Hi. My truck sat for a few years after I bought it, but it had a new motor put in shortly before that. Now it is back on the road, but I cant get it to pass an emissions test. I just had a shop tell me that it has two cylinders not firing and has a vacuum problem, and that I may need to take the intake off. It also has a strong gas smell.
I can believe this, but I need to learn more about it. I have done the basic things to the truck myself, and I may be willing to tackle this, but I'm not sure.
For unrelated reasons I have already done the following:
1)replace fuel tank, sending unit, filter to carb, and add an inline filter.
2) air filters, battery, oil change, plug wires

I know I have a few issues to tackle, as there is no heat shield to hook the preheat hose or the small line out of the back of the carb to, and my preheat valve in the crossover has rusted off the pipe. I can freely move the lever, but the vacuum unit swings from it and is unhooked. The bolt that holds it has rusted off.
I have not changed the plugs, as the truck starts quickly and runs ok, despite the two dead cylinders.
This one is going to be a challenge for me, as my time and experience are limited, and I will be working on this outside.
If anyone has any ideas where to start looking, or if any of this sounds ridiculous, let me know.
thanks,Dan

Edited to add that I am pleased with the shop. The mechanic showed me how to detect the leak in the manifold by spraying carb cleaner near the manifold. When he did it the engine ran smoothly, and he explained that that meant the cleaner was being sucked in through the leak. He thinks the fuel smell is coming from the base of the carb. How tough is it to remove the intake manifold and replace the gaskets? I will start reading the manual tomorrow.

 

it might help if you told us what year of truck, what engine, what trans, is it stock or modified? Is it carb or FI?

 

Sorry. Its all in my signature so I didn't repeat it. 84 f250, 302 with 2 barrel carb, manual tranny. No mods. Thanks.

 

Ah, there's the problem. You have no sig.

 

I don't know where it went, but I think it came back. It worked in the test section, lets see if it works now....

 

There you go. The mysteries of computers.

 

It's pretty easy to change the intake manifold gaskets on that engine. You just need to drain some coolant and remove all the stuff from above it. The hardest part is to clean off the old gasket, and not let any of it fall into the engine.

 

Even if your sig was in your first post how are we to know that's the vehicle your asking about? You know when you assume!

 

Okay, I started taking things apart today and I am hoping I am not in over my head. As I said in my first post, the motor had been replaced before. Now I am finding broken connectors and things as I go along. I have the front half of the manifold cleared off, but I am wondering if I should pull the carb off or try to keep it all one piece. I have a couple more brackets to pull and then all of the bolts should be exposed. While I am at this I am replacing plugs, wires, coil, cap and rotor. Should I replace anything else? The distributor is out now, as well. I hope my signature comes through this time, I am working on the truck in the signature. Thanks.

 

Replacing the intake gasket is pretty straight forward. Forget the front and rear gaskets and use a 1/4" bead of sealant and a dab in all four corners. Two cylinders with low compression concerns me if they are side by side. Could mean a blown head gasket between cylinders. Go on and pull the carb, only four nuts and you can replace the gasket for precaution. Make sure to install and torque intake bolts in proper sequence. Good luck.