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5 psi fuel pressure could cause stumbling or hesitation at low rpms????

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5 psi fuel pressure could cause stumbling or hesitation at low rpms????

Old 03-06-2016, 06:27 AM
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5 psi fuel pressure could cause stumbling or hesitation at low rpms????

My 1972 240z still presents a slight hesitation (back and forth shaking) after releasing the clutch and accelerating from 1,000 to 2,000 rpms. After 2,000 rpms the hesitation is gone. This is also present whenever you drive through a broken road. I already changed the differential mount thinking it could be worn and could be causing this issue. The problem is still there. I am using ATF as damper oil!! Should i switch to 3 in 1 motor oil?? (Blue label)??? Ztherapy recommended to use ATF when they refurbished my carbs two yearz ago

THe car has an Airtex 8012s electric fuel pump installed which advertises as 5 to 9 psi. Measured the pressure at the rear carb and it shows 5 psi. However no overflooding off the float bowls. I have never opened the float bowls due to Ztherapy recommendations when they refurbished both SU CARBS (3crews type).


I need to solve this issue as it is driving me nuts.

Last edited by jalexquijano; 03-06-2016 at 06:33 AM.
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Old 03-08-2016, 02:03 PM
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Make sure your distributor is advancing the timing. Just checking vacuum is not enough. Make sure the breaker plate is moving.
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Old 03-22-2016, 05:39 PM
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Originally Posted by theramz View Post
Make sure your distributor is advancing the timing. Just checking vacuum is not enough. Make sure the breaker plate is moving.
A simple way to check this is to set up your timing light and then watch the timing mark move as you rev the motor. It should advance with RPM up until somewhere between 3000 and 4000 and then advance no further.
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