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Engine Specific Info and Questions => IDI Engine => Topic started by: haybayian on May 04, 2008, 07:31:09 am
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As I am putting together the wiring harness in a VW AAZ powered homebuilt sportscar I cannot help but to wonder at the wisdom of the solenoid driven fuel cut-off VW device. I have two diesel engines in my boat both equiped with a manual shut-off lever. They work fine and nothing can go wrong really. On the other hand our German marvel relies on a solenoid and a 15 A fuse.....What were they thinking?????
Does anyone know of a manual system, with a push/ pull cable and a knob?
Or do I have to fabricate my own?
Thanks,
Haybayian
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X2. Maybe you need to change your sig :P
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If, in fact, you have an automatic, then the pump is equipped with a manual shut-off lever. If the pump solenoid fails to not supplying fuel, then the plunger can be removed and the engine will run fine and the clutch dumping can be used to shut it off.
Andrew
Thank you for reacting to my post. I don't think that the magnetic valve in the VW is "wrong", I just think it is unnecessary and that a manual device would be "simpler". Now what is right/wrong, simple/complicated is a matter of perception, agreed. For someone with a perfectly running Jetta it would make little sense "fixing" what works. My own situation is different, I see this AAZ engine from the eyes of someone who is building an entire car from scratch..... this is the sort of adventure that triggers constructive criticism.
Your suggestion about the manual cutoff system to be found on automatic VWs is welcome, I will investigate.
Haybayian
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One thing about putting a separate manual shutoff (not the auto pump) is unless you can incorporate it into where the solenoid is, you are still going to be getting fuel for as long as the IP's vane pump can pump what is in the IP. Kind of like shutting the fuel off on a motorcycle, but having to run it a while if you want to drain the carb.
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One thing about putting a separate manual shutoff (not the auto pump) is unless you can incorporate it into where the solenoid is, you are still going to be getting fuel for as long as the IP's vane pump can pump what is in the IP. Kind of like shutting the fuel off on a motorcycle, but having to run it a while if you want to drain the carb.
Thanks,
I was sort of hoping that early 1.6 diesels VW might have a manual lever where the magnetic cut-off valve is now on the VE. I understand your point. I never considered shutting off the fuel upstream from the pump.
Haybayian
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My guess is that the VW engineers designed the solenoid to be the easiest system to integrate into the ignition key... they were working hard to remove barriers to people moving from gas to diesel engines and there are many documented instances of design decisions made to remove objections to the diesel engine. In my mind a manual fuel control is not as driver friendly as the good old fashioned ignition. The glow plug light and cold start knob are confusing enough ??!! :wink:
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My guess is that the VW engineers designed the solenoid to be the easiest system to integrate into the ignition key... they were working hard to remove barriers to people moving from gas to diesel engines and there are many documented instances of design decisions made to remove objections to the diesel engine. In my mind a manual fuel control is not as driver friendly as the good old fashioned ignition. The glow plug light and cold start knob are confusing enough ??!! :wink:
Thanks Vince,
Yes that was my guess too.
By throwing the question at this group I was assuming that most folks here are less focused on their rig's driver friendlyness and more on performance "mods" and that they would have an opinion. I guess in the big picture the cut-off system is not all that important.
Philippe.
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well why not integrate a system like on the mercs??? i believe those pumps use vacuum to stop. sure beats dumping the clutch all the time :lol:
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I'd like to have a manual shut off as well but I like having lots of knobs and shifters and whatnot. It would increase reliablity in a system that's not known for failure, so I guess that's a moot point. And it could save your butt in the middle of nowhere with a dead battery.
My Bosch distributor-type IP book mentions that there were cable operated fuel shut offs used in marine applications - theory being that you can still get home even with a complete electrical malfunction. Anyone seen a marine spec VE pump?
Chris
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I'd like to have a manual shut off as well but I like having lots of knobs and shifters and whatnot. It would increase reliablity in a system that's not known for failure, so I guess that's a moot point. And it could save your butt in the middle of nowhere with a dead battery.
My Bosch distributor-type IP book mentions that there were cable operated fuel shut offs used in marine applications - theory being that you can still get home even with a complete electrical malfunction. Anyone seen a marine spec VE pump?
Chris
I think Pathfinder was the name of the marinized diesel VW. Probably a 1.5 L. In a marine application you would still need a functional starter and battery. On the road (unless I am missing something) a good slope would fire her up.
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Yea, I was just repeating what I read. Maybe they meant for times when the engine is already running and the electrics fail? Not easy to bump start a boat...
Chris
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the dodge cummins with a ve pump also have a lever for manual pump shut off .
the vw's don't have this lever .
to make a shut off lever for a vw would require a person to have a very good knowledge of the ve pump and the ability to make a "hybrid " pump , combining vw parts , and a pump with a manual shut off lever .
this would be expensive and overly complicated to avoid what problem ??? the posibility of solinoid failure on the injection pump ?
i've never seen the solinoid fail in any vw .
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....plus the solenoid fails safe anyway.
It fails, it stops.
Simple.
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Has anyone made any progress on this? I was thinking about it because I would like to be able to start without electricity in an emergency. If you think about it one of the great benefits to this motor is that it can run completely mechanically. I thought that was the root of the original post, as in "why would VW make such a great mechanical motor and then 'ruin' it with an electrical keystone?"
