Classic 1989 SAAB 900 N/A: Hard Starting and Stalling Issues

About a month ago I bought an '89 SAAB 900 that had hard starting and stalling issues. To help clarify things, I’ll describe those issues.

First, the hard starting. To start the car, it would require several cranking sessions of about 5 seconds or longer to turn over.

Then, the stalling. Once turned over, the car would idle normally for a few seconds, hanging around the 1K RPM mark. After that, it was start to stagger and begin stalling. If you applied some throttle, you could delay the car dying totally for a couple more seconds, but it was obvious that it had less and less effect. After which, the car would stall out.

Here’s what I’ve done to the car so far:

- Checked for vacuum leaks (replaced old bushings, valves, bad hoses and tightened other hoses)

- Replaced the NTC sensor

- Thoroughly cleaned out the AIC valve

- Replaced the (fouled) spark plugs

- Cleaned the throttle body plate

- Recharged the battery and cleaned the terminals and connectors

- Re-adjusted the throttle position sensor with a multimeter

- Replaced the Air Mass Meter

- Replaced the ECU

None of these things worked, unfortunately. The one interesting thing is that unplugging the Air Mass Meter allows the car to remain idling, so that’s why I tried replace the AMM and ECU - which did nothing. I still haven’t found a possible fix for the hard starting, though.

At this point, I’ve ordered a timing light to see if it’s possibly the crank position sensor/hall sensor. If that doesn’t do it, I suppose I’ll replace the whole fuel pump assembly. And if that doesn’t do it, I’m stumped. Any input or advice on this would be greatly, greatly appreciated.

It could very well be a failing fuel pump. This is not unheard of because those Bosch pumps really take a pounding and not changing the fuel filter on a regular basis can shorten their lives to boot.

What could be causing the stubborn starting, stumbling and dying upon startup, etc. is a lack of fuel pressure.
When the engine is at rest some residual fuel pressure should be retained in the system. If fuel pressure leaks off then what happens is that the pump is having to purge air out of the system, or burping the baby I guess you could say.

The pump has a replaceable check valve in the top of it but if that’s the original pump I would probably replace that. Since they’re a bit pricy, you might check eBay as original new Bosch pumps pop up there somewhat regularly for a lot less money.

The pumps are pretty easy to change; usually. It’s located underneath the rear trunk floor cover. Remove the round plate on the left and out she comes.
The one glitch might be if the large nut that holds the banjo bolt in place has rusted due to age/water. Use care in removing it as the fuel line is hard plastic and may have a tendency to twist, which will ruin it.
Hope that helps.

Do you have a hard start troubleshooting chart? have you followed it? how far are you getting? I am going to take a leap here as I don’t remember but 89 is still a CIS year? Why did you replace the ECU? (I know the car won’t start correctly) but why did you decide on the ECU? did a chart take you there?

I do have a contact that would send me a replacement fuel pump for $45 plus s&h, so I might just try that. Luckily, I do have a Bentley manual to aid me in replacing it, if I decide to do so. To be honest, I don’t know how old the existing pump is, but I do know that the previous owner claimed to have changed the filter and I’m fairly certain he changed the fuel pressure regulator. Also, to start it, he had a habit of pumping the gas like a carbureted car, so you might be right about that pump. I have been forewarned to be careful with the fuel lines since they are fragile - Do I need a special tool to do the fuel pump removal, installation or can I make do with standard tools you’d find in a garage (I’m fairly well stocked).

Oldschool: the only chart I have is the guide in my Bentley manual, and I’ve only followed it loosely. Most of the stuff I’ve done has been as a result of internet research and advice from a SAAB enthusiast site. I replaced the ECU because I was grasping at straws and I was hoping, since the car seemed mechanically fine, that it was a bad ECU (I’ve heard other anecdotes pointing to this). It was pretty much a situation where I was getting to the bottom of the barrel for ideas, so in came the ECU (also, because the swapped AMM didn’t do anything).

EDIT: Would the fuel pump assembly from a 1989 SAAB 9000 n/a be interchangeable with the fuel pump assembly from my 1989 SAAB 900? I mean, it is only a ‘0’ off! Just kidding…

ok4450: I had something to add to my other post - the check valve you’re talking about…is it an internal, metal check valve? I replaced the plastic, L-shaped sender and return line check valves to no avail. If it’s potentially as simple as replacing the pump assembly for $45, I’ll do it. The reason for the whole assembly is because I hear that they’re hard to disassemble/repair without breaking them.

I am having trouble with ECU. Is this a CIS car which is basicaly mechanical(OK hydraulicaly controled) fuel injection and you are talking about the control unit for the spark not a combined fuel injection ignition control unit?

When I don’t know something I will admit it what is the AMM?

I think I have the 2.4 Jetronic FI system. Beyond that, I’m not sure how to describe it. It should either be the Bosch or the Lucas, and in my case I think it’s the Bosch. The control unit I replaced, as I understand it, does control both fuel and spark and anything of that nature.

