The Stovebolt Site Forums The Parking Lot Big Bolts 1966? GMC 9500 dump truck

I ran across a late 60's GMC 9500 series dump truck with a Detroit diesel, just wondering what model that monster Detroit is and how many gears the tranny has. I'm pretty sure it's a '66 or '67 the keys are the old Briggs&Stratton octagon head. It has a regular 2 speed electric shift axle with 20" Dayton cast spoke wheels. The engine is really clean and the oil level was full and looks normal, not sure why the truck was parked other than the cab being rusted beyond repair.

Well, most likely it is a 6-71, but it also could be an 8V-71. How many cylinders does it have? The trans could be many different ones, but since you mentioned 2-Speed Rear, it is most likely a 5-Speed Trans.

Any pictures available?

Winn Dixie grocery stores ran a bunch of GMC 9500 tractors with a dead pusher axle and a 2-speed 23,000lb. single rear. I saw one many years ago made into a tandem dump, but most were scraped out for parts. Most other 9500 GMC's were full screw tandems with mainly 6-71 Detroits. A few were 8v-71 Detroit. Most all of them had either 10 spd or 13 spd roadrangers. We ran 3 of these trucks until the mid 80's and they gave fairly good service. The motors had to run at high RPM's to provide adequate torque. The motors were bad about leaking oil at the blower tube and the one piece heads would easily crack when hot. Properly run the 2 cycle Detroits would give good service. I miss hearing them out on the road, they made an unforgettable whine when wound up under load! JAMES

Not sure how many cylinders, i'll check tomorrow. And it's a single axle, not a tandem. I'm sure it has more than 5 gears, I climbed in the cab to check but a swarm of red wasps made me get out quick! Might get a battery and see if she'll crank over just for kicks, heck we might even try to fire it up. I'll be sure to get some pictures once we tow it to the yard, sad thing is it's probably going to the scrapper.

Be careful starting a long time sleeping Detroit Diesel.
If an injector is stuck open, or sticks once started, you can't cut it off just by moving the lever on the governor as you normally would.

To check for stuck injectors remove the valve cover, and twist on the tube with all the fingers reaching into the racks on each injector. If the tube and racks mover very freely things are probably OK. Check this under both valve covers on a V engine.

When you start it for the first time you can put some vice grips on this tube to force it into the no fuel position if they get sticky and the engine tries to run away.

Also be sure the emergency air shutoff on the blower inlet is functioning, and handy to get to, as this will kill the engine if it tries to run away.

And it won't hurt to have a CO fire extinguisher beside you when you start it, that directed into the air intake will also kill a run away engine.

If none of the above take the air cleaner or hose off the blower inlet, and have a 2X6 or similar to cover the air inlet and starve the engine of air.

If it has fuel chances are it will start and run, Detroits are really good about starting.

If you don't see any white smoke when cranking, then either won't help, it's not getting fuel. Use the either very sparingly if needed.

Grigg

Oh yeah she's got fuel, plenty of it the driver side saddle tank looks like it holds at least 50 gallons and it's half full. Thanks for the info on starting a sleeping Detroit, last thing we want to do is screw it up if it's a good runner. I heard WD40 is the best starting aid to use on a diesel engine when it's needed, nowhere near as bad as ether. Man I hope we get it fired up, I've never heard an old 2 cycle Detroit run in person. It's even straight piped, one big 6" rusty stack behind the cab!

If there is a primer pump, usually a hand operated plunger one somewhere, use it.
If it won't start use a small electric pump around the gear pump on the engine to get fuel in everything, then reconnect the gear pump and give it a try. If you have some good batteries it should even prime it's self as is, or if it needs help you can get a can of fuel connected to the suction side of the primary filter (where the big fuel tank is connected) and hold it above the pump on the engine.

Good luck,
Grigg

The old screaming jimmies were very hard to start if they ran out of fuel. They have a primary and secondary filter that has to be full and all the air has to be bled out of the lines. The best would be to find an old mechanic that is very familiar with them. Most of them are retired now and would probably help for nothing. There is a very good chance that blower seals leak and they will run away on oil. Most of them had an emergency stop kind of like a stove damper. Have the intake piping off so you can completely shut off the air supply if it runs away. Many of the old drivers stuck a pillow in the air intake to stop a run away. I would put fresh fuel in. Fuel gets stale and if you're in S. Texas it probably has fungus growing in it. Fungus looks like black powder and stops up filters in a hurry.

