I have spent countless days searching the forums to questions about the answers that I need and few seem to offer what I would like.

I have a 1987 Iroc Z-28 Convertible 305 TPI and have to make it smog legal in CA. After using some state money and having it smogged twice, the ECU has been swapped out with a new one and grounding issues fixed.

Now the shop guys is telling me that I have an air leak in my gas tank (the reason is failed the low evap fuel pressure test) and that my cat may be bad as well. He's currently working on an estimate for those two jobs and says "hopefully that will fix your smog issues." I don't want to pay him all that expensive labor but may have to if I can't get the right guidance. I looked at a lot of parts websites to see the costs for those parts and it's feasable for me if I can perform most of the work myself along with my buddies.

Where can I go to find out step-by-step instructions on gas tank replacement? I realize that the cat will probly have to be cut out and the new one welded on.

Any help is greatly appreciated.

 

Sounds like a second opinion is in order. Tank removal is very labor intensive and a PITA. If you have friends AND you're sure a replacement will solve your problem I recommmend trying it yourself. Surprised you didn't see that on search. I'm not knowledgeable enough to say that problem you state could be fixed with a new tank though.

Use a Sawzall to take out old cat, new aftermarket high flow cat and sometube clamps will save you some dough from having someone paid to weld together. Now you saved money and have that sense of satisfaction

 

I know it's labor intensive. All I have to go by is the Chilton and Hayne's manuals but I would like some more detailed info if it's out there. I'm in the Navy and we have auto hobby shops with car pits and all kinds of tools available for our use at a very, very cheap price per hour to use the pits. I would just like to go as well prepared as possible so that I don't fudge anything up. I read in another post somewhere "Do it once, do it right." Which I totally agree with.

 

btw, I just passed smog on my car lowering NOx from 720 to 210...by replacing the leaking egr valve. I did put a new cap and rotor on it and ran some techroline additive but think the valve did 99% of the cleanup to the NOx. also btw2, have low fuel in the tank when you drop it, surprising how much at 8lbs per gallon 15gallons of gas adds to the weight when its sloshing around above your head.

edit: and maybe scrounge around for a 10"x12" piece of plywood, e.g. wood shelf or something, to put on top of their transmission jack, to help lower your tank.

 

well i live in jersey and our emissions are slightly lower then yours i just installed a full msd and gave it a good tuneup and im taking it tomorrow to check it to pass my mechanic friend said the exhaust smells ten times better then before and he feels it will pass he drives a dsm so i think he knows about emmisions lol

 

Before you cut the cat out try using a sharp steel chisel down the side of the pipe starting at the lip and driving towards the cat. It will cut /rip the cat pipe while leaving the stock pipe intact. ( use heavy gloves and safety glasses) Thats how I removed my stock cat. The auto parts store ( high end racing/performance) would only sell a replacement cat if you had internal damage/ broken cat. I think that's CA. Smog law of some sort. In other words you cant gust throw on a high flow cat because you feel like it. At least that's what I was told. I dont think this will apply to your problem but my gas cap needed a new rubber washer to make a proper seal.If you do have to drop/replace your tank you may want to consider a new pump while your in there. By the way I had to replace the intake manifold gasket to fix a air leak in order to pass smog in CA. So I can relate to the hassles of trying to pass CA smog.

 

How is that test conducted? Typically, it's a pressure test of the gas cap. Replace the gas cap, pass the test. If the tank itself is being pressurized and is failing (I've never heard of a test like that being conducted), it's more likely something away from the tank that is leaking (rubber lines, check valve, etc.).

"May" be bad? What's the evidence of that?

If you have sniffer test numbers, post them (conditions, readings, standards).