300Tdi (hopefully) starting after 2 - 3 year lay-up; plus immobiliser question for a newbie

[Northwards]

Hi guys, 

Over the next three days I'm working on a mate's 1998, 300Tdi 90. It's been a bulkhead swap that's grown arms and legs and all sorts of other appendages.

I've decided to focus this time on getting the engine ancillaries re-assembled and hopefully starting it up for the first time in a long while. I'd plan initially to disconnect the fuel solenoid and crank it a few times to get some oil around, as well as doing an oil and filter change, and a fuel filter.

So I'm confident I can manage the basic stuff, however I have two areas of concern (perhaps I should have more? 😁) as this car is newer than mine and has two 'systems' I'm unfamiliar with: an alarm/immobiliser; and an EGR which we're deleting. 

For the immobiliser, we have the factory immobiliser bypass plug fitted. In theory would that allow the engine to start with the car in a 'stripped' state, or will I need to get other stuff like bonnet switch/courtesy light switches/alarm sensor wired in? I'd like to just do a basic start first if I could to check whether there's anything else wrong that I need to worry about. As I say I know zip about the Defender standard alarm/immobiliser system so it would be good to know what the possible pitfalls are. If no-one wants to post that sort of stuff publicly then hopefully I've been around long enough now to be trusted with PMs...? 

For the EGR the wires to the cap on top of the fuel pump have been cut. The various (?) relays that were on the bulkhead, and the "diagnostic" gubbins that sat under the cubby box are not connected. Is this likely to cause us any starting issues? As with the immobiliser, my '94 car left the factory with none of this stuff, so this is the first time I'm working around it. 

Any help very gratefully received. 

By way of proving it's a genuine request! This is roughly where it's at now, but as I say I'd like to try starting it this weekend, if I can.

Ta

[Maverik]

Regarding engine start and immobiliser. 

If its 100% factory alarm and immobiliser, then as long you have the key fob, to lock/unlock, then this is what will turn off the immobiliser part.

[Northwards]

Thanks Maverick, 

As far as I know it's completely standard.

I'd read that the immobiliser units could be 'iffy', and this one's getting on a bit so that's why we got the bypass plug. I think it's supposed to take the immobiliser out of the picture - but I don't know if that's to a 100% level or not, and/or how it integrates with the alarm. 

[Maverik]

The 10as (2 button) alarm systems have multiple immobiliser elements, the bypass plug sorts out the main bits, you should not have an issue starting it.

[Peaklander]

I've sent you a PM with my two penneth (just to maintain a bit of security). It might help.

[Northwards]

Well, things didn't go entirely to plan, including a detour via a new timing belt; P gasket; and waterpump. Having the crankshaft pulley, and timing belt sprocket glued on didn't help matters...

But onwards and upwards, and the plan is to continue assembling this engine's essential systems on Saturday and then hopefully to turn the key. 

Thanks for your answers and messages so far.

To avoid any doubt this thing here is fitted in place of the immobiliser black box 'spider'. 

So my understanding is that this takes the 'immobiliser' itself out of the equation, and avoids me having to run bypasses to the fuel solenoid and starter motor

But I think I understand that the 10AS unit is still 'masterminding' the process, and could block a start because it can't see/find all of the door switches/key fob/bonnet/ultrasonic sensor etc?

Or to put it another way, with the car in the state it's in in the picture above have I got a snowball's chance in h*ll of getting it to start? Or should I press on and get it all re-assembled to make sure (!?) that all the other electrics are in place and working and not interfering with an engine start? 

Even without any electrickery I can imagine that there could be a few things which could cause a laid-up engine to be difficult to start; overlaying that with a bunch of wires doing different things and I'd just like to have an idea which part of the octopus I'm fighting with... so to speak!

 

 

[steve b]

If that thing doesn't work then it's a live to the FIP solenoid and a wire from the starter solenoid to touch on the battery live to start it (with main earth and live connected correctly)

I usually remove the intercooler to intake pipework to avoid any self fuelling disasters with a cold start and a stuck open FIP and also have something to block the inlet manifold should it rev and not turn off on the solenoid.

