One for the Lucas fuel-injection experts.....
Discussion
I've just been writing a description of the operation of the Lucas FI as used on the TVR/ Rover V8, and the schematic I have appers to show some form of wound component (i.e. a coil ;-) within the Airflow Meter. I can't work out what it must be; it could be a temp sensor I suppose, though that would normally appear as a resistor and not a coil. There is in fact ALSO a fixed resistance that may well be a temp sensor, but I can't tell that for certain either.
Now before I go and rip my car to bits, can anyone shed any light?
Cheers!
Ian
Now before I go and rip my car to bits, can anyone shed any light?
Cheers!
Ian
if the schematic you have is the hot wire version it could be the hot wire (!) .. actually it's something like a wire through which the current is varied to maintain it's temperature difference over another fixed current wire or something .. not really up on the internals of the hot wire airflow meter .. but could account for the two items in the diagram ..?
Not having seen the schematic, I'm just guessing that the circuit works as a wheatstone bridge. The 'hot' wire will have a current passing through it that heats it and it's temperature and thus resistance will vary in proportion to the airflow. This is 'compared' against a 'control' or fixed resistance that will enable a temperature compensated signal to be sent to the ECU so that the fueling can be adjusted.
E&OE
Graham
E&OE
Graham
Errrr.... Joolz et al: it's not a hotwire. The diagram is from the Haynes manual for the SD1; titled Injection System Post '84 or similar. Everything else on it is as my car AFAICT.
Ian
Edited to add: Joolz, don't have your email address handy, but wondered if you might have any use for a 500Kg electric hoist? Runs from 3-phase, that's the only limitation.... the price could be right if you play your cards etc. etc....!
>> Edited by wedg1e on Thursday 9th January 15:24
Ian
Edited to add: Joolz, don't have your email address handy, but wondered if you might have any use for a 500Kg electric hoist? Runs from 3-phase, that's the only limitation.... the price could be right if you play your cards etc. etc....!
>> Edited by wedg1e on Thursday 9th January 15:24
OK, thanks to Danny (and Joolz!
for the airflow meter diagram and test procedure. I have just about completed my thesis on the Lucas EFI and its applications in a wedge-shaped projectile 
, but feel it incumbent upon me to add to the aforementioned diagnostics routine with the following:-
"Disconnect the air hose from the OUTLET side of the flowmeter; with the multiplug disconnected, connect ohmmeter across pins 36 & 39. This should measure open-circuit. Insert a finger into the exit port of the flowmeter and swing the flap to the right. The meter should show short-circuit within a few degrees of swing. This is the safety switch that kills the fuel pump if the engine stops without the ignition being turned off. If the switch or its associated wiring went open-cct., you would have the symptoms that the car fires fine on the starter but dies as soon as you release the key."
The coily object I remarked on originally is actually a thermistor or similar: it has the correct symbol printed on one of the Haynes drawings but is shown as a coil on others. Confused? I was.
One thing I did notice from the diagnostics that Danny sent me is that the variable voltage from the flap pot does not alter during the first few degrees of swing of the flap. Obviously I don't know where the flap sits at idle, may have to find a way to get a fibrescope in there to see! In case anyone's interested, the voltage spans 3.65V to 1.55V as you move the flap through its travel.
There are two versions of the EFI circuit in the Haynes manuals for the SD1/ Rangey etc., one of them has the injectors numbered incorrectly as far as I can establish from comparisons with other diagrams and my own car (the implication being if you wired the car accordingly it may not run correctly since it would have some of the injectors in each bank 'crossed' - this is actually what I'd set out to verify in the first place). The correct version (100% to my '87 car and many others I'm sure) is Fig.13.86 on pp.248 of the SD1 manual. The injectors read (l-r) 1-3-5-7-2-4-6-8.
It may look complicated but it's not once you grasp what order things happen in: I've written an analysis and will email to anyone who's interested.
Ian
>> Edited by wedg1e on Tuesday 14th January 20:05
for the airflow meter diagram and test procedure. I have just about completed my thesis on the Lucas EFI and its applications in a wedge-shaped projectile , but feel it incumbent upon me to add to the aforementioned diagnostics routine with the following:- "Disconnect the air hose from the OUTLET side of the flowmeter; with the multiplug disconnected, connect ohmmeter across pins 36 & 39. This should measure open-circuit. Insert a finger into the exit port of the flowmeter and swing the flap to the right. The meter should show short-circuit within a few degrees of swing. This is the safety switch that kills the fuel pump if the engine stops without the ignition being turned off. If the switch or its associated wiring went open-cct., you would have the symptoms that the car fires fine on the starter but dies as soon as you release the key."
The coily object I remarked on originally is actually a thermistor or similar: it has the correct symbol printed on one of the Haynes drawings but is shown as a coil on others. Confused? I was.
One thing I did notice from the diagnostics that Danny sent me is that the variable voltage from the flap pot does not alter during the first few degrees of swing of the flap. Obviously I don't know where the flap sits at idle, may have to find a way to get a fibrescope in there to see! In case anyone's interested, the voltage spans 3.65V to 1.55V as you move the flap through its travel.
There are two versions of the EFI circuit in the Haynes manuals for the SD1/ Rangey etc., one of them has the injectors numbered incorrectly as far as I can establish from comparisons with other diagrams and my own car (the implication being if you wired the car accordingly it may not run correctly since it would have some of the injectors in each bank 'crossed' - this is actually what I'd set out to verify in the first place). The correct version (100% to my '87 car and many others I'm sure) is Fig.13.86 on pp.248 of the SD1 manual. The injectors read (l-r) 1-3-5-7-2-4-6-8.
