Fuel Valve Identification - No Start Situation

[brianzero]

HI All,

I've got a crank-no-start situation, after rebuilding and cleaning of my fuel system, including removing and cleaning my fuel tank. I also verified that my racks move freely and my injectors arent stuck. I feel that it should just fire up, but no. Its got new fuel lines, filters and a new fuel pump too. I carefully primed the system from both sides to verify no air is stuck in the fuel the system.

I'm trying to identify this, valve shown in the red square. Would this valve, if not working be responsible for a no-start? It has a broken terminal which is spinning in the valve body:

[Bill Gerrie]

That is a switch to stop the starter from renaming after the engine starts and there is fuel pressure present.

[Bill Gerrie]

Are you sure the fuel lines are hooked up correctly at the tank. The return line is not in the fuel so won't supply fuel if hooked up as a supply line. Is the governor in a no fuel position?

[brianzero]

Yes, the tank lines are hooked up correctly. The large line is the fuel pickup and the small is the fuel return.

As far as the governor is concerned, Im not exactly sure which one on top of the engine is the governor. Here is a picture of the top of the engine, which is numbered (tell me which number is the governor). Im not sure what controls what. I can tell you that everything moves freely, the throttle cable and everything moves just fine. All of those air solenoids work and move reasonably freely:

[Bill Gerrie]

I am more familiar with electronic engine controls since 2006. I would say that #2 is the shut off solenoid but with no air in system it won't shut off the fuel. Have you used an electric fuel pump to prime the system? Any air and they will not start. Prime till you see fuel returning to the fuel tank.

[brianzero]

What I did is draw fuel via vacuum from the return line at the tank. I get a steady steam of fuel from the return line, so I'm certain the system is primed.

If I knew which on that numbered image was the fuel governor, I could take a closer look at it. Somebody will eventually tell me what number is what.

[Bill Gerrie]

With air in system the shut off solenoid will move out and push on the lever when yoi shut down. No air it has no pressure on the fuel shut off lever. I know you feel the system is primed but I would pressurize it with fuel rather then use vacumn. Also make sure the filters are full. Maybe even just try to remove the filters and fill them and try to start. Maybe a little shot of Ether but don't overdo it. Batteries must be fully charged to spin fast enough to fire.

[brianzero]

I heard there is a flap attached to some sort of governor that can stick shut preventing a start. Ive read that a few times.

[Dave5Cs]

#1 ?
#2 fast idle solinoid
#3 Shut down solenoid
#4 Governor
#5Cable from fuel peddle and governor control
#6 ?

[brianzero]

#1 ?
#2 fast idle solinoid
#3 Shut down solenoid
#4 Governor
#5Cable from fuel peddle and governor control
#6 ?

Thanks Dave! I knew somebody would know what those numbers were. I can feel the governor flap moving around in there, which is a good sign.

[Coach_and_Crown_Guy]

#1 ?
#2 fast idle solinoid
#3 Shut down solenoid
#4 Governor
#5Cable from fuel peddle and governor control
#6 ?

NOPE. NOPE. Definitely NOT.

#1 is Fast Idle air cylinder that pushes the interior governor parts raising idle to about 900rpm. It's all internal to the Governor workings.
#2 is shutdown air cylinder that pushes on the shutdown lever #6
#6 is shutdown lever on the top of the governor housing #4, the governor assembly itself is inside. The Governor is a whole series of parts working together for control.
#4 Governor housing with internal parts that control the fuel racks in both banks.
#5 Throttle lever with attached cable to the pedal up front.

But don't take my word for it. Get the MCI book and check it out yourself it's all in there. You Do have an MCI book.... Right? If not, go get it, you NEED it. It wouldn't be a bad idea to also get a real Detroit Diesel Engine book for the 6V92. You'll need that too.

