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Discussion Starter · #1 ·
HI, have a '96 900S (non-turbo 2.3l). After a long trip, the car started having power issues. At any speed, any temp (engine and outside) and at any degree of humidity, engine randomly losses power on acceleration. I go to accelerate and engine acts as if it were missing fuel....(not misfirering). To resolve this issue when it happens, I must either let go of the accelerator and try again or throw the accelerator to the floor. Very anoying especially in Montreal where people drive 1.2 inches behind your bumper.

What I did:
- Changed fuel filter
- Changed sparkplugs (NGK)
- Checked HD wires
- Changed Orings on intake resonator
- Cleaned Idel Air Valve
- Checked for vacuum leaks
- Checked for bad connections

I did not check the fuel pressure since I do not have the proper equipment and the fuel pump and filter are under the car in the rear. I took the Fuel Pressure Regulator out this morning. When sucking on the vacum hose attached to it, should I be able to detect movement?...Sound? At first, nothing would happen, then I hit it on the pavement a few time in case it was sticking...then I could here a small click when releasing the vacuum rapidly. Put it back on the car and the problem persists...maybe different now, but still there.

Any suggestions would be greatly appreciated.

Thanks.
 

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I don't know too much about the fuel pressure regulator, but I have one more suggestion, which is to check the throttle position sensor. You'll need a volt meter, but I think there's a spec somewhere that will tell you how much resistance you'll get at a certain position.

Another possibility of course is a fuel pump on the way out. Can you hear it running or have you ever noticed a change in pitch?

Also, you might want to double check the silencer "o" rings. I found it was tricky to get the seated properly. A little grease on them will help make a tight seal.
 

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Throttle position sensor

idle resistance is 2.4 to 3.4 volts
full throttle is......0.7 to 1.0 volt

Fuel pressure regulator

opening fuel pressure is 3.0 bar

these numbers are from Haynes

Use a thin layer of silicone paste on Orings

This sounds as if it may be a fuel pump (Napa around $100 -pump only).Many threads -I like the idea of cutting an access hole above the pump...
 

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It sounds like this might be one of my (many) problems too. Where is the fuel pump located, on top of the tanK? What is the cut-through option?

Can you think why the fuel pump performance would be triggered sometimes by the use of any of the electrical options, ie. use of windows, wippers, AC, turn signals, etc.?
Thank you,
Patrick
 

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Can you think why the fuel pump performance would be triggered sometimes by the use of any of the electrical options, ie. use of windows, wippers, AC, turn signals, etc.?
Thank you,
Patrick



This seems to be a voltage problem; check out the battery/charging system.

There is an excellent thread on this(fuel pump access), it was in my favorites, now I cannot find it..
There is a port, that I have seen, on the fuel rail for testing purposes....
Use search
 

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As remote as it sounds, maybe the best thing to do is buy a new battery and/or check the voltage. If you buy a volt meter (<$20.00), there are plenty of sites on the web that tell you how to test your battery. Basically, you check the voltage with everthing off and then crank the car for a few seconds and measure the voltage drop while someone else checks the voltage. It will also vary with temperature. I don't know the specs, but a quick google search will turn them up for you OR you can just go to Autozone and the like and they'll do the test for you (free, but then you don't get to own a volt meter).

Anyhow, many weird problems have been solved by a battery replacement. The fuel pump is actually inside the gas tank, and it, like most everything else that makes the engine run is electric. The gas tank has to be taken off the car to get at it, OR there is a thread out there (the one earthworm mentions) that tells you how to cut through your cars floor to get to.

Because the pump and all the other engine support things are electric, an iffy battery can cause trouble. Also, summertime is a big drain on the battery. The radiator fan runs a lot, especially if you use the a/c., so the fact that this is happening in the summer (even on coolish summer days) is an interesting clue.

I just replaced my battery because it the starter would barely crank after a long drive with the ac on. With a new $35.00 wal-mart battery the car seems much much happier.
 

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Any progress?

Howdy djt,

I had the same thing as you describe happen to me this morning. It's hard to know where to start looking. Could it be the DI, or what happens when the DI goes out?

