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87 Superliner surges constantly down the road.


Super Liberty
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Hey Yall, wondering if you could help us? We have an 87 Liberty Superliner with a 350 Mack that has started giving us problems with surging while you drive it down the road.

We thought that we would change the fuel lines that look old which were a braided line with reusable fittings. They still hold pressure, but thought we would change them anyway. Cannot find braided fuel lines except for stainless steel, which I am not wanting to use them. Any ideas?

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The dealer would have the braided line or any shop that is doing heavy duty truck repair or equipment repair.

Fleetpride in Williston, Clark's Truck Center in Jericho or Vermont Mack.

You may have some worn parts in the injection pump governor giving you a surging problem.

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Jim

It doesn't cost anything to pay attention.

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We changed all the fuel filters, and changed the fuel lines and thought we cured the surging. 200 miles later it was back. The injection pump has approximately 100,000 miles. Changed the harmonic balancer because it looked like it was leaking.... We just noticed air bubbles in radiator, but not overheating and we tested for the head gasket with the bottle off of the overfill line, and it looked fine, but there is pressure in the radiator. The truck has more power than it ever has had before in the higher RPMS. When you are in lower RPMS the truck surges so bad it is almost not driveable.

We appreciate any input.

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I,m thinking you broke a spring on the governor, but check the lift pump before removing the whole injection pump you may have some trash in the check valves.

you could also try the buffer spring adjustment, back out the buffer set screw, adjust idle to within 50 rpm of spec then thread in buffer set screw until idle speed is reached and give it a try.

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