problem cold-starting 81 turbo - engine dies after firing

[saab_o_naut]

Posted this on saablink.net and the forums at my site a few days ago...

My 81 turbo is exhibiting a starting problem when cold - it's fuel-related since the engine fires without a problem after a few seconds of cranking then the revs die down and the engine stops. Cranking again gets it going. I'm thinking either fuel accumulator or the fuel pump check-valve but haven't yet done a lot of diagnosis. I have a K-jet fuel pressure testing kit so I'll try that on the weekend and see what that reveals, but if anyone can think of anything else, I'd appreciate your ideas.

As an aside, I need to see what's going on with the cold-start injector control too - there's no lambda control so I don't quite know what drives the cold-start injector if anything, and it's possible that it's not doing anything. My understanding is that when cold, the thermo-time switch should allow the cold-start injector to run for up to 10 seconds when starting, but the Bentley manual is completely wrong for my car as all the sections talking about emission control, etc. assume the car has the extra relay panel which apparently all the US/Canada c900's were equipped with.

and yesterday posted this...

Started checking out possibilities today. First thing I did was see if I have a matching spare warm-up regulator in the shed.

The warm-up regulator fitted to the engine in the car ('H' engine, 8V, non-APC) is the -070 version (Bosch # 0 438 140 070) while the one fitted to the cylinder head I removed from the 82 non-APC turbo car last year is the -085 version (Bosch # 0 438 140 085). According to the ATP Electronics warm-up regulator listing, the -070 version is used on with turbo 'B' engines only, and the correct version for my engine should be the -085 or -102 version.

Anyway, I'll be doing the full range of checks tomorrow (electrical, etc.) and I might also connect in my K-Jet fuel pressure test meter and see if the the measurements are within the specifications in the Bentley manual.

Has anyone encountered any unusual problems with warm-up regulators on non-APC turbo 8V 'H' engines in 81 or 82 build-year 900's? I haven't ruled out other things yet (like the fuel-pump check valve, or the fuel accumulator) and the K-Jet test kit will help to identify any possible problem with that part of the fuel system if indeed that's where the problem is.

Another possibility may be the fuel-pump relay since it's the longer metal-can type with a 'terminal 50' connection. Not sure if I have a spare, but I have a spare fuel pump relay from a non-turbo 8V car that could be used if need be.

I'm going outside shortly (nice sunny winter day in Sydney!) to do the electrical testing and if need be hook in my fuel pressure tester...

If anyone can think of something to consider, please let me know.

Thanks,

Craig.

[Alexander B]

Seems like you know what you are talking about and what to look for. FYI, some years ago SAAB decided to exclusively sell the "warm up regulator" ending with -020 as a replacement for all cars without a hose connected to it. (And "yes", the regulators often break...)

Check fuel pressures warm and cold, look for leaking check valve and make sure the warm up regulator reduces the pressure in the correct way.

The cold start injection time seems correct, be it from Bentley manuals or not...

/Alexander

[saab_o_naut]

Since I've had the 81 turbo c900 for a couple of years now, I've had more time to think about this. All I can figure is that because the car has the older full-tank pressurisation pump setup, it takes longer after the pump starts to build up enough fuel pressure. I changed the fuel filter about a year ago so I know that's not an issue.

I am planning on sourcing a spare (preferably new) fuel pump in the near future and also looking at replacing the rubber pickup 'bellow' sitting between the inlet of the pump housing and the plastic filter unit that sits into the tray at the bottom of the tank.

The engine runs very well otherwise.

Craig.

[Kongo]

Otherwise, the ignition system of these cars often tend to be a bit problematic. The system almost always work to the point that the car starts and runs, but can cause some small problems like for example that the engine requires a couple of starting attempts, engine misfires or engine not running on all cylinders for the first few seconds after start and such.

If you´re not sertain the problem is with the fuelpump or such, i suggest that you make an service of the ignition system. Replace the distributor cap, rotor, ignition cables and spark plugs.

Make sure to use the right brand and type of spark plugs and preferably also original spare parts for the other ignition parts since the ignition is rather sensitive on these models.

[saab_o_naut]

Otherwise, the ignition system of these cars often tend to be a bit problematic. The system almost always work to the point that the car starts and runs, but can cause some small problems like for example that the engine requires a couple of starting attempts, engine misfires or engine not running on all cylinders for the first few seconds after start and such.

If you´re not sertain the problem is with the fuelpump or such, i suggest that you make an service of the ignition system. Replace the distributor cap, rotor, ignition cables and spark plugs.

Make sure to use the right brand and type of spark plugs and preferably also original spare parts for the other ignition parts since the ignition is rather sensitive on these models.

As my 89 900i hatchback had a rear-end hit recently (check my Saab pics on flickr to see pics of the damage) and needs to go for insurance assessment (I'm suspecting it'll be a repairable write-off), the 81 turbo sedan has now become my daily driver until the 9000's repairs are finished. It uses a fair bit more fuel so I'm mindful of that when planning trips to/from work (85 km each way).

Today is far too warm to test the warm-up reg, etc., but since the car has been driven a lot recently I'm focusing more attention on it.

I've got brand new NGK BP7ES plugs for the engine. The distributor rotor and cap are new along with the leads (replaced before I drove car interstate in October). I'm tracking down a spare ignition unit as the reluctor ones are not easy to find and I want to keep a spare. Getting a spare reluctor ring itself too.

The engine will start fine when warm (apart from the starter solenoid itself sticking when the engine is very hot) and when cold it will go ok if I give it a lot of throttle when cranking.

I'm looking at what to do re the fuel injectors and fuel distributor as I'd like new or reman spares for them. The fuel distributor is a 6-port type with two ports blocked off. I don't know what the part # for the injectors currently in the engine is though I'm working on tracking down some new ones.

Craig.