Let me know what the results of your research and testing shows. I hate to send the car to the shop again, having spent considerable amounts of money for new fuel pump, water pump, clutch, etc :eek: .

It was running fine prior to this though. And my wife loves driving it, so I'd like to keep it running for a while longer.

Thanks,
Henko
 

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Thanks JMarket,

I did have it at the shop last week, but they could not a fault code, so he asked me to make another appointment (for next Thur) because he was so backed up, but he says he spent a couple of hours trying to figure it out. I would think he checked that battery, maybe not.
We have only had the car a little over a month, but it is always warm here in the tropics, so I do not think it is season related.
It would make everything a lot easier if it were just the battery, but it seems to have plenty of juice to crank over and over again when I cannot get it started.?.
Thank you,
Patrick
 

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It's just a guess, really, based on what i've read here and my own indirect experiences (my car generally seeming happier after the new battery, hardly objective :) ) Of course it could be a lot of other things too. When it's back at the shop, you might ask him to load test the battery first for laughs, if nothing else. The electronics that run the engine might be more sensitive to voltage than the dumb motor that turns the engine, if that makes sense.

He'll be able to check the fuel pressure etc. too, so that might rule in/out the fuel pressure regulator.

Now I bet you know why the old owner sold it -

Um, so papaquebec is from hawail and djt is from montreal?
 

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Discussion Starter · #11 ·
humm...

Thanks for the replies.
The battery concept was the first one on my mind since the problem appeared after a long tri where an electric cooler ran the batt flat several times. nIt now seems very week...a few minutes using the power windows with the engine off will kill it. On the other hand, pulling the FPR off and hitting it on thr ground a few times, then putting it back in, seems to have altered the problem. Hell, its still too early to conclude. I guess I will have to change the batt before winter. In the mean time, I will see if the problem persist after the FPR intervention (does not seem to starve as much now). Hitting it on the ground would be a cheep soln. Could a FPReg stick?

Thanks.
 

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Discussion Starter · #12 ·
New Battery, same problem...

New Battery, lots more power in this one, but the problem percists!

Why is there a vacum hose on the FPR?????? I do not seem to see how this should be.....

Can the FPR be the problem?

No way I can test the resistance values in the throttle position sensor....I would need a test plug since I have no access to the connection to put my probes on it.

Both Orings on the sinlencer are new and greased....if that were the problem, I doubt it would be intermittant....

I'm running out of ideas.....could the fuel pressure (pump problem) be a cause to such an intermitant problem??

Any suggestions would be greatly apreceated.

Regards,

DJT.
 

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The vacuum controls the fuel pressure, during wide open throttle (WOT) operation, the pressure is allowed to increase as the vacuum decreases.

Do a fuel pressure test.
Was a battery test even performed ?
 

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Sorry earthworm, just occurred that it may be possible to cut an access hole for the fuel pump from underneath :eek: :cheesy:
 

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JMarkert said:
It's just a guess, really, based on what i've read here and my own indirect experiences (my car generally seeming happier after the new battery, hardly objective :) )
Once the engine is running power SHOULD come from the alternator and not the battery. The voltage is maintained at a steady 14V by the voltage regulator which is part of the alternator (replaceable for around $70 retail). The alternator supplies current to run the car, lights, accessories etc., and charge the battery.

The only time the battery would have an effect would be if almost fully discharged (large load on alternator), or if the alternator brushes are worn and becoming intermittent (like they did on my car around 100k). If a new battery seems to fix something that happens with engine on, it is time to test the alternator, check the cables, terminals, grounds, etc.
 

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Discussion Starter · #16 ·
Thanks for the info on the FPR vacum line. That's what I though it was for. I changed the battery withou testing it. It was pretty old, and was recently drained several times in a row...therefore...it was shot. I had to change it anyways before winter....it had hardly enough power to crank the engine...the alternator is in great shape.

For the FPR, when the prblem occure, I have to step on it (full throttle) to get the car going....I guess this points towards a fuel pressure problem. I brought the car to the local Saab specialist, but he is not of the most efficient workers....only one mechanic in the garage. He said that testing fuel pressure had to be done (in this case) while driving the car, which is difficult since the filter (on which he hooks up his apparatus) is in the rear, under the car.