A real question I have is what the hell that other unnumbered and apparently useless
extra air cylinder placed to push on the unusual shaped throttle lever weirdness is all about. Never seen anything like it and it's so far back it obviously doesn't or intended to do anything at all. All I can think of is that it is supposed to prevent the throttle lever and thus the pedal from being advanced, as if some function is interlocking the engine from being revved up. I've only ever encountered this in some GMC Suburbans I drove that had 4-spd manual transmissions and the wizards at GMC thought it was a great idea to prevent the driver from slipping the clutch when shifting and prevented the throttle from functioning until the clutch was mostly engaged. It was an air driven setup not unlike this one pictured. All it ever did was contribute to the potential of a fiery death and destruction of the bus and all it's pax while the driver fought to overcome the damn thing while needing power to get out of a situation. Made normal shifting almost impossible too. Pretty much hated it.

You stated this MC9 has a 5-spd..... Would that happen to be one of the nice 5-spd MANUAL transmissions, that I would like to find for myself, or the 5-spd Allison??

I'm going out on a limb and guess it's the Manual and this extra air cylinder may have been there to do something similar to what I described. If so it deserves to be completely disabled and even removed, which it seems someone may have already done by moving it so far away from the throttle lever as to have no contact with it. In case it still woks I'd get it out of there as fast as you can. It's a definite PITA and only contributes to fighting the driver in the proper operation of the bus. Learn to drive it correctly and you'll never miss it, and the bus will likely be easier and more fun to drive.

As to your problem of crank no start. I'd check to make sure the air cylinder #2 that pushes on the shutoff lever #6 is really retracting and allowing for the shutoff lever to turn counter-clockwise to it's run position. The cylinder may be sticking and not retracting, for instance. An easy test is to unscrew the entire cylinder #2 from the cover and see if the shutoff lever moves freely. This is a simple thing to run down and if the fuel shutoff lever is not going to run and remains in shutdown (clockwise) then the governor won't let the engine start. It could also be an electrical problem where the Skinner valve that sends air or releases air from the shutdown cylinder is not working properly or has a broken wire etc.. Another possibility is that the mechanics' switches on the rear panel may be set to safety and won't let it start. Usually the safety won't let it crank either so probably not this, but the electrical systems should be checked.

The easiest thing is to remove the shutdown air cylinder and see if the engine will start. This defeats ALL other interlocks trying to keep it from starting. If it starts you know to look somewhere for where the fault is and fix it. If it starts you can easily reach in and turn the shutdown clockwise to stop the engine with your hand when you're done, but I'd let it build up air too. I do this all the time and it's how you can keep a mechanical DD up and running when all else fails.

Concerning the emergency air shutoff dampener you mention, it isn't on the turbo-charged engines. It's located on the inlet to the Roots blower where the air induction hose comes in. Only the non-turbo engines had it. You didn't say but I'm assuming it's a turbo'd 6-92 which was the default configuration for that era, especially if it has the 5-spd manual shift linkage sweetness, which came toward the end of production. That's what I'm hoping to find for myself someday. If it is a non-turbo you may really have tripped the damper and it's very easily reset but you need to provide a little more info on your engine and then we can help you with resetting it. This info is definitely in the DD engine manual and should be in the MCI manual as well. You should have them both as well as a transmission manual.

[Dave5Cs]

So whats 3?

[Bill Gerrie]

When you replaced the fuel lines did you leave the check valve in the suction line and the restrictor fitting in the return line? They must be there.

[tr206]

Did you make sure when you or whoever made the new fuel lines that all are unrestricked (could you blow air through them both ways freely?) it happens.

[brianzero]

NOPE. NOPE. Definitely NOT.

#1 is Fast Idle air cylinder that pushes the interior governor parts raising idle to about 900rpm. It's all internal to the Governor workings.
#2 is shutdown air cylinder that pushes on the shutdown lever #6
#6 is shutdown lever on the top of the governor housing #4, the governor assembly itself is inside. The Governor is a whole series of parts working together for control.
#4 Governor housing with internal parts that control the fuel racks in both banks.
#5 Throttle lever with attached cable to the pedal up front.