It sounds over the top but better to be ready than have a long lay up cold start go bad..... I know from experience and it's not fun 

Steve

[Peaklander]

3 hours ago, Northwards said:

So my understanding is that this takes the 'immobiliser' itself out of the equation, and avoids me having to run bypasses to the fuel solenoid and starter motor

Not quite - it only takes the immobiliser out - that's the device that takes inputs from the 10AS, creates the enable signal and then splits it out to the fuel pump and starter. It does not replace the cables to those items, it just replaces the electronics in the box.

 

3 hours ago, Northwards said:

But I think I understand that the 10AS unit is still 'masterminding' the process, and could block a start because it can't see/find all of the door switches/key fob/bonnet/ultrasonic sensor etc?

Yes, it still needs to be in the correct state to allow the start. What @steve b says is the ultimate get-around.

[Northwards]

2 hours ago, Peaklander said:

 

 

Yes, it still needs to be in the correct state to allow the start. What @steve b says is the ultimate get-around.

Thank you 👍. If 'correct state' means the 10AS being happy with all its switches and wiring, and I guess it does, then at least I know not to bother trying "properly" until I have all of the rest of the bodywork and wiring in place; and just as importantly I won't waste time and energy by trying, failing and being disappointed. 

4 hours ago, steve b said:

If that thing doesn't work then it's a live to the FIP solenoid and a wire from the starter solenoid to touch on the battery live to start it (with main earth and live connected correctly)

I usually remove the intercooler to intake pipework to avoid any self fuelling disasters with a cold start and a stuck open FIP and also have something to block the inlet manifold should it rev and not turn off on the solenoid.

It sounds over the top but better to be ready than have a long lay up cold start go bad..... I know from experience and it's not fun 

Steve

Thanks Steve, that's a succinct explanation of what I'll need to do. I do think it's worth trying to get it turning over at this stage; as a wee confidence boost for us both; and if we discover anything's wrong then it's easier to deal with when we have the front end still stripped and giving good access. I wouldn't have thought of the engine running away on us, so that's really handy. 

3 follow up questions if anyone has the patience:

1) I have never had to try 'touching a wire' to the starter..! My own vehicle layups have never been longer than 3 or 4 months, and I've just turned the key.  My first thought was that it would need to be a pretty big wire, but I've watched a few youtube videos, and looked at some pictures (so now I'm an expert!).... Do I just touch a reasonable 12v cable to the terminal at the back of the starter solenoid - marked up in yellow here? 

2) I just remove it once the engine's started....? (hah!)

3) Just a more general question. If the 10AS unit is always checking/needing all the switches to be in the correct state, and the stars to be aligned, does this mean that you couldn't start it with one of the doors open? Makes me realise and appreciate how deliciously simple and straightforward my '94 300 is, with none of this stuff to worry about. 

[simonpelly]

It can be started with doors open. The 10AS needs to be not in an "alarm/immobilised" state for the engine to start. Suspect the most important one being the key fob sensor.

[steve b]

If you bypass wire it , connect a wire to the starter solenoid terminal and touch to battery live- either at the battery or a shorter wire to touch the main live starter post

Steve

[Peaklander]

1 hour ago, Northwards said:

at the back of the starter solenoid - marked up in yellow

You are touching the solenoid connection which is a spade. It’s low current. Not the big connections with thick wires. It will spin the starter and engage it to turn over the engine. Just hold it for as long as you would hold the key in the ignition. 

[Eightpot]

A 98 300tdi with 10as will have a sealed solenoid won't it? Unless someone has already smashed the top off it..

If I recall correctly, after trying to repair a particularly manky old example with rotten wiring, the 10as operates the spider which controls earth paths rather than lives via little relays inside. I couldn't get it to run even with a spider delete plug in as the terminals were corroded so just cut short the solenoid earth wire and grounded it. 

[Northwards]

^^ Ta. In this instance I can’t say what might have happened to this car previously, and whether the solenoid might have been covered at some stage, but it certainly isn’t now. But tidying up the terminal and loom wiring is never a bad idea.

