Silly Electrical Questions
Discussion
Help!
My 1986/7 280i is in bits, as I am working on several things as the mood tales me.
I have not yet fitted my new fuel pump. Putting a voltmeter across the fuel pump wires I have no voltage with the ignition switch in the Off and Run positions, but 11 volts in the Start position. At the engine end, I have the plenum off as well as some of the emissions controls disconnected.
Question 1. How do I get 12 volts to the pump in the Run position?
When cranking I do not get a spark, using an ignition wire from the distributor to a new spark plug which is well earthed. However I do get a spark with the ignition wire from the coil to the plug, when I turn the ignition switch on and off (the spark is when I turn it off)
Question 2. Does this mean the electronic ignition module is buggered, or is it something much simpler?
I have played with cars for many years, but am having a mental blockage on these two very basic things.
Wilf.
My 1986/7 280i is in bits, as I am working on several things as the mood tales me.
I have not yet fitted my new fuel pump. Putting a voltmeter across the fuel pump wires I have no voltage with the ignition switch in the Off and Run positions, but 11 volts in the Start position. At the engine end, I have the plenum off as well as some of the emissions controls disconnected.
Question 1. How do I get 12 volts to the pump in the Run position?
When cranking I do not get a spark, using an ignition wire from the distributor to a new spark plug which is well earthed. However I do get a spark with the ignition wire from the coil to the plug, when I turn the ignition switch on and off (the spark is when I turn it off)
Question 2. Does this mean the electronic ignition module is buggered, or is it something much simpler?
I have played with cars for many years, but am having a mental blockage on these two very basic things.
Wilf.
Fuel pump - on the 2.8 the fuel pump should only run when the engine is running.
You will (or should!) have either standard relay(s) connected to the fuel metering head, or a purple/pink relay.
The early type had a switch on the metering head, so that when the metering flap lifts, the pump runs.
The later type has the pink relay module, which runs the pump every time it sees an ignition spark. It should run the pump for 2 secs after power switched on..
I know there was added emission stuff for US models, but I don't think the pump setup changed
The pump being live when crank/start engaged on switch sounds a bit strange to me..
You will (or should!) have either standard relay(s) connected to the fuel metering head, or a purple/pink relay.
The early type had a switch on the metering head, so that when the metering flap lifts, the pump runs.
The later type has the pink relay module, which runs the pump every time it sees an ignition spark. It should run the pump for 2 secs after power switched on..
I know there was added emission stuff for US models, but I don't think the pump setup changed
The pump being live when crank/start engaged on switch sounds a bit strange to me..
pasogrande said:
When cranking I do not get a spark, using an ignition wire from the distributor to a new spark plug which is well earthed. However I do get a spark with the ignition wire from the coil to the plug, when I turn the ignition switch on and off (the spark is when I turn it off)
Question 2. Does this mean the electronic ignition module is buggered, or is it something much simpler?
I have played with cars for many years, but am having a mental blockage on these two very basic things.
Wilf.
Rotor arm?Question 2. Does this mean the electronic ignition module is buggered, or is it something much simpler?
I have played with cars for many years, but am having a mental blockage on these two very basic things.
Wilf.
Wow! That was quick!
Andy, that surprised me. I expected the pump to run both when cranking and when running; also when the ignition switch is in those positions. I have two ignition relays (numbers 14 & 15 on diagram) and they both tested good.
Ian, that's too obvious! I didn't check it. I'll go out now and see what I see.
Thanks,
Wilf.
Andy, that surprised me. I expected the pump to run both when cranking and when running; also when the ignition switch is in those positions. I have two ignition relays (numbers 14 & 15 on diagram) and they both tested good.
Ian, that's too obvious! I didn't check it. I'll go out now and see what I see.
Thanks,
Wilf.
Is the carbon centre brush still present inside the distributor cap? Without it you'll get no connection through the distributor from the coil lead to any of the plugs... and just because the rotor arm looks mint doesn't mean it hasn't tracked and is leaking your HT current straight to earth. Try another 
Ian,
Yes, the carbon rod is still there and in perfect condition. It is a Bosch, so maybe I can buy spares here.
