850 Won't start... Has good spark, help please.

cudatime71 · Post by **cudatime71** » 15 Feb 2010, 22:15

This is my 1st Volvo, so any help is greatly appreciated. I have a 1993 850. My daughter left the key on two days ago and drained the battery. No problem. I jumped it and it started fine. Today, I tried to start it... turns over strong, but won't start. I pulled the center plugwire and see good spark. I sprayed some starter fluid in, but that didn't help. Where should I start? Could I have damaged something when I jumpstarted it? Thanks for your input.

Post by **jblackburn** » 15 Feb 2010, 22:25

You've got spark, that's a good thing.

Do you hear the fuel pump start running when you've got the key in position II? Push on the valve at the end of the fuel rail and see if any fuel sprays out of it.

Post by **kcodyjr** » 15 Feb 2010, 22:42

I assume it turns over strong but does not sputter, or try to start, at all.

You're at the first stage of troubleshooting; spark, fuel, compression. That's the three things any Otto-cycle engine needs, even one as whacked out with computers as a Volvo.

You've verified spark, at least for one cylinder, though you haven't ruled out fouled, worn, or mis-gapped plugs. That seems unlikely though, you should be able to tell when that's coming by how bad the engine sucks.

Compression doesn't go suddenly either, you'd have reason to suspect it, and it should still sputter and try to catch but just fail to.

That leaves fuel. jablackburn suggested a direct sort of pressure test, +1 to that, just be sure to shield your eyes. A rag in your hand will do.

The fuel pump relays are notorious; search the other threads for where to pull the relay and short the right conductors. A bad relay can be repaired if you're savvy with a soldering iron.

- Kevin

cudatime71 · Post by **cudatime71** » 16 Feb 2010, 11:15

Well I just disconnected the fuel line over the fuel rail. When the key is turned, the fuel pumps out fine. Does this mean I can rule out the fuel pump and filter? I thought maybe the filter was blocked. I looking over some of the other threads here, I thought it could possibly be the camshaft position sensor. Does that sound like a possibility?
Thanks for your input so far.

Post by **jblackburn** » 16 Feb 2010, 12:31

USUALLY a camshaft position sensor would give you a no-spark condition. You said you're definately getting spark, and if you're getting fuel flow, then it all sounds good.

Try this: pull out all the spark plugs and place a tablespoon or so of oil in each cylinder. Put them all back in, and then crank it for ~30 secs or so with your foot held all the way to the floor until it begins to catch. Once it starts to catch (if it does), let up on the gas, and hold the idle up with your foot until it can idle on its own. It will smoke a lot, but if the compression has run down (e.g. if the car was moved quickly and shut off) it will build up the compression washed away from the rings by the sheer amount of gas dumped in when the car is started.

cudatime71 · Post by **cudatime71** » 16 Feb 2010, 13:40

Shes up and running again!!! I had seen the tip to hold the pedal to the floor for 30 sec. to burn up the fuel and build up compression. I tried that a couple of times and it almost started. So I figured I was close. By now the battery was getting low, so I hooked it up to a jumpstart, put it to the floor and cranked it over. I didn't let up until it finally started. I'm not sure if it got some bad gas or what. I'm going to add some fuel cleaner and cross my fingers.
A huge THANK YOU for your advice and this forum in general. I am glad I joined and I hope my experience helps someone else out.
Jon

Post by **stone36** » 09 Apr 2010, 16:28

jablackburn wrote: but if the compression has run down (e.g. if the car was moved quickly and shut off) it will build up the compression washed away from the rings by the sheer amount of gas dumped in when the car is started.

Can you explain this a little more, My 850 wont start right now and the last time I "drove" it was yesterday, I started it just to move it back 3 feet and immediately shut it off. So it ran for maybe 10 seconds.

thanks

Post by **jblackburn** » 09 Apr 2010, 16:45

That's exactly what you did then

I think it's generally a good idea to run them for 30 secs-1 min at minimum. I've never had a problem just switching cars around in the driveway, but that usually takes a bit of maneuvering so mine's running for about 1/2 a minute or so.

Basically, when you start the engine, a car DUMPS gas into the cylinders to get it started. Similar to the choke setting on a lawnmower or old carbureted car. All that gas washes down the oil from the rings and you lose compression, so it's not able to build up enough to start again if the engine's quickly shut off before it has a chance to get running normally. Once it's running, it doesn't have any problems, as the oil pumps around and the compression builds back up again.

Try the holding the pedal to the floor trick, if you can't get it to start in 5 minutes or so, pull out the spark plugs and take a straw full of oil (put your finger over the top and stick it in a container and pull it back out) and put it in each cylinder, put the spark plugs back in, and crank until it catches, then hold the idle steady with your foot til it can run on its own.

Post by **stone36** » 10 Apr 2010, 16:22

Worked, the key is to not worry about killing your starter, I had to let it go for a good minute and a half and just when I though I had it I let off the key and it died, did that one more time, and on the third go, I just kept the key on and the pedal to the floor until I hit about 4K RPM... Let it run for 10 minuts or so and this monring it started up fine. I also had to hook it up to a jume because of the time it took to get it going.

thanks

whoa · Post by **whoa** » 10 Apr 2010, 19:27

jablackburn does it again!