The AMM is the Air Mass Meter, also known as the Air Flow Meter, the unit that snaps on between the air filter and the intake manifold.

The fuel for any CIS system is controled by the position of a rod inside the fuel control head. The position of this rod is controled by the position of a arm that is connected to a plate inside a air box and the position of this plate is determined by how much air is flowing past it.

The electronic part of your type CIS is in the use of a oxygen sensor and a knock sensor.

Your system does not have electronic fuel control in the sense of varying pulse width fuel injector.

And yes I do know the AMM by thr name Air Flow Meter.

Have you inspected the function of the cold start injector and have you inspected the wiring at the big terminal on the starter? This is a main bus point (including F.I. systems and I have seen the wiring break at this point.

Has anyone suggested observing fuel injector spray patterns? and have you removed the metering rod in the control head and inspected it for ease if operation? The arm connected to the metering rod is connected by a little wheel and this wheel can sieze up and cause erratic operation, and this big flapper plate can come loose.

Last of all those big rubber tubes (on top of where the flapper is and along to the intake) must seal perfectly

Here is what the check valve looks like. It’s located on the top of the fuel pump.
This one’s for a Porsche, but it’s the same thing.

The only other difficult thing about changing the pump instead of the assembly is weaseling the pump out of the canister that it sits in. The pump fits tightly in a rubber sleeve. Over time that sleeve hardens and dries out due to gasoline. It can take some serious twisting and yanking to get it out. I usually put a few drops of oil around the pump and try to work the pump in and out while also twisting it around. Even then it can be a wrestling match.

This car should have a “normal” fuel inj. system and is not CIS. (Lucky you.)
In theory, and according to parts house lookups, the pumps are not interchangeable but I think they are up to a point. My CIS '83 Turbo has the same fuel pump (down to the exact numbers) as my '89 900 even though the former is a CIS car and the latter a “normal” one.

Generally the pumps can be changed without special tools. I’m an ex-SAAB tech and even when working at the dealer always used garden variety tools to do this job.
Hope some of that helps.

(Just another note here. As I mentioned, those Bosch pumps really work hard and if it comes down to a check valve I would replace the pump too. I’ve got a pump that is torn down on the table right now. I’ll see if I can get a pic of the armature commutator, post it, and show you just what a beating those pumps take. Commutator failure is generally what does them in and the rest of the pump remains like new. The pump in my '83 dropped dead last week and I’m trying to work that job into my life right now.)

I am finding only variants of CIS used on the car KE-Jetronic LH-Jetronic some with hot wire air flow meter some with knock sensor some with 02 sensor (Lamda)But all appear to be some form of CIS.

I have only been using Wiki to reasearch and I know Wiki is not always correct or complete.

In my writing class last semester we were not allowed to use Wiki or anything found by google,thats as strong as the Professor objected to Wiki and Google.

Are you refering to some type of multi-port either sequencial or non-sequencial fuel injection.

Or perhaps you are refering to the more electronicaly controled KE version of CIS but at the base they are all looking like CIS. Wiki is listing different versions of F.I. if the car is Turbo or 8 valve or 16 valve.

Perhaps you are refering to the earlier VW AFC type F.I.

ok4450: Thanks for the great reply! Your link to the Porsche check valve answers my question and suspicions.

For what it’s worth, I did find an '89 SAAB 900 n/a fuel pump and after checking, it appears that’s on the same compatibility list as my 900. It looks like it’s complete, except for possibly a fitting that’s on the bottom of the assembly. I’ll try to mentally prepare myself for the potential wrestling match ahead. Any tips on safety when swapping out the pump (fuel spray, high pressure, etc)? Finally, are lubricants like Marvel Mystery Oil and PB Blaster safe to use to get that canister out? Otherwise I do have plenty of standard oil. Thanks again for the info.

I have a '93 classic SAAB 900 Turbo (2.4 Jetronic FI) that is new to me with the same problem as described by you, mphilleo. The car will start, run for a few seconds with erratic idle and then die. I replaced the spark plugs and checked all the vacuum hoses and swapped in another AIC, without joy. When I disconnect the cable to the AMM, the car will idle uniformly and never stall, just like yours. I am awaiting shipment of a copy of the Bentley manual and was ferreting for info on the internet when I found this discussion, so no further troubleshooting as yet, but I do have a few thoughts on the discussion so far.

If the fuel pump is to blame, I’m wondering why it would produce sufficient juice for a stable idle with the AMM disconnected. I would suspect that the pump would cause a more generalized failure. But my only experience with Saab fuel pumps was my '87 8v w/ CIS. When its pump failed, it warned me with a few months of progressively louder pump noise, and then failed suddenly and completely.

You mentioned the hall sensor. I think that acts like points on an old style distributor and if it were to blame I would think that we would not have a stable idle with the AMM out of the circuit.

When I get the manual/wiring diagram I will join you in tracking down this problem. I think the car running with the AMM disconnected is the big clue, but not sure what to make of that info without knowing how the system works.

Hope this all ends with a solution!