Can you think of any simple test to be certain nothing is tracking?
I mentioned I got a spark using a plug wire from the distributor to a new earthed plug, when I turned the key off. It was not as strong a spark as I would have expected. I doubt if it affects anything, but I noticed the blue ballast wire is disconnected.
Wilf.
Yes, the carbon rod is still there and in perfect condition. It is a Bosch, so maybe I can buy spares here.
Can you think of any simple test to be certain nothing is tracking?
I mentioned I got a spark using a plug wire from the distributor to a new earthed plug, when I turned the key off. It was not as strong a spark as I would have expected. I doubt if it affects anything, but I noticed the blue ballast wire is disconnected.
Wilf.
pasogrande said:
Ian,
Yes, the carbon rod is still there and in perfect condition. It is a Bosch, so maybe I can buy spares here.
Can you think of any simple test to be certain nothing is tracking?
I mentioned I got a spark using a plug wire from the distributor to a new earthed plug, when I turned the key off. It was not as strong a spark as I would have expected. I doubt if it affects anything, but I noticed the blue ballast wire is disconnected.
Wilf.
It may well be an ignition module fault. Essentially what is happening when you turn the ignition off is the same as when the module (or points in the good old days) switches primary voltage off: the electromagnetic field in the coil collapses and this produces HT in the secondary (spark plug) side. If you turned the ignition on and off rapidly you'd probably notice a stream of sparks as if the points (or ignition module) were firing. HOWEVER... you did say that some of the wiring is disconnected so the ignition module could be OK but something else is at work to prevent the HT firing. I know that later V6 installations as used on the 'S' series cars and very late 280i's had certain electronic modules added (one looks for the spark plugs firing before it'll start the fuel pump) and if this has been removed it would cause starting problems... depends on whether your car has it.Yes, the carbon rod is still there and in perfect condition. It is a Bosch, so maybe I can buy spares here.
Can you think of any simple test to be certain nothing is tracking?
I mentioned I got a spark using a plug wire from the distributor to a new earthed plug, when I turned the key off. It was not as strong a spark as I would have expected. I doubt if it affects anything, but I noticed the blue ballast wire is disconnected.
Wilf.
The ballast resistor being disconnected may or may not be a problem: on a ballasted system the resistor is in series with the coil primary side, the coil being rated for typically 6 or 8 volts. The resistor acts to drop the nominal 12v to a point where the coil can run happily.
Then, when you turn the key to crank the engine, the massive load put on the battery by the starter motor causes the battery voltage to drop, so the coil doesn't 'see' enough voltage to work properly. So the ignition switch (or, usually, the starter solenoid) has another wire from the cranking position direct to the coil, bypassing the ballast resistor so that the full battery voltage is available to run the coil while the engine is trying to start. When you release the key, this feed breaks leaving the ballast to run the coil.
Now, if the coil has been replaced with a 12v type, it won't require the ballast as otherwise the 'dropped' voltage would be too low to run the coil, so the ignition live feed goes direct to coil (+) instead of via the resistor.
Diagnosis by remote control is always a tad difficult so don't be surprised if it turns out to be something totally unrelated
Wilf,
Compared to some of the others on here I feel quite under qualified to reply, but I wanted to throw in a couple of things... Your fuel pump having 11V only during cranking is correct. There is a pink relay that receives a signal from the ignition module when it is trying to fire. The pink relay provides power to the fuel pump, extra air valve and warm up regulator.
I don't know how to check with a voltmeter, but I would confirm that the distributor is sending a pulse signal to the ignition module. It has 3 wires, brown goes to ground, then black/red and green/yellow must be the signal. If it is an inductive sensor, you should be able to see a very small voltage change across these as you rotate the shaft, or crank the engine.
If all else fails, rockauto have an ignition module for $28, and I have bought a distributor cap and rotor from my local Autozone. The cap wasn't a perfect fit with the leads, but it works fine. Mine is a 1987 S with the same engine, so I am assuming that the parts are common.
