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Discussion Starter · #1 ·
I've been working through improving my mpg (another thread), and in doing so I've had my original lucas injectors cleaned and tested, new ecu, and new wires/plugs, distributor cap, rotary arm as well as new cats and O2 sensors. All parts from rovers north or AB.

I did this massive replacement of many parts because my gas mileage has been terrible, (6-8 mpg).

Over the past 2 tanks, my O2 trims started looking strange. My even bank of injectors was -25%. Odd bank seemed within reason.

I had noticed a chuffing on the even side (also another thread), so I replaced gaskets on the exhaust manifold. It fixed the sound, but I can still hear it happening inside the manifold. There sounds air puffing. As of this eve, I picked up a popping/crackle from the exhaust. So it SEEMS like I'm working with a foul injector, or bad harness. Thing is, the injectors were cleaned and tested, and I used a test light at each harness and it's flashing.. showing each is getting pulse. Now, one of the harnesses looks kinda ugly/stripped, but it seems to be working ok.

I have tried pulling the injector harnesses to see if one is suspect, but they all have about the exact same effect when I pull. Drops about 50 rpm... stabalizes. Plug it back in, and it goes up 50 rpm... then stabilizes.

I've tested spark, and each works, all new champion rovers north defender/rrc plugs.

I can't really figure out how to move forward. I also swapped the O2's around to see if one was reading weird, but they show ok... and I'm sure I'm still getting rich readings on the even bank.

Only thing I can think of is to swap the injectors left/right and see if it follows sides. That might indicate I'd just need new injectors all around. But, thing is, I get the exhaust pop no matter which injectors on that bank I disconnect. It idles weird, and seems to cycle through rpm dips randomly.

Rovergauge doesn't turn up anything remarkable. All sensors working/reading ok. Drives ok just fine, just idles rough, and I've got this overfueling on that even bank.
 

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1970-1995 Range Rover Classic
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Compression test it, burnt exhaust valve?
 

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Discussion Starter · #4 ·
Compression test was good, 110 psi all around. Plugs look good. Cam was replaced with a crower before I purchased. Injectors cleaned and tested, took oscilliscope at injector harness and the signal looks clean and even. I was pulling the harness off injector 2, and as the harness moved around I got a near stall... then the fans kicked on. I turned the car off and the fans ran for 10 min. That was really strange, and I couldn't repeat it.
 

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Discussion Starter · #5 ·
I'm going to check the alternator, ignition coil, and ignition amp. I am also going to check the color of the spark. I'm not sure it's blue, like it should be.
 

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1989 Range Rover Classic
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Compression test was good, 110 psi all around. Plugs look good. Cam was replaced with a crower before I purchased. Injectors cleaned and tested, took oscilliscope at injector harness and the signal looks clean and even. I was pulling the harness off injector 2, and as the harness moved around I got a near stall... then the fans kicked on. I turned the car off and the fans ran for 10 min. That was really strange, and I couldn't repeat it.
Hmmmm 110 psi all round is pretty low. Assuming your 4.6 has the later rotating assembly, you should have 9.35:1 compression, and should see betwee 160-170psi per cylinder. If not even with the lower 8.13:1 compression pistons you should see 140-150psi.
 

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Discussion Starter · #7 ·
Well, that may be the case. Can we discuss this though? I'm seeing a massive variation in spark color across 1 and 6. 6 is orange. 1 is bluish.

New wires and plugs, cap and arm. Coil on the way out?

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1989 Range Rover Classic
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Well the coil should generate a uniform spark each time, indescriminate of which plug is being fired; all it does is make the spark, it doesn't know which cylinder it's going to. If it's cylinder specific, I'd say wires and/or plugs and or cap, but since you just replaced those I know that's not super helpful. While you had them out like in the photos above, did you swap plugs and or wires around, just to see if the orange spark followed a particular plug or wire? If so, maybe a bad wire, otherwise there may be a defect in the cap, if it's consistantly the same cylinder.
 

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1985 RRC 3.5, LT230, LT77. 1996 Disco1, 4.0
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If you're not running a "red" rotor inside the dizzy, give it a try. Helped increase proper spark to the plugs on mine....
 