When the Air Mass Meter (AMM) is disconnected, the engine computer (ECU) goes to built-in table of values to use instead of live data. Therefore, there is something wrong with the signal reaching the ECU from the AMM. Disconnect the wiring from the AMM and the ECU. Use the multimeter to check the ohms values of the wires from the AMM to the ECU. The wires should be the same color, at both ends, so that shouldn’t be a problem.
Check the ohms of the AMM. Your repair manual should list the values expected.
With everything connected, backprobe (needles) the wires at the AMM, and check the voltage values. Again, your repair manual should give the expected values.

hellokit, what you say is very interesting. I’m still trying to determine if the symptoms have one root cause or multiple problem points. Regardless, you make a good point about the wiring between the AMM and the ECU. I do have a multimeter, so I can check those against the values listed in my Bentley manual.

The big question is, if those values may be off, on one end or the other, do I have to replace the whole wiring harness or an individual wire, etc?

That fitting on the bottom is probably the fuel strainer. These can be cleaned and reused if necessary.
(On a side note, I changed a similar pump in a Benz 190 recently and that strainer was an impossible item to find. EBay, parts houses, internet, etc. and apparently no one makes a strainer for it even though the strainer fits various Benz models over a 10+ year span. What a crock.)
Any lubricant will work on the sleeve; just anything to provide some slippery to it.
Loosen a fuel filter fitting a tiny bit and this will allow the pressure to bleed off.
Make absolutely SURE there are no sources of spark around the tank opening when the pump is removed. No electric tools, cigarettes, or even any nylon/rayon type cloth materials as the latter can generate a static spark.

As far as I know, CIS was last used in '88 on the 8V models and that was an electronically controlled version in which the Control Pressure Reg., etc. was done away with.

The reason why the vehicle may idle fine with the MAF unplugged is that it will have a tendency to richen up and this may be offsetting a slightly lower than normal fuel pressure, air leak, or a bad injector spray pattern. (Just theory there.)

I took a pic of a failed commutator but haven’t downloaded it yet. Since I also had a couple of other failed Bosch pumps lying around (I’m a packrat) I popped those apart too. Both pumps are like new as to armature windings, bushings, etc. but those two also have badly worn commutators.

ok4450: When I was replacing the valve cover gasket to keep myself busy the other day, I pulled out the plugs and noticed they were heavily fouled, though I hadn’t done anything more than crank the car as described and idled it a few times briefly without the AMM connected. Would fouled, new spark plugs fall in line with your theory about the overcompensation/richness of the FI system fall in line with this? I’m tempted to think so. In any case, even if it’s not the pump, the fuel pump check valve on my existing pump could be bad, which is causing the long cranking times. I’ll definitely see how it goes when I try to swap in the fuel pump I ordered. Aside from that, do you know if there are any trouble points in the vacuum system I should check before hand? I’ve already gone over most of the hosing under the hood and hose clamped anything that was remotely suspect, along with any bad bushings.

Well, I think the stalling problem was likely the fuel pump. Here’s why.

I got my $15 used fuel pump last night. I took out my existing one and swapped the best parts between them, which pretty much meant swapping the pumps and fittings since my existing assembly housing was much better. Anyway, I finished it up, plunked it in, made sure the check valves were snug and called it a night. This morning, I started the car and it still took several cranks to turn over. Once it got starting, it idled for much longer than it did before. Then it died again.

I started it again and the car seemed to want to die after about 20 seconds, maybe 25. Then the check engine light came on and I gave it some throttle to keep it going. After that, the idle evened out and it kept going on its own for at least 5 minutes before I turned it off on my own. By the time I turned it off, the CEL was off. I haven’t tried it again since then, but I imagine it’d be the same scenario and now that the FI system should have the pressure back from the new pump and such, it should at least idle steadily.

Then it’s on to the hard starting problem. In the mean time I’ve got an ignition coil coming, new, that I found for $20 and an ignition control module I got for $25. When I get 'em I’ll swap 'em out and see if it helps the hard starting problem. If not that, maybe I’ll have to find a dizzy.

When these cars were new they would start in seconds (with the air already on) you could slap a automatic in gear and take off without hesitation. Absolutely no warm-up time required just start and go. It does not sound as though you are there yet.

I understand that it has a way to go, but it’s running a lot better than when I bought. A steady idle is better than a failing one. Now it’s just a matter of getting it to start quickly and consistently.

Who’s to say the used pump is doing what it should?
Anyhoo, in refernce to the part about badly fouled plugs (assuming they’re black and gas fouled) that could point to several things.

One would be a leaking fuel pressure regulator. This could cause hard starting due to pressure bleed-off, bad idle and eventually stalling when the engine “loads up” as it’s called, and fouled plugs.
Two could be a problem with the injectors not pulsing. Have someone crank the engine over and carefully listen to the injectors clicking by probing them with a mechanic’s stethoscope or even a long handled screwdriver with the blade placed against the injector.
(You could also get a Noid light from the auto parts house(they’re cheap) and check the injector pulse with that.)

Hope some of that helps.