Hope this isn't too long, but want you know everything. Last summer had my '80 242DL M45 B21F rebuilt @130K miles. Six mos prior had local Volvo dlr. clean K-jet sys. I installed new OEM rotor, cap, wires & plugs. Base car, no A/C nor PS; like it that way. No problems at all with the O/H, really felt all 107hp!

Then,about 2 wks. ago started an 870 mi. trip fr. FL to VA. Started with a fill-up & threw in a bottle of Techron. Hadn't used it in years. Fifteen minutes into trip it started bucking & stalled out. Waited 10 minutes, started up fine & continued on trip to VA with no other problems. Couple days later started return to FL. After 15 miles bucking started again but this time very bad. Crawled back to VA, couldn't take more than 40 mis. of that. Fortunately, there is a Volvo indy in the area with about a dozen 240s around his place. At first it drove fine for him. Later he got the same bucking. Found a leaky fuel accumulator. Replaced it with a used one. Started the 870 miles back to FL. No problem for 500 plus miles, then bucking started again but went away by itself. Then about 20 minutes from my brother's place in GA I stopped at a light & the bucking started again. Stopped for 15 mins. started again & everything's fine. Replaced fuel filter. Last 350 miles went OK except for 2 more bucking episodes. At home in FL my local indy replaced the in-tank fuel pump & sock. No change - still bucks. Today replace ign. coil (Beru) because plug tester showed weak spark. Still bucks! Don't know where to go next.

Thought we solved problem in VA when indy saw low fuel pressure. Thought replacing pump & coil would do it but still have problem. Main fuel pump (aftermarket) has about 100K on it. Why is a ballast resistor needed on electronic ignition? Haven't replaced it. Really frustrating is the randomness of this. Still drive it locally. Sometimes drives like no problem at all; next drive is bucking all the way. Seems all this started with that bottle of Techron. Thanks for reading - any suggestions really appreciated.

Cal

I would suggest that you stop looking at the fuel system and consider the ignition and wiring harness - from the distributor to the ICU on the fender by the washer bottle.

the thinking here is the intermittent nature of the missing/bucking is ignition related...since you've done a lot to the fuel system and it still comes back

1) a fault in the impulse sender in the Distributor.
2) failed insulation at the connector to the sender, on the side of the distributor

3)failed insulation on the ignition wiring where it passes under the crankshaft as they go to the ICU. All the wires are inside a plastic sheath, which must be cut so you can inspect.

Use the web site Kitty posted

http://www.volvowiringdiagrams.com/

open the Trouble Shooting Giudes Folder and Download
Volvo Problem Solver Advanced Edition

Go to the Ignition Folder and download

TP30432-2 Ignition Systems.pdf

This is great advice. I would add to check ground connections for the ignition system and fuel management which will be shown in diagrams. Poor ground connections and invisible corrosion in ground wires will absolutely cause problems.
--
I own a Volvo or Does Volvo Own Me? Try the easy to search Expanded Style FAQ Index http://40mph.com/Brickboard_700-900_FAQ_Expanded_Index_Version/

Hi,

Pull off your distributor cap and check for moisture.

Travis

Will do. Heard spraying a little WD-40 in there helps. Agree?

No. Clean and dry, just the way Bosch intended.
--
Bob: Son's XC70, daughter's 940, my 81 and 83 240's, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles

Why did you have the K-jet fuel system cleaned? Rust in the tank or fuel delivery paths? Did you replace the fuel filter then?

Kind of doubt Chevron/Amoco/Standard Techron fuel system clean is fault?

How are the fuel return lines? The low-pressure rubber fuel line or lines from the tank to the main pump intake and the low pressure fuel return line from the front of the car back to the tank? If it is the original fuel line, you REALLY want to replace it.

The black hard nylon lines are pretty durable and resistant to the ever more light petrochemical compounds in the gasoline. It ain't just octane, heptane, hextane, nonane (nine carbons) in the mix now a days!

The rubber lines deteriorate inside and out. On the inside, the reduced rubber loses the vulcanization and chucks may inside the small orofi in some places.

What won't cost a thing is a complete inspection and diagnosis of all the electrical components that are part of the fuel AND the ignition system. Though I'll bet the faulty lay in fuel delivery system. Yet, check the ignition.

Start with the fuse box and work through the wire harness with careful inspection of connectors, spade connectors connected to sensors like the cylinder head mounted temp sensor used by the K-jet (there's a second thermistor for your temp gauge unrelated to K-jet or ignition).

Pay close attention to the fuel system (fuel pump) relay. I think you have the green one. No matter the 240, we've all soldered broken solder welds from the heat produced by the energized electromagnet as well as the fuel pump load on it.

You may need to remove the fuel sending unit at the top of your fuel tank to inspect the fuel tank interior, the in-tank fuel pump state (running or not), the in-tank fuel pump sock-like filter.

DANGER: Any operation involving fuel, the fuel tank, opening the fuel tank, exposes the operator to potentially DANGEROUS, EXPLOSIVE, and potentially LETHAL conditions.

Use proper tools made of brass or a bung nut tool to remove the fuel level sending unit. Striking steel on steel, as some do to remove the bung nut can cause spark. So please don't do that.

Please read more here:
http://www.k-jet.org/
http://www.volvowiringdiagrams.com/

Just some speculation based on your symptoms.

Please perform any fuel injection work safely and in the most sanitary of conditions.

Hope that hep-kats (helps).

(As kitty-cats are always so very help, if very fuzzy, and the more fuzzy the better.)

MacDuffed Mac Duff (the Middle Lander of the Clan MacDuff [after some pints of the Wee Heavy])

I had K-jet sym. cleaned 'cause of my preventive mtnce mentality. Driving a 33 yr old car cross country gets that into your head. Agree Techron most likely not cause of problem. Didn't mention but replaced fuel pump relay. Checked all fuel-rel lines under car but will recheck. Cleaned w/emery cloth all contacts in fuse box. Will check all electrical connections in eng. comp. Thanks for your comments.

Cal

...because I could'nt see any text for quite some time. Now I wonder if it was my browser or the Brickboard...

For what it's worth (little) I was sprucing up an '82 with K-jet before selling it and tried the "Seafoam treatment." It developed very similar symptoms, and I never did get it fixed. Had to have the car gone quickly, so I wound up giving it to a friend.

Good luck.