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Old 04-10-2010, 10:38 AM
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Hesistation/Bog/Cuts out

I recently had an issue with spark. It now has brand new cap/rotor/module/coil and a repaired CD ignition box (All mallory)
Car starts now and it runs fine. I can have it sit and idle in my driveway all day long at 170*
I went to get gas and drove about a mile to the station - filled up and on the way back home i got on it pretty good then just was cruising. It began to bog/hesistate then just died. Pulled over hit the key and it fired back up - drove about 1/4 mile and it began to happen again. Pulled over hit the key and it fired back up.
Checked my fuel pressure and it was at about 5 PSI so i upped it to 6.5 same thing is still happening.
When i mess with the mixture screws and idle in the driveway the car runs great it will just run. When i go to drive it it happens again.

Engine info
Demon 750 silver claw (flows 900cfm)
Electric pump - inline filter - bypass with return line
fresh 454 10:1 CR
comp magnum 280H 230/230 @ .050

Before my spark issues the car was running fine. I would drive it on 50 mile trips with out this issue. I was having some fuel issues at the same time so there have been tweaks to the carb and its been pulled apart a few times to clean it up.
Currently the fuel mixture screws are set at 1 1/2 turns out and i am getting some black soot on the driveway from idling so its running rich but i dont think that would make it hesistate, then get to the point it bogs so hard there is NO power and i have to hit the key to turn it off or it just dies. But it starts right back up like there was no problem....

Halp!

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Old 04-10-2010, 02:58 PM
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Are you using any type of insulator under the carb? The fuel lines well protected from header heat, etc.? Fuel filter fresh? I'm guessing w/a return line'ed electric pump, vapor lock shouldn't be a problem, but you never know. But percolation in the carb itself is another thing.

I'd wonder if the timing wasn't retarded some from where it was- this will cause additional under hood heat.

The engine won't clear its throat w/some throttle revving in neutral when the symptoms first start?
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Old 04-10-2010, 03:25 PM
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No if i pop it into neutral and try to feather the throttle it only seems to get worse. The only way i can keep it running after its in neutral is to not touch the throttle.

All lines are well far enough away from heat. No under carb protection though. If it were heat related wouldnt it show up on my temp gauge?

Fuel filter is a few years old but just 2 months ago i had it out and it looked brand new.

Pump is about 6 years old. I was noticing that it would try and push 8-9 PSI even with my bypass set to only allow 4psi. Then yesterday i was able to adjust the bypass again back to 6 PSI with the adjuster screw. Could the pump be going out?
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Old 04-10-2010, 03:49 PM
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Quote:
Originally Posted by Ignitrous
Pump is about 6 years old. I was noticing that it would try and push 8-9 PSI even with my bypass set to only allow 4psi. Then yesterday i was able to adjust the bypass again back to 6 PSI with the adjuster screw. Could the pump be going out?
Yes, it could. In my experience, if an electric pump does anything other than what it's supposed to- like pressure falling then rising w/no reason, running noisy, getting hot, etc.- it needs attention.

Most pumps can be rebuilt for far less than the replacement cost of a new one, you might want to look into that.

On a related note, the regulator can also have problems. They, too, can often be rebuilt.
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Old 04-10-2010, 05:11 PM
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Well here's an update. Been outside messing around with tuning the carb. While tuning the carb it begins to bog while idling in the drive way. I look over at the ignition box and see a 3 (Which is completely out of place because its supposed to show the RPM limiter which should be at 6.0)
Then i watch as the box changes and shows 4.4.4.4 all across the screen. I just got the box back from being repaired by mallory so i guess ill be calling them on monday so they can fix it again.
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