But don't take my word for it. Get the MCI book and check it out yourself it's all in there. You Do have an MCI book.... Right? If not, go get it, you NEED it. It wouldn't be a bad idea to also get a real Detroit Diesel Engine book for the 6V92. You'll need that too.

A real question I have is what the hell that other unnumbered and apparently useless
extra air cylinder placed to push on the unusual shaped throttle lever weirdness is all about. Never seen anything like it and it's so far back it obviously doesn't or intended to do anything at all. All I can think of is that it is supposed to prevent the throttle lever and thus the pedal from being advanced, as if some function is interlocking the engine from being revved up. I've only ever encountered this in some GMC Suburbans I drove that had 4-spd manual transmissions and the wizards at GMC thought it was a great idea to prevent the driver from slipping the clutch when shifting and prevented the throttle from functioning until the clutch was mostly engaged. It was an air driven setup not unlike this one pictured. All it ever did was contribute to the potential of a fiery death and destruction of the bus and all it's pax while the driver fought to overcome the damn thing while needing power to get out of a situation. Made normal shifting almost impossible too. Pretty much hated it.

You stated this MC9 has a 5-spd..... Would that happen to be one of the nice 5-spd MANUAL transmissions, that I would like to find for myself, or the 5-spd Allison??

I'm going out on a limb and guess it's the Manual and this extra air cylinder may have been there to do something similar to what I described. If so it deserves to be completely disabled and even removed, which it seems someone may have already done by moving it so far away from the throttle lever as to have no contact with it. In case it still woks I'd get it out of there as fast as you can. It's a definite PITA and only contributes to fighting the driver in the proper operation of the bus. Learn to drive it correctly and you'll never miss it, and the bus will likely be easier and more fun to drive.

As to your problem of crank no start. I'd check to make sure the air cylinder #2 that pushes on the shutoff lever #6 is really retracting and allowing for the shutoff lever to turn counter-clockwise to it's run position. The cylinder may be sticking and not retracting, for instance. An easy test is to unscrew the entire cylinder #2 from the cover and see if the shutoff lever moves freely. This is a simple thing to run down and if the fuel shutoff lever is not going to run and remains in shutdown (clockwise) then the governor won't let the engine start. It could also be an electrical problem where the Skinner valve that sends air or releases air from the shutdown cylinder is not working properly or has a broken wire etc.. Another possibility is that the mechanics' switches on the rear panel may be set to safety and won't let it start. Usually the safety won't let it crank either so probably not this, but the electrical systems should be checked.

The easiest thing is to remove the shutdown air cylinder and see if the engine will start. This defeats ALL other interlocks trying to keep it from starting. If it starts you know to look somewhere for where the fault is and fix it. If it starts you can easily reach in and turn the shutdown clockwise to stop the engine with your hand when you're done, but I'd let it build up air too. I do this all the time and it's how you can keep a mechanical DD up and running when all else fails.

Concerning the emergency air shutoff dampener you mention, it isn't on the turbo-charged engines. It's located on the inlet to the Roots blower where the air induction hose comes in. Only the non-turbo engines had it. You didn't say but I'm assuming it's a turbo'd 6-92 which was the default configuration for that era, especially if it has the 5-spd manual shift linkage sweetness, which came toward the end of production. That's what I'm hoping to find for myself someday. If it is a non-turbo you may really have tripped the damper and it's very easily reset but you need to provide a little more info on your engine and then we can help you with resetting it. This info is definitely in the DD engine manual and should be in the MCI manual as well. You should have them both as well as a transmission manual.

Wow, thank you for this. This was the most helpful post that Ive seen in a while (no offense to the others who responded)!

Yes, you are correct, this is the Allison 5 speed. That throttle arm does at its maximum sweep make contact with #3 and that seems to be the valve you suggest to delete.

You are also correct about it be a turbo.

All of the rear controls are in the start position to start from the rear control panel.

The new hoses are clear of obstructions, and fuel is moving through them.

The anti-drainback valve on the fuel return line is clean and functions just fine.

I will try to move that governor in the clockwise direction during a start at the rear panel.