good spark + fuel + air = no start?

percolate · Post by **percolate** » 02 Mar 2011, 21:53

Hello all,

I'm a brand new member and this is my very first post, though I am seasoned in the ownership and accompanying labor of Volvos. This site has been a fantastic resource over the last couple of months. Thank you! And now I have a particular question of my own. (Upon proof reading, I see that this post has gotten rather long winded. My apologies in advance but I wanted to include as much detail as possible.)

I have a teal 1997 850 T5 with 160k. I got it in December and have done a goodly bit of catch-up maintenance over the last couple months. When it runs, it runs great! Holy moly it has some go! This is my first turbo and wow! But when it doesn't run, it's a little bit of bother (winter camping in northern MN - hiking out seven hours at night through 1' of fresh snow on top of 3" of slush that would then accumulate into grapefruit+ sized balls of ice on our snowshoes, -15 temps, get to the car, car starts right up! blower seizes!!! no heat!!!!!! it got down to -35 that night!!!!!!!!!! a new years experience to remember - brrrr).

I got the blower motor sorted out sometime in January (FYI - the FCP aftermarket blower motor is a bad fit! the glove box insert won't go all the way in and so the glove box door struggles to close. finally found a working one at the pick-n-pull. : ) As of two weeks ago, the car just won't start. Here's the story as best as I can recall (not a very exciting story):

Starting around the end of January, when I would cold start it in the morning (minus zero temps), it would sound really throaty. Growley grrrrrr of a much larger, freer flowing exhaust. From inside the cabin, it sounded like it was coming from behind the console, in the neighborhood of the down pipe. From outside the car it sounded COLD so I would just rush back inside and have a cup of coffee. I would let it warm up a bit in the driveway and then it would quiet down and drive normally. If I did drive right away, it would bog down in reverse some, and shift rather roughly in the forward gears. I'm guessing a loss of power issue related to the engine, because shifting would become smooth again when the car was driven for a while. As a side note regarding the cold start grrrr, the flexible part of the down tube has a little tear where it meets one of the tubes, but it is a small tear, and the grrrr sound would go away once the car warmed up.

A couple weeks ago it was unseasonably warm (high 30s low 40s) for about five days. Really humid, damp days when the sun wasn't shining. Car ran kinda rougher and so without checking the conditions under the hood I ordered tune up stuff from FCP - all OEM - plugs, wires, cap, rotor, and coil. I had already changed air and fuel filters when I got the car. (Also did oil/filter, transmission fluid, and a bunch of other unrelated stuff.) On the last day of the warmer temps, I was driving home on the highway and noticed some intermittent missing. Got home fine but it wouldn't start later that evening. Cranka cranka cranka cranka - not really even trying catch and fire. Friends have suggested timing issues - t. belt was repaced 10k ago along with tensioner and WP.

Soooo, plugs and wires etc. arrived and I installed them, making sure to place the wires on the correct terminals on the cap. Still no start. Good spark though. I only tested #1 for spark, but given the brand newness of the ignition system, I'm assuming that the rest of the plugs are getting adequate spark.

It seemed to me like a fuel delivery issue, and it wasn't the fuel pump relay, so I made myself a fuel pump tool and swapped the pumps between this T5 and the 96 GLT that's sitting in my garage that also doesn't run. Now with adequate fuel pressure it does the exact same thing. No start. At this point I got fed up with bundling up in the winter cold so I can turn wrenches on my car in the driveway, so I had it towed to my mechanic. He is a friend that charges me very little, but in turn, I consistently fall to the bottom of his priority list.

We worked on it on Monday night - replaced the cam sensor (he has a spare engine sitting in the shop), but same result. Still no start. Oh, and the ECU is not kicking out any codes. Hopefully I'm heading back over there tomorrow night with an ocilliscope from work (mecanic's is suffering from a broken screen). He suspects the wiring harness for the cam sensor. He saw bad corrosion in the female part of the connector (it looked ok to me) and suspects that the issue lies there - he wants to look at those wires with the scope. I have my doubts that this is the problem, but I'm at the absolute fringe of my understanding of how things work in there. It's mostly magic as far as I can tell.

Any thoughts? Suggestions? Other places to investigate?

Thank you in advance.

Post by **jimmy57** » 02 Mar 2011, 22:03

No cam sensor, no spark. erratic cam sensor is rare but gives coughs back through intake, sputtering, pinging.
I would make sure the hose between MAF sensor and turbo inlet is free of leaks.
That includes the crankcase vent hose that meets near to turbo end.
IF no leaks found then unplug the MAF sensor so it runs in limp-home mode and see if that is better.
When it is cranking is the cranking speed normal or would you maybe describe it as maybe the sound of an engine with no compression, i.e., turns over too fast.

percolate · Post by **percolate** » 02 Mar 2011, 22:10

I've tried unplugging the MAF for the limp home mode, but same no start.

Cranking speed? I'd say it's pretty normal. Maybe even a tad slow.

I'll be sure to check on the crankcase vent hose.

Thanks.

Post by **Ozark Lee** » 03 Mar 2011, 09:08

Soooo, plugs and wires etc. arrived and I installed them, making sure to place the wires on the correct terminals on the cap. Still no start. Good spark though. I only tested #1 for spark, but given the brand newness of the ignition system, I'm assuming that the rest of the plugs are getting adequate spark.

What did you use as a reference for the plug wire locations? If you used a Haynes Manual it is dead wrong.

This is how they go:

http://volvospeed.com/volvo_repairs_how ... plugs.html

...Lee

percolate · Post by **percolate** » 03 Mar 2011, 16:36

No, I didn't bother with the Haynes on this one. I pulled the old cap with the wires still on it and copied it. Also cross referenced with the markings on the new cap and the little wire holding clip that the wires come bundled in (OEM cap etc.). I'm sure they're on there correctly. Thanks.

I'm off to see my mechanic with oscilloscope in hand. I'll post whatever we learn tonight. Hopefully it will include how great the car runs again.