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ECU Ground Connections Under Manifold Location?

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
1997 - 2004 C70

warmblood58
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warmblood58

ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Sat Feb 27, 2016 1:26 am

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!

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abscate
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abscate

Re: ECU Ground Connections Under Manifold Location?

Post by abscate » Sat Feb 27, 2016 1:30 am

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?
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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
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erikv11
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Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Sat Feb 27, 2016 7:05 am

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.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

warmblood58
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Year and Model: 1995 850 T5-r
Location: SF Bay Area
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warmblood58

Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Sat Feb 27, 2016 11:29 am

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.

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erikv11
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erikv11

Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Sat Feb 27, 2016 1:08 pm

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?
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

warmblood58
Posts: 141
Joined: Wed Feb 24, 2016 9:42 am
Year and Model: 1995 850 T5-r
Location: SF Bay Area
Has thanked: 4 times
Been thanked: 0
United States of America
warmblood58

Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Sat Feb 27, 2016 2:04 pm

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!

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erikv11
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erikv11

Re: ECU Ground Connections Under Manifold Location?

Post by erikv11 » Sat Feb 27, 2016 3:06 pm

Ok good luck then! Sorry I don't know more about the ECU grounds ...
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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abscate
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abscate

Re: ECU Ground Connections Under Manifold Location?

Post by abscate » Sat Feb 27, 2016 3:26 pm

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
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

warmblood58
Posts: 141
Joined: Wed Feb 24, 2016 9:42 am
Year and Model: 1995 850 T5-r
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warmblood58

Re: ECU Ground Connections Under Manifold Location?

Post by warmblood58 » Sat Feb 27, 2016 9:35 pm

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.

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abscate
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Posts: 20447
Joined: Sun Feb 17, 2013 5:54 pm
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abscate

Re: ECU Ground Connections Under Manifold Location?

Post by abscate » Mon Feb 29, 2016 6:53 am

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?
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

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