Hemtt Detroit idle adjustment?

[Elideclan2]

I'm looking to adjust the idle speed on my Hemtt as it is running too high.
does anyone have the best method for doing so?
i have googled it and have an idea but would like to here from the collective.

 

[Gunzy]

What is it idling at? The tach should show about 6-700rpm. The sound of those 2 strokers is misleading as they sound a lot faster than they really are.

 

[Coffey1]

I agree mine sounds like it's running faster than it.

 

[Elideclan2]

This one is running at 900rpm at idle. It slams into gear at this rpm.
I have another Hemtt that shifts into gear much easier at 600-700rpm.
I need advice to lower

 

[jjb]

You can try backing out the buffer screw. If not there is a procedure in the TM for adjusting idle. You need to remove the intake tube. You need to be real careful working around the turbo though.

 

[jjb]

 

[Elideclan2]

Thank you. I'm haven't found all of the tm's. Is there a place that has the collection?

 

[jjb]

Some are on here but I have downloaded others from different places. I can try sending them.

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[jjb]

Thank you. I'm haven't found all of the tm's. Is there a place that has the collection?

I also have all of the paper manuals.

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[JDToumanian]

My HEMTT also idles too fast... About 825 rpm. However I haven't adjusted it yet because it's a big job. Unless I'm mistaken, the above snapshot from the TM is only the idle adjustment step, part of the larger fuel system adjustment procedure which, from my memory, includes adjusting governor gap, no-load rpm, fuel racks, and injector linkages. The reason you're not supposed to adjust just one parameter is that changing one adjustment, without checking and adjusting all the others, can cause binding in the linkages which must move very smoothly or you can have the engine run away. Most of the later 8V92s in HEMTTs don't have the 'mouse trap' emergency shutdown, so a runaway will detonate your engine since I doubt you'd be able to suffocate it at the air cleaner in time, if you were even brave enough to approach the screaming runaway engine.

Just search for 'runaway Detroit' on YouTube, that should be all anyone needs to reinforce the criticality of proper fuel adjustment....... Of course, the idle speed being wrong in the first place is probably the result of unauthorized tampering or incompetent mechanics, but in my mind it should all be made right. Get some valve cover gaskets and do the whole thing.

Jon

 

[74M35A2]

You can easily adjust the idle speed down without having to "run the rack" on a DD. The buffer screw is for adjusting out the "hunting" that occurs at first cold start. DD specs say that 2 hunts are a perfectly adjusted buffer screw, during first cold start of the day. A DD typically will not destroy itself even in a runaway condition, unless left that way for a long time. Even a butterfly valve that chokes off the air, as supplied from the factory, is not the best way to stop a DD runaway, as it can cause the blower to suck in its seals. A DD 2 stroker engine is at highest probability of a runaway when it has not been operated for a long while, and one injector is sticking, locking the entire rack from being able to move, since the rack goes to full throttle when the engine is shut off. Best way to stop any runaway engine is to have a CO2 fire extinguisher on hand, and discharge it into the air inlet of said engine. It will stop instantly, with zero damage or cleanup mess. We do it all the time.

 

[JDToumanian]

You can easily adjust the idle speed down without having to "run the rack" on a DD. The buffer screw is for adjusting out the "hunting" that occurs at first cold start. DD specs say that 2 hunts are a perfectly adjusted buffer screw, during first cold start of the day. A DD typically will not destroy itself even in a runaway condition, unless left that way for a long time. Even a butterfly valve that chokes off the air, as supplied from the factory, is not the best way to stop a DD runaway, as it can cause the blower to suck in its seals. A DD 2 stroker engine is at highest probability of a runaway when it has not been operated for a long while, and one injector is sticking, locking the entire rack from being able to move, since the rack goes to full throttle when the engine is shut off. Best way to stop any runaway engine is to have a CO2 fire extinguisher on hand, and discharge it into the air inlet of said engine. It will stop instantly, with zero damage or cleanup mess. We do it all the time.

Good tip about using the C02 fire extinguisher, thanks... I reread the TM and I guess you're pretty much right on about the idle speed, which is good! I like being wrong when it makes life easier. I still intend to do a full tune up - My radiator is leaking, and since taking it out is such a big job, I'm going to do a bunch of PM on the engine, especially stuff that is hard to get to otherwise... Overhaul the fan clutch, replace water pumps and hoses, etc, and then adjust valves and fuel system. Probably paint the engine at that time too since it's currently ugly paint is multi-colored and peeling off.

 

[74M35A2]

You're good. Anything DD powered should have a CO2 extinguisher in it. But as long as they are ran occassionally, it is not a problem. If it has sat for a long while, that is when you want to be ready with it at first crank up. Take the good lessons learned from others for free and use it to all's advantage. Now turn your idle down and save your trans and U-joints. detroitdiesel671@hotmail.com if any questions (wink).

 

[Elideclan2]

Thanks for the amazing advise. Looks like I can turn this thing down without much trouble. I am headed to the store to purchase co2 extinguishers!

 

[bsteinborn]

Anyone know what controls the idle speed when using the HEMTT crane? The TM says it should be idling at 1500 RPM, but mine is at 2000 RPM when I engage the crane. Thanks.

 

[jjb]

Anyone know what controls the idle speed when using the HEMTT crane? The TM says it should be idling at 1500 RPM, but mine is at 2000 RPM when I engage the crane. Thanks.

Same place you adjust the idle and no load speed. It's controlled by an electric/air solenoid.

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[bsteinborn]

Check section 19-9 in TM-9-2815-224-34.

 

[brazengoat06]

bump. i just tried to adjust mine and lowest i could get it was 800ish. the idle adjust screw just gets loose and the rpm doesnt respond. any tips?