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Discussion Starter · #10 ·
So, new Bosch is arcing. Pics included.

In my reading I've been reminded that spark will find easiest path, and it may be that the spark plugs aren't gapped right. Good news is there's a strong white/blue spark! But not in the right places!

Guys, I'm frustrated. Here's why: Old wires and plugs, dizzy cap and arm replaced. Same thing. New wires replaced with new NEW magnecor. Same thing. New coil... same thing but now arcing.

By SAME, I mean it runs rich on the right side only. And it's a weak spark I'm sure. But just on that side. If I pull one injector harness at a time, it corrects to mid range.. .slightly adding MORE fuel. This is ANY harness... so it's a bank thing, not one cylinder or injector.

To me this supports the weak spark on that side. Now, what would cause that? Left side, closest to coil is fine. Right side, furthers... longer path?... I know it sounds weird but spark on the left side has seemed just fine.

It almost seems like the resistance is too high on just that side, so the coil arcs on those... and I'm losing strong spark over there.

Note, I thought the boot maybe wasn't tight enough on the coil, so I adjusted it all the way down. Also, you can see the arc between the terminals in the 2nd pic, both sides. And yes I've tested 3 sets of wires, all seated correctly with a pop... then covering with the boot. This doesn't seem like a simple whoops.

I can put the old coil back in, but since THIS one is jumping, it seems like a stronger spark, which is what I was hoping for.

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296011
 

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While it seems incredibly odd that one bank would have higher resistance than the other, for absolute assurance you could temporarily attach a grounding wire from the right side of the engine (maybe under a valve cover bolt or something easily removable) to the engine ground strap on the right side, eliminating any potential resistive issue, but I would be staggered if that changed anything. I'm just spitballing here........You could check the ground path resitance too, with a multimeter between different areas of the engine and the ground strap location on the frame. Its all one connected chunk of metal so it should be negligible, but who knows.
 

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Discussion Starter · #12 ·
That's a good idea. I have had a few good runs where it runs like a sewing machine. But, once up to heat it starts to run like s**t. I've gapped all the spark plugs, timing is good... de-oxit'd the coil to prevent more arcing. And, it doesn't until it's warmed up. Resistance must be increasing enough somewhere that it's not arcing at the spark plug. I've got a new ignition amplifier module. I am going to do more testing, but this is irritating the absolute crap out of me. It's not THIS complex, so I feel like it's a small thing that's off.
 

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Discussion Starter · #13 ·
I was hoping someone might be able to help me understand, as it pertains to the Lucas EFI system, the purpose of the ignition condenser and why it doesn't appear in the RR service manual anywhere.

As I understand it, the condenser (which connects to the secondary circuit on the ignition coil) "absorbs the energy and prevents arcing while the circuit is open between sparks, and aids in the rapid collapse of the magnetic field." I've also read that a condenser going bad will weaken the spark as it's not holding the charge between contacts, but dissipating.

A third point I'm reading is that if it's going bad, you'll see excessive damage under the distributor to constant sparking, which I do in my original cap and arm. I assumed in my newness to this, that they rubbed because they literally look work from friction, but it's melted. So, that would indicate a condenser failure, and weak spark.

Fourth point, my coil is arcing, which would mean it's got nowhere to dissipate the energy between sparks. It's not storing it in the condenser, so it's just arcing back to itself constantly. While the engine is running, its crackling like a bug light.

There are other posts that it simple reduces electrical "noise" which seems like a secondary purpose.

My condenser looks like absolute dust, and I would guess is original. It would certainly explain my rough running, and crap mileage. It's a $5 part. I'm replacing this week.

Replaced so far: Wires, Cap, Arm, Plugs (gapped to .038 in all around), Coil, ignition amp, (tested pick up coil while dizzy was out at 2.5 Kohm, which is within tolerance), so all things are good.. but not this little part.
 

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95 Range Rover classic SWB, 2016 RRS Td6
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I was hoping someone might be able to help me understand, as it pertains to the Lucas EFI system, the purpose of the ignition condenser and why it doesn't appear in the RR service manual anywhere.

