2001 v70 cranks, but no spark...at all

crosscut237 · Post by **crosscut237** » 03 Dec 2018, 21:02

I'm fairly new to volvos, but not to cars, I do much of my own work. I have a 2001 v70 2.4t, the engine had 256000 and started knocking, then a rod let loose, ok, high miles, not that uncommon, I bought a lower mileage engine, spent the weekend removing the old one and installing the new one. New timing belt, new water pump, ect. Once it was installed I noticed that it cranked really slow.....but then it started....seemed to run a little rough, but not terrible.....for about a minute.....then it quit and I have not been able to get it started since. I found the source of the slow cranking, the grounding strap came off, so I reinstalled it....cranks good now, but no spark. I removed the injectors and did a crank test, they all pulsed like they should. replaced the crank sensor and the cam sensor, no change. the only thing i can think of is that the poor grounding situation fried the ecm. but I cannot explain why the injectors fire just fine.....all the ignition coils are new, I even tried a set of old ones....no spark at all. Fuse in the engine compartment is good too. Any ideas or advice? thanks in advance.

Post by **abscate** » 03 Dec 2018, 22:47

Check for 12V at the coils, it should match B+

With no grounding, it is possible the ECU fried, indeed, though. You can confirm that by watching the ground wire waveform on an o- scope

crosscut237 · Post by **crosscut237** » 04 Dec 2018, 07:29

I appreciate the advice, I am working without a scope for now, would I be able to measure for voltage at the coils by backprobing the connectors? What is meant by B+? Battery Positive? Assuming I can backprobe the coils, I am guessing it will be a red wire that carries the voltage? Thanks again!

crosscut237 · Post by **crosscut237** » 04 Dec 2018, 07:55

Also, if I replace the ECU with a unit from a used auto parts place, will I need to have that ECU reprogrammed?

Post by **abscate** » 04 Dec 2018, 18:26

Yeah, a 2001 has to be cloned or married to the car to work.

The coils get B+ or battery voltage from common power relay. The ECU grounds them to fire them

crosscut237 · Post by **crosscut237** » 04 Dec 2018, 19:39

Cloned or married.....that's going to require Vida I'm guessing?

crosscut237 · Post by **crosscut237** » 04 Dec 2018, 20:47

Ok, so I checked and I do have B+ at the coils......so then the ECU is not grounding them to fire.......I have no codes whatsoever, so what is my next step? when the vehicle stopped running the codes present were indicating primary coil voltage, for coils 1, 2, 4, 5, 3, in that order....also the random misfire code. I'm hoping that the ECU is not damaged, but I don't know what else is interrupting the signal to ground the plugs???

Second....I have been reading that I cannot use a "used" ECU because it has the VIN burned into it. Can anyone confirm this? the junkyard is willing to sell me a used ECU for $80.......but if I can't use it.....Please Help!!!

Post by **precopster** » 04 Dec 2018, 21:08

If you get Vida/Dice we can hook you up with a couple of guys who can clone over the internet. You'll need a laptop with internet connection and a Skype or Viber account.

You don't need to install the complex Vida software but you'll need to install the interface tool and have the USB drivers for it loaded. Also a Team Viewer version 11 installed; you can get V.11 from the Team Viewer website

Post by **abscate** » 04 Dec 2018, 21:38

Figureabout $250 for the hardware and service, about 1/4 of what the dealer would charge , minimum

crosscut237 · Post by **crosscut237** » 05 Dec 2018, 06:25

Ok, thanks for the info....I'm going to try a local import shop and see what they can do first (Indy shop). Also since I have no codes, could it somehow be a problem in the harness between the ECU and coils? I realize this means all five ground wires are open, but maybe?