Uncle vacuumhead,

Sorry I'm late in my reply. Hope all's aces with you and yours and your awesome, if venerable, 1991 Volvo 240. I also have a 1991 Volvo 240. Solid. Like the 1979 240s. I lay me head down on that Swedish iron alloy (steel) and call it home.

Welp, you did perform the OBD-1 (on-board diagnostic test) I suggested in the prior post where you access the black box on the aft side of the N. American driver side inner fender adjacent to the brake master cylinder vacuum booster chamber? You may find fault codes from the fuel Bosch LH-Jetronic system and the ignition Bosch EZK system.

Did you encounter any fault codes from sockets two and six or no fault codes with merely an all's clear 1-1-1 blink from the red LED from both sockets two and six?

If you hear well, a failing fuel pump may sound like bees in a glass jar trying to get out. If the fuel level falls below ½ to ⅓ tank, and you get a bucking, the in-tank fuel pump may have failed or is failing. The in-tank fuel pump keeps the main fuel pump (under the driver side rear seat) primed at all times.

The "bees in a jar" sound may come from the main fuel pump at any time. I believe the "bees in a jar" sound may suggest a wearing fuel pump. That sound may occur at random and on occasion. Or that sound may occur more frequently if the main fuel pump strains or the armature bearings are way worn. (I may be repeating myself - please blame the ibuprofen.)

Another way to test for a failing fuel pump is to check the main fuel pump fuse and, with the car running until well warmed, whether the fuse is ambient temperature, or warm, or hot. If hot, a straining fuel pump may be:
- pushing fuel through a clogged fuel filter
- indeed, a wearing or worn out fuel pump
- the in-tank fuel pump may be failing, though you'd encounter the engine bucking symptom from fuel delivery interruptions

I'd rather you look into these matters I list below before opening up any fuel system matters that are filled with fuel, please!

However, please consider another cause for your mighty 1991 Volvo stopping the engine at a stop light with it in drive. You do have an automatic transmission, yes?

Causes can include:
1 faulty or misaligned throttle position sensor
2 dirty (internally coated in carbonized gunk) auxiliary air valve
3 leaking control pressure regulator
4 the preheater control flap valve thermostat in the air filter box has failed, forcing primarily preheated air to enter the engine through the air filter and through the AMM (air mass meter - what some call an MAF, mass air flow meter).
5 Air filter?
6 Throttle body.
7 HT distributor side?

1. Your Bentley bible contains the procedure to both test the throttle position sensor, I think, as well as realign it. Sometime the teeny Allen head screws that secure the throttle position sensor can come loose causing the throttle position sensor to move.

2. You have the auxiliary air valve that turns on when you close the throttle by removing your foot form the accelerator pedal at the stop light. The auxiliary air valve merely opens to maintain a set engine RPM when the throttle is closed, and the throttle position sensor clicks closed, turning on the air valve. The air valve itself can have some gunk build up that prevents it from opening fully to allow the engine the air it needs to run at the factory preset RPM with the automatic transmission in gear and you have your 1991 Volvo 240 halted as you have your foot on the brake pedal.

3. You did not indicate that you encountered and recorded any fault codes. Have you checked the vacuum line between the fuel rail control pressure regulator that goes to the intake air intake port (manifold, an air port for injected engines). If this leaks fuel into the air intake port, that may cause you an engine that slows to a stop while at stop lights with the auto transmission in gear.

4. In the air filter box, you have a round flap valve controlled by a spring loaded thermostat. The spring loaded thermostat is placed downstream of a dedicated orifice so it responds to ambient air temperature. The spring loaded thermostat fails over time (dunno how much time or miles). When the thermostat fails, it fails to allow preheated air to enter the engine. The preheated air comes in through the silver hose that is connected to the preheater plate / shroud on the exhaust manifold. Some may remove the hose from this plate and allow it to rest along the passenger side frame rail. Some may replace the thermostat with a new one in the interests of reducing cold engine warm up time and reduce emissions (if you reside in some auto emission restrictive states like CA, you may have to, yet doubtful.) Some may remove the silver hose all together. The choice is yours. If the round flap valve has remained stuck open, and where you reside hosts hot Summers, your AMM (or MAF) may have suffered for it. Though you may have received fault codes for this condition.

5. If your air filter clogged or not so clogged or recently new?

6. How dirty is your throttle body? You may to inspect it and clean it, along with the auxiliary air valve.

7. Faulty HT side of the ignition system? Crudded up under the cap or worn spring carbon thingy inside the distributor cap? (Be careful with distributor retainer clips, they can get you good!) The power stage? Cranks in ignition wires (see for sparks as the engine runs at night).

You may want to examine the air intake system piping for vacuum leaks, though you would have received fault codes for lean fuel air mixture at idle or cruise speeds and the like.

Questions and comments?

I think that does it unless other say thing like, "oooch, captain, the warp drive, she's out of anti-matter!"

... off topic ...

Sorry if I was short on my prior reply. I also suffer from aphasia and a host of neurological disorders I did nothing to earn like dyslexia, perceptual myopia, and other silly things.

Irony. Yeah, I may enjoy some irony with the wheaties. Welp, actually, I have the little plain label unsweetened shredded wheat by the handful with the morning cup of earl grey tea, and the hunny and the milk. Raisins have a little iron, too. We men don't need to be to loaded up on the iron or calcium as we age. Just enough, yet not too much. Sorry, I'm all hopped up on the ibuprofen funky goofer. It makes me woozy and sleepy.

Welp, in producing knowledge transfer products within the narrow range of the didactic and pedantic, we are process people, primarily. We are those that apply the social sciences, the arts, and are very best of our ethical selves to imbue understanding in others. We depend on the subject matter experts to provide us the accurate truth of a thing and verify the knowledge transfer content. Though it does help to have some background in an area related to the content we develop. I usually work as an instructional design and, primarily, a technical writer.

Sort of like mechanical engineers applying little more than (Fig) Newtonian (Cookie) physics. I gotta have that treat angle in there somehow.

Welp, questions and comments?

Ooooooooh, I see your rotor was cracked. Oh well. Glad you found it!!!!

Kitties and puppies?

Hamsters and horsies?

Walnuts and raisins?

The Pacific NorthWest at my Volvo 240 tips, about.

Please let us know with your replies to your thread as to progress.

I do go on so. Sorry.

cheers,

Buttermilk MacDuff
--
Have you been duffed today?