one for REAL professionals!

[nightman01]

ok gentlemen ive got one for you. I have a 1995 s-10 Blazer with a 4.3 W motor that has a fresh rebuild on it, I did it myself i have several chev. rebuilds under my belt with 0 problems until this one! now simply put EVERYTHING on this motor is new, if you can name it, it has been changed. BUT at idle it misses badly and the new plug wires ark a little especially on the right bank. it will always start and run like a scalded dog down the highway and fuel mileage is good. i occasionally get a rotten egg smell from the exhaust. but with $2000.00 in this engine i am not going to rest until i figure this out! ANY ideas would be extremely appreciated!

[BlazerLT]

Is the CPI injector new?

Why are you asking what the problem is when you see the plug wires arcing?

fix the wires!

[tom3]

Wouldn't hurt to pull the EGR valve and look close for a small chunk of carbon in the pintle/seat area holding it open a bit. Real common problem.

[jsgold]

Can your see the wires arc or just hear it? If you can't see the arc maybe not the wires. Could it be something as simple as a cracked plug??? Does not take much to crack one... Just a suggestion.

[nightman01]

I am on my third set of plugs and wires on this motor. however i did check the fuel pres. with it running and it is 48 psi steady but the pressure bleeds off during static testing it takes it about 5 min to go to zero. when you pinch the return line it holds at 54 psi. i think the fuel pump may be tired. the cpi unit is about 3 months old but as anyone who has worked on vehicles knows new does not mean good!

[nightman01]

well i am on my third set of plugs and wires on this engine and they still arc. you can only see this at night. the cpi unit is about 3 months old but we all know new does not mean good! I checked the running fuel pres. and it is 48 psi. steady, however the pressure will peak at 54 psi and bleed down to near zero in about 5 min with the engine not running. so i think the cpi unit is still bad unless it is supposed to do this. to my knowledge this engine should be running at anywhere between 54 and 62 psi. how would you tell if its the cpi or the fuel pump?

[BlazerLT]

Originally Posted by nightman01

well i am on my third set of plugs and wires on this engine and they still arc. you can only see this at night. the cpi unit is about 3 months old but we all know new does not mean good! I checked the running fuel pres. and it is 48 psi. steady, however the pressure will peak at 54 psi and bleed down to near zero in about 5 min with the engine not running. so i think the cpi unit is still bad unless it is supposed to do this. to my knowledge this engine should be running at anywhere between 54 and 62 psi. how would you tell if its the cpi or the fuel pump?

Where do you see the arcing?

[rlith]

Originally Posted by nightman01

well i am on my third set of plugs and wires on this engine and they still arc. you can only see this at night. the cpi unit is about 3 months old but we all know new does not mean good! I checked the running fuel pres. and it is 48 psi. steady, however the pressure will peak at 54 psi and bleed down to near zero in about 5 min with the engine not running. so i think the cpi unit is still bad unless it is supposed to do this. to my knowledge this engine should be running at anywhere between 54 and 62 psi. how would you tell if its the cpi or the fuel pump?

If your wires are still arcing after the change, I would start examining the coil and the cap regardless if they are new.

As to the cpi/fuel pump, pressurize the system, clamp off the fuel line, turn off the car (while you have a pressure gauge at the shrader valve). If the pressure holds, you know it's your fuel pump, if it doesn't it's the CPI losing pressure. If you repeat this process, after installing a new CPI unit, you ALSO have a bad fuel pump. Pressure needs to be 56-60 at start, 61-65 at running.

[nightman01]

Originally Posted by rlith

If your wires are still arcing after the change, I would start examining the coil and the cap regardless if they are new.

As to the cpi/fuel pump, pressurize the system, clamp off the fuel line, turn off the car (while you have a pressure gauge at the shrader valve). If the pressure holds, you know it's your fuel pump, if it doesn't it's the CPI losing pressure. If you repeat this process, after installing a new CPI unit, you ALSO have a bad fuel pump. Pressure needs to be 56-60 at start, 61-65 at running.

ok thats whats happening! thank you all for your help! I plan to put a new fuel pump and strainer in and check again. I will let you know how it turned out.