Has anyone ever taken the plunger out of the solenoid like Andrew said you can? If that is quick and easy to do in an emergency I would be satisfied.
edit:
Ah I found this killer pump rebuild thread Andrew put up on VWdiesel parts:
http://www.vwdieselparts.com/forum/viewtopic.php?t=6694 Lots of pictures, fifth one from the bottom. The plunger looks like it falls right out. Yea?
(http://bricofoy.free.fr/voiture/pompe/dsc05410.jpg)
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you could make it run like the mercedes do... they use vacuum as the fuel shut off.
i think the solenoid is a good idea.. it's proven technology that is simple, yet effective. but i too would like to have a completely mechanical engine :)
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As I mentioned previously, you can remove the plunger from the solenoid with an adjustable wrench and fuel flow will be unobstructed. You can then start the vehicle by rolling (assuming glow plugs aren't needed). I simply do not see any advantage to a mechanical control over the current one. To each their own.
Andrew
I second that. A simple 12V solonoid is the most simple way to go, especially since there is an existing 12V system in place already. A cable setup would be much more complicated and prone to problems/failure.
I can see with some industrial/marine applications where there is no 12V system, a lever or cable would be practical, but definitely not in a car.
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As I mentioned previously, you can remove the plunger from the solenoid with an adjustable wrench and fuel flow will be unobstructed. You can then start the vehicle by rolling (assuming glow plugs aren't needed). I simply do not see any advantage to a mechanical control over the current one. To each their own.
Andrew
I second that. A simple 12V solonoid is the most simple way to go, especially since there is an existing 12V system in place already. A cable setup would be much more complicated and prone to problems/failure.
I can see with some industrial/marine applications where there is no 12V system, a lever or cable would be practical, but definitely not in a car.
Yea but what if your 12v system is dead or your wires fry?
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Well, in the unlikely event your driving with a completely dead battery (hopefully not at night) you can remove the plunger out of the solonoid (but then you'd have to pinch the fuel line off to shut it down, or stall it out)
I have driven a Rabbit far with no charging, it would get to the point where lights were very dim, of course it was at night in the rain so I had no heat/wipers/defog either. The shut off solonoid never dropped out, I never had to remove the plunger, very little current to keep it energized.
I can see your point though, a manual override would not be a bad thing, they probably opted against this so crazy folks like us would not drive with no light, blinkers etc.
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if you could implement a 12v toggle switch, you could keep it electric and mechanical... easier said than done though :lol:
i wish i had that about 3 years ago... battery died on me and couldn't figure out why it wouldn't start when it was being pushed :roll: :lol:
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You can then start the vehicle by rolling (assuming glow plugs aren't needed).
If the hill is steep / long enough, or you have a push / pull vehicle, you can indeed start the car sans glow plugs even in the dead of Michigan Winters. The engine just needs enough speed - far more than the starter motor. I have had to do this when my glow plug relay failed on and burned out all 4 plugs.
So, if you converted to a manual shut-off, I could see the advantage of an all mechanical IDI.
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how do the detroit engines start without glow plugs? i've seen this guy's tow truck with i believe an 8.7L turbodiesel engine :shock:
truck sat for at least 2-3 months, and he wanted to show how quickly it started WITHOUT glowplugs. it took one revolution and the thing fired right up, no hesitation, just pure diesel growl and smooth idle. now how on earth did they do it??!! granted that was on a fairly warm day, about 24-25C. but he said it's the same even when its pretty cold.
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I made a switch for the fuel cut off....a line goes from to the cut off to the switch inside and back to the Positive post on the battery...switch on fuel on...switch off motor shuts off...simple and easy
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well... thats how VW does it :roll:
I have run a IDI without the plunger (alternator died, battery died)
and also push started a TDI with a completely dead battery by energizing the selenoid with a 9v battery (the small TV remote kind).
it was a cold night and it took us 10 meters to start it at the first try :D
we did a few attempts without the 9v bat, but the TDI needs about 8v so the ECU awakes and allows the selenoid to be energized and the alternator couldn't supply that much from pushing the car.
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I have to agree with Andrew. The cutoff system that VW derived is far simpler than any other kind of mechanical device.
Think about how many times you have had problems with the throttle lever or cold start. A lot more than with the solenoid I'm sure.
Easy cutoff: tap into solenoid line, put in a simple electrical switch.
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I got an old 80 Kenworth, with a big Cat 3406A, my Emergency kill is air actuated 4" valve with a gate inside, it cuts off all the air going to the motor through the intake tube... What I noticed when I rebuilt it was the gate is spring actuated, with a manual override (cable), it would actuate. I've seen smaller valves like this in the big Fords of the older variety, I'm sure it could be grafted into place, albeit, you gotta pop the hood and reset the after setting it off :roll:
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(http://www.rodadeaco.com/images/pCable.gif)
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Personally, I'd be far more interested in a mechanical air shutoff than a fuel shutoff. It would actually be useful in the event of a runaway.
Andrew
I agree, this would be much easier to build as well..
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how do the detroit engines start without glow plugs? i've seen this guy's tow truck with i believe an 8.7L turbodiesel engine .
Its probably because they are direct injected (not IDI), have a faster starter - 24v likely, and might even be computer controlled injected with multiple injection events.
I bet if you hooked up an extra battery in series with your starter, you could start our IDI cold at 20 C without glow plugs. I wonder how long the starter would last ;-)