Idle speed when parked for a/c or charging

LDB · May 13, 2007

Ok, so your expensive generator drops dead and you have to idle the main engine to charge the batteries or run the a/c. What speed do you idle it? I've been told whatever speed gives 40 pounds of oil pressure and I've been told not below 900. Anyone go along with one of these? Other ideas?

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davekc · May 13, 2007

Unless it is a non computer truck, there are several Q's within the ECM that control it automatically. If not, or it is too low/high, it may need to be reflashed.

On a side note, what kind of generator quit?

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LDB · May 13, 2007

Rigmaster. Changed oil, oil filter, air filter and fuel filter. Now it doesn't even crank. It gets about 1/3 second tap at starter and then nothing.

My question is whether I need to speed up the idle using the cruise or just let it idle at it's standard idle speed. I've never seen the idle changed by the ECM or anything else while stopped to go in a shipping office etc. so just wondered if I need to change it myself. I get about 38psi oil pressure at stock idle.

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davekc · May 13, 2007

Could be several things on the generator. Loose ground wire, blown fuse/breaker, or lid is not on correctly. The rigmaster has that electric clip in the front. That usually will show up on your program screen. They also have a new upgraded breaker that you may or may not have.

On the ECM, whatever they change would be permanant unless they go in and change it again. We had our C9 tweaked alittle as they came out with a few software changes. With the ECM, many things can be set/adjusted to determine idle speed.

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LDB · May 13, 2007

I've looked and can't see any loose wires or anything else. I don't think the ECM needs any adjustments, as far as I know anyway. It idles about 650 or so when just sitting. I've just heard from some people that is too low if you are parked idling. Some say around 900 is minimum for idling for these purposes. Some say it's based on oil pressure. That sounds more logical to me than an arbitrary rpm number. I presume it would use the least fuel at the standard idle speed so that appeals from mpg and money standpoint. I just want to do what's best for the engine though so that's why I'm asking about parked idle speed for charging and a/c.

Leo Bricker, 73's K5LDB, OOIDA Life Member 677319
Owner, Panther trucks 5508, 5509, 5641
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rollnthunder · May 13, 2007

I always idle right around a 1000 rpm or so to make sure the fuel is all burned.Some may say you only need to do this in the winter but before i had a generator i always idle the truck around a 1000 rpm for ac and heat.That way the motor seems to smooth out a little and the ac usually works better.

unorthodoxneon · May 13, 2007

On the generator maybe when they changed the Fuel filter they maybe moved the fuel flow to off and forgot to turn it back on. I know when i worked on the Aux gen i did that. And then another problem was i had to wait for the air pocket to get out of the system. Also maybe there is a shutdown switch for not having enough oil pressure. Is the oil at the correct level? Did it work before leaving the shop?

My latest problems with the aux was a wire came off the fuel pump, fixed that got it running then it quit again and it was a blown fuse. Now (knock on wood) its running like a champ now.

heel4you · May 13, 2007

Hey Leo,
We were told by a mechanic to run it at 1000 rpm. He said that the fuel burns properly at this rate.
Laura

LDB · May 13, 2007

I was under the impression any fuel not needed was returned to the tanks. That made me think the slower the idle the better to minimize fuel burn. I've also heard a certain rpm is needed to keep the egr clear. I don't know. Thankfully I'll get it to the shop tomorrow and by end of day be on the generator again I hope.

I thought of the fuel valve and the fuel filter prime but both of those would not keep it from cranking, just from lighting. If those were the case it should crank indefinitely but just not start. If it was a fuse it wouldn't even hit the starter I don't think. It hits the starter for a half second and then quits. I think it could be the computer for it maybe but just don't know what it could be. I will get the dealer to fill me in though.

Leo Bricker, 73's K5LDB, OOIDA Life Member 677319
Owner, Panther trucks 5508, 5509, 5641
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unorthodoxneon · May 13, 2007

Interesting, please keep us updated for those of use that do or plan on having Rigmasters put on their trucks and know what to look for. Its a pretty new unit to give troubles but if its moves its going to break.

JustUsTrucking · May 13, 2007

We had the same problem with our rigmaster after an oil change. I would bet the problem is the oil was put in too fast and it ran over the camshaft and down one cylinder. This will cause a hydrostatic lock. All that needs to be done to correct this is pull the glow plugs out and turn the engine over until the oil is pushed out. This info cost me $200. I will accept any and all donations. LOL

bamamule · May 13, 2007

what kind of eng do you have?
volvo says no need to up rpm while idling
cat requirs 40 psi oil
det and cumapart requires 30

LDB · May 13, 2007

I've got a C9 and if 40 psi is the requirement then I will have to bump it up just a little. I get about 37-38 at idle.

Leo Bricker, 73's K5LDB, OOIDA Life Member 677319
Owner, Panther trucks 5508, 5509, 5641
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Support the entire Constitution, not just the parts you like.

Refer Hauler · May 13, 2007

This is very unscientific, but my Detroit Series 60 appears to use less fuel at 1000 RPM. It also does not puke out a load of blue smoke upon throtling up and the A/C is much colder.
Just my observations.

RLENT · May 15, 2007

The correct terminology is "wet stacking" (or "over-fueling" in laymans terms) - this is when the temperatures in a diesel engine's combustion chamber are not high enough to completely burn all the fuel that is being injected, or when there is an excess of fuel for a given load. It typically occurs when diesel engines are run for an extended periods with low(er) engine speeds and light (or no) loads.

What happens is that unburned fuel remains on the cylinder walls - which tends to wash off oil and reduce lubrication (which of course results in increased wear) It will also contaminate the oil with unburned fuel, carbonize the fuel injector assemblies, and pass unburnt fuel out through the exhaust (the black ooze)

It is my understanding that an idle speed of at least 1100 to 1500 rpm is necessary to avoid the condition. The stock idle setting on my Kubota B2910 tractor (norally aspirated - no turbo) is about 1100 to 1200 rpm. The rpm required quite possibly varies by specific engine design.

The Dodge Sprinter has a particularly cold-blooded engine - and often comes equipped with a "Heater Booster" - which is simply an Espar coolant heater that is to be run in temperatures less than 40 degrees to avoid having the engine run overly cool. HTH.