8.2L Detroit No Start

[OmniEquipped]

I'm working on an old tree service truck for an estate, 1987 Chevy 7000 with an 8.2. Was running when parked several years ago. Starts and runs easily with ether or gas rag, but won't run on its own. It has the newer style electronic governor with no visible shut off solenoid. I think it's pumping fuel because I noticed a small leak in the return line, which I fixed. I took the lid off the governor and inspected the motherboard, but I don't see any signs of shorts or melted spots. I removed the motherboard to access the rods that push the injector rails. I cannot move them manually more than a fraction of an inch, but I don't know exactly how it works so that may be normal. Anyone have any thoughts on diagnostics? Things to check?

 

[OmniEquipped]

I reckon nobody's probably dealt with one these in years. Anybody know a forum where some old timers might hang out?

 

[Birken Vogt]

This is as good as you are going to find, but you probably know that the 8.2 was not much good when new, and hasn't gotten any better with age.

Electronic governor on one of these is something I have never even heard of.

 

[hvy 1ton]

I don't know much about detroits, but have you checked the pressure coming off the fuel pump?

 

[JPV]

I think most guys that knew about them have tried hard to forget! I have a little experience, from what I remember on the mechanical governor to shut it down it moves the rack to a no fuel position which is done with a solenoid that pushes with a spring to shut it down and when energized releases to allow the racks to move. There is also a small lever to shut it down with a pull cable if it doesn't have the solenoid. I have never heard of one with an electronic governor so I have no idea what makes it work. If you pull the valve covers and disconnect the linkage to the rack you can see if each side moves freely. If an injector rack is stuck it could be keeping them all shut off but it seems like it should only be the one injector that is sticking that would be not firing if I recall.

 

[John C.]

We had one in a service truck years ago. Everybody hated the thing.

As I recall the fuel injection pump was mechanical with an electric solenoid to shut it down.

 

[OmniEquipped]

I think most guys that knew about them have tried hard to forget! I have a little experience, from what I remember on the mechanical governor to shut it down it moves the rack to a no fuel position which is done with a solenoid that pushes with a spring to shut it down and when energized releases to allow the racks to move. There is also a small lever to shut it down with a pull cable if it doesn't have the solenoid. I have never heard of one with an electronic governor so I have no idea what makes it work. If you pull the valve covers and disconnect the linkage to the rack you can see if each side moves freely. If an injector rack is stuck it could be keeping them all shut off but it seems like it should only be the one injector that is sticking that would be not firing if I recall.

JPV, you mention a stuck injector rack...is that prone to happen after setting a long period of time? The rods controlling the injector rack are on a mechanism under the mother board shown in the pic. Should I be able to manually push these rods? If so, one or both are stuck but I don't know if they are stuck by the rails or by something driving the governor that I can't see under there.

 

[RZucker]

This is weird. I've owned three 8.2L powered service trucks (newest was an '86) and have never seen this. An add on from the bucket boom manufacturer for throttle control? Or possibly some last gasp at a DDEC style control from Detroit Diesel? But that is throttle linkage, right?
And "parked several years" leads me to think stuck injector rack too. I see this all the time on the 2 stroke engines that sit for a few years.

 

[JPV]

I would guess it would be an injector sticking like Rzucker says, they are basically the same injectors as the 2 strokes.However I am thinking that if there is a shutoff solenoid that isn't working properly you wouldn't be able to move the rods as it holds the racks in the no fuel position. Even with that gizmo it is still a mechanically injected engine so there must be something that pushes or pulls the racks when you shut the key off. You have the key on when trying this and have checked all fuses? If you were to check the racks by disconnecting the linkage under the valve cover and making sure they move freely that is probably the best way to narrow it down. If someone asked me to trouble shoot one and I saw that thing in the picture I don't know for sure what I would do!

 

[d9gdon]

Yes, that computer board is controlling the throttle and had to be added there by the bucket lift manufacturer or whatever attachment is on that bed of the truck.

God I hated that Fuel Pincher just slightly more than the 3208 Cat engine. Eye burning and nose stinging sum beaches.

That fuel solenoid was a common problem on them, but I would agree that the rack is probably stuck after sitting.

