One day suddenly without warning my ’97 V90 wagon became hard to start. I spin it and after half a minute it finally kicks over and runs, At first it runs with a hint of roughness; that is some noticeable stumbles but within seconds it smooths out and drives well. After I shut it off and restart immediately it starts normally but give it a little time and try to start it and it takes a lot of spinning to get it to catch and start. The starter spins the engine like a top.

The fuel pump is something I was thinking and had I been trying to figure this out on my own I’d have replaced it on a bet. I took the car to my mechanic, Independent Volvo in Bakersfield, and I did mention the fuel pump as a possibility but because it ran after starting I still thought something else is the cause. Paul went ahead and replaced the fuel pump and asked me to take it home and drive it to see how it does. He saw some improvement which is true speaking to the likelihood that the old fuel pump was getting close to failure anyway. But even if not running like it should it beats leaving it at the shop over a long weekend. It's drivable but still behaves badly and the new fuel pump's help is marginal.

A significant aspect is that on a day before it ran like a new car. The difficulty starting was sudden and a complete surprise when I came out one morning to start it.

To be clear, you're saying it takes cranking the engine over for ~30 seconds before it finally fires, runs rough for a few seconds, then smooths out and runs fine after that.

This still sounds like a fuel supply issue to me. Not the pump, not the fuel filter but a leak in a fuel supply line from the pump to the engine.

Do you have the ability to connect a fuel pressure gauge to the fuel rail and see how long it takes for the fuel pressure to bleed down after engine shutdown? You may be able to rent one from a parts store. You need the kind with the Schroeder valve (like an air fitting).
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1998 S90 088,900 and 1995 964 154,100

I think Dave's suggestion to pull the plugs after a long struggle and no start,
Is a good way to diagnose. See if they are dry, wet, fouled?
I didn't see any response to his solid suggestion.

Check OBD codes and see if there's any clues there.

Bill

Have you replaced your coil packs yet? If they are original they are way overdue. How many miles on your car? Coil packs are normally good for 100k+. There are no ignition wires or clips. There is also no ignition coil or distributor. The coil pack is mounted near the spark plug hole. There is a coil pack wire that runs to it. There is a cover you need to remove to access the coil packs and spark plugs. Suggest asking your mechanic to test the coil packs as they can cause all sorts of problems when they go bad.

Here is a link from the 700/900 FAQ on this site that might help. Check out the spark plug removal section for picture and more info.

https://www.brickboard.com/FAQ/700-900/960_90Info.htm#960PartsSources

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Will I buy another Volvo??? We'll see....

With a long crank, pop the hood and pull then firmly reseat both ends of all ignition wires to see if it's a loose boot clip or bad wire. If it now starts up (or now never starts) then you'll know.

I'm thinking too much fuel, not too little. There have been RWD posts here in recent years with similar symptoms that mentioned leaking injectors could cause both fuel rail pressure loss and initial flooding making for a long hard cold start then running normal after initial rough running coughing out the fuel. Any initial black/grey smoke out the tailpipe when it finally catches? Check fuel rail pressure when left overnight vs.right after running. Pull and read all plugs after a failed long crank to see if any are wet or fouled notably different. If you've got a cold start injector then add that to the equation.

One low tech approach would be a couple of tanks of super premium with mostly high revving long trips through the mountains (aka an Italian tuneup), maybe even add some rxtra injector cleaner like Techron. If that makes a notable diff for a few weeks of cold starting then that would suggest fouled injectors and/or plugs are involved.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Yes. Black smoke on startup. Clears up shortly after.

Black smoke after finally catching is likely a build up of fuel, so less likely to be a fuel delivery problem, more likely to be ignition or as I mentioned leaking injector(s). You haven't answered my other basic questions to further help isolate the problem and eliminate possibilities, including too much, too little fuel, or badly fouled plugs. Check the plug gaps while you're at it. When you cleaned up the oil in the plug recesses, did you remove the plug? That might lend credence to the leaky injector possibility. Based on your new info of no longer smoothing out, I'm heavily leaning to the ignition side. I'm guessing two or more cylinders, if not all cylinders, are involved. If it was just one cylinder not initially catching then I'd expect it to start right away, but run extremely roughly until you got normal combustion in that cylinder.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Dave, Thank you for taking the time to post a response. Your reference in the first line to the ignition wiring caused me to open the cover over the coils & spark plugs. I discovered the front four plug chambers had oil in them along with more oil in the casting ribs on top. This apparently had come from spills (sloppy me) at the fill port.

I cleaned out all the oil and using electrical contact cleaner cleaned up the plugs and the coil seats and boots. Now the car runs fine.

Well I wrote too fast. The started and ran for a day. None of the long crank time, and initial stumbling before smoothing out to run normally. Then the problem came right back. the idle isn't really all that smooth but the stumbling stops after feathering the throttle to help it catch, start and run. After it warms up it is smooth as it was out of the factory decades ago.

Thanks, guys for your posts. While it's not fixed yet this gives me good direction to figure it out. This isn't the first time in my life where I've run into an intractable technical or mechanical problem that makes no sense and I presume it won't be the last. Keep 'em rolling!

It would be helpful if you told us the mileage of your car and any related repairs. Do you or your mechanic have the ability to diagnose/test the coil packs? The type of symptoms you have could be one or more bad coil packs. If the coil packs have over 100k miles on them they could be going bad. If bad, ideally you replace them all. In a pinch, you can get away with replacing just one. However, if one has gone south the others will usually follow...:)

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Will I buy another Volvo??? We'll see....

As long as the plugs aren't throughly fouled then I agree that the coils are a prime suspect here. Pulling each plug and testing for a strong spark to the block in dim light should give a good idea if there is an ignition problem and which coils might be involved. Both the plugs and ignition wires should perhaps also be replaced on spec if they haven't been done in living memory.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

You really need to study and understand coil packs/modern ignition systems and the white block engines before you talk about them. There are no ignition wires. The coil packs are mounted directly on top of the plugs. Maybe you should consider skating in your lane and stick to the older ignition systems and the red block engines.

Check out the picture in this link.

https://www.brickboard.com/FAQ/700-900/960_90Info.htm#960SparkPlugRemoval

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Will I buy another Volvo??? We'll see....

Noted. Just trying to be helpful.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

In an earlier post, the OP said he cleaned the plugs. Yes, pulling and checking them now would tell a story.

Even if the car has only 70-80k miles, if the coil packs are original they are most likely toast at 27 years old. They have far outlived their useful life.

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Will I buy another Volvo??? We'll see....