John Deere 690B high idle when hot

[Gerald Chungus]

Hi everybody, maybe someone has had the same problem and can help me with my John Deere 690B with a 6404T engine.

Ive owned this machine for over a year and done some repairs and overlooked some to save money. While running this excavator I notice that when the engine is up to operating temp I have a very high idle when there is no load on the pumps. Its running at such high rpms that I dont let it idle for long when hot for fear of engine damage. It doesnt smoke and lab testing of the engine oil results are good. I can hear the sound of the turbo and the gauges all work and does not show that its overheating. I took the fuel pump apart and cleaned it couldnt find anything wrong and replaced the check valve and fuel filters. The breather for the crankcase smokes a bit sometimes but I was told that is normal for an older diesel. Anyone had a similar problem or idea where else I should start to look?

Thanks - Bill.

 

[thepumpguysc]

Just turn the hi speed stop screw in to get your desired rpm..

 

[mg2361]

See if the throttle lever on the injection pump is against the low idle stop screw. if it is not, disconnect the throttle cable and check to make sure the lever on the pump goes against the idle stop screw. Most likely it will and you just need a throttle cable adjustment.

 

[Gerald Chungus]

Got it. Thats what I needed to know. The middle adjustment screw on the left side of the injection pump needed to be backed out by about 3/4 turn. The service manual makes no mention of this or of the top screw which controls idle speed. There is a good Youtube video explaining.

Thanks for the advice - Bill.