Help 351M Dies After Acceleration

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Nov 9, 2005 | 10:10 PM

ladiabla74

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From: Austin, Tx

Help 351M Dies After Acceleration

Engine is dying when accelerating and then letting go of the gas quickly when in gear only. Ok so I bought an eddelbrock 1406 and it had the acceleration pump plugged out of the box. It was bogging at start of acceleration. Got that fixed somewhat after unplugging accel pump for now but engine still dies when I accelerate quickly and let got of the gas pedal quickly. I tried a holley carb that I know was working good and it does the same. Timing is set to 12 TDC. Distributor is MSD but don't know the history on it. All I know is it is brand new. Do I need to mess with the springs? If so where do I start? I have been tackling this problem for a while now. I even got the calibration kit for the carb and it didn't do much. I have a brand new summit gas pump. Also checked the floats and they check out good. Can the vacuum secondaries be acting up? Thamks for any help...

AC

Nov 10, 2005 | 09:28 PM

danlee

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From: Delaware

Does it die when you go back to idle after accelerating?

It could be rich. Check the color of the plugs.

Check the fuel pump pressure, it could be blowing the needle valve open.

I use an off-road needle and seat in mine.

Nov 11, 2005 | 02:50 PM

ladiabla74

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From: Austin, Tx

Yes it does die after I let go of the gas. I step hard then let go quickly and it dies. Only when in gear though.

Nov 11, 2005 | 06:37 PM

danlee

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From: Delaware

Call or email Edelbrock, they have tech support for this kind of thing.

Here are a couple of possibilities that I can think of.

Too much accelerator pump.

Step up springs too strong. This could be a result of low vacuum.

Float too high.

Dirt in the needle & seat.

Nov 11, 2005 | 07:26 PM

ladiabla74

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From: Austin, Tx

OK, so I called edelbrock and they basicaly told me to get a fuel line pressure regulator that their carbs were very sensitive to pressure. They told me to check the float level as well and that was it. I did check the level for the third time it still is at the same place (in spec). No dirt anywhere that I could see. The only thing I did not check was the pressure. Didn't have a gauge handy but will get one tomorrow. I did have someone step on the gas while I looked into the carb. Acceleration pump is puting enough gas. Primary venturies are squirting gas. All still works good with no load (not in gear). Once it goes in gear the primaries still look good. The secondaries on the other hand don't do a darn thing. There is no gas coming out of anywhere (venturies or anything). The butterflies at the very bottom of the secondaries move but the ones with weights don't budge at all. Could there be something wrong with the mechanism on the carb? It is a brand new carb.

danlee,

I have the accelerator pump on the first slot ( lean) but also tried the other two with no diference. I also tried different springs and it still died with all of them.
Thanks for the advice... Please keep it comming....

Nov 11, 2005 | 07:37 PM

danlee

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From: Delaware

With the engine idling, look into the primaries. Look for any dripping fuel. This is a sign of high float and/or excessive pump pressure.

Mechanical pumps put out more pressure as RPM increases. So even if it is OK at idle, the pump can overpower the needle valve at higher RPM. The fuel pump pressure is regulated by a spring in the fuel pump. When they assemble the fuel pumps, they don't check every spring to see if it is in tolerance. I use a Carter Electric Fuel pump and no regulator. Electric fuel pumps do not increase pressure with RPM, and are more stable.

Nov 12, 2005 | 10:20 PM

ladiabla74

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From: Austin, Tx

Did that and no drip at idle. I did see it dripping at full throtle but only on the driver side. Should it not be spraying instead of dripping? Should there be gas comming out of the venturies on the secondaries when in gear and at full throtle? I am not getting any on the carb at this point only on the orifices below the venturies. I think I read somewhere on the manual that those orifices serve a similar purpose as the acceleration pump. I did nto get to buy the gauge or pressure regulator today. No one has it localy. Will have to buy from summit. Will post results once I get it.

AC