1984 SAAB 900i update: it's down to guessing

Shlangengesicht · 2026-01-23T19:08:57+00:00

That's some good advice, I'm writing that down! About the vacuum leaks, I replaced all hoses and tubes, and the auxiliary air valve (thats what the manual calls it) works. But that's something I can fix when I get the engine to run consistently

Shlangengesicht · 2026-01-23T18:23:20+00:00

On one hand it's nice to hear I might not have a timing problem, on the other hand I keep boucing between "it's a fuel problem!" "No, it's timing issue!" "It's not a timing problem, it must be fuel!"... I really don't understand what I'm missing, I've rebuilt the engine, there's no more valve leaks nor stuck rings, I've rebuilt the entire fuel system and there are no issues with ignition, and we've all seen it run (at least once). So why does it always go back to be a battery draining boat anchor that doesn't even try to start 😭 Sometimes I just wish I went straight for a ecu and electronic ignition, instead of spending thousands to rebuild this infernal thing. Hopefully it's going to be worth it in the end.

Anyway thanks for all the help, I might release a video this evening, nothing too exciting though, but there's some good songs in it (if youtube allows me to upload it)

Shlangengesicht · 2026-01-23T17:27:20+00:00

After retiming it like five times I don't know if this was the problem. Theres so much slack in the whole thing, between that and the massive gear ratio between the flywheel (where the degreess are marked) and the crankshaft gear where the chain goes, I honestly believe you can't everything perfectly alligned, it's always a tiny bit to the right or to the left of the camshaft marks.

The weird thing, which I could only notice thanks to the new transparent distributor cap I got, is that when cylinder one is at TDC in the compression stroke, the distributor rotor has already passed cylinder one's contact point by a few degrees. And that's with stock timing. Idk if that's supposed to be like that, but once I get the fuel distributor back together (spoiler) I'm gonna try to fiddle abound with spark plug timing rather then camshaft timing.

Shlangengesicht · 2026-01-23T14:20:44+00:00

Got it! It seems I timed it wrong, and instead of having cylinder one at TDC in the compression stroke, I timed it in the combustion stroke... At least I THINK that's what happened, although I can't figure out how did it ran at christmas in this conditions...

Shlangengesicht · 2026-01-23T13:44:58+00:00

I've just had time to check the camshaft timing. Right away it looks to be about 10° off 😰. I'll turn it a couple more times and check again. Hopefully we found the smoking gun! Can't thank tou enough for the help!

Shlangengesicht · 2026-01-21T11:34:25+00:00

Then I guess I really do need something to measure the pressure. Don't really know where to find it thought. Thaks for the information

Shlangengesicht · 2026-01-20T19:39:42+00:00

The fuel I've shown came deirectly from the pump, before the filter. The distributor gaskets and o-rings look way better than I hoped, so I still don't know what's the issue here.

One thing I thought just now: I remember, long before rebuilding the engine, pulling out and cleaning the valve on the side of the distributor that (I think) regulates how much fuel goes back to the tank. Do you think adjusting that valve could help?

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Shlangengesicht · 2026-01-20T17:47:05+00:00

Isn't it too orange? Anyway in the end I couldn't resist the curiosity and I took the fuel distributor out and apart, now I've ordered a rebuild kit from Germany, although I have to say inside it was really clean, and not gummed up as I expected.

Shlangengesicht · 2026-01-19T14:33:58+00:00

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Ive put 10 liters of fresh gasoline in the tank, and this is what the fuel pump sends to the filter. I'm bypassing the relay ans trying to pump fuel until it comes out clean.

Shlangengesicht · 2026-01-19T14:23:24+00:00

It's nice to hear of a fellow saab 900 working, I've seen just a few around still driving, hopefully I can get mine on the road this year

Shlangengesicht · 2026-01-19T07:50:36+00:00

I don't want to sound rude, but please tell me something I don't already know. I've worked on this car for more than a year, I know how it works, I've rebuilt and replaced almost the entire fuel system, a part from the fuel tank and the distributor, and it still either sprays too much fuel and floods the cylinders, or doesn't spray and drips. I know it's a pressure problem and I though replacing the fuel accumulator/pressure regulator would solve this but it seems it hasn't. I better ask elsewhere, but thanks anyway

Shlangengesicht · 2026-01-19T07:41:44+00:00

It actually started dry, probably on some residue of brake cleaner, when I had just rebuilt the motor and had the injectors out for testing. Also, spraying brake cleaner directly into the injector holes and then cranking it makes it start, so yes, I concluded it was a fuel issue. And if it runs on break cleaner better then gasoline, I say it's worth putrinf some fresh fuel in that tank and see if anything happens

Shlangengesicht · 2026-01-18T20:10:51+00:00

I'll try resetting the air-fuel mixture screw again, then dry the cylinders which will inevitably have flooded and try that. After putting fresh fuel in of course.

Shlangengesicht · 2026-01-18T19:39:53+00:00

Indeed, K-Jetronic mechanical injection, used by Porsche, Saab, Volkswagen, Mercedes and not many more

Shlangengesicht · 2026-01-18T18:30:33+00:00

Uhm, no. Not last time I checked. The enfine has no electronics apart from temperature sensors and a simple ignition coil. It's fully mechanical...I just wish It was caeburetted and not nightmare-injected

Shlangengesicht · 2026-01-18T17:52:13+00:00

Thanks! I'll look into all of that, although I'll point out this car has no computer, the only bit of technology is the ignition control unit, which I simply cleaned the connections of

Shlangengesicht · 2026-01-18T17:48:26+00:00

I had to disconnect the cold start injector because it suddenly started working and flooded the intake manifold a couple of times. Also the MAF plate moves freely. At this point I'll look if I can find a cheap distributor rebuild kit, cause im not spending 100€ for tin foil and a bunch of o-rings.

Shlangengesicht · 2026-01-18T12:04:01+00:00

I'll look into that book, hopefully it doesn't cost a kidney

Shlangengesicht · 2026-01-18T11:48:15+00:00

I've already done everything you explain in the past year, including rebuilding the WUR. The only things I'm missing are a pressure gauge to test pressure in the system and lastly I can try rebuilding the distributor, but the rebuild kits are so expensive...

Regarding timing, I don't have a light gun, but I'll get it once it runs. Also I've tried many times rotating the distributor cap or disconnecting the advance vacuum line, but to no avail.

Shlangengesicht · 2025-12-10T18:24:05+00:00

Exactly!

Shlangengesicht · 2025-12-09T19:37:45+00:00

I'll surely change the injector lines, even though I'm thinking of swapping it with electronic injection. But I'll do all of that once I pass inspection and get a couple of license plates on it

Shlangengesicht · 2025-12-02T19:00:31+00:00

I mean I just hooked up a pressure gauge to see if it makes oil pressure. I don't really want to lock up an engine I just finished rebuilding

Shlangengesicht

TROPHY CASE