FIXED?! 20/2 electrical problems 944 2.7

[doctor924]

Hi All,

Last year I rescued a 944 2.7 from 5 years layup under a cover outside.
After 6 months renovation - the car was back on the road. With such a long layup - electrical problems were expected (and duly appeared). One persistent problem I have had trouble tracking down is the wash/wipe - and which has now caused me other problems. Here is the story:

Originally the water pump for the washers was faulty and this was changed - all OK
After a few months several wiper functions failed at the same time:

1) Wash and wipe, intermittent wipe and the first (slowest) wiper speed

I checked the wiring diagrams - but do find them hard to read. I did a couple of checks today and the following is noted:

a) No power to the water pump for the washers when I pull the switch
b) When checking power feed to the 'T' of the wiper relay - the 30amp fuse for the wipers blew (I had a multimeter between the T connection and earth)- again when the switch is pulled
c) When checking power feed to the wiper motor (connection no. 2) on the first wiper setting - the same fuse blew- when the switch is pulled

I removed the fuse board looking for any poor connections - found none.

Now - upon trying to restart the car - she initially fired - but I heard a loud click and then she wouldn;t start at all and the lovely "!" symbol lit on the dash.

Bypassing the DME relay (I have a spare direct feed to the fuel pump) - the car fired as usual - and I can energize the fuel pump relay by jumping the relevant connections as per Clark's garage.

So - here are my questions (and thanks for reading so far):

Q1) How likely is it I can have a failed DME relay just at this instance?
Q2) With the fuses blowing - I am getting power to the wiper relay and the wiper motor - but why are the fuses blowing when I try to insert my multimeter?
Q3) Any guidance on why I have lost the three wiper functions I noted at the start?
Q4) Are there any common points to account for the failed wash wipe/wiper/intermittent wiper function?

Thanks for reading!!!

Ian

(Car is 944 2.7 with Pro tuning chip)

 

[robwright]

Seized motor causing a high current drain???

 

[doctor924]

Thanks for the reply - I did check the motor (removing it) and its OK - wipers work on setting 2 but it is true that on setting three - the wipers actually slow down and a groaning noise can be heard...? Link to washing system? CHeers

 

[robwright]

Will have a look at the diagrams after Top Gear mate.

 

[robwright]

What are your thoughts about the steering column switch mate?

 

[doctor924]

yes - picked up a spare and swapped it in - no change. It is possible that was faulty - so will bypass it and try to see if that causes the functions to work.... What do you think about the highest wiper speed being quite slow?

 

[robwright]

From what I can see the speed control is all internal to the motor but activated from the stalk.

 

[doctor924]

hi-yes you might be right -had it apart and looked ok-but will look for a spare i think

 

[doctor924]

Hello Update for engine running porblem 1) Replaced DME relay with a new one and still no start (fuel pump not running). I checked the DMEs I have - and all of them (I now have 3!) pass Clarks tests So - car runs on jumpers between 87,87b and 30 Will not run with DME relays in situ. So with power to post 30 and looking at the circuit diagram - I need to check : a) If I have 12v to post 86 with ignition on b) If I have earth at post 85 c) If I have ground at post 85b Any other ideas anyone 2) Replaced the Wiper relay - and now when I turn the lever - the relay does click - but nothing else happens (before there was no click) - I'm still leaning towards a mechanical problem on the wiper motor? Any other ideas? thanks ian

 

[doctor924]

Update - after checking the 3 points above - the car started fine with the relay in place if I earthe post 85b (which should be earthed through the DME). So - looks like I have an earthing/DME fault - albeit a minor one.

 

[Hilux]

Post 30 is a permanent live so is the switched circuit supply Posts 85 and 86 are the ignition live and cause the permanent supply to be switched on to post 87 when the magetic coils are energised In most relays the larger circuit (and in some cases larger terminals) is through posts 30 and 87 with `b` designated terminals as subsidiaries. The post 85b will also be subsidiary ignition live. To properly test a relay energise posts 85 and 85 and see if the relay clicks. If it does it doesnt mean its ok as it may be earthing internally and preventing full power going through the switched terminals. To test fully you need to power the ignition terminals and also the switched terminals and measure the resistance across them once connected. It should be a fully open circuit with battery voltage. The ignition terminals will have resistance due to the magnetic coils.

