The problem the Blazer had with jerking at steady speed is gone.
But the running rough problem is still there some times......

I think my fuel pump is OK, but I thought I double check with you guys

Key On - 62psi, Running at idle - 55psi, Key Off - 60psi, Down to 55psi after 10 minutes. Test is performed at the engine test port.

Does this sound OK? How fast is OK for the pressure to drop to 0psi?'
Or should it never drop that low?

I'm beginning to suspect a leak at the CPI......

It also has some sulfur smell from the exhaust. Made a video with it's readings from autoenginuity, and maybe you guys can have a look at it and give me some hint and help? Here's the link : http://www.youtube.com/watch?v=OK7TBovsRog

You must click the video frame to open the video on youtube. com and make the video big size to see the small prints

 

your fuel pressure readings seem fine. have you ever thrown a vacuum gauge on it?

 

Yes, I did do a vacuum test just last month. It came up with restricted exhaust and if I'm not wrong, retarded ignition timing. I changed the CAT and the restricted exhaust was gone. But I havent checked it after I did a tune up (plugs, wires, cap, rotor, and coil) ,to see if the retarted timing is gone.

I did have the distributor out when I changed my LIM gasket, but I'm almost sure I got it in the same way I took out. If it was a whole tooth off, would that give more massive symptoms?

What else could cause this? The sulfur smell from the exhaust got me thinking off the dreaded CPI leak.

 

what makes you think the timing is off? and weird, my next thought was a plugged cat. do you have one of those pressure gauge adapeters that thread into the 02 sensor bung?

 

Does the pressure continue to drop? If so, I too would suspect a leak inside the plenum.

 

This is what makes me think of retarded timing : http://www.secondchancegarage.com/public/186.cfm
My test came back like senario 11...........

I checked it two hours ago, after I hooked up the fuel pressure gauge before I sat down to watch a movie. 1 hour and 48 minutes later it was down to 10psi. Now I'm just back inside after one more test.
I primed the fuel pump after the last test, and clamped the feed fuel line, to see if the leak was at the pump side of the fuel system, even now it's down to under 10psi. That's yet another sign of a leak inside the plenum,
isn't it?

That would also explain the suflur smell, rough idle and erratic engine feel right?

swartlkk: did you watch the movie? Anything that stands out as not normal? The temp and speed is set to celsius and km/h

 

Nothing seems too out of the ordinary. In the future, I would recommend you show TPS reading instead of calculated engine load.

You should test pressure at the fuel filter to isolate the pump.

 

OK, back inside, after some more fuel pressure tests.
At the fuel filter it holds the KEY ON pressure for at least 1 hour, couldn't wait any longer

Also did some more tests at the fuel test port, and it seems to give me different leakdown times going from a cold to hot engine. At cold it holds the pressure much longer then when the engine is hot! With a hot engine it is down to 10psi after only 15-20 minutes. What could explain this?

I'm really glad that you guys take the time to help me! I would be LOST without the help!

 

Sure sounds like you have a leak inside the plenum then (providing you have no external leaks).

 

This problem seems to get worse real fast. After only a 20mile drive today, the engine has even a deeper growl and a much worse rough feel to it.

If I have a leak at the CPI, would the plugs be fouled?
But shouldn't a leak also trow a to rich code?

I'm not sure but I have a feeling that this engine is on it's way out.

Unhocked the egr just to try, and it felt like that gave it more power.
Drove the blazer as I always drive it, and it took me by surprise spinning out on the gravel. Before this would have needed more throttle.