I have a '98 Marea TD75 which died suddenly apparently due to the factory immobiliser. The engine turns over but there is no immobiliser key light and no diesel heater light. The immobiliser has power and I've tried the red key with no response.

Does any one know how the immobiliser affects immobilisation on this car as there doesn't appear to be an engine ECU - can the immobiliser be bypassed?

Any help would be appreciated.

Hi,
Check this out.
http://codeman.org/fiat.html

Thanks for the link but I don't think the fault is with the keys as I would expect the immobiliser key light to stay on if an unrecognised key is presented but the light doesn't come on at all. Also, as far as I can see this is a fairly low-tech diesel that doesn't appear to have an ECU as such. I certainly haven't been able to find anything ECU-like under the bonnet.

When you look at the fuel pump, does it have a throttle cable going to it? Also, are there any wires going to it? If so, how many?

If it's running a basic rotary pump there will be a fuel shut off solenoid. This is what you use to stop the engine and it can be by-passed. If you can post a picture of the pump it will help me identify it and I may be able to help you out.

Hello, here's a picture of the pump (Bosch):

https://www.fiatforum.com/gallery/showphoto.php?photo=4266

As you can see the throttle is cable operated.

There's a throttle position pot (C) and I assume that (A) is the fuel valve solenoid, there's also another device on the side of the pump (B) with 3 wires coming out of it - don't know what this is for.

I think you're right about the shut off solenoid being 'A'. Have you checked for any voltage at the terminal when the ignition is switched on or any resistance in the coil?

I'll see if we have a similar pump tomorrow and confrim what the other wires do (we don't use the potentiomater on the throttle though).

There's no power at 'A' and I measure around 30-40 Ohm (seems reasonable for a solenoid) but according to my Porter manual 'A' is the "Auto cold injection-advance device" and the unidentified 3-wire device on the right is the fuel cut-off solenoid - I think that the manual may be wrong.

The manual shows a diagram of the pump and says that it's a Bosch VER 679 but it also says that there is no mechanical throttle linkage on these pumps which is also incorrect.

I'm fairly sure your pump is a Bosch VP14.

The single wire is your shut off solenoid, the poti is obvoiusly for your throttle position and the other wires are for the pump timing signal (going in).

Stick 12 volts onto the solenoid and you'll get fuel delivery to the pump however the pump still has some electronic control ref timing so it still may not run then. It's still worth a go though!

I was hoping it was just the solenoid that had gone.

It appears that the manual is correct and that the single wire device is for aiding cold start. The three wire device is a secure solenoid that requires something from the immobiliser before it operates the valve.

I'm trying to find out exactly what it requires but I read somewhere that if all else fails that the plastic casing and electronics can be removed (with some effort as it's held on with tamper-proof screws) and the solenoid operated directly.

Before I take extreme measures I'm waiting for a wiring diagram to help with eliminating the obvious just in case the immobiliser is fine and it's something as simple(?) as a missing feed somewhere.

Re: Marea TD75 immobiliser fault..Success !!!

After wasting a lot of time I finally decided to have a go at removing the secure casing and electronics covering the cut-off solenoid. I was expecting it to be difficult but by grinding away the sides of the casing with a dremel type tool I was able to get a screwdriver onto the side of the head of one of the two anti-tamper bolts and tap it round with a hammer. Once one bolt is undone the other becomes loose because they are both attached to a block of metal seperate from the pump itself which acts as a clamp.

There is a standard solenoid under there and since one of the wires for the secure solenoid controller is an ignition feed it's a simple job to connect it directly.

So, there is a viable alternative to giving Fiat lots of money when the immobiliser or keys fail on these mechanical pump diesels, I just wish I'd done it weeks ago.

Re: Marea TD75 immobiliser fault..Success !!!

Well done
Rep given for a good effort and write up.

Mmm but was this actual cause of the problem.?? there is a small black box next to the battery with relays and fuses in it, i cant remeber which one it is but if you get a poor connection on one of them it does a similar thing to what you have described.

The relay box appears innocent in this case as all connections look OK.

Shortly after fixing the starting problem the speedo and tacho became intermittent and barely work at all now, not only that but the cooling fans don't work either!

I don't know if any of these problems are related.

Fiats are great!!!!