David
Compared to some of the others on here I feel quite under qualified to reply, but I wanted to throw in a couple of things... Your fuel pump having 11V only during cranking is correct. There is a pink relay that receives a signal from the ignition module when it is trying to fire. The pink relay provides power to the fuel pump, extra air valve and warm up regulator.
I don't know how to check with a voltmeter, but I would confirm that the distributor is sending a pulse signal to the ignition module. It has 3 wires, brown goes to ground, then black/red and green/yellow must be the signal. If it is an inductive sensor, you should be able to see a very small voltage change across these as you rotate the shaft, or crank the engine.
If all else fails, rockauto have an ignition module for $28, and I have bought a distributor cap and rotor from my local Autozone. The cap wasn't a perfect fit with the leads, but it works fine. Mine is a 1987 S with the same engine, so I am assuming that the parts are common.
David
Just to clarify that last post - if you have TWO standard relays for the pump, then you should also have a connector on the metering head (as Zig says above). Pulling the connector of should start the pump running.
Two relays are required because the metering head switch makes (i.e. is ON) when metering flap is at rest (engine not turning), so first relay effectively reverses the signal for the second relay, which is the power feed to the pump.
If you don't have a connector on the metering head , THEN you should have the pink relay type setup.... I don't know of any other arrangements, and you did say you have two relays.
I don't know much about the ignition modules, but I guess there are several things which can go wrong, standard type mechanical stuff (rotor arm, pickup, leads etc), and then the electrical side (faulty pickup, faulty module) .
Have you checked the dizzy turns and the valves go up and down ? (not as stupid as it sounds... the cam drive can fail quite suddenly - I've had that happen to me !!)
Two relays are required because the metering head switch makes (i.e. is ON) when metering flap is at rest (engine not turning), so first relay effectively reverses the signal for the second relay, which is the power feed to the pump.
If you don't have a connector on the metering head , THEN you should have the pink relay type setup.... I don't know of any other arrangements, and you did say you have two relays.
I don't know much about the ignition modules, but I guess there are several things which can go wrong, standard type mechanical stuff (rotor arm, pickup, leads etc), and then the electrical side (faulty pickup, faulty module) .
Have you checked the dizzy turns and the valves go up and down ? (not as stupid as it sounds... the cam drive can fail quite suddenly - I've had that happen to me !!)
Thanks Everybody,
I am getting confused-er and confused-er.
I do not believe I have a pink relay. There is a cream colored safety control module which is fitted on US models (not the purple one on UK models)
I have no electrical connection to the fuel distributor (is this the metering head?). I do have a connector to the frequency valve, which is like an extension to the fuel distributor, kind of where Ziga indicates a green plug.
Yesterday I drove across Florida to a seafood festival and got nothing done here. In a few minutes I am heading up to a local British car show; I did check that the rotor arm rotates. I will be back on it this afternoon - or tomorrow morning.
Wilf.
I am getting confused-er and confused-er.
I do not believe I have a pink relay. There is a cream colored safety control module which is fitted on US models (not the purple one on UK models)
I have no electrical connection to the fuel distributor (is this the metering head?). I do have a connector to the frequency valve, which is like an extension to the fuel distributor, kind of where Ziga indicates a green plug.
Yesterday I drove across Florida to a seafood festival and got nothing done here. In a few minutes I am heading up to a local British car show; I did check that the rotor arm rotates. I will be back on it this afternoon - or tomorrow morning.
Wilf.
Not seen a cream coloured module in UK....is one of those 'impact' ones ? (i.e. it has a little button which pops up if module senses more than a defined impact force. The ones I've seen require the button/plunger to be pushed in to reset ?
Yes metering head = fuel distributor - the one with all the pipes !!
Another thought from your description - does anyone know if the US spec TVRs had the KE injection system instead of basic K ??
KE system was used in Audis and VWs (and others) and has a small electronic module to trim the fuel mixture to get extra low CO emission. It has an extra module on the side of the fuel distributor/head to trim the fuel pressure to control the mixture. It does have a plug on the side, but BELOW the head itself, on the body by the main fuel pipe (= fuel in). I don't think Ford UK used it, but possibly for US ??
I guess going back to basics is the only way then. I would start with...
