I disagree. A throttle controls the flow of air into the engine. Whether it’s diesel or gasoline engine with fuel injection it changes the flow of air into the engine and that represents half the fuel needed for combustion.
Now you don’t need a throttle in either type of engine but if they’re on one they absolutely affect how air is metered into it.
No, does that change anything? If it has a throttle with an electric idle circuit then that would be the way to go. Cut off the air and the engine is dead. If the engine doesn’t have this then the cheapest fix would be an electric fuel cut off valve. It’s not rocket science to shut an engine down. there are only 2 variable keeping it alive.
If this is not too much of hijack, how does a diesel with mechanically actuated injectors accelerate? Is it just by increasing fuel pressure to get more fuel in each injection? Can the injectors be held open longer somehow?
Diesels don’t have throttles- the air intake is always wide open. The engine speed is controlled by how much fuel is injected. More fuel, higher RPM. The amount of fuel injected is controlled by varying how far the plunger in the pump for that cylinder’s injector travels.
I believe you fail to understand how this diesel engine system works. There is no electrical circuit involved in keeping the engine running, and the engine cannot be stopped by interrupting any circuit, not even by disconnecting the battery.
Now, I’m not a diesel expert so I’ll grant it’s possible I’m mistaken, and welcome correction if that’s the case. But if you want to contend that there is “disconnect this wire” answer to the OP’s query, then specify EXACTLY which wire, EXACTLY what it goes to, and EXPLAIN how that will shut off the engine. Saying in effect “there must be some wire somewhere that will do it” is almost certainly flat out wrong.
So how is this done mechanically? Are the mechanical actuators actually solenoid controlled and the mechanical action is simply to start the injection process?
I already posted a picture of a diesel with a throttle on it. Here’s one for a VW.
I understand how a diesel works but they’re putting throttle bodies on them for whatever pollution control requirements are needed. I simply made a suggestion on how to use one for the op’s benefit if it used an electric solenoid to stay open. Looking at pictures of his engine I don’t think it has one. My other suggestion was to install a relatively cheap 12 volt fuel valve.
You’re quite right, at least for older ones. I drove some old dump trucks that you could turn the key off and continue driving them around. Turning the key off simply turned off electrical devices like the radio, fan, etc. It had a big red knob you had to pull to kill the engine.
Somewhat modern ones like the 89 F250 I used to drive have an electrical fuel cut-off switch. More modern ones are controlled by computers. It sounds like the OP’s diesel has no way of shutting down the engine electrically. Unless killing the starter suits him, he’ll probably have to install a fuel cut-off valve as was mentioned. I’m thinking that wouldn’t be a very challenging task.
I like the idea of disabling the starter.
Also another fun thing I could do would be to have the relay engage the horn. The truck has a rather loud air horn and that’s gonna draw some attention. This will have the added effect that it will slowly bleed the air from the reservoirs so the brakes would eventually lock, hopefully not too rapidly to cause the truck to go out of control.
it’s not easy to explain (and I can’t find any pictures that make it any clearer) but I’ll try. for an in-line mechanical injection pump, you have a case. inside the case is a camshaft which is driven by the engine at 1/2 crankshaft speed. riding on the lobes of this camshaft are pistons (plungers) which move back and forth inside their own cylinders (one for each cylinder that the engine has.) fuel enters the plunger’s cylinder, and as it rides up the lobe of the camshaft the plunger pressurizes the fuel line to the injector. when the pressure overcomes the injector spring, fuel flows into the combustion chamber.
with this simple plunger-on-cam setup, the pump will inject the same amount of fuel each and every time which means you’d have no control over engine power output. So, the plunger cylinder has a hole in its side partway up the bore. The plunger itself has a partially helical groove machined into its side. When the cam pushes the plunger up and any part of that groove lines up with the hole in the plunger cylinder (the “spill port”) the fuel diverts back into the supply instead of being used to pressurize the injector. So if you can control the position of the spill port relative to the groove in the plunger, you can control how much of the plunger’s travel actually is used to pressurize the fuel. So when you push down on the pedal, you’re controlling how much fuel spills back vs how much is injected.
I do agree that I have a lot to learn about diesels.
But doesn’t (nearly) every vehicle have a key-operated ignition switch, located in the steering column or dashboard, with wires connected to it?
And when the driver turns the key to the “Off” position, the wire(s) coming from the back of the ignition switch lose power, and the engine ceases to operate?
For the purposes of making the engine not run, one not need concern oneself with what circuit(s) are powered by the wire coming from the ignition switch.
All we need to know is that if we interrupt the “power with key in Run and Start” wire from the key switch, the engine stops working. And we can accomplish this by any of the following: Turning off the key, cutting the wire in half, or interrupting the wire’s continuity with a relay.
The only reason I don’t mention a specific wire color or location is because I am not familiar with the OP’s vehicle.
But it should be a simple matter of accessing the backside of the ignition switch, testing for a wire that shows positive during the Run and Start positions. Start engine, cut wire in half, observe that engine stops running. Then connect the normally closed contacts of a relay to the cut-in-half wire, and configure the GPS unit to energize the relay when desired.
Actually, I think that would be great.
Depending on your wiring savvy, you could have the GPS unit trigger relay(s) to activate the horn, hazard lights, and/or high beams, as well as your starter interrupt.
Hopefully, this would create enough confusion and attention to upset the thief enough to pull over and abandon the vehicle, but not lose control of it.
Then, once the vehicle is shut off, it won’t start again.
P.S. Not sure what you have for output(s) from your GPS, but ideally you’d want the horn to time out after a period, so as to not cause too much of a disturbance wherever it gets abandoned by the thief. Although if the air tank will run empty, that should accomplish that for you.
Thanks** jz**, that’s a pretty good explanation.
Go back and read post 7. On an old diesel once it starts the engine consumes NO electricity.
There is no cut the blue wire.
The OP can either disable the starter solenoid, or activate some other accessory or install a fuel cutoff valve.
The OP has a very old diesel which has no throttle body. Posting pictures of a modern Ford power stroke is the diesel equivalent of a guy with a 1960s gas engine car posting a question about his ignition points and carb, and you posting pictures of a MY2013 engine and telling him his engine doesn’t have points or a carb.
IOW Not correct and not terribly helpful.
Yes, I went on to post in 23 that his engine didn’t appear to have a throttle and then suggested a 12V fuel cutoff valve with a link.
I like his idea of using the air horn to bleed down the air brakes but wouldn’t the engine keep the reservoir filled while running?
It’s an air horn and would die when the air reservoir empties.
If you had read posts 5 & 7 you would have known it didn’t have a throttle.
The only issues I see with triggering the air horns are
That sounds like a fun thing to do. The thing about that is that the relay (if it’s like the one on my motorcycle alarm) is going to switch to off when the alarm is triggered so you can’t just splice it in directly to the horn wiring. You need to invert the signal or find some other way to do it. If you know much about electricity, it won’t be very hard but it’s more than just “run this wire to the horn and this wire to positive”.
I’m also in favor of a starter disable, as if anything in the setup fails, the vehicle will simply refuse to start. A nuisance, but not a safety hazard.
However I’m still failing to understand how the truck’s owner would turn the engine off at the end of a trip. I’m not familiar with the OP’s truck, but does it not have a key-operated electrical switch that one would move to the “off” position when done driving? Or does the driver shut the engine off another way?
P.S.: I’m more of a lurker than poster, but I always look forward to answers from you and Gary whenever an automotive question comes up here.
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