6.5 L Diesel Fuel Injection Pump Fails the 2000 RPM Test

Written by Bill Heath Thursday, 17 December 2009 17:05

Volume 1 Issue 3 - 6.2/6.5 Issues and Answers

Recently, our truck began to take spells of stalling and we were told our fuel injection pump had failed. In an effort to get this done as cost effectively as possible, we bought the unit and did the installation at home. When we got it started, we took it to our local GMC dealer who set the TDC. The replacement unit came from a rebuilder who we understood to be a reputable one, but now we are not so sure about our choice. The engine is hard to start and smokes like heck until it gets pretty well warmed up. We read about and tried your 2000 RPM test (not until after the new pump was put in) we find we cannot put the tachometer on 2000. It either runs way above or falls below. In addition, it sometimes winds up to 4000 RPM when you touch the throttle. We have to turn the key off to stop it. The rebuilder says the pump his company supplied could not be the problem and that we have a bad computer. Please help. We have parked our truck until we can fix this problem.

A factory stock 6.5 runs a boost pressure low enough to not require intercooling so no meaningful benefit would be gained with an air to air system.
When performance modifications are made that increase boost pressure, intercooling can help to recapture power otherwise lost to the decrease in volumetric efficiency that increase boost causes.
Air to air systems for these trucks do not employ a properly sized grill mounted heat exchanger. Instead, they use a too small unit mounted between the frame rails. The tubing used to route air from the turbo and back to the engine is sized to fit the available space. These two design factors; small heat exchanger and restrictive tubes result in poor intake airflow.
Yes, these systems can lower intake air temp, but they also impose a considerable restriction to intake airflow, offsetting a good portion of any gain.
The type intercooling we like best for the 6.5 is water injection. There is a new water injection intercooling system available that employs solid-state control over multi stage function to provide fuel economy gains in addition to towing performance improvements. And it can be used as a stand alone upgrade with stock level boost pressures.
This system very effectively cools the intake charge and does so without imposing a restriction to intake airflow.

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