fuel pressure issues
 

weird issue: 4.3 V6

2002 Blazer Jr., has trouble starting sometimes, it will crank repeatedly and then eventually start. Aftermarket anti-theft device installed.

I suspect fuel pump but lets find out what the pressure is 1st. Put on the gauge, crank engine. 10psi. Whoa! I thought for this car fuel pump pressure should be around 40psi(I m thinking Ford Multiport systems), but nope. If you have the Vortecs fuel pump pressure should be ~60psi and in the TBI it should be 9-14psi. OK, fine, but everything after 1996 has the Vortec in it, so I m lost as to why this Blazer, stuttered during cranking initially BUT started AND has fuel pressure of 14psi.

I originally suspected the check valve in the pump is bad and I still do but with pressure that low the car shouldnt even start for a Vortec.

Once it is running it will run fine but over night, it has a long cranking cycle. I left the gauge on it so tomorrow morning we can see what the bleed down is and what the buildup is.

Man, I m stuck. This car is A 2001 NOT a 2002 but still it IS a Vortec. Fuel Pressure reads 15psi. The car shouldnt even be running at pressure this low for a Vortec. The gauge is new, this was the 1st time I have used it. I hate to recommend throwing parts at something but seriously??? If the system should be in the 60s and it is at 15, BUT RUNNING? Nuts.

I would try a different gauge, new does not mean good. Or try it on a different vehicle (one with no problems). When it is running good what does your fuel pressure gauge read?

I m on it.

My thinking is that it is NOT fuel related but electrical(the hard starting symptoms). These guys when they install the aftermarket anti-theft system they splice into anywhere there is power. And I dont even know what kind of system this is. If it is one of those with a fuel cutoff, this thing could be sucking excess current from the fuel pump circuit. Who knows? This is why I hate aftermarket theft systems. To me it could also be the PASSKEY system.

Tried it on a Chrysler Town & COuntry and it read 10psi on crank and 15psi when running. Too low. I gave it a couple of whacks on the intake and it jumped up to 52psi which is factory spec for a Chrysler minivan. Tried it back on the Blazer, read 54psi. Higher reading but I dont know how accurate it is.

Don't trust that gauge it may very quickly lead you down the wrong path.

Yea, I do agree.
In any event, I still think it is the aftermarket anti-theft system which is causing the hard starting occasionally. But the guy, who lives down the street is going to wait until the symptom becomes more permanent. At least then you can get a surefire repeatable condition.