The engine of my 1993 240 on a few occasions, while running normally, has simply quit running, no idea why.

A couple of times for a fraction of a second the check engine light lit but engine “restarted” on its own; and twice while traveling at normal city speeds the engine stopped, and had to be restarted, which I was able to do as per normal.

The radio code was lost in some or all of these instances. My experienced mechanic (decades of 240 experience) could not determine the reason.

My beloved 240 is quite well maintained I believe. Perhaps someone in this knowledgeable group has some inkling as to what might be going on. Thank you in advance for any thoughts.

The clue is in your report that the radio programming is lost. That means battery is lost to both the engine management and fuse 8 supplying other constant battery voltage to things like the glove box lamp, central locking, radio memory, and the clock.

How that can occur might be different depending on whether you have early or late production 1993.

http://cleanflametrap.com/emfuse.html
--
Art Benstein near Baltimore

If you tell the truth, you don't have to remember anything.

Art--

It was manufactured in April, 1993, so the last full month (I believe) of the 240 model production.

Also, yesterday, I checked the engine grounding strap (if that's what it's called, the woven cable that goes from one of the valve cover nuts to the firewall). The cap nut at the valve cover was not rock solid tight; in other words, I was able to tighten it a little (not sure how many degrees I was able to turn it, but it did turn without having to apply "a lot" of torque. I'm wondering and hoping that this was the cause of the problem. And also wondering that if this could cause loss of the radio code (an ungrounded, I guess (?), battery).

Charles--

So late production with the PAL fuses on the battery terminal. There is where you'll find the trouble if your two symptoms are related. The braided jumper between the firewall and the cam cover is not needed for engine performance or radio code maintenance.

Once the car is running the battery doesn't need to be grounded, or even connected, although I'm not recommending you try testing that theory, as it depends on the charging system being without flaw.

As to the torque on the cam cover acorn nuts, ah, check a few of them and duplicate their torque by feel. Oil and gasket age, leaks, etc. make this difficult to advise on, even if you had an inch-ounce torque wrench.


--
Art Benstein near Baltimore

"Carefully pry (If this were a Jaguar you would prise)..." -BrickDad

a break internally w the ground cable?

Hi,

I love ground cables too!
There are two of them off the negative post.
When a ground goes sour, that is one half of all circuits in a car.
Counting the whole car blinking off and on all the way down the the radio memory, becomes a nice clue!
The quickness of it all makes it electrical.

The other thing is a positive wire going over the the little junction box on the fender. It’s also my favorite for being frail and subject to corrosion.
The factory wire is IMO slightly undersized for it duty but it works until Mother Nature creeps in.
That wire feeds into the cars fuse panel and interesting enough goes bad right out there on the battery terminal nut.

Phil

While you are cleaning up your wiring, consider adding fuses at the junction box for the hot wire going to the Volvo fuse box.. It can avoid a wiring harness fire, which will for most owners be the last time you drive the car.
Of this I know too well.

Hi,

You know, I haven’t given it enough thought, when you put it that way!

Just because it is hidden deep in a wire loom, out of sight, out of mind, it could become very lethal if a ground point should be acquired.
The overall cabin current load to the panel, coming on at the same time, is always possible too!

That wire is rated for what (? 12ga.) 20 amperes. Fan, main pumps, all the lights, two heaters for winter times (seat and defrost), magnetic AC coil for humid southern nights can make be right up there!
Repeated heating and the consequent degrading of any “biodegradable insulation,” on older cars can make one double think that!

It should have been common electrical practice to “fuse” any running length that is directly connected an “unlimited power source”.
Positive cable-Fusible links have been used on starter motors even though it’s an intermittent use device through a relay. Was or is that overkill?

Yep, you have a point!

Phil

That is an interesting thought.

Curiously, I just had a similar experience with my 1980 242DL and B21F. A few months ago I had installed a new distributor, distributor cap, rotor, plugs, plug wires. So, I checked all electrical connections, and all seemed OK. Had a friend, retired Volvo mechanic with 45 years experience, come over and double check what I saw. He thought the main fuel pump fuse was a bit loose in its holder, so we cleaned connection and tightened that up. While our two sets of eyes and hands were checking wiring under the hood, we thought that the coil wire (which had NOT been replaced along with the plug wires) seemed unacceptably loose at the distributor. Put in a new coil wire, and all seems fine now for a week or more. New coil wire was soooo much tighter than the old which basically slid right out of the distributor with very little resistance.

All of this makes good sense, but always a question with very intermittent electrical glitches.

Main fuel pump / ECU relay is failing. Sometimes it's just re-soldering the relay circuit board fixes the problem. Check and clean your ground wire cluster under the the engine hood.