Thank you for viewing this post. Having driven and repaired Volvos exclusively since 1978 I'm reached a point w/ my current ride where I know the problem - No Spark - but I can't figure out what is causing (or preventing) my ignition system to spark from the coil/primary wire. This post is kinda long but in order to obtain advice the more information the better the advice and wow, do I need advice!!


The CAR:
1994 850na, manual trans, 250K+ miles wagon, I’m second owner, always serviced from new
it was running fine, no intermittants, good mileage, etc. Good, good, good.

I also own a 93 850 that runs, (important as it became a “swap parts” car) except for a bad water pump. This 850 was starting and running on the day problem arose.

I was setting up to replace the water pump on the 93 Volvo 850 (the one that starts and runs) when:my Wife backed out of her garage and bumped the front end of the 94 wagon. No big deal as there was no minor scrapes but not even a cracked grill.

Is there an electrical or other coonection near front grill that could have been cut, crimped or otherwise broken?

But now the 94’ 850 wagon won’t start. It apparantly has No Spark. To test this I replaced the primary coil lead w/ a spark plug and wire to ground. I also tried grounding the primary coil w/ just a speaker wire #14 but in each case - No Spark. I’ve repeated this test each time as “repairs” were made but -no spark!

I also went over the No Gas Problem before determining it was a No Spark Problem; Schrader valve, fuel pump relay , etc Fuel is fine

From the A6 receptacle on the OBD I’m reading two fault codes: 314 and 214. The 314 is “314 “Camshaft Position sensor (CMP) signal missing or faulty” and
the 214 is “214 Engine speed (RPM) sensor signal missing sporadically“ I now also get a 121; “121 MAF sensor signal” from A2 but when I first started this 121 fault was not indicated. Apparently I subsequently damaged the MAF while working on other problems. I have tested w/the MAF disconnected, and I have tested w/ the MAF connected but still no spark. I am under the belief that with the MAF disconnected I can still start the engine. At least get a spark. Pls advise if true or not.

So NO Spark, CPS fault and after reading this blog I also assumed the 214 was related to the crank sensor. So I replaced both the CPS and crank sensors and the primary coil in the non-starting 850 with the same parts from the starting 850. Still no spark. I cracked the Bakelite connector on the CPS while swapping so I went to the bone yard and got additional CPS, crank sensors and coils. Still no spark. I’ve swapped in two sets of CPS, crank sensor and coils one from a known working motor. BTW the parts from the boneyard were from a car w/ deployed airbags so I assume it was running up to point of collision

BTW: I’m jumping the battery from running car so the volts/amps are good. +13.5 at battery

W/ a VOM, w/ jumper cables & running car attached, I read:
Battery terminals: +13.57
at the CPS connector: +12.5V, +5V and 0V
I am dropping 1volt from battery to here but a) its more than the required 11.5 and b.)it’s probably due to line risistance
At the crank sensor connector: 0v, +1.67v
at the COIL: +12.5 at both “nuts” , connector: 0, 13.5, 00.15v (transient)
MAF (what the heck): 0,13.5, 0, 0

I am lost...
The battery volt/amps are good.
CPS, Crank sensor & coil have been swapped out. Voltages good
Schrador valve emits gas. fuel pump relay (103) has been swapped, I can hear the fuel pump when I turn key to position II. Fuses etc checked and good. Little stuff done
And yes the IAC humms, buzzess quite happily when key in second position. swapped out primary coil wire (twice)

Yet still no spark!!!!!!

ECU bad??? I hesitate to think this as it is a difficult TS w/o risking my spare car. What’s the deal w/ the ECU’s? Are they interchangable between a 93 850na manual trans and a 94 850na manual trans. The “numbers” are different on the labels between my two 850’s.
ECU numbers (standing in front facing engine)
Non-starter:
Right ECU (nearest to engine in BIG #’s) 4.1;
also on label: PO9146296; CP01, 1T2250685; T94050203
Left ECU: 1.2
plus PO9146476; CP01; 1T2852395; T94020348
Can someone provide an explanantion of ECU’s and interchangeability. On my (previously) running 850 I have a (previously) good engine
rightmost ECU 3.1; P03517961; CP03; 1T2250646; T92462263
Left ECU 4.2; P03517962; CP03; 1T2852210; T92480274
Can these be swapped w/ broken 1994? If you’re not sure pls don’t guess I don’t have another

Anyhow I don’t know what to do next other than giving up and throwing in the towel. I have a signal tracer with which I can trace for continuity on the wire harnesses but I don’t have a complete wiring disgram that goes to the CPS, crank sensor, ECU pin-outs etc.

Can anyone point to link to ECU pinouts? I’d like to know if the CPS and crank sensors are connected to their respective ECU connections

I’d try swapping ECU’s but that can be an expensive rathole. And since I don’t know enough ECU’s are a potential landmine for me

It appears I may have been following the wrong supposed “problem” with my emphasis on CPS, crank sensor etc but I just don’t know what to do next. I may get a buddy to come by w/ a truck and drag the 850 trying to jumpstart it but wow for the first time in a long time I’m clueless.

so:
no spark, fuel ok, good battery source (cablejump), swapped out supposed “bad” parts; CPS, Crank sensor, Coil for known good, and coil wire - still no spark. HELP

Any suggestions from those on this forum will be appreciated and tried.

Paulfr

"...Wife backed out of her garage and bumped the front end of the 94 wagon..."

So if the dead car (manual trans) was in a forward gear and she bumped the front of the car, it could have spun the engine backwards some unknown amount.

