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View Full Version : 2 6.5TD's, same odd problem



HiwayDiesel
10-30-2007, 00:30
First off, I have been searching the forums for a match to this problem, with no results, so I thought I would describe the problem and see if it strikes a chord with another member.

I have a '98 6.5TD and a '00 6.5TD, both engine code F's in 310 (135.5 wb utility) chassis, both high mileage (220,000+) and they have both recently started having an intermittent problem. Most times they will start and run perfectly, but occasionally they will turn over great, fire once, then continue to turn over with no start. This can happen hot or cold. The starters turn them over fast, the batteries are new, and the grounds are good. Generally if you leave it alone for 20 minutes or so, it will start and run just fine. Both trucks have remote FSD's with coolers, the lift pumps work fine and once running, and other than this problem, run great. We have switched out FSD's when the problem occurs, and still no start. I have loosened a injector connection and it gives one quick squirt of fuel and then nothing. Then you wait a while and they start up and run like always with no stalling problems. These trucks are driven approximately 100 miles 7 nights a week and have had no problems, other than this. Trucks are stock, with original turbos and IP's, and have been maintained in a fleet environment. I have not had a chance to check for codes, but will do so tomorrow and post results.

Any thoughts?

HiwayDiesel
02-01-2009, 22:20
Just a followup on this problem: I learned that with a well-used keyswitch, if you do not turn the key firmly to the stop while starting, the PCM (ECM) may see this as a security issue and turns on a "do not start" command for about 15 minutes. We have taken to call this "short starting". Evidently a switch in the keyswitch relating to antitheft has worn down its actuator and if the key is not fully turned it makes the PCM think that the switch has been tampered with. It also seems to happen sometimes when you release the key before the engine is fully running.

I guess replaced the keyswitch assembly would be the fix for this, but I just made my guys aware of the problem and they now perform the start sequence with rarely a problem.

If you wait the 15 minutes (might actually be 12) the truck starts right up.

DennisG01
02-04-2009, 14:03
Well, sorry I missed your original post back in '07. I could have helped you figure it out faster. I had EXACTLY the same problem - but needed a new ignition module/switch - not the actual key switch. IIRC, I timed it to a 12 minute "grace period" before it would restart. Oh well, glad you got it figured out, though!

john8662
02-06-2009, 08:54
Was there ever a "security" indicator light turned on during these events?

Just curious...

DennisG01
02-06-2009, 09:14
It's been a while, but I think so - in my case, anyway. But, I honestly can't say for sure.

HiwayDiesel
02-08-2009, 15:33
Yes the security light comes on (or blinks?) during the event and 12 minutes is right according to the GM manual. This is one of those little "gremlins" I could do without.