For everyone who ends up here (like I did 2 months ago) because they have the same long crank hard start tacho jump or similar problem, I found my issue, and it was not the cable routing on my vehicle. My vehicle is a 2000 S80 T6 with engine code B6284T.

The story below is long, but it seems like there are loads of people with this starting issue that cannot resolve it by sorting the cable routing, and I am hoping it rings bells and saves people the money and heartache it cost me. If you have read all of the Volvo forums and watched all of the videos on Youtube, you will note that basically every one of them has discussion regarding re-routing the cable, transmission not mated correctly or starter motor faulty and creating too much draw. Typically there has been no substantial follow up on the forums I had read showing the cable fix was a long term fix, and I could not get my mind around how this could be the cause of my problem.

Think about this if you have the intermittent hard start problem with tacho jump: If the cable or starter is the problem, why does the car run like a dream and start first go every time after you have driven it earlier that day, but will not start easy at times it has been left overnight or especially when left for a couple of days? Why does it randomly appear then start fine for days then appear again? Why do failure codes such as Crank Angle Sensor appear then disappear without any parts being changed?

So, what was my nightmare and the process involved? I purchased this car after I test drove it, and everything was fine during test driving and getting it home, until a couple of days after I got it home. I had hard starts later that week when the car was left a day or two without staring, and the hard start issue was intermittent in the following weeks(thanks previous owner for shafting me and not letting me know about the problem). After starting the car for the first time on any given day (half of the time I would crank until the battery died and then required jump start from another vehicle), if I used the car regularly there was no problem and it ran like a dream and started first crank all day long no problems. Sound familiar?

I ended up searching the web and finding numerous forums and videos outlining numerous diagnosis such as the starter cable creating issues, with no further discussion on confirmation of long term resolution.

I started to wonder, how does the car start fine later in the day after it was warmed up in the morning without tacho jumping or any other problems? I was thinking if the starter cable or starter motor was the problem, it should exist at all times during cranking. Sometimes I would try to start the car in the morning, and have the same problems the forums describe: Long cranking, tacho needle jumping, timing appearing to be out by miles and "popping" sounds like a backfire coming from under the bonnet, smoking like crazy for a few seconds when eventually started etc, but then running like a dream.

I hit the forums online for other possible causes. Mass Air Flow sensor or Crank Angle Sensor seemed like other popular culprits according to the internet. I took out and cleaned the MAF as per the directions given online and made sure the housing for the Crank Angle Sensor was not cracked, and that the wiring for it was away from other cables. Car went fine for 2 days, 3rd day problem back. Then back to basics including new plugs, and also more technical with my mechanic mate using a very high quality diagnostic tool to check for codes. No codes and car went fine, then problem back after a couple of days.

Finally against my logic, re-routed the starter cable as described online, split the gearbox and used a rifle brush to clean the mating faces of the bell housing and the engine. Everything fine for a couple of days, problem back again. I did not want to sell the car to an unsuspecting victim, and I did not want it to beat me, so I persevered.

During the next hard start event, I heard the usual "popping" noises coming from under the hood while the tacho danced during cranking. This time it blew out a cam seal. Needless to say, a very short time after jump starting the vehicle, I noticed a cooking oil smell and shut her down. Everything in the engine bay was covered in oil, as it had leaked onto the serpentine and timing belts and was thrown everywhere. After a discussion with my mechanic mate, he wanted to take the car to repair the seal and try and find the start problem. This was the event resulting in the discovery of the real problem with the vehicle.

