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Fuel/Power Issue - 940T 900 1991

Newb here. This fall, I purchased my first brick, a 940T named "The Snail". Sole purpose of having a project car to take care of and learn on.

The Snail smelled of gas days before the sale, and the previous owner had his local garage install a new fuel filter. I was actually at the garage when it happened, which gave me an opportunity to inspect and familiarize myself.

I took her to my (very knowledgable) friend's garage to perform an oil change, and she died under idle about 15 minutes in. We didn't think anything of it, really. No problems during the following weeks, including a few hundred-plus mile trips.

A few cold weeks later, it puttered out in the middle of Harvard Square. My friend brought over a new fuel pump relay and she started right up. (He's my Volvo angel). I haven't yet tested the old relay or investigated other possible causes. Seemed cut-and-dried.

Cue the worst winter ever. It sat at the top of the driveway waiting for spring.

During this miserable season the battery died. I pulled and trickle-charged it, taking several days to go "green" and register as full. I did not take a voltage rating before I dropped it into the car. I've driven it around town a few times, and at low RPM the engine vibrates as if it's not getting enough fuel (as it did when it died earlier). Foot on the throttle and everything seems well and fine.

I'm thinking there's (still?) a voltage problem to the fuel pump. I can hear the relay switch on, but the car doesn't always start up. I also don't know a good way to tell if the fuel pump is actually functioning without someone else.

Multimeter reads 11.7 on the inside and outside of the terminals. Not great.

Should I get a new battery? If so, which have you guys found to be good options? Seems batteries are almost all from the same factories/same components nowadays, I don't trust the "compatibility" of the big distributors.

My thanks!








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    Fuel/Power Issue - 940T 900 1991

    Start the car, check the voltage at the battery idling and rev'ing to about 2000 RPM (no tach...just guess). Then turn everything one and check the same.

    1 12.5 V
    2 13.5+ V preferably 14+
    3 12.5 V
    4 13+ V

    If that all checks out, the battery is fine...for now.

    If this behavior happens when the tank is less than 1/3 full, suspect the in tank fuel pump or the hose between it and the fuel line.

    As mentioned also, there are grounds, another relay and the ignition power stage. That last one can often be fixed by a $3 tube of thermal pasted an about 20 minutes of work.








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    Fuel/Power Issue - 940T 900 1991

    Start with the battery, make sure you have a decent one before complicating things. What kind? I don't think it matters as long as it holds charge and keeps 12+ volts.








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    Fuel/Power Issue - 940T 900 1991

    What year? Fuel pump is single on 95, two on earlier ones.

    Although the relay may have been a problem, you don't seem to be clear that now the problem is spark or fuel. There are several common causes of no starts on these, I Strongly suggest you look for lucid's 'start-run sequence'. It is invaluable IMO, and should be printed out and kept in the car.

    Do you know how to read the codes? It's in the FAQ.

    I always, I mean ALWAYS, carry
    fuel pump relay
    Radio suppression/fuel injection relay
    power stage/ign amplifier
    Crank position sensor

    and the tools to install them.

    Oh and as I'm from the North Shore/Salem/Marblehead, I know about the corrosion issues there. Check the ground plates inner fender behind/above the headlights.







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