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We may be getting sidetracked here by battery ground points in the 944.
Clearly late UK and Euro cars have the battery in the boot well whereas ROW (rest of world) cars have the battery under the bonnet or hood .
Whilst the battery negative ground point attachement points are in different places they achieve the same result.
Getting back to the issue of where the DME relay and ECU grounds are attached to the car chassis I can see no difference in ROW or Euro/UK cars.
The DME relay conprises 2x relays in one housing.
The first DME relay coil has two terminals 85 & 86 (marked on the socket and relay base).
When the ignition is switched on 12v+ is fed via a black wire to terminal 86 ( going through the relay coil to terminal 85 . Terminal 85 is then grounded by a brown wire to ground point GPlll
GPlll is therefore the point at which the DME relay is grounded and a crucial ground point to keep clean.
The first DME relay coil switches the 12v+ sitting on DME terminal 30 to the ECU supplying the ECU with power all the while the ignition switch is on.
(Terminal 30 on the DME relay is constantly live with 12v+ whether ignition on or not.)
The second DME relay coil comprising terminals 87 & 85b is energised by the ECU depending on the data received by the various sensors .This coil switches a second switch which supplies the 12v+ sitting on terminal 30 to the Fuel pump via Fuse 34 . The fuel pump is grounded to the chassis on the rear valence under the hatch lock (GP1) this is therefore also an important ground point to keep clean and conductive.
The fuel injectors and ignition system are pulse grounded within the ECU as are all the sensors and a crucial ground point for the ECU housing goes to GPll although I am unable to locate this on a schematic atm
If anyone can see any errors in this explanation please say so that I can correct it. My intention is for it to be an aid to those with poor starting /running issues as the schematics are not the easiest to follow.
The only thing to add would be that the ground point you are unsure of the on the rear of the engine, below the heater control valve. And does get very corroded.
Just so I know for the future, how does a euro car run it ground cables? Myassumption would have been 1to the body and 1 to the tail of the transmission, since this is how I did it on my battery reloction.
The only thing to add would be that the ground point you are unsure of the on the rear of the engine, below the heater control valve.
Mark
I'll have to check this physically on my car to be certain. There is a huge brown cable just beneath the heater control valve as you say but I cannot see where it attaches . Is it to the engine or to the transmission tunnel ? this must be the earth from the ECU or GPll yes ?
Everyone talks about the importance of the ground points on the bell housing. Could someone tell if there is any way at all to get at these without removing the intake manifold and everything that goes with it? Please be specific. It looks like you could possibly get to them with a long socket extension and removal of the heater hose. Which brings up a probably dumb question. Is it okay to remove the heater hose without draining coolant? One other thought, has anyone ever tried cleaning these grounds chemically? In other words get the bolts loose enough to get some kind of liquid corrosion cleaner in around them and then tighten every thing back up. Thanks much for any assistance. 87 Turbo by the way.
Last edited by dinodanny; 09-10-2012 at 02:20 PM.
Reason: error
it doesn't matter where you connect the engine to chassis you can put a strap wherever is convenient . On the 944S2 the strap is between the rear of the cylinder head to the bulkhead or firewall so its reall easy to get to. What you are trying to achieve is to supply a good earth to the starter motor because otherwise your starter would be isolated by the rubber engine mounts
If you suspect that you have a poor earth then connect one end of one of your jump leads to a clean point on the engine and the other end on either the chassis or the earth terminal of the battery .If the car starts more readily then you need to improve your earthing.
Everyone talks about the importance of the ground points on the bell housing. Could someone tell if there is any way at all to get at these without removing the intake manifold and everything that goes with it? Please be specific. It looks like you could possibly get to them with a long socket extension and removal of the heater hose. Which brings up a probably dumb question. Is it okay to remove the heater hose without draining coolant? One other thought, has anyone ever tried cleaning these grounds chemically? In other words get the bolts loose enough to get some kind of liquid corrosion cleaner in around them and then tighten every thing back up. Thanks much for any assistance. 87 Turbo by the way.
OK, you are on the right track - IIRC, using long 3/8" extension(s) and a universal joint makes it possible to get to the bellhousing ground point. The real issue however is making sure not to drop the 10mm bolt, washer, or socket down into the bellhousing through the inspection hole that is open! If that happens, you have to remove the bellhousing to retrieve the lost item and that is a BIG job. If you can get access to the inspection hole, you can put a piece of 2" wide duct tape over it to save the headache you will get when something drops in there. You really want to avoid that from happening.
If you remove the heater control valve, drain some of the coolant - at least below the level of the HCV - otherwise it will drain into - yep you guessed it - the bellhousing.
If you suspect the bellhousing ground, try tighten/loosen/tightening the 10mm bolt without completely removing it. That might help. I don't think spraying corrosion cleaner down there will help much, but it probably won't be good for the clutch.
When you get it all apart, sandpaper the lugs to clean the contacts and follow with some electrical conductivity grease before reassembly - this helps keep the corrosion issue at bay.
Well I got to the grounds without removing the intake manifold but it was a pain. I disconnected, moved, and removed all of the wires, hoses and brackets that were in the way and shoved a rag in the inspection hole. With an extension and u-joint I was able to get to the ground bolts. Got every thing cleaned up nice and shiny and put it all back together. Unfortunately it didn't solve my gauge problems. The temp gauge still jumps around and then settles at the third mark and the oil pressure gauge stays pegged. Back to the drawing board.
Have you already cleaned all of the grounds for the instrument panel underneath the dash, pulled the instrument panel and cleaned the ground points on the board, and checked the wiring to ensure it is still viable? The newest of the 944/968 cars are over 15 years old making the wiring suspect... I will be replacing my battery and starter wiring this winter.
Have you already cleaned all of the grounds for the instrument panel underneath the dash, pulled the instrument panel and cleaned the ground points on the board, and checked the wiring to ensure it is still viable?
Yep. Other than the grounds in the rear hatch I've cleaned them all including the football grounds on the back of the instrument cluster.
The temp gauge has been acting up for some time and the oil pressure gauge more recently. I should have also mentioned that the temp gauge will sometimes return to normal if I tap on the cluster lens. I think I'm going to check the connections and then start testing the individual components and maybe bleed the coolant system. Never done that before but I'm sure someone on the forum has and can pass on the info.
The temp gauge has been acting up for some time and the oil pressure gauge more recently. I should have also mentioned that the temp gauge will sometimes return to normal if I tap on the cluster lens. I think I'm going to check the connections and then start testing the individual components and maybe bleed the coolant system. Never done that before but I'm sure someone on the forum has and can pass on the info.
Lol. Obviously at this point the gauge is bad. It happens. Replace the cluster (or that part of the cluster, all 3 units come out and are replaceable, so to keep your odo on, you can just replace that part). Heck, if it wasn't in storage I could sell/give for shipping what you need.
Also, your oil pressure sender could be bad (or again, cluster component). If it's pegged as soon as it gets power, it's wired backwards. If not, it's the sender, or the gauge. No biggie either way.
To revive this, I am about to clean some of the ground points in my S2 (LHD German delivered). Here is a photo of the LH side under headlight chassis rail...
And the one's behind the engine...
Meanwhile though, in an attempt to rectify my fuel gauge under-reading when full, and also voltmeter reading, I went under the dash and found 4x ground points... thought there were only two?
Oh, and slight off-topic, but still under the dash - anyone know what these plugs may have been connected to?... if anything? ...
09-21-2010, 07:09 AM
. You really want to avoid that from happening.