Since this is an intermitant problem, what is the best method of testing fuel pressure? I guess it must be done while driving (?)

Thanks for any info.

Regards.
 

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hunt.dogshome said:
Sorry earthworm, just occurred that it may be possible to cut an access hole for the fuel pump from underneath :eek: :cheesy:
???
The access hole is cut from topside..
But I have yet to see the all important dimensions and measurements..
But I am good at guessing..
 

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djt said:
Thanks for the info on the FPR vacum line. That's what I though it was for. I changed the battery withou testing it. It was pretty old, and was recently drained several times in a row...therefore...it was shot. I had to change it anyways before winter....it had hardly enough power to crank the engine...the alternator is in great shape.

For the FPR, when the prblem occure, I have to step on it (full throttle) to get the car going....I guess this points towards a fuel pressure problem. I brought the car to the local Saab specialist, but he is not of the most efficient workers....only one mechanic in the garage. He said that testing fuel pressure had to be done (in this case) while driving the car, which is difficult since the filter (on which he hooks up his apparatus) is in the rear, under the car.

Since this is an intermitant problem, what is the best method of testing fuel pressure? I guess it must be done while driving (?)

Thanks for any info.

Regards.
Sorry about the battery not working - although it's good that it's money well spent before winter in Canada.:D

You're probably sick of buying parts, but since you're at a shop the costs are rising anyhow. If you really suspect the fpr, maybe you should buy one and pop it in? They are about $70 US from thesaabsite and eeuro, or about the cost of an hours worth of your mechanics time. I think they are easy to put in, with the only caveats being you should buy the new washers you'll need and you should be careful taking the old one out because the gas lines are pressurized and gas will spray out (ie watch your eyes!). {edit: but of course you know this, having already banged it on the ground}

I know it's usually not prudent to just swap parts, but if diagnosis is more expensive....
 

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Djt, the only thing I can think of ,that may be possible, is to test, using the mechanics set-up, at an idle and compare figures.

We had a procedure, back in the good old days, of using a 28" length of hose at the fuel pump - this was so easy - these cars, now antiques, were made to be serviced and worked on.
What has happened with all the auto-makers in the past 10 to 20 years is NOT good..
And the days of operating economy are over...
Maybe at the better dealers, they have some $$$$rig that can be used to test pressure..
Your fuel pump may still be OK, perhaps the check valve is sticking...
Also, NOT good, is that one has to either drop the tank or locate and make an access port - the real Saab had an fuel pump access hole...
 

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djt said:
Since this is an intermitant problem, what is the best method of testing fuel pressure? I guess it must be done while driving (?)
As far as I know, there is no easy place to test the fuel pressure at the fuel rail. Something has to be disconnected to hook up a pressure gauge.

However, I don't see why fuel pressure can only be tested while driving.

The fuel pump circulates fuel through the filter, fuel lines, fuel rail, and regulator continuously while the engine is running regardless of the amount required. The engine has sequential fuel injection where the amount of fuel is controlled by the ECU adjusting the length of time the injector is open to the cylinder. Fuel pressure is controlled by the FPR.

Fuel injectors, FPR... conceivably the CPS because it is used differently on cars with the Bosh ecu.

On the NG900 turbo, the CPS connector is just behind the fuel rail, and you do not have to touch the actual sensor on the engine to test it, or need any special plugs or tools. You cut one cable tie to get at the connector, unplug it, and the pins are right there. The turbo will not start if the CPS is bad (or unplugged... do NOT ask how I first noticed this) Not sure if the n/a engine will run with a faulty CPS, but I understand that they tend to fail intermittently when the engine is warm...

Throttle position sensor connector, on the side of the throttle body, faces down, so it is more difficult to get probes on it. If you suspect the TPS, the resistance has to be measured both with closed (1 +/- 0.2K ohms), and wide open throttle plate (2.5 +/- 0.5K, pins 2 and 3, from the same page of the Haynes manual as the CPS spec)
 
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