Car has 150K miles. Base model - No turbo, No VVT. We just bought it, and I'm a little skeptical at the previous owner's claim that the timing belt is OK, so changing it was on my to do list.

Yesterday morning the car started up as usual, then within a half second stalled. I tried to restart it, it cranked fine, sounding like the starter was turning the engine over faster than usual. (sinking feeling comes over me) No bad noises when it first stalled, or when I tried to restart it.

Thinking the T Belt had snapped, I pulled the cover off, and saw nothing out of the ordinary. Belt looked good, as much as I could tell. I put a wrench on the crankshaft nut, and was able to turn the engine over through two complete revolutions - felt fine, but I couldn't feel any resistance from compression as I wrenched it over.

The two camshaft pulley marks align on the timing cover, as they should, but I can't see the crank timing mark.

So, a friendly mechanic loaned me a crank alignment tool. It has a round steel bar about 3/8 diameter that has a chamfer and taper on the end. (lousy picture below) The handle has a tang on one side. He couldn't remember where it is inserted into the engine.

So here's where I need help:

1. What's the best way to position the crank so I can check my hunch the T belt has slipped?
   
2. Is it possible to crash the valves into the pistons and not hear bad noises?
   
3. Or might I have been really lucky?
   
4. Where the heck does the crank locking tool go on a 98 S70 engine? Do I have to remove the starter?

Thanks!

 

Before you go to all of the effort you are describing just pull each spark plug and dump a teaspoon of oil into each cylinder. Replace the spark plugs and wires and crank until the car starts.

Only do this out of the garage since there will be a huge smoke cloud after the car starts.

We can discuss how this happened but for right now just get the car running again.

Google "lawn mower syndrome" for various explanations, most of them being wrong as it has nothing to do with the valves or the lifters.

...Lee

 

brick: why not just do a compression test?


lee: "lawn mower syndrome"??? seriously?
I did google it and found your explanation here. Hey, 999 times out of 1000 you're the MAN, but I've never experienced this; not even on a lawnmower.

 

Compression test sounds like the easiest next step, with no risk of further damage in case the belt did slip, as I'll first wrench the engine over by hand. Id not expect much compression, but if there's zero, that'd have to be the result of a valve/piston crash.

I did find the answer to one of my questions - the starter has to be removed and the alignment tool gets poked into a hole behind it...

LMS sounds interesting, but I don't want to risk further damage in case the belt did slip... Prior to this,(the night before) the car was started and moved a short distance. with the engine running for only 30s or so, so I'm not totally discounting your suggestion on the LMS thing..

Thanks guys!

 

Ok, I doubt that the timing has anything to do with your problem. Do you have spark, good fuel pressure, compression, and air? Any CEL?

If you turned the crank and the cams did align, with the belt still tight, you are running down the wrong trail.

I have read many stories and actually asked the victims of timing belt failures with valve contact, none ever heard or felt a thing. It's like high blood pressure, a silent killer.

 

Thanks for your response. When you say that you doubt timing has anything to do with my problem, what do you mean? Do you mean you doubt the T belt slipped? Why do you doubt this?

I don't have any other clues yet, as I've been reluctant to crank the engine over in case the belt has slipped.

I turned the crank with a wrench, and the cam marks aligned with each other. BUT, I haven't been able to see the crank mark, so can't rule out the T belt having slipped...

 

Lawnmower Syndrome happens when you start the car for a very short period of time and shut it off, or in the OPs case, it dies. This is much like what would happen if you go to quickly move the car a couple of feet to make enough room to get the lawnmower out of the garage, hence the name. I didn't make the name up, that was done well before I had my latest fleet of Volvos.

Whiteblock Volvos start very rich and unless they continue to run for several seconds the raw fuel can actually wash the oil off of the cylinder walls. The net result is zero compression due to the tight tolerances that the engine is made to.

The upshot is that you can have a car that runs perfectly one day and then have zero compression on all cylinders the next day.

It is quite rare for a timing belt to slip. I had a tensioner fail on my '94 and the belt didn't slip even though the belt was quite loose. The worst failures are when the belt actually breaks of something like the water pump fails.

If your timing marks on the cams line up there is a good chance that the crank mark is OK as well. The crank mark is obviously hard to see, I have had good luck using a digital camera to see what I can't really see with my eyes.

Back to one of your original questions, if you insist on making this hard, the starter does need to come out to insert the crankshaft lock.

...Lee

 

Actually, I'm not insisting on making this hard. And I appreciate the education on LMS - it may very well be the case here.

I just don't want to take any risk in the (remote) chance the T belt slipped. (I think that IF the T belt slipped, and IF the engine were to be restarted now, I'd risk doing more engine damage. No?)

Your digital camera idea is a good one, I intend to give that a whirl...

 

I do respect the fact that these cars have a timing belt and interfierence motors, however, if I have evidance that the belt has been changed, i.e. marks on the cams, sticker, receipt, I DON'T WORRY ABOUT IT. The car that I now have had a sticker that was 6 years old and 50,000 miles old. I changed it a year later with 75,000 miles on it (trying to get it back on schedule with the 70,000 mile change schedule).

