GM-GMC: GM Diesel engines, 5th wheel trailer, electronic fuel injection

Question
Am looking at buying a 1993 Chev Siverado 3/4 ton with 6.5 Diesel engine for towing a 5th wheel trailer.  The truck has very low mileage but I seem to remember reading that the 6.5 diesel engine was prone to lots of problems.  Can you confirm or comment please.

Answer
Hi Warner - you did hear right about the poor reliability of the 6.5's but let me be more specific.  

In 92, the 6.5 was introduced.  It was only in HD trucks because of emission certification.  In order to clean up the exhaust, GM needed a more precise fuel delivery system than the old tried and true mechanical fuel injection that diesels have used for years.

GM and Stanadyne came out with an electronic fuel injection for diesels.  This allowed GM to use the 6.5 in the 1500's and meet pollution standards.  What they did not do was research the reliability of the new injection system.  The pumps have had problems with varying things, from soft metal rollers which increase tolerances and change fuel pressures, to an optic sensor that fouls.  Then there is the fuel driver on the side of the pump that can quit and leave you stranded.

If it were me, I would be staying away from the 94-early 97 6.5's.  They came out with some improvements that helped later on, but those early ones were dynamite.

In 92 and 93, GM was still using the venerable mechanical fuel injection pump.  Anyone with diesel experience can work on these and they stand up VERY well.  In short, the motors were always good - it was the pumps that were a problem.

One thing you should check for towing, is what axle ratio you have, as this can affect the load you are carrying.  In the glove box, there is a label with the RPO codes on it.  Look for one of these codes:

GU6 - 3.42
GT4 - 3.73
GT5 - 4.10

The best is the GT5, and the least liked is the GU6.  Each axle ratio changes your engine speed by about 2-300 rpm, so the bigger the trailer the lower (higher numerical) axle ratio you want.  The engine will be revving more at any given speed to produce more power for hauling.

Hope this helps, but do also check out the Diesel Pageat http://www.62-65-dieselpage.com/  Excellent resource here for all of the 6.5's - mechanical and electronic pumps.

Anything else, drop me a line!

Automotively yours,

Dean