As I understand it, the condenser (which connects to the secondary circuit on the ignition coil) "absorbs the energy and prevents arcing while the circuit is open between sparks, and aids in the rapid collapse of the magnetic field." I've also read that a condenser going bad will weaken the spark as it's not holding the charge between contacts, but dissipating.

A third point I'm reading is that if it's going bad, you'll see excessive damage under the distributor to constant sparking, which I do in my original cap and arm. I assumed in my newness to this, that they rubbed because they literally look work from friction, but it's melted. So, that would indicate a condenser failure, and weak spark.

Fourth point, my coil is arcing, which would mean it's got nowhere to dissipate the energy between sparks. It's not storing it in the condenser, so it's just arcing back to itself constantly. While the engine is running, its crackling like a bug light.

There are other posts that it simple reduces electrical "noise" which seems like a secondary purpose.

My condenser looks like absolute dust, and I would guess is original. It would certainly explain my rough running, and crap mileage. It's a $5 part. I'm replacing this week.

Replaced so far: Wires, Cap, Arm, Plugs (gapped to .038 in all around), Coil, ignition amp, (tested pick up coil while dizzy was out at 2.5 Kohm, which is within tolerance), so all things are good.. but not this little part.
I mentioned checking this a few posts ago. A condenser fixed mine.
 

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Discussion Starter · #15 ·
Bill, you're absolutely right. I did read that on the other topic, and to be honest it was WAY over my head at that point. After working on this issue for the last few weeks, my nose in the service manual and youtube, I understand it now and I had MISSED this massive post. My apologies.

So, it seems like there are two schools on this part. One understand it as we do, imperative to the operation of the distribution of voltage by creating a store of energy between sparks. The other school seems to think that it prevents static on the radio. I have a hard time believing it's THAT simple.

You mentioned in the other post that you used a 2 microfarad capacitor? Do you know what the spec is for the OEM one? If I can grab at auto zone or something it'd be amazing.
 

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Bill, you're absolutely right. I did read that on the other topic, and to be honest it was WAY over my head at that point. After working on this issue for the last few weeks, my nose in the service manual and youtube, I understand it now and I had MISSED this massive post. My apologies.

So, it seems like there are two schools on this part. One understand it as we do, imperative to the operation of the distribution of voltage by creating a store of energy between sparks. The other school seems to think that it prevents static on the radio. I have a hard time believing it's THAT simple.

You mentioned in the other post that you used a 2 microfarad capacitor? Do you know what the spec is for the OEM one? If I can grab at auto zone or something it'd be amazing.
I ordered two capacitors after experimenting with my 2uF 50v axial electrolytic capacitor.
ADU7242LP I fitted with -ve end (The tongue of the case) under the amp relocation heatsink and the lug/wire end on a spare tab on the coil +ve terminal.
AEU1296 I fitted this from the alternator +ve terminal to alternator case bolt. I made sure the case was zero ohms to engine block.
Using a Picoscope digital oscilloscope the voltage spikes at the coil +ve terminal went from about 40 volt to about 2-3volts. I used the second channel of the scope on the -ve side of the coil and the spikes matched in time so the ignition was definitely generating these secondary spikes. I checked at the battery +ve terminal and there were none there, battery is a big capacitor, but at the alternator +ve output terminal they were there. I checked the brown cable from the alternator to the engine bay fuse box and at the input end the spikes were there. The outputs from the fuses showed smaller spikes so concluded these spikes only came from the coil. The engine ran so so with the old Lucas coil, distributor but when I changed to a Power sparks distributor, amplifier and coil it became undrivable with all the symptoms mentioned. Misfires, intake backfires, petrol smell at exhaust, trim levels way off and banks reading wildly different from each other. Erratic idle/rpm, inability to set base idle, also had about 9mpg when it would run. After seeing those 40v spikes I came to the conclusion that the new ignition parts were too good at the job and generating excessive voltage spikes which were getting onto the +ve coil supply and so confusing the ECU and playing havoc with the plug firing. Trying a spare ECU made no difference. Once I saw exactly what was going on on the Picoscope it was only too clear. As soon as I put a low value capacitor, 2uF 50v in it was a different vehicle. Idle became steady. I could set base idle, trim values became normal. No more misfires, exhaust smelled good. Could blip the throttle and no intake backfires or bogging down. I still had crap mpg but found for some reason, after rear brake pads wore out in 200 miles, that the brakes were slightly on. This was another head scratcher but eventually found, thanks to a previous poster, that the brake pedal to master cylinder link was in the lower hole on the brake pedal. I moved it to the upper one and the brakes became great. Since 2010 it has had a hard brake pedal but mileage was good, but now pedal has softer travel at first then hardens up, this is ABS, ETC system, just as you would expect. How it drove for 11 years normally is a mystery.
I have read thousands of posts on erratic idle/ misfire on rover V8, not just on LR sites, and though there are lots of fixes never had I seen anything about the ignition coil condenser being the real issue. Exactly why those spikes appear on the supply side of the coil I don’t know, coil is grounded, wires are shielded, my system is better than the day LR built it. I tried a super capacitor, 22000uF and it did no better than the 2uF one.
If it wasn’t for Rovergauge, Picoscope and a suspicious nature I would still be swearing at it.
Hope that helps.
Good luck
Bill
 

