoline is a sure sign of a leak. Which SIDE that the leak is on can indicate where your issues are. A leak on the left side, washing all black carbon off the intake and leaving it a golden color is more than likely a regulator leak. Fuel washing on both sides is regulator, poppets and possibly fuel lines. (All lines are teflon/plastic and will eventually degrade and crack) Fuel washing on the right side of the plenum (Driver's side) is poppets and/or fuel lines.

*IF* you have high rev missing or no power at or above 2000 RPM, check/replace fuel filter. Fuel filter on these trucks needs to be swapped every year, two years tops. *IF* You replaced a fuel pump in the bracket, rebuilding your sending unit w/new sock and pulsator, one should replace fuel filter, and fuel injection system. The new, strong pump will likely blow apart all of the aged, brittle plastic inside the plenum.
GM AC/Delco names the parts as follows:

Injector "Kit" For CPI Vin "W" engines - MAXI injector, fuel regulator, poppet valves and integrated lines for poppets. One piece, but really an assembly.

Nut Kit: This is the set of white teflon fuel supply and return tubes to the injector/regulator kit above - connecting to rear of plenum and external to the block. It's stainless steel up to the back of the engine, plastic inside.

Upper Intake Plenum Gasket. DO NOT remove and reuse the gasket no matter how good it looks. These engines are sensitive to air leaks - extremely so. Even if you loosen the plenum bolts, remove and replace this gasket. You will DEFINITELY need this if you have to go in there and swap the CPI/MAXI injector kit.

I am no expert, but I had to rebuild the entire system after a fuel tank sending unit died. The new pump destroyed the aged 10+ year old CPI injector, first pin-holing my fuel regulator and then bursting three out of 6 poppet injector lines for me. Not including the tank work, replacement of all the plastic inside the upper plenum and a new gasket took just 90 minutes of lazy garage work and a 10mm deep socket wrench. Good luck!

Posted on Jul 05, 2012

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I replaced fuel pump,and filter,spark plugs/wires , rotor button, and spider injector still wont run...its a 94 blazer someone checked pressure for me by putting a screw driver in the valve and fuel shot up but i need a gauge.

Posted on Oct 16, 2009

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First thing to do is a fuel pressure chk. bad fuel pump they are notorious for that to, even if it dosent run you can still do pressure test. a few pounds under and it will not run, on injection its critical, i don't know if you can hear pump run or relay click when you turn on the key or not, if relay dosent click pump won't run, if pump runs don't be fouled by thinking its alright just because you can hear pump run, they can sound like there running, but they may not be putting out any pressure or at least enought. i don't remember what the pressure is but you can find out at your local auto parts store. you could be right about the regulator, but do the test, at the very least you can elimanate that and narrow it down.

Posted on Jan 28, 2009

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First you need to have your fuel system tested. It sounds as though the relay and pump have gone out. When you turn the ignition to on the pump should energize for 2 seconds and stop. The pump will deliver fuel after startup. Poor performing pump equals poor performing vehicle. With the vehicle not staying running when it did start, I would check the fuel pressure and then replace the pump. You can check the fuel pressure regulator by pulling off the vacuum line and see if you have fuel in the line. If you do the regulator is shot. The fuel pump relay also needs to be checked for operation especially if the fuel pump is not working. Also check your rollover valve to be sure it has not tripped.
RPM Norhtwest

Posted on Jan 28, 2009

  • cavelier0101 Aug 07, 2011

    Mine is acting this way too! Also a '95 Blazer. Mine Will start up and run til I get around 2000-2500 rpm. There is alot of noise (electrical snapping noise) coming from the relay. I'm gonna try blowing the relay out w/ airhose & cleaning with eather or alcohol. Sometimes the gunk will cause a bad connection.


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