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Volvo 240 Won't Start in Wet Weather

Hi folks,

My 1988 Volvo 240 DL often has trouble starting in the rain (I’ve usually managed to get it going, but it often takes several attempts). I have been told by a friend that he had the same problem with his '86 and replaced the distributor cap, solving the issue. My mechanic told me that he would need to replace the cap and wires, costing about $275. He said that replacing the cap alone won’t solve the problem, and would just lead the cap to wear out faster. He told me this without looking at the car. Just want to know if he’s right–do I need to replace the cap and wires? Is it possible that changing the cap alone will solve the problem? Could I change the cap and see if there’s still a problem, or is it better to just do it all at once? I’m a poor grad student, so any money I can save is valuable…

If you are a poor grad student, an old Volvo isn’t going to help your budget. Do you have any idea when the cap, rotor, plug wires, and plugs were last replaced on this car? These old Volvo’s need caps and wires replaced much more frequently than most owner’s realize. For a dependable starting car you have to do all of them about every 30K miles.

The good news is the parts are available at any good auto parts store and you should be able to do it yourself. The trickiest part of changing the cap and plug wires yourself is making sure you don’t mix up the wires. Have a good system so you know where every individual plug wire goes on the cap. Taking a picture before you start might help too.

I have changed caps and rotors without changing the wires when I know the wires aren’t very old. If a plug wire is bad and has so much resistance that the current won’t go through it the spark could arc inside the cap. The energy finds somewhere to go, and when the path of least resistance isn’t the plug wire anymore it arcs to ground somewhere causing a misfire. Moisture makes it easier for the energy to jump to places it shouldn’t go and that causes the hard starting and poor running until the motor heats up and the plug wires dry off.

The cap itself is not the problem. Odds are that moisture is accumulating inside the cap during rainy or high humidity conditions after a warm engine shut down and that is the cause of a no-start and/or rough running.

Try spraying the plug wires and both the inside and outside of the distributor cap with WD-40 and see what happens. This may sound hokey but it works.

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I’m with the mechanic here. Plug wires are notorious for poor starting and misfires in an engine when it’s raining. There are other components that can cause a problem as well but the plug wires are most often at fault.

Thanks, all!

Do you have any idea when the cap, rotor, plug wires, and plugs were last replaced on this car?

I believe they were changed some time between 2009 and 2011. But I do not drive it very much, and doubt I have gone 30k miles in that time. If it was 2009, I might be getting close… if 2011, I’d guess it’s under 20k since they were changed.

Regarding changing them myself, I would certainly be interested in giving it a try. As may or may not be clear (probably is), I have not really done any car work before, and it makes me a little bit nervous. If I do choose to do it myself, it might be a little while before I can get to it. Do I risk any further damage by not addressing it right away, or will the wires just eventually burn out?

Try spraying the plug wires and both the inside and outside of the distributor cap with WD-40 and see what happens.

Are there any risks here? I know that will dry it out, but I am a little worried about flammability. Also, I’m guessing this is more of a temporary fix?

It would be advisable to replace the plugs, wires, rotor and cap. And an old Volvo 240 is an expensive hobby.

There are no risks with spraying WD40 while the car is running or about to be started.

Changing the plug wires and getting them right is the only thing that you may find frustrating.

Any good parts house will be able to print you out the firing order and explain what the print out means.

I find it easiest to pull the longest plug wire, then reroute the longest new one. Then move to the next longest.

Once you pull off the old cap the old rotor can be pulled straight up and off. Then just slip the old one on…you may have to line it up for it to drop all the way into place.

When replacing the cap, it will have a tab that has to fit into a slot. Be sure the cap sits square and level on the distributor before tightening it down.

Plugs…pretty simple too.


As Yosemite stated, the WD-40 is not a fire hazard. Another more long lasting option would be to use a fingertip and wipe the cap down, both in and out, with a very thin haze of electrolytic grease.

I mention this because I’ve seen caps that looked like the inside of a sauna. Moisture is attracted to warmth and when the environmental condition are right moisture can accumulate inside the cap after the engine is shut off.
The same goes for headlamps, the inner surfaces of windshields and door glass, etc.

I used to own a Mercury and it had a factory rubber shield around the cap which was an effort of sorts to prevent moisture buildup.
Over the years some vehicles have been fitted with vented distributor caps to which a vacuum line is attached. The purpose is to keep moisture, etc pulled out of the inner cap area.

Thanks again, everyone! I think I’m going to attempt the job myself; may try the WD-40 approach first as a quick fix. Hopefully this will save me a little money and make for a fun, small project.

Start by removing the cap and taking a look at the rotor and the contacts on the inside of the cap, without removing the plug wires. This isn’t rocket science and $250 is nuts! Wipe the inside of the cap with a paper towel and verify there isn’t a crack somewhere.
Make sure you get good parts and they will last a very long time, more than 60K miles. Bosch cap and rotor.

In addition to what other have suggested you might want to replace the ignition coil as well. On my 245 that seemed to be sometimes a problem when the weather was damp. I recall having to replace it every two or three years.

The '88 had a Hall effect impulse generator in the bottom of the distributor that initiated the spark. A common problem with those was that the wire that went out through the coil housing disintegrated. The insulation degraded and the wire oxidized, sometimes exacerbated by metal fatigue in the wire from engine vibration. Because that is a very weak, low voltage signal at that point in the circuit, the wire and insulation have to be perfect for it to initiate spark.

According to the parts list, in '88 it looks like they went to a removable impulse/pickup coil rather than the earlier pressed-in unit with the wire permanently attached You probably cannot buy that wire, but you may be able to rebuild it for just a few cents with some patience and a soldering iron.

If that is not the problem, I would next suspect the coil.

Also, I think that the '88 may have still had a main fuse under the hood, driver side inner fender. That fuse housing may no longer be very waterproof. Check it for corrosion and heat damage.

P.S. A lot of 240s ran 25 years and a half-million miles. I notice, however, that nearly all of them have vanished from the roads in the last decade. There is a reason for that. You probably don’t want to plan on keeping that '88 much longer.

I know this thread is over two years old, I just wanted to say thanks for the suggestion. I was having the same problem, googled around about it and found this suggestion. I took off the distributor cap and plug wires and sprayed them with WD-40 and sure enough it starts right up, rain or shine. Good suggestion, anyone else who has this problem should give it a shot before bringing it in to a mechanic or doing anything more complicated.

Good work-a-round, but if spraying wd 40 on the plug wires and cap helps, the plug wires and cap need to be replaced.

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