Hello All,

The problem, on damp rainy mornings after the first start. While pulling off from my fist traffic light, about a 3-4 minute warmup. The car stumbles and stutters for the next 3-4 minutes and then runs fine for the rest of the day, until the next damp morning.

The Cause condensation in the cap. I didn't know until yesterday that the gray insert inside was referred to as a condensation trap. I also was unaware that the bottom of the distributor had four holes in it. Am I missing something? Does the distributor have to breath to work properly, or can I plug all or most of the holes?

Thanks, Bruce
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Bruce S. near D.C.

Check the cap for tracking or cracks. This is what WD-40 is actually for. Spray the inside and outside of the cap with it. Allow to dry and then refit. Spray some on a rag and wipe your plug leads and coil lead down from end to end. You might just cure the problem with spraying the outside. In the dark you might see sparks arcing around the cap and leads. WD will cure that. As an alternative a bit of silicone grease on your finger tip rubbed around the inside of the cap may also do the trick.

The cap and wires are in great condition. I think I will experiment with WD-40.

Thanks
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Bruce S. near D.C.

How did you determine the cause is condensation in the dizzy cap?

Once when I had the problem, I immediately pulled over and checked the obvious things. I popped the cap and noticed condensation.

I dry and cleaned everything up including all the contact points, and it runs great for two or three months rain or shine. After the normal carbon buildup returns and you get a damp morning, the same scenario repeats.

When I say normal carbon buildup, I mean nothing unusual. The kind of thing that any car should fire rigth through, but not when you add moisture. This is on a car with a well maintained cap and wires. The same issue also happens with my 93.
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Bruce S. near D.C.

Does it make any difference if it's winter or summer?

I can't say I've noticed a difference with the seasons.
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Bruce S. near D.C.

In that case I'm not so sure your problem is actually condensation.
If I understand "near D.C." right, then you're in a pretty similar climate as I am, but with hotter summers. And I wouldn't link condensation to anything occurring in the summer (unless it's on a nice cold glass of beer, of course).

I can't say that I have ever experienced problems in the first minutes after a cold start on a damp day. Not even when my car had literally been sitting in the clouds in the Alps for some time.
I also don't think 3-4 minutes after a cold start on a damp day is enough time to clear the dizzy from condensation.
The only thing you can be reasonably sure about is that, somehow, humidity plays a role.

Either there's something missing on your distributors, or the symptoms may seem to point towards a cause which is not the actual cause.
What spark plugs are you using?

I'm using standard replacement plugs, NGK BPR6ES. The only thing in the distributor is the condensation trap. There is about a 1/8 inch gap between it and the post of the rotor. Is something missing to fill that gap?
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Bruce S. near D.C.

Both sound correct to me. In fact, I seem to remember that condensation trap to be a bit loose.
I will recheck when I have time. BTW, the last couple of days have been unusually rainy and damp over here, but every morning it starts and runs just like on any other day. Which had me wonder: do you still have that big plastic shield below the enigne bay (called "protecting plate" by Volvo, part# 1382407)?

I think you may have solved the problem. All of my years of 240 ownership, since 1980. I have maintained my cars with the belly pans intact.

Many months back I pulled the pan off of the 90 245 to inspect the rack and boots. I saw a bunch of issues that were going to need attention, parts to be ordered, and new bolts needed for the pan.

Then life got busy, Covid, a ton of other projects stacking up. Then there was the 93 245 in the garage with the front suspension and steering pulled apart, getting all knew bushings and hardware.

The needs of the 90 got put on hold because it was my daily driver with no backup.
Once I finished the 93, I left the pan off. The plan was to take it to alignment and then reinspect everything.

Well 1 month later what prompted me to start this post is that the 93 developed this problem for the first time. Now both cars were doing the same thing at the same time. And there are both belly pans staring at me from the corner of the garage.
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Bruce S. near D.C.

Unless you are constantly running through standing water and so keeping the engine bay wet to some degree, I doubt if that is the problem. The pans are there for protection of all types, keeping dirt and water out just two of them. Best to have them. Refitting is easy if the pans are intact where the fixings are. Proper fixings should be cheap from a dealer.

However unlikely it may seem, the absent bellypans MUST be excluded as a possible cause.

Condensation inside the distributor should normally be dealt with very well by the insert already spoken about. This assumption is based on the fact that I cannot find a single mention on distributor condensation on a Dutch forum on these old Volvos that has been running for some decades now. NOT ONCE! And as I already mentioned, we don't have a particularly dry climate (same as the UK).

Since distributor condensation in itself seems not that common, how likely is it that BOTH Bruce's cars exhibit the same problem?
That means there must be something in common between the two, and right now, the absent bellypans are the only thing I can think of, especially since the condensation problem on the second car did not developed until after removal of the pan.

It may be a red herring, but that still has to be determined.

the dist. needs to be vented or the condensation will be worse. on early 90s lt1 gm 350s, venting was phased in to prevent the condensation problem.

That's something I didn't know. I now have a few options. Thanks for the info.
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Bruce S. near D.C.