Engine Clatter with ODLO ?????

[Jomar]

Installed the ODLO switch today and everything went together fine. Diconnected the batteries and removed the ECU/TCM from it`s mounting,removed both the red and gray connectors from the unit, then put the unit in the drivers seat out of the way. Put the three little pins in the proper holes and then put everything back together again. Plugged in the connector in the relay block under the dash, hooked up the batteries and closed the hood. Started the engine, set the clock and took her for a little test run. At 50 mph I pushed the button, the light came on , the rpms went up about 500 and there was a brief fairly loud clatter in the engine, I pushed the button again and it went back in to OD. I did this twice and it clattered both times right after disengaging OD. Anybody have any ideas about what`s happening?? I`m taking it to the dealer in the morning for the reflash and quick learn as per the GM ODLO install doc. Was wondering if anyone else had this clattering after installing the ODLO switch.

[Modified]

Maybe the pilot injection is being disabled, as designed. Here's some info from GM,that I received with their ODLO installation info:

Diesel engine fuel injection systems that use a common rail system, as the Duramax diesel does, may or may not have what is referred to as pilot fuel injection at the lower engine speeds. Pilot fuel injection is defined as a pre-injection of a small quantity of fuel 5 to 20 crankshaft degrees before the main fuel injection. This pre-injection softens the main injection pressure rise and reduces combustion noise. At engine speeds above 2600 RPM, and a fuel quantity supply greater than 35 cu mm, it is necessary to eliminate pilot injection to meet emission requirements. When driving at or above these speeds, main injection combustion noise may be noticeable. It is normal and not harmful to the engine.
When traveling in 5th gear, the pilot injection to main injection transition is typically in the 136km/h (85 mph) range, however it may also be heard under heavy acceleration and when pulling loads up a hill during shifts at or above 2600 RPM. Customers that install the fifth gear inhibit switch, (ODLO), may encounter the fuel knocking of main fuel injection at speeds around 107 km/h (67 mph) in fourth gear between 2600 and 2700 RPM. This sound is considered normal and is to be expected.

This has been discussed previously at :

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=005485&p=

[Jomar]

Modified :
Thanks for the info. Your explanation sounds reasonable to me and I will check out the previous postings about this. The service guy at the dealer told me that it was wastegate clatter, but I`ve never had it before and it would be awful strange that it would start right after i installed the ODLO. My question now is why does it only do it for a brief period and then quit and do it again a few seconds later and not do it at all when the OD is working. I`ll check the other posting and again thanks a lot.


jomar

[dmaxalliTech]

Ditto with Modified, you loose overdrive and raise the rpm your truck runs, your into the range where the pilot injection is shutting down. perfectly normal and will not hurt anything

[Jomar]

dmaxalliTech ;
Muncho Gracias !!!! It`s sure nice to get info from people that you feel they know what there`r talking about. Thanks again, and by the way, thanks for the TSB`s you sent me. I left town right after I got them and forgot about it til now.

Jomar

[txguppy]

Mine does it quite often, 'course its a GMC !! :D :D Guess I'm running her at higher RPM's than you, what was your MPG from Clute?
p.s. now that you're an expert on ODLO, maybe "we" can put one on mine????


see ya Friday
larry

[ 04-14-2003: Message edited by: txguppy ]</p>