Hi all,

I have a 1994 Volvo 850 that up until a month or so ago ran like a champ. It died while driving (still had electric - the engine just stopped). I ran through the volvo diagnostic tools on the car and because of those readings I have replaced the camshaft and crankshaft position sensor. I have good fuel pressure going to the plugs, the rotor turns, and the spark plugs appear to be in good condition.

My issue, as far as I can isolate it, is that I can not get spark across any of the spark-plugs. I have tried checking directly from the ICU and I also am unable to get any spark from there.

At this point I have checked everything that I know how to or have had a recommendation to. Could it be the ECU? I have read some articles online indicating that that could be the case. Does anyone have any other ideas of what I could be checking?

Thank you so much for your time and brain power.

David

 

does the check engine light come on with your key in the ignition II position?

 

It does have a check engine light on currently. After making the previously mentioned repairs I tried to clear the light to see if new codes showed up however it would not clear.

 

I think that rules out the ECU as the culprit. You can try reseating it but I'd also check for the crank position sensor and any connectors etc. How's your system voltage?

 

That is good to know. I'm assuming that if the ECU was bad that there would be no Check Engine light? I've been looking over the car checking any connection that I can think of and/or reach and so far. Voltage from certain components or right off the battery?

 

start measuring voltage at the battery. should be 12.5 with the car off. start the car. should go to 14+ with the engine running (but not higher than say 15 or so). Add electrical loads - blower fan on high, rear defogger, high beams etc. Voltage should stay in the 13V+ range.

I'd also read up on fault trees for no spark (volvotips.com is a good resource) and maybe look into issues with the immobilizer. Does your model have the red LED on the dash?

 

Check the "fuel injection relay" in particular. It has the round pins that are subject to failure of the plug. The contacts inside the plug are held in place by a clear plastic that just rots away after 20 years. On a Turbo 94 that relay is on top of the radiator. NA might be the same.

 

Sorry about the delay, work has been crazy.

I will check as many points as I can as far as voltage goes. Last I checked all of the usual culprits were getting the recommended amount of juice. One thing that I want to make sure is clear is that the car won't start and will not run, so some testing will be impossible currently.

I'll check on that fuel injection relay firebirdparts. Will that control spark or just getting the gas there? Currently after trying to crank it over you can pull out the plugs and smell fresh gas.

Thanks all

 

Did you check the coil to see if you are getting voltage into it and a nice strong blue spark out of the coil lead?

 

I don't recall checking that off the top of my head however that will be the next thing I check and report back. Thanks for the tip.

 

The fuel injection relay powers some pins on the ECU, so when it goes dead it kills the spark, but I think it kills fuel too.

 

So I haven't checked the coil lead yet as the car is a couple cities away and hard to visit while carless. If I remember correctly it did not have any spark coming off the coil when I had the wire coming off the coil and a spark plug near ground to see if I could get an arc.

Also I did try a replacement ECU for the ignition side of things and it is still doing the same thing, trys to turn over but just won't start.

 

Also one thing to mention, we have tested the ohms on the coil to check and it appeared to be in a safe range. It also was replaced probably 8 months ago. Is there any system or module that comes to mind that may not be sending the ignition message to the ICM coil?

 

Ok, if you are not getting a hot spark out of the coil, check the input voltage to the coil when you are trying to crank it. You should have a +12 Volts going into the coil. If you have good voltage going into the coil and no hot spark coming out, the coil is bad. If you do not have 12 volts going into the coil, you most likely have a wiring issue. The attachement I provided gives some good troubleshooting from the Volvo Service Manual

 

I think this is terrible advice. I don't think any car has over 12 volts going to the coil during cranking. Let's all go check and report back.

Okay, 10.6 volts for me, cranking on a 1995 NA. Most cars would be somewhere in the 10 volt range but that doesn't mean they won't run on less. That is a different question.

 

Ok I guess I should have stated you should have BATTERY VOLTAGE going to the coil when cranking. If you have NO VOLTAGE, then you have a problem. If you read the attached troubleshooting guide I provided it says the same thing......So I guess Volvo gives terrible advice in their manual. Have fun, I'm done.

 

After looking over those documents and links I was still at a loss. I ended up taking it to a mechanic to see if they could diagnose it. Turns out it was the ICU that had been replaced about 6 months ago.

 

That doesn't sound good. I don't have a backup for mine.

 

if you don't mind my asking, how much did the replacement ICU cost?

(firebird and Psaboic have been leaping heroic hurdles trying to help me with the same issue)

 

Including diagnostics and part and labor it was right about $400. You can get a fairly good part for somewhere in a mid $100 range if you are comfortable with changing it.