my turn-stupid question - Benzworld.org - Mercedes-Benz Discussion Forum

krisinak · 10-07-2006, 10:20 AM

being new to diesels , ive got to ask....on my om352a ( 1300L) is the the max rpm supposed to be limited by a govener/rev limiter/fuel control to 2800 rpm? if i put my foot down and dont watch the tach it will keep right on past 28oo rpm....ive looked down and flinched to see it near 3000 several times.....does this mean i need to adjust something? ( besides my attention span?) thanks, kris

black_diesel · 10-07-2006, 10:57 AM

While I don't think 3000 rpm will kill it, that is higher than spec. A lot of people adjust the max governed speed up to 3000 to get some more road speed. You can adjust this down usually by the high idle adjustment. I haven't looked very close to these injection pumps but usually on one side of the control lever will be your slow idle adjustment and on the other end will be the high idle. The high idle adjustment stop usually has a tamper evident safety wire on it so repair facilities would know you had upped the max rpm. If there's nothing on it then whoever had the truck before you likely adjusted it up themselves. There are some pics on this adjustment on the net somewhere but I don't recall where.

Mogasaurus · 10-07-2006, 06:33 PM

Sounds like someone turned it up a bit or the adjustment stop has slipped. I think the IP is the same as on a normally aspirated 352, so this should help.

http://www.unimog-forever.com/Grease...lk/eDiesel.htm

I doubt 3000 RPM will hurt it much.

krisinak · 10-07-2006, 07:03 PM

is the adjustment on the IP limiting the eng speed by limiting fuel delivery volume? or does it have a real governer/ speed control? thanks for the link.

black_diesel · 10-07-2006, 08:06 PM

Well the only way to control engine speed on a diesel is to limit the fuel delivery volume. There is a governor that's integral to the IP that controls the fuel rack via a series of springs and a flyweight.

One thing worth noting is that the governors on the Unimog IP is not like a car or pickup truck. They are tractor type governors where your throttle controls RPM, not fuel delivery. If you're going up a hill at 2200RPM and you start losing speed, flooring it will make no difference. The IP is already delivering the max. fuel it's set to in order to try and maintain 2200RPM. It's like a built in cruise control although I wouldn't advise using the hand throttle for this.

krisinak · 10-08-2006, 09:42 AM

thanks b/d