Thanks in advance for any help I can get.

My 1995 Blazer S-10 4.3 Vortec had a return fuel line leak in the plenum, which made the cylinders wash out with gas and oil, and then started leaking into the exhaust. I fixed the fuel lines, and thought my problem was solved, no such luck. Now it runs good until it gets to closed loop, and then it starts idling real sporatic and dies after a bit. Also, it will keep running with the o2 sensors unplugged.

Was wondering what others thoughts are on my o2 sensor being ruined from the oil/gas washing into the exhaust. Looking forward to hearing what you guys think. I'm trying to get the o2 sensor out now, but it's really froze in there.

One more thing I wanted to ask:

I have tried an Actron II obd scanner and it links up but not sure if it's working right, and pulling proper codes. I do get an ICM low curcuit not toggling code, and a camshaft range/perf. code. I have checked the wiring and curcuit on the ICM and all are good, and when I unplug TPS, MAP etc... it does give me those codes properly. unfortunately my Cen-tech obd scanner will not link up at all. This is a late model 95 and obd I compliant is listed on the fan shroud, but I'm confused why the Actron works, and the Cen-tech will not., maybe just not software supported ? If anyone knows the answer please respond. I think the o2 sensor might be causing these codes, but not sure.

Thanks,

Sluggo

 

What kind of fuel pressure are you getting at key on? And for getting that pesky o2 sensor off a 18" pipe wrench works well. I have yet to have a o2 sensor beat it.

 

Thanks for responding.

I could use a bigger wrench but the exhaust is kind of rusty from when I lived in Minnesota, and I don't want to ruin the pipe. I will probably try some mapp gas on pipe tomorrow.

Just checked fuel pressure, and it jumps up to about 60 psi when I turn the key on but it drops to around 40 psi fairly fast. I'm going to check it with my other fuel tester right now. I'll post the results.

Thanks,

Sluggo.

Test with second tester yeilded the same results. It should stay at 60 when the key is turned off correct ?

Thanks,

Sluggo

 

it shouldn't drop below 55 psi after 10 minutes

 

Thanks,

I checked it for leaks when I put the nut kit on it, and I did not see any leaks.

Ugh, this is getting ridiculous. You have any ideas on where I should check first ?

Thanks,

Sluggo

 

*Moved to '2nd Gen Tech'*

 

Its either the spider assembly is bad. or the check it valve in the fuel pump.

do you have the engine with the silver intake manifold with the orange vortec logo over the top? or the black plastic manifold? i dont remember for 95. if its the silver,remove the vortec logo,you will see a sensor,remove it. then take a bright led flashlight and shine it inside and look for any washed walls etc. you want the inside to look black and carbonized. if you see any clean walls etc then fuel is leaking inside the plenum. Sorta like this,doesnt need to be this clean,but any clean spots and the regulator or a line is leaking.


if its all black and carbon colored,id look at the fuel pump.
Remove the fuel filter off the side of the frame. attach the fuel pressure gauge to the line before the filter. and check it at key on. if it falls below 60 etc,then its the pump. anything else will most likely be the spider assembly. If it is the pump buy ONLY ac delco or delphi brand pumps. these blazers are picky as hell on pumps. This is very important.

 

Thanks Chris,
I don't think i'll be able to tell if fuel is washing it out because it already has from when the return line was leaking. I'm going to do the pressure test before the filter and see what happens there.

Thanks again,

Sluggo

 

Can someone tell me the specs for the pump when vehicle is running.
My fuel pressure is 56 psi when idling, I'm thinking this a bit low.

Thanks,

Sluggo

 

I believe it's listed in the tech article... Should be the same for the CPI engines as it is for the newer SCFI/MFI engines.