 

[doctor924]

Thanks for the reply Paul - I checked the DMEs according to the Clark's guide and all had the stated correct resistance when the relay was energised.Does this still sound like I have an earth problem from the DME?

 

[peanut]

first of all you do not need to run a direct +12v supply to the fuel pump as well as use a 3xwire DME relay bypass at the same time or you'll have 2x independant power supplies to the fuel pump simultaneously which will cause problems. When you use the 3x way bypass a +12v supply is fed directly to the fuel pump permanently even with the ignition off. (the fuel pump is constantly earthed to chassis on the rear valance underneath the rear hatch lock GP1/MP1 ) if the fuel pump runs and the engine starts when you insert the DME relay bypass ..... but doesn't run when the DME relay is inserted there are only a few possibilities. 1. The DME relay is faulty 2. One or more of the ECU sensors supplying the ECU are faulty 3. ECU is faulty 4. Faulty ignition switch or supply wire from ignition switch to the DME relay terminal 86 5. Terminal 85 of the DME relay is not being grounded at earthing point MP ll 6. faulty alarm or immobiliser Explanation The DME relay has two independant relays contained in one case. Terminal 30 of the DME relay is fed with a constant +12v from the battery. Inside the DME relay It feeds both relay switches When you switch the ignition on, +12v from the ignition switch is fed to terminal 86 on the primary coil of the first relay. The +12v passes through the coil to terminal 85 and then to earth at earthing point MP ll (see car earth schematic) thus switching on the first relay. This causes the +12v sitting on terminal 30 of the DME relay to be connected internally to terminal 87 which then supplies +12v to both the ECU and the fuel injectors. So before you crank the engine the ECU has a +12v supply ,your fuel pump has been activated for about 1/2 second to pressurize the fuel system and the injectors have a +12v feed and various sensors have a +12v supply. When you crank the engine ,( providing the ECU sees the correct /data voltages from your crank sensor , engine temperature sensor, 02 sensor etc ) the ECU earths the +12v sitting on terminal 85b of the DME relay which switches +12v to terminal 87b of the DME relay which then feeds +12v to the fuel pump. Now that both the DME relays are activated the ECU , fuel pump, injectors, and various sensors are all supplied with +12v and the engine shouls start and run. When you replace the DME relay with a 3 x way bypass you effectively bypass both of the DME relay switches ,all the sensors and the ECU .

 

[doctor924]

Thanks Nick - I followed Clarks guide for these points and agree that the diagnosis is limited as to what the causes can be. I do see 12 v on terminal 87 when cranking and then in position 2, but as noted above - I have lost the earth which the DME supplies to terminal 85b. So by your list: 1. The DME relay is faulty - all those I have have been checked as per Clarks guide (and energised) and pass those tests 2. One or more of the ECU sensors supplying the ECU are faulty - possible - I'll have to check 3. ECU is faulty - aargh I am already running on a replacement ecu as the original (which had stood for 5 years was past it) 4. Faulty ignition switch or supply wire from ignition switch to the DME relay terminal 86 - checked and OK 5. Terminal 85 of the DME relay is not being grounded at earthing point MP ll - this seems to be the first cause of the problem - earthing here with a bypass does allow the car to start - it seems this is an electronic switched ground from the DME rather than being a fixed wired ground? 6. faulty alarm or immobiliser - I'll run the Clarks bypass and see if this allows a start How many of the above though - would result in a lack of earth to terminal 85? Are all these causes independent or dependent though?? Thanks Ian

 

[peanut]

ORIGINAL: doctor924 . I do see 12 v on terminal 87 when cranking and then in position 2, but as noted above - I have lost the earth which the DME supplies to terminal 85b.

The DME ? ( a less confusing description is ECU ) does not provide an earth to the DME relay terminal 85 according to the electrical schematics I have. The ECU receives its power supply from the primary relay so it cannot work at all until terminal 85 is earthed. (It is terminal 85b of the secondary DME relay which is earthed by the ECU so that the ECU controls the fuel pump supply.) Terminal 85 goes directly to earthing point MP ll on the chassis. If there is no earth to terminal 85 and the primary relay coil is not being energised when the ignition is switched on I would suggest that you take a piece of insulated cable from terminal 85 and take it to a good chassis earth and try that.! If you do that the primary relay will work providing you have +12v on terminal 86 when you switch the ignition on. (Or clean up the terminal 85 earthing point MP ll which is just forward of your relay/fuse box.) If a direct earth to terminal 85 doesn't start the car then it would suggest that you have a problem with the ECU not grounding the secondary DME relay which supplies +12v to the fuel pump ..Probably a sensor issue. Ian I have written a complete explanation of how the DME and ECU work to start the engine because at some point it may help other members understand what is happening to their cars and help others fault find their starting problems. These DME related non-starting problems are becoming increasingly common and are very frustrating.