 

[JPV]

It seems like the fuel shutoff solenoid made a pretty loud click when energized, if you don't hear anything when turning the key on it is probably not working. It should be sticking out the back of the governor, I don't remember how it is removed.

 

[RZucker]

It seems like the fuel shutoff solenoid made a pretty loud click when energized, if you don't hear anything when turning the key on it is probably not working. It should be sticking out the back of the governor, I don't remember how it is removed.

IIRC, it should be a screw/bolt on each side of the solenoid. They were energize to run so yes it should retract with the key on.

 

[Birken Vogt]

I can now see why they had an electronic governor. Probably not to do with driving but to do with working with the bucket up. The stock governor would not hold at any particular RPM with a light or no load. I learned this with fire trucks. With the pump engaged (load) they would behave. But if you just used the hand throttle to try and get say 1500 RPM to warm it up it would either creep up and run at governed (3300 RPM!) or drift down to slow idle. So for running the hydraulic pump they probably added this contraption.

 

[OmniEquipped]

I'm an expert at encountering weird crap that no one has seen before. It's a finely honed skill that took years to develop.

Anyway, I wonder if it was a factory option, because it all looks totally factory with the engine and harness. There is a high idle knob but it is attached directly to the pedal in the cab. The throttle cable goes from the pedal to the arm on the governor, but inside the governor cover there is no mechanical linkage. Instead, there is a potentiometer (like a TPS) so the throttle is totally fly-by-wire. The TPS goes to the circuit board and the circuit board has wires that go down under the mechanism with the rods that push the racks. Form the outside, this governor only has two tiny wires going to it, a ground and a key-on hot, both go directly into the circuit board. I don't think it is a fuse issue because I have 12v at the governor with the key on. However, I don't hear or see anything move...which brings me to the next weird thing, there is no fuel solenoid...at least not in the traditional sense, and certainly nothing matching the pictures of the solenoids on the mechanical governors. Two of the wires that go under the circuit board go way down to a small round object held into the very bottom with a snap ring. Could this be the fuel solenoid?

I'm going to take another look at it tomorrow evening. I need to get it running to sell, otherwise it's not going to bring anything. Hopefully, the amount of time I dump into this thing won't negate all my sales commission. I wonder what it would bring over the scales?

 

[kenh]

According to the Google listings for inf o n the governors there are herds of them around!

https://www.google.com/search?q=ele...t+8.2&ie=utf-8&oe=utf-8&client=firefox-b-1-ab

 

[OmniEquipped]

...and I've been to most of those links. Haven't found much useful. The only one exactly like mine (pics from a google image search) are from a post on truckmechanictips.com and there are no replies to his post.

 

[thepumpguysc]

You have to figure out WHY the rack wont move..
Which in most cases means, the valve cover has to come off..
Once the vc is off, you can follow the linkage to "the controller" & disconnect IT.. {whatever is shutting the machine down} THEN you can see if the rack is free..
IF it IS free.. back track..
WHATEVER YOU DO.. DO NOT try to start it without some sort of "shut down plan" in place.!!!
Those things will take-off in a heartbeat..{stuck injector}
You'll HAVE TO choke off the AIR.. cuz when they start to run away, they run on OIL splash> NOT fuel.. so shutting off the fuel is a waste of time..
A THICK piece of wood is used in most cases..
Good luck & let us know how its going..

 

[OmniEquipped]

I was running out of daylight yesterday, so instead of pulling valve covers I unhooked the rods at the governor to manually move the racks. The driver side moves and is spring loaded in both directions. The passenger side only moves and springs in one direction, so it's possibly stuck. In addition, the governor itself does nothing when the key is turned on or off...doesn't move, doesn't make noise, nothing. It's getting 12v and fuses look good. So you reckon the governor is bad, or some part within it?

 

[JPV]

I would get the rack moving properly first before doing anything else, there must be a crank sensor of some sort that tells the governor rpm so if it isn't spinning it might not move. If it is trying to move but the stick injector won't let it that could be the whole problem. When you try to start it after getting things freed up make sure to have a good method in place to put cover the intake in case it tries to run away like pump guy said. If you want to know why just watch a few youtube videos of engines running away.

 

[OmniEquipped]

It's not even trying to move that I can see. Just to be sure, I unhooked the rods so they wouldn't interfere with the governor and spun the engine over. Still no movement from the governor.