I have had a time with my 850 2.4l non-turbo. The transmission went out and it sat for a couple of years. We started it regularly, but about 4 or so months ago it wouldn't start. Replaced the trans., starter, fuel pump. Tried new camshaft sensor, crankshaft sensor and installed new ignition module. None of them worked. I have had this at the Volvo shop and they claimed that it wasn't giving out good codes, but the next shop I took it to said he got codes right off the bat. He did a bunch of testing and first found out that the coil was good but no communication from the coil to the spark plug. Put new ignition module on and now the guy is saying no communication from ground to coil? What could this be? Computer? Which one...main or ignition? How hard is it to replace those computers? My husband can do some things, would this be something that a non-pro can do? We have put a ton of money into this, and I am just sick that it isn't running. It was in excellent condition until the service guy left the trans fluid bay loose and the fluid drained out without my knowledge and the trans got trashed. BTW, Volvo said it had jumped timing. I said how could it jump timing when it hasn't been running? Just replaced the timing belt 2000 miles ago. Could this be a possibility? The next shop said it doesn't look like there is a timing issue, or if it is off, it's only slightly.

 

All the things I mention here can be easily done with the help of the write-ups you’ll find here. Just take your time and search for them one by one! Many of these can be done by your husband or you – women who work on cars are pretty hot!

The ECU is very easy to swap, if that is your problem. It’s in the box behind the passenger headlight with the hose coming off the top. These things are pretty sturdy, so it may not be the problem. I’d probably swap this as a last resort.

What year is the car? If it’s a ’96 or earlier, you can use the on-board diag box to pull codes. Post them here and we can start getting into the nitty-gritty. If it’s a ’97, you’ll have to pick up a ODBII scanner. Fifty bucks from AutoZone and it pays for itself the first time you avoid having a mechanic take a look at it for you.

When you say it didn’t start, would it turn over but not catch? Are there any codes?

Since the car needs fuel, air and spark to start, do a quick check of all three of them. If the car’s been sitting for a long time, it’s possible that some small rodents have found their way into the air pipes. Cars sitting around for a long time can need new hoses, so check them too.

If the shop is saying there’s “no communication from ground to coil” then you should be able to clean the contact point for the ground – it may be rusty or corroded.

Are the spark plugs . . . sparking?

If the car has been sitting for some time, it’s possible that the fuel filter is gunked up. Did you treat the gas with an additive, like StaBil? You may also check the fuel pressure at the fuel rail.

The timing belt may have slipped if the tension arm is shot. You can search the threads for replacing the timing belt to view pictures to check if everything is lined-up or not.

 

Spark plugs are sparking, it turns over but not catching. It's a 95 BTW. We did the codes a few weeks back, and this is what it showed:


Did the OBD and these are the codes:

in the 3 socket

4-4-4 I know that this is saying that there is no power supply to valves in hydraulic unit. What could be wrong here?

In the number 7 socket, we got the following:
122 - Temp. sensor interval too long
113 - Fuel gauge open circuit
231 - Vent damper motor position open circuit or short to 12 volts

The guy said he knows the coil is good but communication "from the coil" is not happening. Said they "checked" the spark plugs. Can you just look at them and know that they work?

Said fuel pressure is OK.

Is there an ignition ecu and an engine ecu? When you told me that those are sturdy, which were you referring to...or both?

thanks!

 

I heard two different things here about the spark plugs but the last is that they are no sparking. It is turning over, but no spark.

thanks!

 

This is the kind of thing that's going to draw differing opinions. I just went through an issue with a computer, and oddball codes ( https://volvoforums.com/forum/volvo-850-16/bad-crank-sensor-43384/ ), and given the ease with which a computer can be swapped, it seems the easiest and quickest way to rule something out.

Find a friend or co-worker with the same car, or as a last resort find one on a used car lot and take it for a test drive. Post the year of your car, and I'll see if I can find a listing of what years will interchange.

Once you have another car, disconnect the battery, and it takes about 10 seconds to pull both computers. You can chase all the stuff you want, but if it's the computer, you'll be chasing stuff forever. And like I said, given that the computer is so easy to swap, you can solve the problem or rule it out in about a 3 minutes.

 

OK, I ordered the computer, said it was for the 1995 850 and it did not look like the right connection. The one on my car looked smaller than the one that I was sent. Any ideas? My car is a 1995 GLT automatic non-turbo. I am so bummed as it is now 5 weeks, and counting, on getting this car running>

 

Thanks a bunch for everyone's help. IT WAS THE ECU! I went and put it in myself. And it ran like it used to!

With all the trouble, and even the Volvo dealer not helping...they said it had jumped timing. I am asking for my money back.

Thanks again!!!

 

Good job. Glad you got it going.