I am hoping somebody on here can help. We have 94 850 Turbo wagon with about 300,000 miles on the original engine. My daughter drove the car from home to her part time job in the morning, after work later that day she went out to start the car and it would only turn over but wouldn't start. (up to that day it had worked great)

We had it towed to a garage where they checked the timing (ok), fuel pressure (ok) and compression. Initially there was very little compression in cylinders 2 and 4, he thought it might be stuck valves, cyl's 1,3, and 5 were fine. He attempted to clean the valve's in cyl's 2 and 4 with a cleaner, checked again, same thing. He put a new computer in, checked compression again now it was down in cyl's 2,3 and 4.

He assumes it is a bad head gasket but says there isn't any real evidence of it other than the lack of compression.

Anyone have any other ideas? I really like this car and overall it is in good shape it would be a shame to have to do the unmentionable...

Thanks for any help,
J-

 

First things first - Did you check to make sure you have spark? This is the typical way a CPS fails.

 

What did they do/use to try to unstick the valves ??

At least that or stuck rings would make sense in causing a loss of compression. Poor maintenance, lack of oil changes can cause such things.

Computer ?? It's function: engine management by way of fuel and spark. Has no control over compression in any way. Anyone else on here think the computer can in any way change compression ?? Compression is a mechanical value and it's measured without the engines computer doing a thing. I hope something is missing in your description as pulling the computer is the last thing any ...... reasonable person would do to correct a loss of compression.

Bad head gasket, ??? it wouldn't move from cylinder to cylinder. It's either eaten or blow out or it isn't.

I hate to cut someones throat as I'm not there and can't put a hand on it but I think you need to find someone else to check out your car.

 

That and most fuel injected cars will run even if you pull one or two of the five wires off. It will run terrible but it will start and run.

Not being there I hate to second guess the guy but I'd still go back to square one and see if it's a good hot, snap of a spark that will jump a 1/4 inch and then check the timing belt to see if it's slipped or slipping. The belt slipping will change ignition timing and WILL change compression. As it slips more the compression could possibly move but ...... not really what I might guess your problem is. I think they missed something and the computer or ECM is the last thing to try. IMO

Can I get a reality check here Rspi, where are you when I need you !

 

If they checked the timing, I'm ASSUMING they checked the spark or had spark to do the check.
It could be that they just checked the timing marks at the crank and didn't pull the cover to see if the cams were lined up.

CPS .. Crankshaft Position Sensor or Camshaft Position Sensor ??

Picture one, crankshaft sensor and two is the Cam.

 

I'm sorry to keep posting on your thread but it bugs me they pulled the computer. It's the last thing to try.

So lets pretend it's sitting in your driveway.
Where are you located? Maybe somebody is close and curious.
How long have you owned it?
How often do you change the oil and do you use a conventional, blend or synthetic?
Do you do any work on it yourself and if so how good are you (what have you tackled)?
Have you or your daughter had any problems with it starting before this?

When you talk to "them" do they make you feel good that they know what they are doing?

 

I have owned the car for about 4 1/2 years. It has been fairly reliable, its had a couple of issues but at 300,000 miles I haven't feel it has been unreasonable.

In the years that we have owned it my daughter has driven it the most, oil changes and repairs have been mostly her responsiblity. I say that, she has paid for oil changes and I have paid for everything else. She has had the oil changed (conventional) roughly every 3 to 4000 miles and almost all of her driving is on the interstate.

The work I have done to the car myself has been mostly "bull" type work, changing the rear shocks, fixing, then breaking, then fixing the odometer, etc. As far as any engine work, checking timing, compression, etc. that is not something I have ever tried before. So if rating myself in that type of work I would have to rank myself at the lowest level of novice.

You ask if we have had issues with it starting before, there has been 2 or 3 times when it wouldn't start, we had it towed to a garage, they take it down off the truck, stuck the key in the ignition and drove it into the shop each time. So yes I have had starting issues but there was never a reason or code or any clue why it did what it did. Also the heater core did fail on the car this winter but that was repaired by another mechanic than the one looking at it now. The car did run fine from February until the end of May when it died.

This time it just wouldn't start when it came down off the tow truck. You also asked if the car had spark, I am quite sure the mechanic said it did.

There is another mechanic that I know who is very capable that I have considered having it towed to, I have just been putting it off thinking the worst. The good thing about the first mechanic is that he would not let me pay him for any of the testing and cleaning that he did. He felt that since he couldn't get it fixed that he hadn't performed his job properly. He just assumed that it had lost the head gasket and that this was something not really worth repairing.

