Fuel Pump replacement `95 S10 4.3 CMFI

[n2dsky]

I'm replacing the fuel pump on a `95 S-10 Blazer, 4.3 CMFI 4x4 w/ 149k on it. It's not been running very well.

Some days it will start and run fine, with only a slight skip at cruise. Some mornings it will start very rough, skipping and stuttering with a very bad raw gas smell. A few times the light came on and the code was set as "random misfire." A few times it would almost die when trying to accelerate from a stop, like a bad accelerator pump on a carb. I've been keeping the fuel level low and on 2 occasions, just before refilling, it seemed to go very lean. Was not out of gas, just very low quantity. Driving along, it started loosing power and skipping some. Pulled up to a pump and it almost died and the brakes lost vacuum assist. It had a very “hot” smell. Pumped in a few gallons, started and ran ok.

I'm thinking fuel pressure regulator or injector/poppet assembly. Talked w/ Doug at Lindertech and he would not discuss much unless I had fuel pressure readings. So . . . bought a fuel pressure gauge. Key on, eng off was 58, running at 52. Pressure will also drop to 0 after 10 minutes, or so. I called him back and he suggested replacing the fuel pump due to marginal fuel pressure. So here we are.

I purchased a new fuel pump from Carquest. It is supposed to from the AC-Delco OEM and is the “re-designed” style. I’m not exactly sure what that means, but I think it does not use the little fuel pressure accumulator that was attached to the original pump outlet. There was a short length of fuel hose and 2 clamps to use in its place.

Pulled the tank today. What a pain!!! Thanks to DelCoch for the detailed description of the process. I looked hard for that vent line at the front of the tank, broke it anyway. Stinking GM engineers! What were they thinking? Such a short piece of hose! Does anyone know of a source of those breathers other than the dealer? I noticed that one of the fuel lines had a lot of rust on it. Will that be a big problem? Is there an aftermarket source for that assembly?

Thanks in advance for any help!

[juanito115]

HI, Im doing the same job right now! as you said it was a paint to get the tank down but it's doable! I ran into a little problem. The locking ring would not seat all the way. seems that the pump is slightly bigger than the original (this is a Carter one). how did it go with you? as for your question, I guess I was lucky because I did not break anything...yet! I would say if you dnt wanna pay dealer price a junk yard would be a good idea!

[DelCoch]

Originally Posted by n2dsky

Does anyone know of a source of those breathers other than the dealer? I noticed that one of the fuel lines had a lot of rust on it. Will that be a big problem? Is there an aftermarket source for that assembly?

To the best of my knowledge it's a dealer part only, about 20 bucks. If you only have surface rust on the line no problem. But, if it looks like it may be rusted through or starting to rust through then it needs replaced, which isn't easy as the line from the tank is crimped onto a short rubber hose, and then the rubber hose is crimped onto the metal fuel line that runs forward. Another dealer item unless you can find a repair shop to make them.

Scratch some of the rust off the line and see how deep the rust goes. If it's the smaller line, (return line) you can replace part of the metal line with a short piece of rubber fuel line and hose clamps. The larger line carries too much pressure for hose clamps.

[n2dsky]

Originally Posted by juanito115

HI, Im doing the same job right now! as you said it was a paint to get the tank down but it's doable! I ran into a little problem. The locking ring would not seat all the way. seems that the pump is slightly bigger than the original (this is a Carter one). how did it go with you? as for your question, I guess I was lucky because I did not break anything...yet! I would say if you dnt wanna pay dealer price a junk yard would be a good idea!

I have not replaced everything yet. I don't think I'll have a problem, seems to fit well. Only issue I can think of in your case is the filter sock on the bottom might be thicker than stock. The pump fits between the hose end and the bottom support, on the rubber pad. My pump does not use the OEM accumulator (I think) and my only issue will be the orentation of the filter sock on the bottom of the pump. Looks like it may need to be adjusted to clear the baffel.

[n2dsky]

3-6-07 Update. Got the pump in and the tank back in place. Fuel pressure was a little better (~60 KOEO) but was still on the low side when running. Pulled the tuning baffle out of the intake and looked inside. Driver side was all gunky, pax side had signs of being washed a bit. The fuel pressure regulator was fairly clean and I could see 2 of the spider lines that were very clean and a golden-yellow color.

Called Doug and Linder Tech and ordered a complete kit - spider, regulator, injector, nut kit and gaskets.

We shall what's next!