I’d actually thought that before I even try to start the car, I might connect the solenoid to power a few times to see if I could hear it clicking (?) but also to minimise the risk of it sticking as per Steve’s post above.

[L19MUD]

29 minutes ago, Northwards said:

I’d actually thought that before I even try to start the car, I might connect the solenoid to power a few times to see if I could hear it clicking (?) but also to minimise the risk of it sticking as per Steve’s post above.

This is worth doing. You will at least know if it opens, making a start possible. Even if it clicks the plunger can still be stuck open but this does help free it

 

Steve's advice re having something to directly block the inlet is well worth taking up. I have started 300tdi's that have stuck pumps before and try to run flat out, if the solenoid sticks you need a backup plan to immediately stop it. 

[Northwards]

I bought a new solenoid 'just in case', but we'll see what happens with the old one. 

On the point about being ready to block the inlet - what sort of forces are we talking about here? Would a balled-up towel do the job, or would it need to be something more substantial like a wooden plug? 

I feel much better prepared for trying this now, so thanks again for all the replies.

[steve b]

A piece of wood big enough to cover the inlet on the manifold works....so does the base of the battery on my rattle gun - wasn't prepared last time it happened

 

Steve

[Peaklander]

12 hours ago, Eightpot said:

If I recall correctly, after trying to repair a particularly manky old example with rotten wiring, the 10as operates the spider which controls earth paths rather than lives via little relays inside

It's confusing because the cable colours in and out of the 'spider' are deliberately all black - maybe in order to make tracing them harder. Some pull down to 0V but others supply +12V.

[simonpelly]

In the back of my mind, always wondered what it might take to effectively delete the 10AS from the system. Especially if in the future it just simply misbehaves.

[Peaklander]

I think deleting the 10AS would be drastic. After all, it controls the interior lights with a welcome unlock 'ON', a 15 second delay ON after the doors are closed (or quicker if IGN is on) and it holds them on for 15mins if a door is left open. It isn't hard to get the door switches and the bonnet switch working, so that those sensing circuits are healthy. The ultrasonic module can be disconnected if needed and doing that doesn't affect the operation. It may also handle central locking alongside the alarm.

The immobiliser part of the 10AS needs the doors and bonnet to be working but then the only other input is the fob, which talks to the passive coil that's around the key lock. After that the 10AS will happily enable a start but you are then dependant on the 'spider' to correctly distribute that enable signal.  

[simonpelly]

Yep. Only considering a delete of the 10AS if is ever became a problem and not repairable/replaceable.

[Eightpot]

The troublesome 10as I worked on previously ended up with it being deleted - just pulled the plug out of the ecu and put a ring terminal on the earth cable between fuel solenoid and spider so it could be earthed and did without the alarm/fob altogether. 

[Northwards]

Well - finally got to the "start" stage today. 

Oil and filter change; fuel filter; and a coolant refill and it essentially started at the first attempt! There's part of me still can't believe it. The phrase 'sweet as a nut' could have been invented just for this. 

I did cycle the fuel solenoid a good few times, then cranked the engine without fuel for about 20 or 30 secs, but when I gave it fuel and starter it fired up so easily. 

All that said, I wouldn't have approached it as comfortably without the advice above, so many, many thanks. 

Still a long long way to go on this car but that's a big milestone. 👍

(Edit - should say this was using 'hot wires' from the battery. Haven't got round to trying on the key yet, but at least we know that if it doesn't go, it's not the engine. 

[steve b]

Good to hear. As you say it will make getting the 10AS to play much easier.

Steve

[Northwards]

An update just to ‘close’ this off. I finished rewiring the battery (new positive and earth leads); connected the ignition switch; replaced the battery in the key fob and laid it on top of the immobiliser ring and turned the key - started first time, stopped on the key. Repeated a few times just to be sure and all was good.

To say I was delighted would be an understatement. The alternative of fault tracing etc etc holds no attraction right now as there’s plenty to do, and this car’s supposed to be in Spain in late August!

Thanks again for the advice and moral support.