So next steps: New cam seal kit, new serpentine belt, new timing belt. Now I had sunk some serious money and plenty of time into this vehicle and would not give up. My mechanic mate noticed the oil pressure light was on during cranking, so we changed the seal on the pickup in the sump. When he dumped the oil, he said there was fuel in it, backing up the bad timing theory. No fix after changing the pickup seal, but at least I had adequate oil pressure now during the hours of cranking. He took out the injectors and cranked the car, and said there was enough fuel coming out of the injectors to start a battle ship and the engine would completely flood almost immediately with that much fuel. This prompted the possibility of temp sensor issue. Only genuine temp sensors were available for my engine configuration at $250.00 Aud. The theory was it had failed and was reading too cold (infinite minus temperature) and flooding the engine during start, and was possibly creating the tacho jump because it was an electrical failure on the temp sensor. Car would not start after temp sensor changed.

My mechanic mate was challenged, and had the vehicle for 4 weeks, working on it over weekends and any spare time he had after work- for free. Without him I would have given up and burned it. He was testing everything and getting codes for crank angle sensor that would disappear or change to other codes.

At the end of the 4th week the breakthrough came. My mate was checking ignition components and turning the key on and off at times. It appeared to be firing all at once or in strange patterns during cranking at times. He noticed sometimes when he turned on the ignition without cranking that the engine light would flash slowly for about 30 seconds and then stop, or continuously flash quickly without stopping at all. On one occasion the tacho was showed 8000rpm when the ignition was turned on but the car was not running, but this only happened once. He could recreate the tacho jump fault, and made sure he had the diagnostic tool set up, and then 1 time out of 100 attempts BAM, "Intermittent or permanent ECM Failure" came up on the screen. Turned the ignition off, tried again, no codes???????

He then worked out that during starting with the Tacho jumping, the car thought the engine was running at around 6000rpm or higher and dumping a shirt load of fuel into the engine. This was also why the timing was out by miles during cranking. Turns out it is the ECM failing intermittently.

For me there is a process to get around the problem: Turn on the ignition and WAIT before cranking. When all of the red lights have gone out and the orange engine light is not flashing, start the car as normal. *If the orange engine light is still flashing after 30 seconds, turn off the car before cranking, and turn the ignition back on again*. It will usually start immediately if the orange engine light is not flashing.

If cranking the tacho jumps at all when you turn that key, even past 1000rpm, stop immediately (so it doesn't flood the engine with fuel), and turn off the ignition. Turn it back on again, follow the engine light process above and crank her over. Away she goes.


It turns out that when I was getting in the car and turning the key straight to "start" as per any normal vehicle, I was flooding the engine because it thought the engine was running at high revs due to the fault. By following the above process, I have been able to now start the car every time, even when the intermittent problem arises by following that process. It's as simple as checking the lights before cranking, or stopping cranking immediately if the tacho jumps, turning it off and starting the process again. It might sound laborious, however the problem is intermittent and only eats about 30 seconds of your life maybe once or twice a week when the problem arises if the car has been sitting for some time. Once driven, it will start first go every time like it always has in those circumstances.

I am not saying that that my process will resolve everyone's problem, but give it a go and save a shirt load of money if you have the same problem as me. You might have the transmission or starter cable issue described all over the internet, but there is a high probability it is your ECM and you are not showing codes because it is intermittent.

One of the biggest causes of my frustration online was the lack of confirmation that others had resolved their issue long term. Reading the stories of vehicles taken to a mechanic with this issue and spending thousands without solving is disappointing. I suspect others had thought they solved the problem by cable routing, only to find the problem re-appeared days later such as was the case in my circumstance. I suspect many gave up and got rid of the vehicle, as I would have done if I did not have a mechanic as a close friend. Either way, the follow up feedback online could be described as minimal. Maybe I was looking in all the wrong places? I have been starting the car without long cranking by following the above process for 4 weeks as it stands today.

Please respond to this post if you had the same issue as myself and it was the intermittent ECM failure. If I can help you or one other person and prevent them shovelling money into new Crank Angle Sensors and other parts for no reason, I will be happy.

Cheers. Bob.

 

I know this is an ancient thread, but this is the only answer and write up I've found which has (so far) solved this problem for my car. Thank you Bob if your'e still around for taking the time to put this up!