I've owned my 1986 240 for 7 years. I drive it only about 1,000 miles per year, on average. No problems until now. Here's the symptom: when driving I suddenly lose power in that pressing on the accelerator does nothing. This generally lasts only 3-4 seconds, although the last time it lasted nearly 10 seconds. Then all is back to normal. It also surges occasionally, but just very slightly. Surging is not as common as hesitation. Both symptoms (surge and hesitation) started around the same time. It usually acts up at least once during a short (4-8 mile) jaunt, sometimes near the start of the trip, other times in the middle, other times near the end (so no pattern there). Speed doesn't seem to matter either -- it's acted up at highway speeds as well as at low speeds.

No trouble starting the car, no sputtering, no stalling, no rough idle, no exhaust smoke. I'll be at the mercy of a $80-90 per hour mechanic to troubleshoot this. Might not be worth it if it ends up costing hundreds to repair, since the car is only worth $1000 at most. I'm hoping I can narrow down the possible causes before going to a mechanic. From what I've read, the most likely culprits are relays, injectors, and fuel filter. But I really know nothing. Any ideas? Thanks.

 

There's not an easy answer to your question you need to test components. What's your fuel pressure when it acts up?

 

fuel system relay, fuel pumps (there's 2, one in the tank, one under the car), fuel pressure regulator would be high on my list of things to check.

and engine electrical general flakiness, 1986 is within the 1983-1987 window of 'biodegradable insulation'

re: fuel pumps, is this problem more frequent when you're low on gas, like 1/2 tank or less? that suggests the in-tank pump may be dying.

 

Hmm, my tank is rarely more than 1/3 full, and usually less than 1/4 full. Wondering: does a low fuel level require the pump to work harder and hence give out sooner? Maybe I should fill the tank and monitor things. One of my theories was that given a low fuel level and infrequent driving a lot of sediment has clogged up the filter or something else along the route. Does that make sense?

(Pierce, we at 34 N. on the left coast love our old Volvos, too.)

 

anything is possible.

Put a gauge on it.

 

when the tank pump isn't working, the main pump has to work harder to deliver gas, and the lower the gas is in the tank, the harder it has to work.

if you pull the fuse 4 for the tank pump, and use a jumper wire between fuses 6 and one side of the fuse 4's contacts, you'll power the main pump (when the ignition is switched off), and fuse 6 to the other side of the fuse 4 contacts, you'll power the intank pump. since the car is switched off, you should be able to hear each of these pumps running. the in tank pump is easier to hear if you remove the gas cap and put your ear near the filler tube.

this works because fuse 6 (and 7,8,9,10) are always powered even when the car is off. fuse 4 is between the main fuel pump and the tank pump power, so by jumpering power to either side of it, you can activate either pump seperately.

btw, for a rarely driven car, its better to have a mostly FULL tank of gas not a mostly empty. a mostly empty tank will 'spoil' faster.

 

Have you tried filling up the tank to see if it helps? If it doesn't do it on a full tank, that pretty much confirms the issue. For a good write up on diagnosing in-tank pump issues, check out this web site: In the Tank - 240 Volvo Tank Pump and Sender