Stopping a diesel

[John Stumbles]

Prompted by the 'dsiabling a LDV van' thread, how *does* turning the 'ignition' switch stop a diesel engine? And a bonus question for another

10 points, how could one hack it to immobilise a vehicle?

[Adrian C]

Something to do with warming glowplugs when they shouldn't be warmed?

And then warming them a bit too much?....

Dunno. Me drink unleaded...

[Adam Aglionby]

as telling me that

Solenoid strangle valve on the fuel pump shuts feed off.

Bonus points for putting too much oil in so that in can go into runaway burning engine oil via breather pipes and air intake, then switching igntion off dosen`t help...

Adam

[Andrew Mawson]

"ignition" (*) switch enables a fuel solenod valve which is usually screwed into the injector pump. No power to solenoid, no fuel, engine stops.

(*) misnomer - no electric ignition on a diesel by definition !!

AWEM

[AJH]

On older ones it removes power from the solenoid that allows fuel into the injector pump, on newer common rail systems it'll just shut power off to the pump and electronics that pressurise it.

On the old system just hide a switch in the line to the solenoid. We also had emergency stops on big tractors that released a spring loaded butterfly valve in the inlet manifold, not many people realised this and it was a classic trick at auctions to flip it and make the thing look like it was a non runner.

Apologies for the e-mail reply!

AJH

[Andy Dingley]

It stops fuel getting squirted into the cylinders - no more, no less. As this is used to _stop_ the engine, not just to prevent it starting, it needs to act quickly and it's not enough to simply cut power to the lift pump from the fuel tank. The "typical" mechanism is a solenoid- activated linkage to the mechanical fuel pump. Modern cars might have something using electromechanical injectors and a signal to the ECU, older trucks used a purely mechanical cable link to the pump - turning off their "ignition switch" didn't stop the engine. There's already a "rack" connected to the accelerator pedal to control the fuel amount delivered, this stop cable just pulls it right back to the "zero fuel" position.

My Dad once had a "ghost" start one of his trucks at dead of night, in the garage a few miles from the house. When he went down there it was idling away to itself quite happily, still locked and with no keys anywhere near it. The driver had pushed the "Stop engine" knob back into the panel between the seats after parking up for the day, as otherwise the protruding knob could easily get bent and broken. This night though there was a fault on the starter motor (cracked insulator) which allowed the solenoid contact to touch the main power to the starter. The solenoid engaged, the starter spun and away went the engine...

[Andy Dingley]

That's why there's a big wooden cone on a chain, hanging up in the test cell. If you can't stop the fuel, stop the air.

There used to be a tennis ball instead, but an engine ate it...

[Dave Plowman (News)]

Operates a fuel cutoff valve.

Hack into the circuit?

[The Natural Philosopher]

It stops the electrionnic injectors usually, and the fuel pump that fees them.

IIRC in teh case of fully mechanical diesels, you have to do something pretty odd to stop them. Like turining off the fuel..I recall an anecdote about a marine diesel that sprang a leak in a fuel pipe near the air intake..I believe the alarmed skipper finally shoved a jersey in the air intake..anyway melle going in, and you can generally shift the injectors right off it..sort of super low idle to nothing..

[dom]

As others have said, solenoid valve on the injector pump on older models (ok - a manual shut off on really old stuff!). There may be engine electronics that also prevent the starter motor engaging without seeing the ignition key transponder, but that's probably easily hotwired too.

Newer direct injection models may need the electronics for the electronic throttle and controlling pump timing.

The latest common rail stuff have solenoid controlled injectors (or piezo valves on the VW pumpe deuse) and are dependent on the engine management for timing.

With the latter two, if you have an ignition key transponder with rolling codes, I wouldn't think extra security is necessary.

For preventing theft on the old stuff, an extra inaccessible solenoid valve in the fuel line, hooked to a modern alarm/immobiliser should offer reasonable protection.

[Andy Dingley]

No, _old_ stuff is where the "ignition key" is the one that padlocks the blowlamp used to pre-heat the hot bulb...

[Steve Firth]

It is best to keep the platinum tubes on a low light under the gas grill if one needs to have an early start in the morning.

That's a paraphrase of the advice given in "Braithwaites Retrospectives in Surgery" dated 1912 to doctors who intended to buy a car.

[Dave Plowman (News)]

On an LDV? ;-)

[Andy Dingley]

Cuts the power to the phone, so you can't call out DafAid

[Michael Chare]

Pass. But it does work. I recently switched off the engine of a bus (coach) when the driver left it running unattended outside my motel room. I just turned an ignition key on the steering column - very much as in a car. I was very tempted to remove the key and drop it through the letter box of the local police station.

[somebody]

In message , John Stumbles writes

Easy. Call it a Transit[1][2][3][4].

Hth Someone

[1] Only for those who have a spare van to pick up all of the other bits that might fall off. [2] Trust me, I got one (or atleast lots of bits that used to make one)! [3] Saying that I was comparing (whining?) about lack of reliability of said Transit in the pub t'other night with a fellow who has an LDV. Nothing has broken on mine for nearly six weeks. We reckon Ford started building Stealth into their problem portfolio. [4] His LDV hasn't broken recently either and we're running out of things to talk (whine) about :-)