So, back to my original statement, good fuel pressure, spark, air, compression and CEL info. There is a good chance that you had just a little fuel and/or pressure in the system and when you tried to start it, it burned that little bit of fuel off and the it sputtered when it tried to start. So, go ahead and try to start it and listen for the fuel pump. If you don't hear it, check the 850 section and test the fuel pump relay.

Also, if the car jumped time, any potential damage is done, crank away.

 

Agreed. Good call. That would explain my symptoms (with the exception of the faster-than-normal cranking speed I saw).

Yeah, I think that's true too, but can't stop thinking convoluted scenarios where the T belt slipped a bit, causing the stall, but not enough to cause a crash, and then upon start up next time, it'd slip more causing a fatal valve/piston crash. Unlikely, I suppose, but I'm suddenly risk-adverse...

Thanks for your insight - I'll post back here w/ more findings soon...

 

Sorry guys but I'm chalking this LMS up to urban legend.

Yes these engines do run rich initially and if they're only run for a minute or so they will be hard to start subsequently, because the plugs are fouled. One of the few weaknesses of these cars is their weak secondary ignition systems. That's why you can get misfires if you gap the plugs more than 0.028"; this is well known.

Lee; why would tight tolerances result in no compression? That's counter-intuitive.

 

We got the car started toady. First, We were able to finally get enough light in the right place, and after moving the coolant tank, see the timing marks on the crank pulley. Timing was good. But the engine still wouldn't start - after 20 seconds of cranking, we pulled the plugs, and lightly sandblasted them and re-installed them. Still wouldn't start in 20 seconds of cranking. We pulled one plug and confirmed it had spark. We put a pressure gauge on the fuel rail and saw about 20 psi, so it had fuel.

So, we pulled the plugs again, squirted in a little oil, and the engine started. Weird.

I'm not saying the oil actually did anything, maybe the additional cranking time was all that was needed. I just don't know. I think the main troublemaker is the Bosch Platinum plugs, which I'll replace ASAP.

We're now in the middle of doing the T belt, as it is due. Going OK, except a lot of trouble getting the T45 Bolt for the tensioner out. It looks like my Torx driver is slightly worn so I've got a new one coming. (It is a T45, right?)



Thanks.

 

Yes, T45. See item #20 of these instructions.

Timing belt replacement instructions on a 1997 Volvo 960

The last few I removed, I used the good bit and a breaker bar for nice smooth fluid motion and they came right out.

LOL, the oil created more compression and it started. I'm willing to bet that this happens on NA's more than on turbo's. The NA's require more compression to run right.

 

What an astonishing coincidence!

I was every bit the sceptic that you were when I first heard about this. I think the actual verbiage I used was that "my BS meter was definitely in the red and it was close to being pegged". And then it happened to me with my '94 N/A. The situation was nearly identical, started the car, let the key fall back to position II and it promptly died and would not re-fire. I was thinking fuel pump relay and since I was heading to my cabin I just swapped the relay (I always carry a spare) and tried again. No start but I did notice that the starter was spinning quicker than normal.

I then remembered a posting on what someone had dubbed "Lawn Mower Syndrome" and gave their cure a try. After about the 5th revolution there was a noticeable change in the sound of the engine (it lugged down like it was actually getting compression) and then it fired right up.

The tight tolerances come into play since the piston rings don't actually scrape the cylinder walls under significant lateral pressure. That is why you can tear one of these engines down after 150k miles and still have good cross-hatching. That microscopically thin layer of oil, filling the cross-hatching, actually seals the rings off with the cylinder wall. At least that's how I am rationalizing it.

I think you are correct but for another reason. Had the original poster done a compression check I think he would have found the compression to be zero (or near zero) across the board. The last turbo engine I tore down had oiler pipes that squirted oil at the base of each piston. I don't recall them being there on the NA engines. This has only happened to me once and that was with a NA engine.

...Lee

 

Sorry Lee; your explanation/rationalizations don't add up.

It's too bad brick didn't ck the compression when he pulled the plugs out; might have helped de-voodoo this LMS legend.

And even if it did have 0 compression on one or more cyls, there's no way that's all going by the rings!! No f****** way! Sorry, I don't care if the pistons/rings are completely dry, wet with gasoline, or whatever. You'd have to have a hole in the piston to get 0 psi compression.

If you have 0 psi compression, then you've got one or more valves sticking open. Here's a thought, maybe the oil is getting on the valve stems and freeing them up???

 

I don't know and it has not happened to me yet so I can't verify anything, however, When you're cranking, the pistons are going up and down, if a valve is stuck open, it would get piston contact, correct? If that happens, it will never run again, bent valves. Also, when you put oil down the spark plug holes, oil wouldn't get on the valves, oil gets on them from up top.

Anywho, it's strange but I'm glad the car is running.

 

Valve(s) only have to be stuck open a tiny bit to loose all compression; i.e. not enough to cause interference and piston contact.


