DI cartridge query

[pete_turier]

Hi folks,
I've just noticed that my DI system has stopped performing it's 'plug-cleaning- function when I turn the ignition off.
Any one know if that's a sign that the cartridge is on its way out?
What's the 'usual' life of these things?
I've noticed a performance drop lately as well, so I'll be trying some of the useful tips that you chaps have given ref. bypass valves &APC units.
Pete
Gloucester
UK
'91 9000S 2.3 Turbo.

[Derek]

Pete,
How do you know the DI has stopped it's plug cleaning function. I've had 2 cars with DI and I've never been aware of it. How do you know it is happening?

The early black units used to give up the ghost quite early, about 70K or so seemed to be common. The later red units seem to last much longer though. Failure is usually accompanied by oil leaking from one or more of the coil cartridges which are not replaceable on the red DI units.

[pete_turier]

Derek,
When I first had the car, on turning off the ignition, a few seconds later you could hear a low pitched 'buzz' for a few seconds.
I queried this with a tame SAABtech that I had at the time (alas no more), and he told me that this was what I was hearing.
I can't remember when it stopped. I've just been out in the car for a blast and it definitely isn't going as well as it used to. It doesn't exactly 'miss', it just seems to be holding back all the time. This is also accompanied by a strange whistle from the turbo, that I haven't noticed before.
Looks like it's time to do some checking.
I've got the red DI cartridge and the car's done 133,000 miles. Still, I'll check the other things first.

Pete.

[Harvey]

Derek,
What you say about coils leaking oil is interesting. I have just replaced the plugs and noticed oil in one of the plug recesses. I thought this was residue from a leaking cam cover that was fixed some time ago. Maybe not though, but car running fine.

Harvey

[Derek]

Pete,
I've never heard mine buzz but then I haven't been listening for anything.
A whistle from the turbo could possibly indicate an air leak. Check all those vacuum pipes - they harden with age and start to crack and split, especially at the ends. You can often get away with cutting 1/2 an inch off the end but they will split again and need replacing eventually.

[Paul D]

In my experience the red DI packs burn out at around 105,000 miles, based upon two units I have had.

A few seconds after turning off the engine, the DI pack should discarge a 1000 times across all four spark plugs to 'burn off' soot. If this sound cannot be heard (with the window down, or jumping out of the car immediately after turning engine off), there is definately a problem, but it might be with the control unit rather than the DI pack. Especially if the plugs are working normally (i.e. the engine actually runs). After all if the plugs fire when the engine is running they should fire during the 'burn off' phase afterwards. I am pretty sure the control unit is the Engine Management Unit (ECU) which is rather expensive!

The DI pack can fail intermittently, (i.e under accelleration), as happened with my first unit, or more usuall completly burn out. In the first instance there was no observable evidence of the DI pack being faulty - only a misfire during accelleration. If the latter occurs, there is usually complete failure of the unit and the the potting compound is usually cracked, making the unit stink(!) badly of burnt oil/compound. The smell is unmistakeable.

If there is oil in the plug area, this is probably from the head gasket, unless the DI pack potting compound is cracked and it smells burnt.

B-regards.
Paul D.

[Paul D]

PS:

Brand new OEM DI packs are approx GBP115 + postage from 2 stroke to Turbo (potters bar) or Neo Bros, (Waltham Abbey) www.neobrothers.co.uk . Which (like most other parts)is about 50% cheaper than the rip off prices the main dealers charge!

[chrisn]

My DI rail (red) went at about 100k, which I was led to believe is typical-failure appears to be in a broad band from 80k to 130k ish. Syptoms were mis fire under heavy load only-ok in normal driving, and oil in the plug wells.

I think Derek is right, Petes problem seems to be more to be with boost than the DI rail.You might suspect the turbo bypass valve-have a look at http//quasimotors.gar.net.hooter.htm

The plug cleaning is performed when the engine is switched ON, but if it fails to start, releasing the key performs a 5 second intensive plug clean after which try a re start. This info from P45 of the 92 handbook.

[pete_turier]

Well chaps, I'm VERY happy to say, I've got my perfomance back. Having nothing to do at lunchtime, I started poking around in the mucky bits. Luckily I started with the APC valve. It soon became clear that all three hoses were split to a greater or lesser extent. Cut the ends off, reconnected, and hey presto, full performance restored!!
I think it must have been getting worse for some time, but the 'smile- factor' is well and truly restored now!
I'm going to leave the DI cartridge for now and see what happens.
Thanks for all the advice.
It just goes to show, check the simple things first!
By the way, has anyone tried installing those pretty silicone vacuum hoses like they seem to use on rally cars etc??
Pete
Gloucester
UK
'91 9000S 2.3 Turbo

[Paul D]

DI Pack 'burn off' occurs if the engine fails to start and when the engine is turned 'OFF'. Never when the ignition is turned on prior to starting. The buzz is an audible sound and can be heard if the window is down and the bonnet is open. This is the design intent of 9000's from 93 to the last edition 1998 (As per my Anniversary).

This concurs with the 1993 Fit Form & Function Saab book.

If the 'burn off' buzz no longer occurs when the engine is turned off, then there is a fault somewhere.

[Gavin Short]

Pete

for lurid silcone vacuum hoses try quasi's website

http://quasimotors.gar.net/vaclines1.htm

If you find a supplier and price pse let us know (and also if they do some more subtle colours!)

I have just tried his tip on the Crankshaft Pulley (harmonic balancer). The paint marks show that the outer part of my crankshaft pulley is starting to slip wrt the inner part. So replacement due soon. Could this be the cause of my engine vibration problem at idle or is it the balance chains. Questions? Questions!!

http://quasimotors.gar.net/slip%20refs.htm

Gavin

[pete_turier]

Hi Gavin,
I'm not sure what happens when the balancer starts to slip. It hasn't happened to me (yet!).
I've just found a source of silicone vacuum hoses. Try the following link to see if there's a stockist near you. Forge Motorsport are about 1km from my house, so I'll go and see them sometime. You'll be pleased to know that they also do black.
http://www.dialspace.dial.pipex.com/town/p.../uk_distrub.htm

Pete
Gloucester
UK
'91 9000S 2.3 Turbo.

[MikeH]

Thank you all for all the Gen,in answer to cdcarlsson , my car hails from 1992,and i am sorry if I doubted you derek , I had not thought of the capacitor holding in the relay.I think I have a leaking water pump so the interior lights will have to wait.ah well aint motoring fun?

[StephenA]

my DI catridge did about 125,000. I have just had to replace it. I had misfires under load at low revs and the ECU kept flashing and reporing a DI fault but the garage seemed to ignore it; lifing it off I found it was leaking oil. So it was shell out a bit over £120 to get a new one put in and... well lets put it this way : the car accelerates again!.

Steve

P.S. if any one wants a faulty DI catridge (red) I have one in the boot!