Excess fuel return dilemma

Same here Paul.
And the cold start button just allows the rack to go even further.
Once the governor takes control the cold start button's spring pops it back out.
This is why the old trucks used to really pull if free revving rpm's were increased and the cold start was locked in.
Modern electronic stuff has the capacity to control all this far more accurately.

Not sure if the model he has is the same as the earlier VE rotary's but they only have a cold start advance system. Cannot see the side of the pump to see what it has.
Nothing that adds more fuel.
The governor may go to full fuel while cranking but will pull back as soon as it fires.

Mechanical governors have two parts, a spring and flyweights. The spring is attached the the throttle lever, and the flyweights are attached to the injection pump shaft. The spring opens the rack (and metering valve) and the flyweights close it. When you have the throttle in a given position, the fuel delivered, and therefore engine speed, is a result of the balanced forces between the spring and flyweight. When the engine slows, the flyweights have less force, so the spring opens the rack. When the engine speeds up, the flyweights apply more force and close the rack.

Before starting, there is no flyweight force, so the small amount of spring tension in the idle position holds the rack open. Once the engine starts and picks up speed, the flyweights counteract the spring and hold the rack at minimum fuel. At full revs and no load, the spring tension and flyweights balance each other and the rack may only be at 30 to 40% open. Once the load comes on, the slight decrease in revs allows the spring to pull the rack fully open, and if the load increases, the engine will eventually slow down until it stalls. This is basically the same as when you stop the engine. The stop lever will pull the rack to zero fuel, against spring tension. Once the engine stops and the lever is released, the rack moves back to full fuel.

This is why older GM’s that have been sitting, may take off when started. The racks are exposed and may stick or bind from a tiny bit of corrosion, and because they are all linked, if one sticks in a certain position, they are all in that position. When the engine is stopped, the governor pushes the rack to full fuel, and the corrosion holds it there. When the engine starts, it will rev as much as the injectors will allow, and can only be shut off by stopping either the fuel or air supply. Later engines got around this by linking each rack with springs, so if one injector stuck open, the governor could pull the rest back to minimum fuel when the engine started.

Not disputing pumps got to full fuel to start but what Dave said was he gave it a boot full and it smoked.
Was already idling so off full fuel unless something was stuck or the boost compensator is out of adjustment.
A ruptured diaphragm will not allow boost to move the fuel pin to full fuel, particularly as free rev-ing will not supply a lot of boost.
Other option would be a very restricted air intake.
Cheers Steve

dieseldog wrote: Mechanical governors have two parts, a spring and flyweights. The spring is attached the the throttle lever, and the flyweights are attached to the injection pump shaft. The spring opens the rack (and metering valve) and the flyweights close it. When you have the throttle in a given position, the fuel delivered, and therefore engine speed, is a result of the balanced forces between the spring and flyweight. When the engine slows, the flyweights have less force, so the spring opens the rack. When the engine speeds up, the flyweights apply more force and close the rack.

Before starting, there is no flyweight force, so the small amount of spring tension in the idle position holds the rack open. Once the engine starts and picks up speed, the flyweights counteract the spring and hold the rack at minimum fuel. At full revs and no load, the spring tension and flyweights balance each other and the rack may only be at 30 to 40% open. Once the load comes on, the slight decrease in revs allows the spring to pull the rack fully open, and if the load increases, the engine will eventually slow down until it stalls. This is basically the same as when you stop the engine. The stop lever will pull the rack to zero fuel, against spring tension. Once the engine stops and the lever is released, the rack moves back to full fuel.

This is why older GM’s that have been sitting, may take off when started. The racks are exposed and may stick or bind from a tiny bit of corrosion, and because they are all linked, if one sticks in a certain position, they are all in that position. When the engine is stopped, the governor pushes the rack to full fuel, and the corrosion holds it there. When the engine starts, it will rev as much as the injectors will allow, and can only be shut off by stopping either the fuel or air supply. Later engines got around this by linking each rack with springs, so if one injector stuck open, the governor could pull the rest back to minimum fuel when the engine started.

Here in the UK I have had experience of the CAV pump racks on Gardner engines sticking, particularly if the engine has not been used for some time. On engines that have been in use I have occasionally come across situations of an engine that has been running at speed, take your foot off the accelerator pedal and the racks sticking in the minimal fuel/shut down position resulting in the engine stopping. Usually a good cleaning of the exposed parts of the racks and a squirt of WD40 solves the problem.

Blackduck59 wrote: Not disputing pumps got to full fuel to start but what Dave said was he gave it a boot full and it smoked.
Was already idling so off full fuel unless something was stuck or the boost compensator is out of adjustment.
A ruptured diaphragm will not allow boost to move the fuel pin to full fuel, particularly as free rev-ing will not supply a lot of boost.
Other option would be a very restricted air intake.
Cheers Steve

I was just offering a little governor theory. In this particular instance, there are so many unknowns- did Dave stab the throttle or hold it there for 30 seconds, what’s the condition of the injectors, where the pump settings changed when it was apart, how many kilometre on the engine, etc. I would look at the injectors. I generally do injectors by themselves, but if I do the pump I will do the injectors at the same time. A rebuilt pump that is now back in spec will be pushing the fuel through worn injectors, which might have a crook spray pattern, a dribble etc, causing black smoke.

I had an old 2.8 Hilux once upon a time. It had a new pump and injectors, and previous owner had the pump advanced. It made a little more power on the top end, but smoked like a bastard getting there. And I mean black smoke so thick that you almost couldn’t see the car behind you. It rattled something mean at idle, but once the revs were up, it ran smooth.

All good,
Have had my share of sticky GM racks, stuck injectors, sticky or moved throttle damper pistons and dodgy blower drives and governor weight splines. 12V71's sure howl when they are fully racked with no governor operation.
Stuck plungers in Cat pumps.
All good FUN but hard on other equipment when they stick on full plus RPM.
Cheers Steve

DD,
Been away from the garage for a few days, was developing "shed-fever", but back in to have another squiz today.
No, just gave it a very quick blurt up to about 3000rpm just to check the boost pressure gauge, then let it idle for about another minute before shutting her down.
Going by what you blokes are saying, it's a bit hit and miss not being able to put the engine under any genuine load.
As far as variables, probably many. Injector pump was done about 3 years ago, condition of injectors unknown, actual km's on the engine WAG about K300-K350 km's, so again unknown.
Can't bitch too much as a mate gave me the complete engine buckshee and it was running quite well when he reefed it out.
Be a while before I get around to any major work on the engine, since replacing the return fuel line has stopped the leaks, and have only started it on the odd occasion just testing the electrics etc.
Don't think there's any restriction in the air intake side of it, has the original canister jerried up to it with a new genuine air filter.
Once again, thanks for all input.
Just as an aside, now know just why auto-electricians earn their crust! Talk about time-consuming, thought doing away with all the electrics pertaining to the original petrol engine would be relatively basic. BAD assessment! All the old wiring was wrapped in some sort of hessian and then must have been coated with either tar or pitch, crumbles in your hands. So, ripped the whole shooting match out altogether and started from scratch.
Biggest problem was trying to locate original colour coded wire to try and at least keep it easier to follow the original workshop wiring diagram. Had to cheat a bit, some wires simply no longer made, but just about got her beaten now. Having bloody nightmares! Wiring in my sleep. Should have taken advice offered and sent the old harness out and had it copied. Too late now! Challenging.
Cheers, Dave

The best way to replicate a wiring harness is to get a sheet of plywood and pin the old harness out with nails/screws. Then it's just a matter of dropping the new wires in between the nails and taping up the branches. Once it's taped, slot it into convoluted tubing and away you go.