Kill switch how-to

[dcb]

Originally Posted by Piwoslaw

...Re fuel pump: I read somewhere in this forum that there is enough pressure in the fuel lines between the pump and injectors that the engine could go another 2 blocks before running out of fuel.

That may be for a gasser, but it IS how you turned off the old vw diesels. I think I will pop the hood and disconnect the solenoid with the engine running and see what happens.

[jtgh]

you need to start a diesel post, "day and night" it's hard enough to talk 20 years of gas.

btw , the newest cars , can run on either the crank or cam sensors.
CAn= SOME CAN and some cant.
Like many Lexus's do.

how ever it is very hard for the engine to run just on a crank sensor. (only)
because the ECU dont know TDC 1 from TDC 4 (4cyl)
see? The cam sensor only tells the Cyl # on many new cars. see?

but some genius designers invented a go to a limp-home mod that uses
bank injection fire (all at once) (no need for cam sensor)
and wasted spark.
Kinda like a carb on the injection side
and like an old 1970 4cyl Honda 750 motorcycle (one of the first wasted spark motors)
the results, motor runs but not too clean (smog).
see?
newer cars are smarter and have more advanced, limp home modes and mimic modes.
study advanced OBD2 for those topics.

mimic is when a sensor dies, and the Brain simulates it the best it can.

in order to fool your ecu, you have to be a bit smarter, than it (joke)


Diesel. Diesels don't have spark and most dont have a throttle.
they run WOT with air full time. (there are exceptions_ on the WOT issues)
so all control is by the injection. (old fuel pumps, new have direct injection)
so that is a whole diffr,matter .
i have no ECU / PCM direct experience.

Again. best is to start a post on a specific car. They are all Different.
How ever you can experiment.
a relay that cuts CAS cam and CAS crank , will kill any gas motor dead.
and switch controlling said switch.

cas, crank angle sensor and cam angle sensor. (cmp , and CkP , old names)

how is that for ODB2 NFO?

[dcb]

It may be better organized if folks made car specific wiki pages w/kill switch and whatnot info.

Main Page - EcoModder

[jtgh]

how to cut fuel on a diesel gets complex , no ?

and how you do it , can cause unintended bad things.

starving fuel pump is bad (some need it to be lubed, so coasting with no lube, oops)
2 stage pumps, one in tank and the injector pump on motor. easy does it.?

and did you know some injectors will not close off , if there is no fuel pressure behind them. Including direct injection.
you really need to study the design of your diesel system first before , guessing.

get the EFI injection schematic first , look at the inputs and outputs and see what is available to play with. there will be cam timing scheme there. we exploit that.

[dcb]

holding in the fuel cutoff kill switch while coasting in gear in your bosch pump style vw diesel is probably not the best idea, no.

[8v fury]

You might cause more problems by doing that to a vw diesel motor.

[dcb]

can you be more specific? Shutting off the fuel at the solenoid is what happens when you turn the key off, VW has been doing "that" to a diesel motor for over 30 years.

[MechEngVT]

Originally Posted by dcb

holding in the fuel cutoff kill switch while coasting in gear in your bosch pump style vw diesel is probably not the best idea, no.

No, but why would you kill fuel while coasting *in* gear?

Killing fuel at the shutoff solenoid while coasting in neutral should be no problem, as that's identical to a normal shutdown procedure (except the vehicle's moving, but the driveline is disconnected from the engine).

Diesels have a fuel shutoff solenoid. Some energize to run (hold power to keep fuel open, fail-safe), some energize to kill (momentary action to shut down fuel). I would imagine that most automakers would prefer the former for legal reasons but continuous duty solenoids do cost more. These solenoids act on the high-pressure side so the injection pump is not starved during shutdown (that would cause a royal PITA to re-prime the fuel line if you aren't running a self-priming electric lift pump). Research your vehicle to determine which shutdown mode your engine uses and kill or activate that solenoid appropriately.

[Piwoslaw]

Originally Posted by dcb

That may be for a gasser, but it IS how you turned off the old vw diesels. I think I will pop the hood and disconnect the solenoid with the engine running and see what happens.

Oh, please keep us informed.
:gone-back-to-impatient-waiting:

[8v fury]

The best people to check with about the vw diesels are people on vwvortex and the tdi forums.