7.3 IDI no shut-off via key.

[derjackistweg]

Hi folks,

I recently replaced my already 12.000km alternator with a new one a had a split second short with the battery cable.
Alternator works now...
Fuel shut-off via key does not. So engine keeps on running.

7 or 8 years before I had the same problem after (!) it came from a shop. But after I did something it worked again. It is an ex.ambulance so I did a lot of de-wireing... probably a fuse that I replaced. I don´t know.

In addition: My key-on starter does not work either, since 7 years or so. Never found out why, I just put on a switch that goes to the starter directly. Works since years so I never wanted to deal with the probably broken starter relay that sits behind the headlight on my 93 E350.

BUT no shut-off is not so cool (I made a switch though ) So I want to repair this now.

Question: Which is the correct wire to the key switch? The Fuel shut-off has power when key-on and it must not have power when key-off. But it still does.
If this has something to do with a short, is there any relay/fuse that I need to check? (I already did all, inside and in the PDB, of course)
So key position and Fuel Shut-off must have a connection, which line is it. Especially from the inside starting, meaning the key

THX

 

[Rdnck84_03]

I don't know exactly how the switch is operated on the aero style but i know the switch actuator is a common failure point in the older ones. Since it doesn't start with the key either I would suspect that first.

Edit: does it shutdown when you pull the wire from fsv?

James

 

[derjackistweg]

Edit: does it shutdown when you pull the wire from fsv?

James

Yes it does! (this is where I place my temporarly fix/switch from the inside)

So the problem is somewhere between key and the shut-off selenoid at the pump. The selenoid itself works.

The starter relay (behind the headlight) is probably gone since 8 years, so it has probably (?) nothing to do with this situation.

 

[Rdnck84_03]

Like I said on my first post, I am not familiar with the internal workings of the newer column. But with what you describe sounds like the actuator from the ignition cylinder isn't working the rod to operate the switch. The actual ignition switch is halfway down the column under the dash.

 

[Rdnck84_03]

Could also be the nuts that hold the switch to the column are loose and letting the switch slide in the adjustment slots.Another option could be that the switch itself is coming apart internally and doing weird things. Does the accessory position of switch work?

James

 

[derjackistweg]

Could also be the nuts that hold the switch to the column are loose and letting the switch slide in the adjustment slots.Another option could be that the switch itself is coming apart internally and doing weird things. Does the accessory position of switch work?

James

Hi James,

ok, mine is the "new" version? in 3 months my car is 30 years old: Means ins GER 300¢ less tax/a, and roughly 500¢ insurance and it it allowed to be driven in urban Areas. Wich is NOT the case today due to emissions.

btt: I checked the switch hardware wise years ago, like the rod etc.. nothing broken.

This must be something electrical, like a burned wire/fuse/fuseable links (whatever these are called)
Besides this (starting and stopping) all works normally, like dash light, lights for GP or whatever is on while igintion-on, like windows.

 

[Rdnck84_03]

ok, mine is the "new" version? in 3 months my car is 30 years old:

Haha guess that being newer is a relative term. My daily driver is either an 83 f250 or 84 f150 so those I am fairly familiar with.

The entire column design changed starting with the 92.

Besides this (starting and stopping) all works normally, like dash light, lights for GP or whatever is on while igintion-on, like windows.

I am guessing this means in the run position? Do the windows and radio work when key is turned backwards to the accessory position?

This must be something electrical, like a burned wire/fuse/fuseable links

Fuse or fuseable link could be possible for the starter issue, I would have to look at a wiring diagram to see what that circuit contains to be sure though.

One way to isolate the the switch shorted or the wiring. While it is running with the key off, unplug the electrical plug from the switch. If it will shutdown like this then the issue is inside of the switch, if it doesn't the you need to start looking at the wiring.

James

 

[The_Josh_Bear]

Doesn't sound like a short or anything like that to me. Sounds like the switch is not being physically worked correctly.

The mounting holes for the switch is adjustable via oval mounting holes. If the screws are loose the whole switch will move back and forth with the actuator rod and you will get neither off or start, but it'll stay in run all day long.

Just drop the column and see what's up with that first. It's the two big nuts/bolts on either side of the column and the whole thing drops down to investigate.

 

[BeastMaster]

I wonder how effective a halon or CO2 fire extinguisher would be, shot into the air intake of a 7.3 idi that refuses to turn off, even if the IP solenoid has been disconnected.

I don't want to shut off fuel because the IP uses fuel as a lubricant, and IP's are very expensive.

I mean, once you get a Diesel started, it will run as long as it sees a fuel of damm near anything ( even it's own engine oil ) and air. And boy, can they suck if they want air...one guy told me he lost a coat because he threw his coat over the intake trying to suffocate the engine, and it just ate his coat.

