I have a 1995 chevy blazer with a CPI 4.3 motor. It will not start without ether. It idles fine, but if you push the gas pedal down too hard it bogs, If you push the gas pedal down slowly it will reach about 2500 rpms before bogging. I just put a new fuel pump and fuel filter in it. Any ideas?

 

Start with a fuel pressure test. I suspect that you have a leaking FPR or supply/return lines inside the plenum causing a rich condition. If the leakdown test shows good results (no more than a 5psi pressure drop) and you have the appropriate (60+psi) pressure, then I would move to checking out the cat.

To check the cat, remove the O2 sensor directly ahead of the cat and recreate the conditions where you experienced the bog.

 

I did the test. When I cycled the key on/off the pump built up the pressure to about 62 psi. It dropped to about 58-59 and stayed there. But when I went to start it with the gauge still connected, the pressure was only about 45 psi and it wouldn't fire. Could that be that the new pump is bad already or could it still be a fuel pressure regulator? Advice?

 

Have you replaced the fuel filter?

 

Yes i did

 

Then it is likely the pump.

 

That was the problem. We put in another new pump and that fixed it. Starts every time now and doesn't bog down while running. Thanks for all the help.