just recently aquired a 84 z28 l69.. trying to get it to start but just cranks... when i turn the key to the on position.. i dont hear the fuel pump prime and i also hear a buzzing/ticking sound coming from the carb.then it stops after a few seconds. also the choke light is on .... how can i test the fuel pump? this is my first carb car.. would appreciate the help

 

Welcome to the world of Carbs!

Firs things first.
I have a CC carb so I may be able to help. Also NAF or Aperion are some of the best here and helped me set mine up.


1. The carb clicking is a GOOD thing. That's the Mixture control solenoid cycling (MCS). This is an electronic carburetor and manages the part throttle fuel in the same way as a TBI or TPI does...you just have jets and rods instead of injectors.

2. The choke light on at this point isn't anything to be worried about. Stress *at this point* It should go out once you start the car.

3. You won't hear the fuel pump prime. Even if it has the electric pusher pump, it's only 3psi so it's too quiet to hear. You have a mechanical pump up on the block. This works via a rod pushing against a lobe on the cam. When the cam rotates it activates the pump. This is the only time you get fuel through the lines.

4. Do you have fuel in the bowls? If it's been a while since it's been run, the bowls may be dry. Might takes several tries to get fuel pushing through the lines to fill them. Couple of pumps of the gas pedal and then it should fire over.

You can check the fuel pump by taking the feed line off the carb or at the pump and put a bucket under it while cranking the motor. If you get fuel, the pump is good.

Remember, this isn't a FI car, you can't just turn the key and hope it starts. Sometimes, they require a little love to get going.

 

ok cool so pouring gas down the carb should get it to start right? also does it need a map sensor to start? mines is mising. but it has the barrometric sensor...also my battery ground cable connects right below the alternator.. is this right?

 

No map, only baro and yup. The rest is good. Not too much gas tjoufh. Or you'll flood it.

 

So i poured down some gas into the carb and it fired right up. It wasnt getting gas. I removed the fuel line and I checked the mechanical fp by cranking and got nothing. the tank has gas. I think it has the electrical fuel pump since theres a 10 fp fuse in the block. how can i test this pump? I tried jumping the pink/white wire with the black/white wire at the relay but i got nothing.

 

There is a good chance that the pump is bad in the tank, that happens all the time.

Even so, the mechanical pump should have enough suction to pull the fuel through the dead mechanical pump. My car ran like this for years and years. I don't have the FI fuse in my fuse box, it's just an empty slot so I was suprised to find one when I dropped my tank.


Its also possible that the feed line or return line is blocked.
Take an air tank and blow air down the feed line and return line to see if you can hear bubbles in the tank. If you do, the line is clear. If not, then that's also part of your problem.

 

Ok so I fixed the fuel issue by replacing the mech fuel pump..... But before I turned it on I wanted to change the oil and filter so I did..... But now when I start it up there is this real bad knock.... Did I do something wrong? I'm thinking I may have installed the mech pump wrong maybe?? Maybe the oil pump??

 

When you re-installed the mechanical fuel pump, did you make sure you put the rod in the way you pulled it out? Also, did you make sure it was properly seated against the pump arm? It's a bugger to put in and get out as I recall.

 

dam i do remember pulling the rod out and reversing it .. could this be the problem? even tho its pumping gas?

 

If that is the only thing you did different, then unless it randomly picked up rod knock..a rare possibility, then yes. Swap it around and see.

 

Also, you have a flat tappet cam, just like a lifter, they wear in a certain way and need to go back in exactly as they're taken out.

I just hope you didn't wipe the fuel pump lobe or otherwise damage it.

Man now I'd almost change the oil and see if you got metal shavings in it.

Chunks or lots of shavings = bad news.

 

ok im gonna remove the mech pump and run it without the pump and see if it still knocks.....will get back to you in a while .thanks lot

 

I'd just flip it around first and re-install it. If you still have the knocking sound, then you know you have problems and at the very least, will need a new cam, or go fully electric fuel pump.

 

Hey thanks for the help. I need to kick back on the herbs . Forgot to mention that i had a hard time removing the oil filter so what i did was completely destroy the oil filter and shoved some needlenose pliers in and got it off that way. But what i forgot to notice was that i had bent the cover for the flywheel Fixed that, all good now. Thanks a lot bro.