So I'd be curious as to whether that sudden jolt backwards could have messed up something like hall sensor, VVT, etc., etc.

Just grasping here for a brainstorm.....

Interesting idea that the push could have moving the engine and therefore the timing etc is off.

To test this I would see if timing marks line up on the cams. Yes?
This seems to be the easiest and most definitive method. I'll give it a try and get back
Paulfr

Confirm that the rotor is turning.

Hi, before starting ecu swapping follow the spark path to the end.
- coilis getting voltage, ok
-"at the COIL: +12.5 at both “nuts” , connector: 0, 13.5, 00.15v (transient)" could mean that the current breaks as planned (hall sensor inside distributor is ok)
-test now the spark directly from coil before distributor
- if ok then test the spark after distributor to see if the cup and traveller are ok, take the ground from engine body to include the ground wiring to the test
br Tapsa

Tapsa thanks for your response...
unfortunately i have tested for a spark AT the coil. Used a spark wire and plug....no spark. I even grabbed the primary wire myself in hand and still no spark. So I'm getting nothing from the coil and the cam sensor (hall effect) is from a known working engine, as well as the coil, wires and crank sensor.

I'm lost...

paulfr

Hi, here I'm refering to the coil primary current breaking device (also hall sensor) not cps. It's located low inside the distributor body. It shoud break the primary current and cause spark high voltage on secundary side = plug wire.
tapsa

Tapsa, thanks for sticking w/ me in figuring this out. Pardon my skepticism but if I'm NOT getting a spark from the primary coil wire could a hall sensor In The Distributor still cause a No Spark from the coil? Just askin
paulfr

Hi, yes.

the coil primary current loads the energy in coil and when it's broken the energy goes out as high voltage sparc on the secondary side and gets distributed by traveller/rotor to the plug in turn.

the primary current breaker device is located low under distributer cup below traveller/rotor which is for high voltage distribution for plugs.

the primary side should show about 0,3-0,7 ohm when disconnected.
the coil terminal 15 to high tension plug should show 8-9kilo ohm (ignition off)

tapsa

Tapsa again thanks for your suggestions.
Re/ the circuit breaker for the primary coil, you locate it low under the distributor below traveler, rotor.
On my 850na (1994) the breaker for the coil "appears" to be the cam position sensor (cps or cmp-- depends). The cpm is a hall effect device located at right side engine rear at the end of the exhaust cam shaft from where is gets its positioning information to pulse the coil to deliver a hi-voltage spark. I have looked and disassembled my distributor to removing the cap & rotor. There appears to be nothing there that would be a Hall effect device.
I can send photos but my main concern is whether or not the cps is the primary signaling device or I'm not seeing something in/ under or affixed to the distributor. Are you certain About a primary Current breaker device being where you locate it in your reply?

Just askin

Also would a bad throttle position sensor TPS prevent a spark? Not run yes, but no spark? I'm guessing no but i'm also out of ideas. It's in a difficult location and the bolts are rusted

Paulfr

Hi,
No, I'm not sure, perhaps had the previous generation of sab in my mind when answering from top of my head-sorry.

the 850 has no manual adjustment for sparc timing, ie it is computer controlled getting the inputs from cps, tps, ect, rmp, ks, load etc...? is getting complicated. but if you short cut the coil primary to earth and break it you should get sparc from coil if this part of the system is ok.

To start anlysing the computer part the system definion is needed LH3.2? with EZ-129K as mine or something else?

sorry for the disinformation and confusion
Tapsa

Correct, the throttle position sensor will not prevent spark.

Dumb suggestion: lift the cover off the computer box. Pull out and gently push the computers back in place? Perhaps the 'collision' jarred them?????

--
My name is Klaus and I am a V ♂ lv ♂ holic

Klaus...thanks for the suggestion but I've done that and more. I'm swapping out the ECU's from the good engine into the no spark beast. Never seen an ECU fail this way but7..hey it,s a Volvo. They do whatever...whenever

Wierd..just got it to "catch" for a split second then nothing. Again checked the coil wire ..nothing. I replaced the relay and main relay w/ good ones although there is gas at the schrader valve and no spark at the primary coil wire

Drivin me nuts

Paulfr

Nice write up! No, the MAF has nothing to do with spark. No, there is nothing in the front bumper area that will cause a no start.

But, check the ground wires at battery and engine. A jolt could have messed them up and jumping the battery will not solve this.

I prefer a test light for determining voltage at the coil, it is more fun to watch a light blink or be on steady. You did the proper things so far with the CPS and crank sensor and coil. While a bad CPS will prevent starting, a push start will overide that.

Because you have a stick shift, the speed sensor message is mute as it mostly relates to the auto tranny.

Klaus
--
My name is Klaus and I am a V ♂ lv ♂ holic

Klaus,
Thanks for your response.

I will check ground connects. The 850 has two stranded & exposed wire leads from left and right ends of the exhaust cam covers. I assume these are the engine grounds you mention. I will also look under the battery but.....

I once had a 740 with a bad engine ground (up in the oil pan area very messy) and the engine would not turn over at all - NOTHING. Can't recall if dash lights lit but engine did not crank.

Since the engine is cranking and there is voltage at various ignitiom points doesn't that rule out a bad ground as problem?????

Just asking. I appreciate your assistance

paulfr

You are correct, battery supplies 12V to the starter and starter needs to be grounded, meaning engine needs to be grounded to frame.

I wonder if the alternator wire is bad, that voltage is needed by the coil.

With the 'new donor' parts, are you still getting the same codes?

Klaus
--
My name is Klaus and I am a V ♂ lv ♂ holic