How to Troubleshoot a 1998 GMC 6.5 Turbo
- 1). Check the main bearing or have it checked for you. The main bearing webbing is notorious for cracking in the 6.5L Turbo engine. Although newer engine designs made after 2007 have an improved higher nickel cast iron alloy and lower block redesign, the 1998 model year had no such improvements. Have this problem serviced by a professional mechanic with extensive knowledge about the GM diesel engine.
- 2). Check to see if your engine starts and runs normally. The GMC 6.5L Turbo suffered from premature crankshaft failure. You'll know if your crankshaft fails because your engine won't run. This is one of the main causes of engine failure on these particular engines. The harmonic balancer that is supposed to prevent this problem doesn't do its job very well and fails prematurely itself. Once your crankshaft breaks, have your engine overhauled by a professional engine rebuilder.
- 3). Check for rough idle and fuel pump related problems. If your 6.5L Turbo GMC is having trouble running smoothly, it may be due to the faulty pump driver installed on this engine. The pump driver is installed from the factory in a high heat area (the intake valley). The driver can be relocated by a professional mechanic to a low heat area so that the pump does not fail. However, if the driver does fail, you'll need to have this, and the fuel system checked and serviced.