 

[peanut]

just to clarify . If when you turn the ignition on there is +12v on terminal 85 (which goes directly to a good earth) it must mean that the primary DME relay is working as it should and that the ECU and the injectors are receiving +12v from terminal 87 and if when you crank the engine there is +12v on terminal 87b it must mean that the secondary DME relay is working as it should and the fuel pump is receiving +12v from terminal 87b If the car is then not starting you will need to look at the sensors

 

[doctor924]

Thanks Nick - that does clarify. So: If when you turn the ignition on there is +12v on terminal 85 (which goes directly to a good earth) - YES it must mean that the primary DME relay is working as it should and that the ECU and the injectors are receiving +12v from terminal 87 - YES and if when you crank the engine there is +12v on terminal 87b it must mean that the secondary DME relay is working as it should and the fuel pump is receiving +12v from terminal 87b If the car is then not starting you will need to look at the sensors OK - but I do know that the fuel pump is NOT energised without earthing 85b (which should come from the DME) - without which of course the secondary relay of the DME will not activate and will not allow 12v on terminal 87b

 

[peanut]

Hi Doc well we are very nearly there methinks.[] if terminal 87 has +12v on it when the ignition is on, then the primary relay is energised and therefore the injectors and the ECU should both receive +12v I presume that you have verified that the injectors are receiving +12v from terminal 87 of the DME relay with the ignition on yes ? To check that the ECU is also receiving +12v from terminal 87 you will need to test on terminals 18 and 35 of the ECU electrical connector. Whatever you do,do not accidently use the multimeter on the actual spade connectors of the ECU itself, just test the wiring loom electrical connector . I can supply the schematic if you need it. ( terminals 18 and 35 are joined together in the loom and are fed by a single wire from terminal 87 of the DME relay. The only way I can see that you can test that the DME secondary relay is energising whilst cranking the engine, is to check if the fuel pump is pumping. Without the engine running there is no fuel used but excess pressure should constantly be being released from the FPR valve so you should be able to feel or listen to the relief pipe from the FPR and hear the fuel going back to the tank. Alternatively you could remove the pressure test nut on the fuel rail ( watch out for the big ball bearing seal ) and wedge a short piece of garden hose pipe over the spigot. Run the pipe into a clear plastic container like a pepsi bottle and crank the engine. As long as the fuel pressure loss is not too great the ECU shouldn't shut the DME secondary relay off which would of course give a false indication . If you try this I would suggest you partially clamp the hose so that some pressure will build and yet some fuel will be passed into the bottle providing the fuel pump is pumping. I must admit I'm leaning towards a problem with one of the sensors the crank sensor or the engine temperature sensor.

 

[peanut]

ORIGINAL: doctor924 Update - after checking the 3 points above - the car started fine with the relay in place if I earthe post 85b (which should be earthed through the DME). So - looks like I have an earthing/DME fault - albeit a minor one.

ORIGINAL: doctor924 Thanks Nick - as noted above - I have lost the earth which the DME supplies to terminal 85b. 5. Terminal 85 of the DME relay is not being grounded at earthing point MP ll - this seems to be the first cause of the problem - earthing here with a bypass does allow the car to start - it seems this is an electronic switched ground from the DME rather than being a fixed wired ground?

seems to be a little confusion here but 85 is the ground to the primary relay (goes straight to earth point MP l ) and 85b is the ground for secondary relay which is grounded by the ECU (provided that it is receiving a +12v supply from terminal 87 when the the primary DME relay is energised)

 

[doctor924]

[8|] Brain engaged....to start the car at present, with the DME relay in situ I need to manually ground 85b - which I am presently doing through an earth connection to the spade terminal of the DME relay when it is inserted. As noted above, this allows the car to start and run fine - but that the fuel pump is now energised on the 2 position of the ignition switch as well as when cranking and releasing the key when the engine fires. []