Connect single spark plug to ign coil (and earth point) and see if it sparks when cranking. If so, module coil and pickup OK...
Take out one injector, check it sprays when engine cranks.... A pain to do, but if there's no other choice....
Electrical - if it's been standing for a while, have you checked earth returns are OK ?
It's my pet hate with GRP cars !! Had a few in my time, and dodgy earths are very common, and can cause all sorts of wierd behaviour. I had a Scimitar which would melt the throttle cable - turns out it was the last earth return for the engine block when proper one wasn't working..
I hope this helps !!
Yes metering head = fuel distributor - the one with all the pipes !!
Another thought from your description - does anyone know if the US spec TVRs had the KE injection system instead of basic K ??
KE system was used in Audis and VWs (and others) and has a small electronic module to trim the fuel mixture to get extra low CO emission. It has an extra module on the side of the fuel distributor/head to trim the fuel pressure to control the mixture. It does have a plug on the side, but BELOW the head itself, on the body by the main fuel pipe (= fuel in). I don't think Ford UK used it, but possibly for US ??
I guess going back to basics is the only way then. I would start with...
Connect single spark plug to ign coil (and earth point) and see if it sparks when cranking. If so, module coil and pickup OK...
Take out one injector, check it sprays when engine cranks.... A pain to do, but if there's no other choice....
Electrical - if it's been standing for a while, have you checked earth returns are OK ?
It's my pet hate with GRP cars !! Had a few in my time, and dodgy earths are very common, and can cause all sorts of wierd behaviour. I had a Scimitar which would melt the throttle cable - turns out it was the last earth return for the engine block when proper one wasn't working..
I hope this helps !!
Edited by RCK974X on Sunday 10th February 19:47
Edited by RCK974X on Sunday 10th February 19:50
Apparently the cream coloured saftey relay fitted in the relay loom to the US cars can be replaced by a standard headlamp relay for testing the fuel injection system but must be replaced afterwards..If the fuel pressure drops for any reason then power will be cut to the fuel pump even if the ignition is still on..Hope this helps...Ziga
Thanks everybody. I took a couple of days off to go to a Seafood Festival and yesterday to a British Car Show. There were about 160 cars, but no wedges; there used to be five or six. There was a 1960 Griffith 200 and a mint 2500. Apart from the usual MG, Triumph, Jaguar & Lotus there were some nice old ones - like a 1937 BSA Scout!
I am trying to follow Andy's method "going back to basics is the only way", as it is also how my slow brain works. On photocopies of the wiring diagram sheets I am marking everything that works; then trying to see what that means. Between my coil and distributor is the electronic control module, which is supposed to amplify the voltage to give a better spark. I took it off - it has those connectors which you are supposed to separate by pulling the wires, not the connector halves! The unit has a lot of oxidation but otherwise looks okay. It is made in USA and has a paper Borg Warner label. Surprisingly all the ones I can find are in the UK.
Do your cars have this module? The wiring diagram shows three wires entering and leaving it; on mine, one plug has two wires the other four.
Tomorrow I will try a regular relay instead of the cream one.
Still confused,
Wilf.
I am trying to follow Andy's method "going back to basics is the only way", as it is also how my slow brain works. On photocopies of the wiring diagram sheets I am marking everything that works; then trying to see what that means. Between my coil and distributor is the electronic control module, which is supposed to amplify the voltage to give a better spark. I took it off - it has those connectors which you are supposed to separate by pulling the wires, not the connector halves! The unit has a lot of oxidation but otherwise looks okay. It is made in USA and has a paper Borg Warner label. Surprisingly all the ones I can find are in the UK.
Do your cars have this module? The wiring diagram shows three wires entering and leaving it; on mine, one plug has two wires the other four.
Tomorrow I will try a regular relay instead of the cream one.
Still confused,
Wilf.
Hi Mate..Is it the same as this as this is the ignition module..It could be playing up but i would do the relay test first...Replace the cream relay with a normal headlight relay and see if you have power to the fuel pump..replace the cream relay afterwards even if the pump works...If it does then the relay is fugged..Replace with the same type...Ziga
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