THE STORY:
Every morning, I go out to my not-so-trusty 1990 Volvo 240 and turn the key with trepidation, unsure of whether or not it will start. If it does start, I drive to work, wondering if I am making a mistake and should really be going to the mechanic's shop instead. If it doesn't start, I call a friend to give me a ride, and do some troubleshooting while I wait. I know that when I come back from work in the evening, chances are it will start after a bit of cranking and my opportunity to find the root cause of the problem will be gone. Initially, I did enough diagnosis to determine that it is indeed a fuel/mixture problem...it started with starting fluid. I replaced the fuel pump and fuel filter and fuel fuse holder and fuse (near the battery). The car started, and I was overjoyed, but over the next few days, I realized that I had not fixed the root cause of the problem. With the same symptoms leaving me stranded and in need of a ride yesterday, I had the chance to do some more diagnosis. Removing the fuel pump relay and jumpering from the red/yellow wire to the red wire, effectively forcing the fuel pump to run constantly, made the car start and run normally. Replacing the fuel pump relay did not.

THE SYMPTOMS:
Intermittent no start, when cold. It always starts when I go back out to the car after errands, and the engine is still warm. When it does start, it typically has an oscillating idle for the first minute or so, before smoothing out to the sound of a good Volvo engine. Even when warm, it will miss a few times just after starting. It starts just fine when a mechanic is with me, even if it is cold.

THE CLUES:
Replaced fuel pump, fuel filter, fuel pump relay, fuel pump fuse holder and fuse.
Forcing the fuel pump to run constantly by jumpering wires at the fuel pump relay causes the car to start and run as it should.

THE QUESTION:
I'm stumped as to what to check next without just starting to replace parts. Does anyone out there have pointers on what to check next? I'd prefer to diagnose the problem rather than breaking the bank replacing parts.

 

It sounds like your real problem is in the cold start circuit. Since you've already hard wired the fuel to run all the time you also need to test for vacuum leaks. Hard starting is typically caused by poor compression or an imbalanced fuel-air mixture. Generally this is due to a failed engine temperature sensor that won't tell the computer it needs to turn on the cold start enrichener, or a failed enrichener. But you also need to eliminate the possibility of too much air by checking for vacuum leaks.

 

FOR MONTHS NOW WHEN TRYING TO START BEFORE 7am --ABSOLUELY NOTHING---NO CRANKING OR IGNITION SOUND. bUT 3 HOURS LATER STARTS FINE. BATTERY IS NEW, CLEANED ALL TERMINALS AND CONNECTIONS, AND TWO DIFFERENT MECHANICS HAVE KEPT CAR FOR DAYS, BUT IT WORKS FINE. ONLY ONCE IT DID NOT START DURING DAY AFTER STARTING, WHEN STOPPED FOR ERRAND. HAD IT TOWED IN , AND STARTED FINE FOR TWO DAYS. BUT ONCE IS ENOUGH TO DOUBT--NO ONE SEEMS TO HAVE ANSWER, AND DAUGHTER IS FEARFUL OF DRIVING TO SCHOOL. ANYONE HAVE AN ANSWER ? OR FIX?
tHANKS

 

I actually had this exact same issue with my first car - a 760. It finally failed for the mechanic after the third tow and he was able to track down the problem to a wire whose insulation was flaking off, which was not part of the main wiring harness, which had been replaced due to the known insulation issue on the pre-1988 volvos. The wire in my case was located along the firewall, just under the hood. The tows "fixed" the issue, by jostling the wire away from the body of the car, so that the wire was not shorted to the frame. When it failed to start, it was because the wire happened to be touching the frame, shorting the power to the starter. You can look for a problem area while the car is starting, but I expect it will be near impossible to find. The next time the car fails to start, I would start going around with a voltmeter, checking for proper voltages and shorted power to the starting system components and ignition. If you don't want to tackle it yourself, I would ask the mechanic to come to your house or parking lot where the car dies to diagnose the problem. The good news is, it was a cheap fix once the problem was found. The bad news is, it can be difficult to diagnose.