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1993 6.5 missing

6

6.5stayinalive

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I've had my '93 6.5 for about a year and a half, and a couple months after I got it, I noticed that if I started it back up after it had been running for a good half hour or so, it would start loping, if I was in gear at a stop when it did this, it would sometimes die. If I was in gear driving when it did this, the RPMs would go up and would accelerate rapidly, then suddenly completely lose power and almost die, before going back to normal. I have recently noticed (within the last week) that it seems to be missing. Any ideas as to what is wrong would be greatly appreciated.
 
The injection pump does weird things when running out of fuel or dealing with air. RPM going crazy then stalling. You may also need to set the idle rpm and maybe increase it some.

Lift pump failed, OPS bad, sucking air, tank sock plugged and causing lift pump to loose prime, plugged fuel filter, failing injection pump, bad, aka sticking, injectors...

Start by testing the Oil Pressure Switch as these fail often. OPS runs the lift pump. Make sure you have pressure at the water drain with the engine running. Put a clear line on the IP return to look for air.
 
Thanks for the input. How would I test the OPS? As for the missing, I'm thinking injectors possibly.

Note: It doesnt stutter every warm start, but once every day or two is common (it is a daily driver). Cold starts are just fine.
 
Fuel pressure gauge at the water drain. Has 6 PSI or so at idle then everything is working. Rev it up and make sure it doesn't go into a vacuum. Otherwise The lift pump is having trouble. Pull the plug on the lift pump. Voltage is great,but, the contacts in the OPS burn up and will NOT carry any current. So you get like 7v with the lift pump connected. You should have 12v or more.

The lift pump can click away and not pump fuel. A plugged in tank sock or air leak can cause it to loose prime.

Your fuel filter can plug up.

Your IP is prone to rotor and head wear causing hot no-start issues.

Make sure you fuel pressure is good from the lift pump in depth here: http://www.thetruckstop.us/forum/sh...t-Pumps-amp-OPS-operation-and-troubleshooting

Then check for air coming out of the IP.

How many miles on the injectors and any biodiesel or WVO used? Injectors are good for 100K that's it. Watch out for cheap Chinese knock off injectors or rebuilds - they don't last.
 
My money's on the OPS. I replaced the lift pump about a year ago when I first started noticing this. It didn't make a difference. I guess I learned to live with it because it didn't happen very often, and it was predictable. But now that it's missing, I'm wondering if the two are linked. I don't know how old the injectors are, the engine was rebuilt just under 30k ago by Portland Engine Rebuilders; I would think that they would have replaced the injectors then, but who knows.

Anyways, I just got out of class and got an OPS ($38), now I'm just waiting for everything to cool down. I'll keep you posted.
 
Another thing: I've always thought that my oil pressure reading on the gauge was inaccurate, for example idling it says that it's at 25 psi give or take, and if I let the engine idle down after heavy towing, the needle will go into the red. I guess this would make sense if there was an OPS problem.
 
actually they're unrelated issues. not thatyour oil pressure issue isn't related to the OPS, but just because the OPS won't run the LP doesn't mean it will affect the guage reading, two seperate circuts inside the OPS
 
I replaced the OPS, and it made a huge difference. Way more power. But it still misses. I ordered a set of injectors, plan on installing them Saturday. I'll let you know how it works.

So far, so good on the stalling though. Thanks again for the info guys!
 
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