ECU Ground Connections Under Manifold Location?

warmblood58 · Post by **warmblood58** » 27 Feb 2016, 01:26

Hi, I have a '95 850T5-r and I understand the ecu connection(s) (are there one or two under the manifold?) create a number of problems when they are corroded, etc. - my car sat for over six months in a non run state. Can someone tell me if there are one or two of these connections and also, their location on a '95 car - thanks! Hope to hear this car run soon!

Post by **abscate** » 27 Feb 2016, 01:30

The ECU is not a common problem on this car for a no start condition.

First step on a six month sitting car is checking brakes for corrosion, then a compression test to confirm you have a working motor. Was it running before in your exoerience or by anecdote from PO?

Post by **erikv11** » 27 Feb 2016, 07:05

What abscate said. For the record, my T5R sat for over 2 years in a state where we have actual seasons, before I rescued and revived it. It has no corrosion issues at all.

warmblood58 · Post by **warmblood58** » 27 Feb 2016, 11:29

Thanks, car ran 6 months ago. I have a mysterious no warning light in key position 2 situation but do have dash lights, car cranks, no power to fuel pump. I did some exhaustive research and came across a long thread that detailed similar problems (these cars absoulutely must have good ground connections) and I believe that I have some bad grounds due to some peculiar electrical problems so step one is to get power to pump and warning light function. I have replaced fuel pump and jumped (it works fine) tank was emptied and cleaned and treated, I pulled FP relay (and tried two others - no result) I bridged 15/87 at FP relay. My understanding is ECU will not power up if it's grounds are affected. I also swapped out FI relay to see if I could change result. Cap has some serious carbon tracking, so cleaned that up along with rotor and replaced plugs. I was hoping for some to tell me the approximate location of these relays vs jumping in and telling me I need to do brakes first . . . Once engine is running, I will flush brake fluid and lube sliders, etc. along with many other details.

Post by **erikv11** » 27 Feb 2016, 13:08

I know I already suggested this in your other thread but, check the electrical portion of the ignition switch. Just grab one from the junkyard and pop it in, super easy. Or if hitting the 'yard is not easy in your part of the bay area then I could send you a crappy (but working) one if you will send it back when you're done troubleshooting. Send me a PM.

Or did you rule out the switch based on wiring diagrams or something?

warmblood58 · Post by **warmblood58** » 27 Feb 2016, 14:04

Yep, already tried two other ignition switches salvaged from other 850's . . . . nada! I am really suspecting ground issues which would explain no warning light and no power to pump . . . I am cleaning as I am going along as this car sat in a garage for 4 years and then PO purchased it and "started it up for a few minutes every month or so" . . . until it died. Not great for the engine, he should have taken it on 30 minute drives as we know - Apparently, 850's can really do some wonky things with bad grounds. This car has IPD's flashed ECU -hope I get to experience this car running. The no warning light in pos 2 seems very odd and telling -all fuses new too -thanks!

Post by **erikv11** » 27 Feb 2016, 15:06

Ok good luck then! Sorry I don't know more about the ECU grounds ...

Post by **abscate** » 27 Feb 2016, 15:26

By agreement with Volvo legal we don't host wiring diagrams here on MVS but they are on the Internet.

ECU grounds will be marked on the diagrams.

Solving that fuel pump relay problem won't involve ECU based on experience here. Trace the 12 VDC back from the fault until you find the break

warmblood58 · Post by **warmblood58** » 27 Feb 2016, 21:35

yep, my next move will be that . . . my favorite work tends to be more mechanical vs electrical but these cars rely heavily on electrical connections everywhere so time to get even more involved.

Post by **abscate** » 29 Feb 2016, 06:53

Just realised you posted you have dash lights but no warning light.

Can you snap a pic of the POS II dash or describe which light(s) are missing?