Think about it; you put oil in the cyl (assuming one or more valves is stuck slightly ajar) via spark plug hole, then replace spark plug. Piston comes up on compression stroke and tries to compress gas/oil/air mixture in cyl; where's the oil/etc. going to go? It will be pushed by the valve and likely get onto the extended valve stem; yes?

 

First off, thanks especailly to Ozark Lee for the help. I probably would have spent a lot of time tinkering around trying to get the car started, without knowing about LMS.

It's still a little curious, but in mulling it over, I've developed an understanding based on these facts:

• As is typical for LMS inflicted cars, there was a interval of running the engine for a short duration, then it was shut off. I actually did this twice the night before LMS hit.
• As I noted, the engine turned over faster than normal, indicating low compression.
• Excess liquid fuel is known to wash down oil from cylinder walls - typically an issue in Diesels, where the low compression will prevent the engine from starting.
• On the cold morning when LMS struck, the engine started and ran for a very short time (under a second).
• Burning gasoline creates water vapor.
• in a cold engine I don't see why some of this vapor wouldn't condense on the spark plug.
• The breakdown voltage of an air gap (aka spark plug) depends on the pressure - low pressure, from low compression = low voltage
• low voltage spark = low energy in spark
• low spark energy, coupled with some water that condensed on POS Platinum plugs = no start

Well, it's a theory that ties all my circumstances together. I got rid of the Platinum plugs, and am hoping not to have this happen again...

On a related note, the T Belt job went off well. As I noted, and lots of other folks have discovered, the T45 tensioner pulley bolt requires extra care. It came out with no drama, thanks to a 4-pronged approach

1. new Lisle "Super Torx" bit (the normal Lisle bit started to twist in a bad way)
2. I welded a hex nut to the Torx bit, so I could turn it with a box-end wrench instead of my socket wrench
3. Block of wood to push the T45 bit into the bolt head
4. Simultaneous use of BF Vise grips on the washer under the T45 head

Next adventure: Parking brake cables...

 

I really hesitate to respond to these posts, because it makes me look like I'm trying to beat people up, but that's not the case. I simply have to refute mis-information when it is posted on this forum (sorry, can't help it ). Otherwise, if it goes un-challenged, then others may construe it as fact, and that's how myths/legends get started.

First off, I have nothing but the highest regard for Ozark Lee, as I have read probably hundreds of his posts here, at matthew's site, and other forums. Like I said before, 999 out of 1000, Lee is spot on with his advice and I have learned a great deal from him.

But that doesn't change the fact that I'm a doubting Thomas when it comes to this LMS stuff. Washing the cylinders down w/gas may lower the compression a bit (and that may make a difference in starting on a weak engine) but not to 0 psi, as LMS was explained.


Brickbat:
I was with you until your 2nd to last bullet; that's actually backwards. The power (or energy) in a spark is a product of voltage and current (P = I*V). The pwr an ignition coil secondary puts out is governed by many factors (construction, battery voltage, etc.) but given those factors are relatively constant, the pwr output will be relatively constant.

I think what you may have meant to say is that increased pressure in a combustion chamber will increase the resistance across the spark plug air gap, and consequently the secondary voltage will have to rise to be able to jump that gap. Since the voltage must go up (and pwr is relatively constant) this means that the current must go down. This is why when you bump up the combustion chamber pressure (by increasing compression and/or increasing boost pressure) you will find you have to get a higher pwr coil, or decrease the plug gap (which you don't want to do since that will make a smaller "fire"). BTW: this is why you should never crank an engine with the plugs not connected to the 2ndary wires unless ignition is disabled; causes 2ndary voltage to go way too high and will stress all 2ndary components; coil, plug wires, etc.

Conversely if you lower the plug gap resistance (say by fouling it w/gas or water) the voltage building up in the secondary winding is effectively shorted out and never generates a spark.

On a different note, I used similar method as you to get TB tensioner bolt out too; good work!

 

Been designing circuits, including some HV, as a EE for quite a few years, so am familiar with P=I*V. Familiar enough to know it's only a part of the story with a nonlinear transient, like a discharge across a spark plug.

The energy in the spark is the integral of the VI product over time. If V is reduced, by say, a lower breakdown voltage resulting from low pressure, then the energy in the spark is reduced. That, as long as the current doesn't change...

I disagree with your constant power assertion. Ignition systems are pretty complex, but they don't have a constant power feature. It just wouldn't be practical to regulate the power of a pulse on a fast transient like that, especially at an acceptable cost point for an automotive application. Due to the high resistances in the path (such as the resistance in the wires and secondary of the coil), they're closer to a constant-current source.

The Volvo ignition system design looks to me like a derivative of the classic inductive system, invented by Kettering about 100 years ago. (I don't think the stock ignition system is CDI - correct me if you know otherwise) I would argue this system does have a mainly-constant-current characteristic. The current in the secondary is approximately the current in the primary divided by the turns ratio. The secondary voltage rises to whatever it takes to allow this current to flow. As you note the voltage can rise to destructive levels, if a current path is not provided.

So, thanks for making me re-think this, but I don't think I have stated anything backwards.

All that aside though, if you disagree with my theory, what do you think explains my symptom and 'fix'?