Will Halon or CO2 kill it cleanly *without damaging the engine*? I believe it will, but I need practical evidence before I will change "believe" to "know".

 

[derjackistweg]

Doesn't sound like a short or anything like that to me. Sounds like the switch is not being physically worked correctly.

The mounting holes for the switch is adjustable via oval mounting holes. If the screws are loose the whole switch will move back and forth with the actuator rod and you will get neither off or start, but it'll stay in run all day long.

Just drop the column and see what's up with that first. It's the two big nuts/bolts on either side of the column and the whole thing drops down to investigate.

Hi,

I made a short and the next thing was: It does not shut-off.
Why should the rod be braking is exactly that moment?

The "rod is broken" theory was mentioned when I had the "not starting via key" issue, back in 2017. I checked, the rod wasn´t broken.
Dito the ignition switch connector at the colum, dito the parking switch at the transmission.

So I just connected a switch between the bat and the starter relay (at the starter). Works since 6 years or so.

Last year in France I deleted a relay connected to the "starter" relay at the fender, that had on-off key. This was made from the ambulance "experts". Didnt work as long as I had the truck.
The result was this, pic #3

so while I was here I just tested conncetivity ....
and connected the wires that were cut by the amulance experts in 1993 (with the "thing" in between)
Pic 4 is before the new connections. But you can see that these are the same colors and actually the belong to each other.

Long story short:
After 6 years the truck starts now again wie key. As it is supposed to be.

= no broken rod.

But this doenst still actually solve my problem, that I started the thread for.

 

[derjackistweg]

I wonder how effective a halon or CO2 fire extinguisher would be, shot into the air intake of a 7.3 idi that refuses to turn off, even if the IP solenoid has been disconnected.

Hi,

I dont know where you want to go with this. Like I said: Power needs to shut down, wich it does not.
This is NOT equal to a non-working IP Selonoid! The IP Fuel shut-off selenoid DOES WORK. Otherwise the truck would be running since weeks.

See below my switch, the red wire going to s switch in the dashboard for now.
It is just connected in between the stardard wiring and the FSoff.

The electric works like that (I think I mentioned that in the beginning): Starting + running = power to the FS. Key in off position = truck off.
You can see this situation on the hood-foto.

Last week the truck actually shut off, once.

When I turn the key to off after the truck is running, the test light does flicker. But it does not go off, like it should.

 

[BeastMaster]

I miscomprehended. I had Diesel Runaway in mind.

Being known your fuel solenoid is good and you can't kill power to it, it looks like the engine power circuit is stuck ON.

I understand the low vacuum warning light and instrument cluster is on the engine circuit.

The other part of the ignition switch controls power to the hotel ( lighting, HVAC, entertainment ) loads.

There appear to be four separate power circuits the ignition switch controls... one for just the engine, one for hotel, one for accessories, and one just for engine start.

I think your ignition switch, engine circuit, may be electrically stuck ON, even if it's mechanically in the OFF position

While the engine start, hotel and accessory circuits are still working perfectly.

 

[derjackistweg]

As an, hopefully final, result:
The truck starts and shuts off like it was supposed to be.

Because .... I dont know. I actually did nothing to the truck but driving it.

The starting issue was not part of this thread and repaired by connecting the original cables back together, simple stuff. There was a switch in between below the bonnet with a relay for a reason that I do not know and cannot image. Was done before I owned the car. I deleted that; in short.

Why the truck now shuts off is unexplaiable. On some shorter runs, below 20 min, it sometimes did not shut off. But now it looks like it works like it should.
The same happend in 2015 but back than I worked on so much things at the same time that I could not figure out if I did something related by accident.
This time I didnt.


So THX for all of your ideas.

 

[derjackistweg]

This is actually a bigger problem now - as I want to sell the truck. And I don´t want to sell it with the switch attached (between the shut-off solenoid and the the GP Relay).

So the following is the problem:
The GP relay is supposed to have no power after key shutoff on the ignition line (the double red one).
It keeps power so the engine does not shut off, as this powers the fuel shut off.

When I press the switch (I attached between) => power goes off, FSO cuts fuel => engine shuts off. No power on the ignition line on the GP Relay!
When I turn the key on again, ignition has power again on on the relay.

So I assume the GP relay is working correctly.

The problem must be an electrical one between the key and the GP Relay.

(No the rod is not broken. And: When I had the false alternator with 15,5V running the shut-off sometimes worked again. On 13.8v nothing happens.)

 

[derjackistweg]

So, this is what I found.

But I am no car electrician.