Backfire and weber tune help -
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post #1 of 5 Old 03-01-2007, 10:27 PM Thread Starter
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Backfire and weber tune help

Okay here is the situation. I have a weber on my 258 with no ECM (82 didn't have it). All the emissions stuff is still intact. Original ignition. Mr. Gasket fuel pressure reg.

I am getting a backfire on deceleration from high speeds 45+. The kicker is that if i keep the accelerator depressed slightly it doesn't do it.

Have checked the timing and taken it as high as 12 and as low as 6. Have re-tuned the carb.

Went to O'reily's today and rented their compression tool and going to check that tomorrow night. also picked up a vacuum gauge and going to check for leaks there.

I don't know what else to include. Any thoughts or suggestions?

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post #2 of 5 Old 03-02-2007, 05:18 AM
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Try here:
Not sure, but it sounds like a fuel pressure problem to me.
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post #3 of 5 Old 03-02-2007, 07:22 PM Thread Starter
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I just did a vacuum test on it and it has a huge spike (6 deg) higher when you let of the gas. It runs at 19 and spikes to 25 when i let off.
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post #4 of 5 Old 03-02-2007, 08:23 PM
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I'm with the feul pressure..I have never been found of those dial-a-matic regulators..Its best if you have one is to put an inline feul gauge to verify the pressure..Also do you have a return line to the tank...The vacume is normal in my circumstances to spike high when reveed and the throttle plates are sharply close,it creates alot of vacuum in the manifold by the higher rpm's wanting to drawl in X amount of air and the throttle plates are closed creating a blockage of sorts..I would check into the feul pressure and timing..

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post #5 of 5 Old 03-02-2007, 08:58 PM Thread Starter
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Okay so i have kinda fixed it. I pulled the belt off the smog pump and no more pop. I will still check the fuel pressure tonight or in the morning.

thanks for the input.

Next question is can I drive my Jeep with the just the belt off the pump and all the hoses still hooked up?
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