Discussion
After losing yet another month that should have been spent sort the wedge rather than moving houses I finally got back to looking at the problems with it's lack of safety relay and omipresent cold start system.
Looks like it's going to be tracing all the wires to work out what a previous owner did. Fortunately I got a mate whose more electrically aware to help.
Quick question, what generates the engine running signal for the safety module the coil of the air flow meter? I've read a couple of articles on the injection system and they contradict themselves on this point. I'm hoping it's the coil as the air flow connector shows 0 resistance regardless of air meter position.
If it's not the air flow meter what is the electrical connector used for? It's on the inner wing side of the flow meter, next to the rubber elbow.
>> Edited by niva441 on Monday 10th October 20:10
Looks like it's going to be tracing all the wires to work out what a previous owner did. Fortunately I got a mate whose more electrically aware to help.
Quick question, what generates the engine running signal for the safety module the coil of the air flow meter? I've read a couple of articles on the injection system and they contradict themselves on this point. I'm hoping it's the coil as the air flow connector shows 0 resistance regardless of air meter position.
If it's not the air flow meter what is the electrical connector used for? It's on the inner wing side of the flow meter, next to the rubber elbow.
>> Edited by niva441 on Monday 10th October 20:10
There's a standard two pin switch (green on my car) on the air metering unit, the only electrical connection on there. Its a simple on/off affair. When the engine stalls the metering flap sits closed, because there is no air being drawn across the flap and this closes the stall switch, causing the fuel relay to open and hence the fuel pump to stop. A simple check is to turn the ignition on (but engine off) and disconnect the connector to the stall switch, in doing so you should hear the fuel pump whirr into life.
Regards
Iain
Regards
Iain
Ah well, now you're asking 
On the original version, there was just the kill switch on the AFM to stop the fuel pump.
Later Ford added two modules, one green and one pink. The pink one samples the coil LT pulses and as long as there are enough of them, it pulls in an internal relay and turns the fuel pump on. Not sure what was wrong with the original idea but there you go.... unless upon crashing, an inverted AFM wouldn't shut the pump off...
The green module has me beaten: I know WHAT it does, I just don't know why. It fires the cold start injector for no good reason that I can establish. All I do know is that several people with this later lashup have had no end of hot starting issues, that as far as I recall was never an issue to start with. Certainly my Tasmin and a Granada hearse that I used to drive never gave trouble, with the original installation.
The best theory that me and a mate concocted in the pub was that until the pink relay starts the fuel pump, there's not enough line pressure to fire the mechanical injectors. So the green relay presumably relies on the line pressure left in the system and empties it through the cold start injector, providing an initial kick to spin the engine fast enough to get the pink relay to turn the pump on...
On the original version, there was just the kill switch on the AFM to stop the fuel pump.
Later Ford added two modules, one green and one pink. The pink one samples the coil LT pulses and as long as there are enough of them, it pulls in an internal relay and turns the fuel pump on. Not sure what was wrong with the original idea but there you go.... unless upon crashing, an inverted AFM wouldn't shut the pump off...
The green module has me beaten: I know WHAT it does, I just don't know why. It fires the cold start injector for no good reason that I can establish. All I do know is that several people with this later lashup have had no end of hot starting issues, that as far as I recall was never an issue to start with. Certainly my Tasmin and a Granada hearse that I used to drive never gave trouble, with the original installation.
The best theory that me and a mate concocted in the pub was that until the pink relay starts the fuel pump, there's not enough line pressure to fire the mechanical injectors. So the green relay presumably relies on the line pressure left in the system and empties it through the cold start injector, providing an initial kick to spin the engine fast enough to get the pink relay to turn the pump on...
Thanks for the answers guys.
My fuel pump runs continuously, although I'll check the airflow switch is connected.
I'm not sure which version mine should have. As it's a black wired car that didn't finish build until 83. When did they fit the engine, although I'm guessing the wiring was done early in the build. So mine should use the orginal flap meter switch and the pink safety module I bought isn't needed.
When I put my multimeter across the air flow switch it showed zero resistance regardless of flap position. Can the switch alone be replaced or does the whole airflow meter need replacing?
However if the air flow meter switch needs replacing, as I've got the safety module then theoretically it should be straightforward to go to the later system. Replacing one of the conventional relays with the safety relays. I'll have to check which relay to replace. Since all the injection wiring diagrams I've seen are equivalent I assume it is a straightforward plug in job, no rewiring required.
So I don't necessarliy need the green cold start relay, the system should sort it's self out. My thermotime switch isn't perfect, so sorting that should help the cold start injector always wanting to be on (except when uplugged
).
Starting handles - one of the great underated features of my old Lada, especially when the starter has gone on the blink and you've just loctited the brake servo above it.
My fuel pump runs continuously, although I'll check the airflow switch is connected.
I'm not sure which version mine should have. As it's a black wired car that didn't finish build until 83. When did they fit the engine, although I'm guessing the wiring was done early in the build. So mine should use the orginal flap meter switch and the pink safety module I bought isn't needed.
When I put my multimeter across the air flow switch it showed zero resistance regardless of flap position. Can the switch alone be replaced or does the whole airflow meter need replacing?
However if the air flow meter switch needs replacing, as I've got the safety module then theoretically it should be straightforward to go to the later system. Replacing one of the conventional relays with the safety relays. I'll have to check which relay to replace. Since all the injection wiring diagrams I've seen are equivalent I assume it is a straightforward plug in job, no rewiring required.
So I don't necessarliy need the green cold start relay, the system should sort it's self out. My thermotime switch isn't perfect, so sorting that should help the cold start injector always wanting to be on (except when uplugged
). Starting handles - one of the great underated features of my old Lada, especially when the starter has gone on the blink and you've just loctited the brake servo above it.
The extra modules came in about '86/'87. The last of the 2.8 wedges had them as did the first S series cars.
I can't quite recall how the AFM switch worked but it was something like a daft bit of springy metal that was moved by the flap closing. IIRC there was an adjustable stop for the flap so is it possible the flap hits the stop but doesn't open the switch?
I can't quite recall how the AFM switch worked but it was something like a daft bit of springy metal that was moved by the flap closing. IIRC there was an adjustable stop for the flap so is it possible the flap hits the stop but doesn't open the switch?
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