850 weak spark from coil

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.
1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
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cet
Posts: 64
Joined: Mon Jun 01, 2009 5:50 pm
Year and Model: 850 1996
Location: Pittsburgh Pennsylvania

850 weak spark from coil

Postby cet » Thu Apr 15, 2010 2:06 am

Strange sequence of events upcomming 'cause you never know what the answer is.

Car had been running well, though some bad carbon out the exhaust after putting in a $27 o2 sensor that got it past inspection then threw a code in 2 days.

Break in nursing school,parked the car, come back 2 days later (and after the battery ran down thanks to the kids playing with the visor mirror) car cranked slow, no start. Charged battery, cranked faster, no start. Checked fuel pressure, none, checked relay, operating as it should. Power to the pump but no pump no pressure replaced pump, nice noisey pump, good pressure.

Start looking at spark, good at the plug furthest from distributer (i think its 5) weak to absent at all others, clean carbon off of rotor and cap contacts, shift test spark plug to the coil output.

original coil, weak spark
coil from Ford Ranger stronger but still orange/yellow not blue

I checked my original posting from when i first got the car, and saw that the red/blue amplifier output to the coil had been showing 5.5 volts AC, it is now 2.5- 3

Is this amplifier going bad or could the output of the sensors before it be throwing the whole thing low. My favorite Pittsburgh recycler dosnt have the coil amplifier in stock and i see that even the used price on that amplifier is ridiculous. It looks to be a 1000x amp (5.5 millivolt to 5.5 volt) is there some kind of aftermarket substitute?

Thanx
CET

whoa
Posts: 461
Joined: Wed Jul 30, 2008 5:00 pm
Year and Model: 850 Turbo Wagon 1996
Location: san francisco

Re: 850 weak spark from coil

Postby whoa » Thu Apr 15, 2010 5:03 am

Hmmm. Have you pulled the codes?
1996 850 Turbo Wagon

cet
Posts: 64
Joined: Mon Jun 01, 2009 5:50 pm
Year and Model: 850 1996
Location: Pittsburgh Pennsylvania

Re: 850 weak spark from coil

Postby cet » Thu Apr 15, 2010 9:51 am

dont have reader, its post 95, should try to borrow one

BEJinFbk
Posts: 3117
Joined: Sun Jan 06, 2008 5:32 am
Year and Model: '98 V70 R
Location: Fairbanks, Alaska
Flag: United States of America

Re: 850 weak spark from coil

Postby BEJinFbk » Thu Apr 15, 2010 11:10 pm

Is the battery Fully charged? Like, overnight?
'98 V70 R - Well Equipped for Life Up North... ;)

cet
Posts: 64
Joined: Mon Jun 01, 2009 5:50 pm
Year and Model: 850 1996
Location: Pittsburgh Pennsylvania

Re: 850 weak spark from coil

Postby cet » Sat Apr 17, 2010 4:29 am

Battery fully charged,ran and got a 49.99 scan tool; no codes (it initially says there are 2 codes which cannot be identified or erased, went out and read and cleared the 0441 code from the Dodge caravan so the tool seems to work) I found this hard to believe so i disconnected the wires from the Mass Air Flow meter and idle air control to see if that would throw one but it didnt. something about the way it is cranking ( a little faster than normal) caused me to take the cover off the timing belt to see if the cams were lining up; looks fine. sounds like 1 cylinder out of the 5 is almost catching.Testing each plug with its wire individually similar news, strongest spark on the plug furthest from the distributer, weak on others. will head to junkyard for cap rotor and wires, should i grab the injector rail while I'm there?Dont have gauge but hitting the valve yieds about 3-4 cc's at what looks like normal pressure. I am running out of time, anybody have a guess.

whoa
Posts: 461
Joined: Wed Jul 30, 2008 5:00 pm
Year and Model: 850 Turbo Wagon 1996
Location: san francisco

Re: 850 weak spark from coil

Postby whoa » Sat Apr 17, 2010 5:32 am

Yeah, you can't pull codes with a regular OBD reader. Here's a cheap way:

http://www.volvoforums.org.uk/showthread.php?p=585182
http://www.volvoforums.org.uk/showthread.php?t=46943

Here's a good thing to look at:

http://www.volvoclub.org.uk/tech/servic ... esting.pdf

Along with some of the other documents:

http://www.volvoclub.org.uk/volvo_works ... docs.shtml
1996 850 Turbo Wagon

cet
Posts: 64
Joined: Mon Jun 01, 2009 5:50 pm
Year and Model: 850 1996
Location: Pittsburgh Pennsylvania

Re: 850 weak spark from coil

Postby cet » Sat Apr 17, 2010 7:44 pm

Thank you for your help on this, i dont think i have been specific enough.This is a 96 non turbo 20 valve with 1 engine computer + an Asian for the tranny. the engine ECU is a GW2 (picked up a FD2 out of a similarly engined 96 at the junk yard dont know if its compatable) the engine numbers under the spark plug cover say it is a B6340 3.1 on the lower right 10001671 PO2
the plate over by the battery has this
854 T3 337520
YV1LS5543T3337520\

31
3650
189-23
EEXAAMS

i broght home everything i could think of which would cause a no start, crank, cam and mass airflow sensors. i have studied electronics so would have no fear of the LED set up if it is applicable to this engine. The cheapo OBD2 reader is nice, it could give freeze frames and all sorts of stuf on the dodge guess the volvo ecu isnt as talkative. thanks again, gotta figure out how to send you a badassed botle of beer when i get this runnin.

cet
Posts: 64
Joined: Mon Jun 01, 2009 5:50 pm
Year and Model: 850 1996
Location: Pittsburgh Pennsylvania

Re: 850 weak spark from coil

Postby cet » Sat Apr 17, 2010 10:03 pm

switched out mass air flow sensor 2X more detonations than before but still anemic. Tried LED no flashes. tryed OBD2 again same as before. it sees 2 codes on initial read but then cannot read them "the modual has no codes stored" and it can not clear them, guess i am stuck in that between the LED and the $10,000 Volvo scanner that was mentioned in the thread.Will search the data you linked and the schematics for anything else electronic that could be causing this. and will try to line up a fuel filter though i dont think that is it , will try changing out the crank and cam sensors first.

whoa
Posts: 461
Joined: Wed Jul 30, 2008 5:00 pm
Year and Model: 850 Turbo Wagon 1996
Location: san francisco

Re: 850 weak spark from coil

Postby whoa » Sat Apr 17, 2010 11:07 pm

No flashes at all? You should get 1-1-1 if all is okay. Plus you pulled the MAF, so that should throw a code.

Do check out that first article; it specifies voltages you should find at the coil and so on.
1996 850 Turbo Wagon

claymore850
Posts: 141
Joined: Mon Mar 29, 2010 5:27 am
Year and Model: 850 Turbo 94, 244 78
Location: Guatemala

Re: 850 weak spark from coil

Postby claymore850 » Sun Apr 18, 2010 4:17 am

Did you test the ground cable on the coil?? maybe its a little rust on it. check if there is no a cracked side on the coil, near the support brace.
A year ago i changed my coil, because it has a crack who leaves the spark go to ground.. I replace with a MSD 8207 at half price on the ebay..good luck


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