Sorry for rambling on so long. The car has been sitting at the garage for about 6 weeks now, I haven't had much of a chance to get to it, work has been very busy. The reason for a little urgency now is my 16yr old son will be getting his license in a few weeks and I need to get this car back on the road. It is one of a very few cars that I feel safe with the kids driving.

Thank you for listening.

 

OK, I'll just assume that they did check for spark.

I'm going to tell you what I would do....

(1) Disconnect the battery from both terminals in order to reset the ECU's long-term fuel/air trim values.
(2) Clean out the throttle body with carb cleaner (wear gloves & glasses!).
(3) Clean out the idle air control valve/motor with carb cleaner (wear gloves & glasses!).
(4) Clean out the PTC valve with carb cleaner (wear gloves & glasses!).
(5) If new plugs were installed, make sure they were gapped properly.
(6) Reconnect the battery, and crank that bad boy up!!
(7) If it still doesn't crank, try unplugging 1 of the injectors. I had a honda civic "no start" issue after it was sitting up for a week or two... and this was the magic touch it took to get it to crank. My friend's theory is that doing this allowed more fuel pressure to be sent to the other cylinders and unclogged something??? It's at least worth a shot if the previous tips fail you.

 

If you can change a shock, you should be able to do a timing belt. Just follow the instructions.

Try this link:
https://volvoforums.com/forum/volvo-...p-relay-64044/

I did not read all of the thread so forgive me if this info has already been offered.

 

Thanks for the tips and advice, I'm not going to give up on the car yet.

 

Sorry man, I have been up to my ears in this head job in the 100+ degrees. Finished it up yesterday. Phew!!!

Now that I have had the chance to read the thread, here's my real input...

One, a car doesn't just burp up a head gasket. It was running daily, a head gasket would not just fail while you're at work, unless someone took it to the race track while you were working.

So, it's either a fuel, spark or air issue. My wild guess would be a MAF failure. But, CPS can cause it as well, you have to make sure it has spark to move past the CPS. As for the ECU, there is probably a 1% chance that you have a problem there.

Make sure they check for spark, make sure the idle air control valve humms when you turn the key on, make sure the fuel pump runs and there is more than 40 psi at the rail, and by all means... make sure the timing belt is on and not loose. It's rare for a belt to break when someone hits the starter but it is possible. The last car I checked on the side of the road the belt was just lying on the cams. If the mechanic checked compression, I'd say the belt is on and working. BTW, what was the copression numbers?

The thing that gets me is that many people, mechanics included, think that any car with over 250,000 miles on it should be retired. I had a 740 GLE that had over 400,000 miles on it and it was running and looked like new.

If you have spark and the idle control valve is working, my guess is the MAF. If you don't have spark, I'm at the CPS.

 

Ok, I know the Mass Air Flow sensor, can you tell me what the CPS is?

 

Figured it out, Camshaft Position Sensor.

Thanks, I will call the shop tomorrow morning to see if they can check these

 

It could be Crankshaft Position Sensor or Camshaft Position Sensor.

 

I thought we were assuming he had spark???

If there's spark, then the CKPS or CPS should both be working, right?

 

They could be intermittent too.

 

Hey everybody, I checked with my mechanic yesterday, he said when he tested the compression it had around 120 psi in 3 cylinders and in the other 2 it was around 20psi, again these 2 cylinders were not next to each other. This was on a cold engine obviously.

He did check the MAF, and the CPS and both checked ok, and he said the car had lots of spark. The Idle air control valve was also working. Because these all tested fine that is why he pulled the computer.

He has no idea why this won't start when it turns over.

 

Did he make sure to have another car hooked to your battery when testing for compression???

We were getting 123 psi in each cylinder in a Honda Civic, but when we hooked some jumper cables up to it with another vehicle.... BAM!! 153 psi in each cylinder.

If you're getting plenty of spark... make sure the cylinders are all wet. spark plugs. get a good flashlight and stick your head inside. that's how I like to tell if you're getting fuel. Had another problem in which unplugging a fuel injector could have possibly sent more fuel pressure to the other cylinders... possibly unclogging something.

Also, were new spark plugs installed??

 

He should have a fuel pressure tester and on an 850 it an easy screw on fitting. Has he tested to see if you have the minimum PSI at the fuel rail for the injectors to be injecting fuel ?? The spec on that is around 43 psi.

This is kind of a dumb question but has he tried to feed it some starting fluid to see if it comes to life and runs a bit. That would be a sure sign your timing is likely ok and it's just a fuel issue.

The battery thing is a good idea as by the time he might be getting around to do the compression test he may have been cranking on it for a while doing other diagnostic procedures. At least make sure the battery was charged up before they started the compression test.