It may look complicated but it's not once you grasp what order things happen in: I've written an analysis and will email to anyone who's interested.
Ian
>> Edited by wedg1e on Tuesday 14th January 20:05
wedg1e said:
There are two versions of the EFI circuit in the Haynes manuals for the SD1/ Rangey etc., one of them has the injectors numbered incorrectly as far as I can establish from comparisons with other diagrams and my own car (the implication being if you wired the car accordingly it may not run correctly since it would have some of the injectors in each bank 'crossed' - this is actually what I'd set out to verify in the first place). The correct version (100% to my '87 car and many others I'm sure) is Fig.13.86 on pp.248 of the SD1 manual. The injectors read (l-r) 1-3-5-7-2-4-6-8.
It may look complicated but it's not once you grasp what order things happen in: I've written an analysis and will email to anyone who's interested.
Ian
Since they aren't sequential (just bank fired) does it matter which injector is fired when?
Peter:
I'd noticed that some of the wiring colours to the injectors on my car differed from those shown in the Haynes manual (the colours were right, but the indicated injector numbers made things seem wrong).
First I wondered whether TVR simply swapped the wires round from the ECU, so it still fired right but the colours differed just for the hell of it. Then I thought maybe someone had had the EFI harness stripped to fault-find, and put it together wrongly (it has slit plastic covering as opposed to tape). Of course the injectors fire in banks, but the inlet manifolds are effectively separate, and if the injectors fired on the wrong bank I figured the fuel could be in the wrong place!
So I found an alternative diagram (for the TR8) that shows different loom colours to the SD1/ TVR, but the injector numbers differ from the Haynes SD1 and Rangey diagrams. With me so far?!
Next I pulled my ECU connector apart and found that whilst the colours conform to the SD1, the actual injectors the wires feed are as shown on the TR8 diagram.
My conclusions are (a) my car is correctly wired as the SD1/ Rangey, using the colours per the Haynes manual; (b) the Haynes diagram depicts the injectors numbered incorrectly. Note that there are two EFI drawings by Haynes; one (titled "Injection '82 -'84") shows a few extras such as the ignition switch, however that and the 'Post-'84' diagram are essentially identical. The '82-'84 diagram has the injector numbers wrong; the Post-'84 has no numbers at all! Helpful....
I've noticed that the wiring around the engine is becoming brittle and some of the injector plugs have damaged terminals, so I've been sourcing cable and connectors to rewire the injectors and so on. There is actually a fair bit of excess wiring tied up under the dash, so I was planning on making a neater installation. Should only cost about 30 quid for the bits.
If I get really bored I'm going to strip the ECU and trace the circuit.... I bet you can't get a diagram of THAT for love nor money!
Ian
I'd noticed that some of the wiring colours to the injectors on my car differed from those shown in the Haynes manual (the colours were right, but the indicated injector numbers made things seem wrong).
First I wondered whether TVR simply swapped the wires round from the ECU, so it still fired right but the colours differed just for the hell of it. Then I thought maybe someone had had the EFI harness stripped to fault-find, and put it together wrongly (it has slit plastic covering as opposed to tape). Of course the injectors fire in banks, but the inlet manifolds are effectively separate, and if the injectors fired on the wrong bank I figured the fuel could be in the wrong place!
So I found an alternative diagram (for the TR8) that shows different loom colours to the SD1/ TVR, but the injector numbers differ from the Haynes SD1 and Rangey diagrams. With me so far?!
Next I pulled my ECU connector apart and found that whilst the colours conform to the SD1, the actual injectors the wires feed are as shown on the TR8 diagram.
My conclusions are (a) my car is correctly wired as the SD1/ Rangey, using the colours per the Haynes manual; (b) the Haynes diagram depicts the injectors numbered incorrectly. Note that there are two EFI drawings by Haynes; one (titled "Injection '82 -'84") shows a few extras such as the ignition switch, however that and the 'Post-'84' diagram are essentially identical. The '82-'84 diagram has the injector numbers wrong; the Post-'84 has no numbers at all! Helpful....
I've noticed that the wiring around the engine is becoming brittle and some of the injector plugs have damaged terminals, so I've been sourcing cable and connectors to rewire the injectors and so on. There is actually a fair bit of excess wiring tied up under the dash, so I was planning on making a neater installation. Should only cost about 30 quid for the bits.
If I get really bored I'm going to strip the ECU and trace the circuit.... I bet you can't get a diagram of THAT for love nor money!
Ian
Steve:
Thanks for the tip, however the 20MOhm per volt meter I use is not likely to cause such damage. Probably a cheapo meter or even an old AVO 8 or similar may do though.
how about a Megger!?
I don't have major probs with my EFI, just wanted to assemble some diagnostics/ understanding of how the system works. You know how it is when the car suddenly develops a problem: unless you know what 'good' looks like, it's hard to decide what's 'bad'!
Ian
Thanks for the tip, however the 20MOhm per volt meter I use is not likely to cause such damage. Probably a cheapo meter or even an old AVO 8 or similar may do though.
how about a Megger!? I don't have major probs with my EFI, just wanted to assemble some diagnostics/ understanding of how the system works. You know how it is when the car suddenly develops a problem: unless you know what 'good' looks like, it's hard to decide what's 'bad'!
Ian
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