I would like to respectfully disagree.
I drove a 61 truck with a 6V53T Detroit across the country three times, and it had no fuel gauge
(other than a stick). Occasionally I would run low on fuel, it would suck air, and sputter, sometimes quit all together. I would pull over, dump 5 gallons in it, crank it over for about 10 seconds or less, it would start, and we would head on down the road. The pickup in the tank was on the left side, so in a left turn the fuel would run away from it, it would suck air, that's when I knew to stop for fuel, or add the 5 gallons.

A Detroit by design pumps a lot of fuel, roughly a gallon per minute at idle is returned to the tank, this volume is what easily and quickly clears out the air in the system.

The gear pump is not always self priming, but if you put the fuel level higher than it, it will do just fine. And as in my case if it just sucks a little air there is still enough fuel in the lines for it to work as usual once more fuel is in the tank.

If you replace the filters fill them with fuel if you can, but generally there is no need to crack any fuel lines and bleed air out.

If you expect to run out of fuel,or have a hydraulic or air starter (limited cranking time) then a hand primer, or electric one, is all you will ever need to get the fuel system ready for the engine to start again.

Grigg

You are right that if you shut them down as soon as you noticed you were running out of fuel it wasn't that bad. I was still driving 150,000 miles a year in the 60's and 70's, mostly with a Cummins, but I saw lots of jimmies on the side of the road that drivers had run completely dry. Also, in those days our shop was the only one around. We were located on the crossroads of US 87 which was a major route from the Valley and the Gulf Coast to Denver and on up to Canada and US 290 which was a major route from Southern California to Florida. This was before the interstate system. There was hardly a day we didn't have a road call to start a Detroit. And yes we did use an electric pump rigged up to prime them. However, I don't think Robert is really prepared for this and there is always a possibility of a runaway if an engine that has been out of service a long time. I still think he should get someone with Detroit experience to help him start it

We didn't get to pull the truck in yet and we're gonna have to hold out for awhile, with all the mud from the rain we're gonna have a hard time getting it out. I also didn't get to check the engine to see which one it is, we did get all the wasps killed though. Oh yeah last time this truck was tagged is '98 so we won't trust the old fuel, gonna drain the tank. And no I don't know a lot about these engines, when I get around to messing with it I'm gonna get a neighbor to help out he used to be a truck driver and knows a lot about Detroit and CAT engines. By the way when y'all say a "runaway" engine what exactly do you mean?

A 'runaway motor' is when the motor runs well beyond the governor RPM limits, it is beyond the operator's control to shut down. The engine will turn so fast that it will sling the belts off and the pistons will strike the valves. The engine will literally self destruct. Its about the worst thing to happen to a motor short of seizing it up due to lack of oil. JAMES

A diesel engine can only be shut down in two ways. Either cut off the fuel supply or cut off the air supply. There is of course no ignition. Fuel pumps can hang, but a worse threat is a blower leaking oil into the intake, and of course oil will burn like diesel. In later models that had a turbo, seals can go out and dump oil into the intake. The engine will self destruct. If something happens that you can't control the fuel or oil in the intake, you must cut off the air supply. Most if not all Detroits had an emergency kill, but they are not always operative. We always had something handy such as a wadded up sheet out of a sleeper to kill a Detroit in case they ran away if we had any reason to think that they might leak oil into the intake.

You are right about a motor oil fueled runaway, we had a Cat 3306 (sorry motor in a truck!) to runaway when its turbo went out. The driver couldn't shut it down so the motor sucked all of its crankcase oil out and then seized up tight. It didn't take long to happen! Nothing good was left on the engine. JAMES

Have a '59 John Deere 435D with a 2 cylinder Detroit diesel that ran away after a fresh rebuild. Began burning oil from its oil bath breather but luckily it had a non original air cut off built in so I was able to shut it off just in time. A fuel cut off would not have helped. I was unhappy with the unoriginal cutoff until after this event happed. I would have had a completely ruined, freshly rebuilt John Deere.

