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By popular request we have introduced the Common Problems/Pattern Failures Category. Just remember:
“If you know of a common problem with a particular vehicle you can post it here. Please stick to KNOWN problems, just because you had a problem with it, that does not mean that it’s a pattern failure. What we’re looking for here are know common problems associated with vehicles. If you’d like more information on Pattern Failures, check out the ETCG1 video of the same name. Thank you for your input!”
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The 6.5l Turbo Diesel:
My 93 6.5l (and apparently virtually everyone else’s 6.5l td from what I’ve seen online.) The oil pressure switch. This particular oil pressure switch also runs the fuel lift pump that’s mounted on the frame rail. Sometimes if the lift pump fails, you don’t always know it because the truck will still run. And if you continue to run the truck without the lift pump, it places undue pressure on the mechanical injection pump, eventually wearing it out (which is obviously much more expensive to remedy – $700 – $900.)
Many long time 6.5 owners claim that the only reliable oil pressure switch made is the AC Delco OPS (which is usually not immediately available.) Besides the dealer, locally I have a Napa, an Autozone, and an Advance. Autozone doesn’t usually carry one. Advance does, but the one they stock has been absolutely terrible in my experience. I purchased the Advance OPS last summer, and it failed within 48 hours! When I tried to exchange it, they wouldn’t honor the warranty.
Napa carries one (I think it’s Echlin) that works for more than a year at least. The one I have in my truck now is the Napa/Echlin OPS.
I’ve been told that the reason for all of this is that aftermarket manufacturers design these switches to handle operating the oil pressure gauge, but they just aren’t designed to (or they can’t carry the load required to) operate the fuel lift pump.
Funny story (now it’s funny); A couple of years back I had an aftermarket OPS go bad, but didn’t realize that it was the OPS at first (had replaced it not much more than a year earlier, and expected that it would be an unlikely candidate.) I was experiencing hard-starting that seemed to worsen rather quickly. I was mostly convinced that it was the fuel strainer/sock on the in-tank fuel pump because of the age of my truck, what others said about this sock, and how it can get clogged over time, etc.
I didn’t much for automotive tools at the time, and dropping the tank in my driveway seemed a little daunting. So I opted to cut a square trapdoor/hole in the bed just above the opening to the fuel tank. I was living in the Tampa Bay area at the time, and out all the different parts stores available to me there, none of them carried this strainer/sock. I finally went to the dealer and picked one up.
I installed the sock, but I was still having the hard-start issue. So I tracked down a parts store across town that had my lift pump in stock, and I replaced that. Still had the issue.
A week later, having installed a new fuel filter, new lift pump, and a new strainer sock, I was beginning to wonder if my in-tank fuel pump was dying. I stopped at an Autozone to price fuel pumps, and my son (who was 11 at the time) says “dad, have you replaced the oil pressure switch?” I explained to him that it was relatively new, but at around $30, I guess it was worth a shot. I purchased the OPS right there and installed it in 5 minutes. The truck fired right up like nothing ever happened!
I know that I wasn’t really properly troubleshooting the issue. At the time I really didn’t have any testing equipment to speak of, but that’s really no excuse. I was/am an idiot sometimes! Good thing my son was there.
But thanks to people who are willing to share their knowledge and experience online (like Eric,) I have been able to keep my truck on the road, and therefore feed my kids! So, thanks sincerely from my family!!!
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