Solved suffering two major issues

windtrader · February 19, 2026, 01:33:00 PM

For many months I had issues with the engine shutting off when the jakes were activated. Earlier I had an issue where the engine would not shut off when turned off. The Jake issue was solved once the root problem was the governor needle jet that controls fuel flow. It seemed clean but cleaned it up and shot some brake clean around and into the jet housing. This fixed the stalling Jake issue.

The second issue with engine not stalling had gone away but when working on the governor jet valve/Jake control it dawned on me that this was the same root cause as I saw the stop lever on the governor works the same jet valve. Got the win! finally

Second ongoing issue was what I thought was fuel in the oil. My hunch was the Jake brake issue was related to fuel cutoff not working and maybe letting fuel get into oil. Then while on the road this month, all of a sudden the oil pressure gauge started reading 20 and stayed there. Thinking a lot of fuel was diluting the oil, I decided to change out the oil. Guess what, new oil, still showing 20psi on both the dash and manual gauge. uh oh, engine wrecked?

After some very beneficial chats with AI, the oil pressure regulator was suspect. Drained and pulled the pan to get to those valves and sure enough there was scratches in the barrel of the regulator valve causing it to stick. Took both apart and smoothed and polished them up. Not having a spare gasket around I decided to put the pan back on and fill it up. The gauges seemed to be reading good but it did not take long to see a massive oil pan leak.

Out goes 8 gallons of oil, pan off, meticulously cleaned pan and block surfaces, learned about Permatex The Right Stuff, indeed, sealed up, oil back in, and no leaks. Oil pressure back up and steady. Win!

Major PIA, lost nearly a week but no way going to cross the Mexican desert unless feeling 100% mechanically sound.

Learned a lot as always about the bus and feeling the love return slowly. Would have driven it into the ocean a week ago but still not quit looking at alternatives, will see

luvrbus · February 19, 2026, 01:38:48 PM

Don you lost me WTH is a jet valve on the governor ? lol I was told you are never too old to learn. I know about the Right Stuff it is the only RTV sealant I use I buy and use when needed in caulking gun tubes sizes about 6 inch a long with the small caulking made for it

windtrader · February 20, 2026, 10:01:45 AM

ok, you got me Clifford, I dunt no crap about diesel motors. this jet thingie that controls fuel from governor and Jake brake and shut down valve. Maybe something was catching inside the housing as the needle seemed clean when I took it out. So far, everything is working again so seems like something was clogging it.

Coach_and_Crown_Guy · February 20, 2026, 08:13:38 PM

Sticking switch. Senses and activates Jakes using buffer and balance arm components inside the governor. Very tricky and touchy to adjust in the best of times. That's merely a micro-switch being activated when governor is in "no fuel". If it isn't moving freely all kinds of things can occur affecting proper operation of the governor. It takes it's motion from the buffer screw assembly and anything that affects that very delicate balance will certainly cause issues with engine operation. I've never liked them much, too touchy and prone to not working correctly. It's the standard and in use on DD's for years, but I'm a bit(?) conservative and prefer the throttle micro-switch mounted outside the governor and taking it's "No Fuel" motion from somewhere not so intimately touching the delicate workings of the governor itself.... But that's just me.

luvrbus · February 21, 2026, 06:18:54 AM

Quote from: Coach_and_Crown_Guy on February 20, 2026, 08:13:38 PM
Sticking switch. Senses and activates Jakes using buffer and balance arm components inside the governor. Very tricky and touchy to adjust in the best of times. That's merely a micro-switch being activated when governor is in "no fuel". If it isn't moving freely all kinds of things can occur affecting proper operation of the governor. It takes it's motion from the buffer screw assembly and anything that affects that very delicate balance will certainly cause issues with engine operation. I've never liked them much, too touchy and prone to not working correctly. It's the standard and in use on DD's for years, but I'm a bit(?) conservative and prefer the throttle micro-switch mounted outside the governor and taking it's "No Fuel" motion from somewhere not so intimately touching the delicate workings of the governor itself.... But that's just me.

I mount a lot of micro switches on the throt cable or linkage, Prevost never used the governor mounted switch. The combo fast idle, Jake switch are expensive if can even find one, I have 3 or 4 that I have removed to keep owners not knowing how to adjust it, a 1/4 of turn to much will send the old Detroit into orbit installed in the governor housing. There are a dozen ways to control a Jake without it. Jake's are so overrated on the 2 cycle Detroit's, the more you use Jake's on one the more the oil consumption increases. On the Allison they only work in the lock up mode, they are useless on the 600 series unless you spend big money to valve the lockup on the converter, they won't work on the 740 either in 1st gear without the valving to lock the converter up lol they sound good though

windtrader · February 23, 2026, 03:41:14 PM

I was screamed at about making sure to loosen the proper nut as the adjusting one will FU up if it gets out of tune.

I always asked about leaving jakes on and feathering with the pedal. This is the first I've heard from an expert who indicated there was a side effect by keeping them on. In the back of my mind art seemed better to leave off until needed but the mechanics that serviced the bus before stated he ran the bus Jakes on al the time. I think I'nm going to keep them off, on only when needed.

luvrbus · February 24, 2026, 05:13:33 AM

Quote from: windtrader on February 23, 2026, 03:41:14 PM
I was screamed at about making sure to loosen the proper nut as the adjusting one will FU up if it gets out of tune.

I always asked about leaving jakes on and feathering with the pedal. This is the first I've heard from an expert who indicated there was a side effect by keeping them on. In the back of my mind art seemed better to leave off until needed but the mechanics that serviced the bus before stated he ran the bus Jakes on al the time. I think I'nm going to keep them off, on only when needed.

Leave the Jakes off that is why they have the off and on switch. On coming down a long steep grade like on Az 68 from Kingman to Laughlin turn the Jakes on at the first of the descent do not let the engine start turning high RPM and turn the Jakes on, all hell can break loose they drop valves or bend all the valves. I had guy a few days ago that wanted me to set his Jakes 0.030 because he read on the internet that they worked better at that setting, I told him no if Detroit and Jake wanted that clearance Jake would have made a 0.030 gauge 0.059 is all you get here because that is only gauge Jake makes for the 71/92.The newer electronic engines like my Cummins ISX 15 the Jakes are not going to engage till they read the engine will not turn over 2100 RPM when engaged ,the turbo on the ISX engine is part of the engine brake system and will help slow it down till it reads the correct RPM's,the electronic world is amazing till it has problems