There was a company in San Francisco in the late 70's called Watson & Meehan that rebuilt lots of diesels, Detroits in particular. Every one got a dyno run as part of the after-buildup testing. One Detroit ran away after an injector rack jammed, and the kid running the dyno test stand panicked and threw a handful of rags into the top of the blower. (No shutdown housing!) Pieces of the blower ended up all over the test room. Fortunately, none of them managed to mangle the operator! (The engine stopped, BTW!)
Jerry

I have heard of them being fed, and eating whole service manuals, in an attempt to stop a runaway condition.

Grigg

Sounds like irony.

I also have a '59 JD 435 which is pretty much original and has no emergency cut off. I have it in my mind constantly, to pop off the standard breather and flip it over to block off the air intake if ever necessary. I was surprise to learn when I first got it that it didn't have one. I always wanted to install one. Is your cut off custom made?

An upgrade for a Detroit with the two screw fingers on the fuel control tube is to use the newer spring loaded single screw fingers.
Often people refer to this as a "spring loaded rack" although not entirely correct.

The advantage is if the rack on one injector sticks in the full fuel position the other one can still be moved to the no fuel position, and likely get the engine stopped.
With the old type fuel control tube with two screws if one injector sticks in the full fuel position, the others are stuck too.

I am not sure if a single screw fuel control tube was ever made for a 2-53, but I am sure a 3 or 4 cylinder one can be cut down.

Call Timothy or Harold at Leid Diesel in PA (717) 776 7725, they will know the answer, and will have or can get the parts.

Not all Detroits have an emergency air shutoff, almost all turbocharged models didn't but they did have the spring loaded fingers.

the truck I had with the twin turbocharged 6V53T had the old style fuel control tubes, and no air shutoff, one of the upgrades I did was swap them out for the spring loaded ones.

When the new style fuel control tube came even most if not all non turbocharged engines did not have emergency air shutoffs any more.
I have the original blower inlet housing from a 4-53N with no air shutoff in it. Last few evenings I have been cutting it apart and welding it back together to work with a front mounted inter-cooler on my engine.

Grigg

Appreciate the info Grigg. I'll check into that.

Bill

Sent PM to ya C10 - C90 Bill

I found out more info on the truck yesterday, the engine has a bad crank. The guy said he was driving it back in '98 and he hit a big hole in the road and I guess it jarred the engine so bad it bent the crank? I didn't really understand what he meant. He told me it'll run but you'll hear the engine knocking really bad, they just didn't want to spend money on the truck since it's already in sad shape. Not sure if we'll get to mess with it for awhile, been busy working but the truck ain't going anywhere.

i just finished rebuilding a tall deck 427 for my 2 ton and it's crank was broken right before the last main bearing it was knocking pretty bad i had to line hone the mains because it warped the block a little.

Now the truck is at the yard and next Friday I might get a chance to crank the old Detroit over, not gonna try to start it yet though. I'll bet it's gonna be knocking like a son of a gun when we get it fired up, if it's really bad we're probably just end up junking it. I'll also get some pictures of the truck for y'all. I put air in the reserve tank today and the system holds air pressure and the parking brakes seem to work. We're gonna try to fix the three flats so it can roll, both left rear duals and the outer right dual are flat but that's no problem we have all the stuff to work on those old splitrims.

Even if you don't intend to start it still check for injectors being stuck before cranking it over. If it has fuel, and the injectors are stuck in the full or partial fuel position it will run. And make sure the air shutoff works just in case.

If they are stuck in the 'No fuel" position (fuel control rack on each injector pulled all the way out) then it can't hurt to turn it over, as it won't start.

If you find it does have a stuck injector, and want to run it any how.. Loosen the finger on the fuel control tube and slide it out of that injector's rack, and tighten it again out of the way, and be sure the other racks can travel all the way out to the no fuel position. Also pull the two fuel jumper lines from the fuel manifolds in the head going to the injector, and use one to loop between the two fittings on the head, the injector is then disconnected from the fuel system, and the fuel won't make a mess on the engine side.

Grigg

itend to agree with grigg the detriot 2 stroke diesels are still going strong in military vechicles such as the hemmit and the palletized load system truck and in the marine corps mk48 series see oshkosh truck for details and ive seen a 8v92 come apart from a runaway its not pretty they will eat tms ive always got a aluminum clipboard made out of 1/4 in aluminum handy if ive got to start a fresh rebiulit it gets the turbo tube intake taken off and the we start it have fun and be safe