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Discussion Starter · #17 ·
Bill:

Thanks for this detail.

I picked up an ignition condenser at Autozone the other day (before your post) to test. There is zero info on it, or on the box. It's measuring roughly (.2 µF) which is much smaller than the one you have used. It's made no difference, but I'm not sure I'm suffering from the spikes you are. Here is my ignition waveform:
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Compared to my searches, this looks ok and I don't have any noise. Another point is that if you had THAT much spike, for SURE a condenser would help at ground. I'm learning that an ignition condensor, really, is a critical compoenent to a points system, but in our electronic distributors it's replaced by a pick-up coil. There's an easy test for that, impedence at the connection for the amplifier. Mine checks out at 2.5 kΩ. I might check ground at the amplifier, now that I think of it. I installed a new amp since I was in there.

One thing I'm currently hung up on (excuse the pun), is if my wires/plugs are a good match for my 3.9 EFI and head on a 4.6 block. I used a tune up kit from Rovers North. Previous owner had much NKG R's and Magnecor competition 8.5's. It might be prudent to replace with the same.

Even as such, I do have a feeling that there could be something wrong with ground. The spark may simply be weak, and I've noticed that it wants to arc just about everywhere it can. Even holding my in-line spark plug tester it has zapped me several times. Could this suggest the ground is dirty on the block? I'm going to check and clean today.

Thank you for the capacitor details. I'll likely go ahead and order and install the small compressor. Not sure I need on at the alternator as I've also got a clean line there.
 

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I like the details in thread with examination of the system and hope to add something to discussion.

The condenser/ capacitor is as you thought a component of points based ignition triggering to fire the coil. I can't immediately see a competent function for it with electronic systems and would be honestly surprised if fault correction came about from installation of one. Mine has always run without one installed.
It's function in points systems is as the points open and cause collapse of the coil field windings to discharge high voltage to plug, just as the plug has the voltage breach the gap it sends an inverse "spike" back through the entire route through the coil. Without the condenser this tries to induce a spark across the points, effectively making them contact to earth again and switching the coil off for HT discharge.
The condenser across the points juncture effectively absorbs this spike, in essence like a little trampoline to prevent the jump across the points. In reality it comes back out of there to lengthen the coil HT output and generally referred to as "ringing" in an electronic representation of a bell sound.
Without it the points arc like mad and very weak sparks are produced.

The points (switching to earth or not) aren't present in electronic systems, and so don't need the condenser.

The switching is not done by the distributor trigger either, that just acts as a starting pulse on time to start the coil working. This pulse is "read" by the amplifier which then switches the coil earth load with a power transistor to give solid state switching according to logic contained in the amplifier. Because of the ringing process described above (it's still there as part of HT discharge being exactly the same) this transistor although switching notionally 12v has to be rated at somewhere close to 400v to handle the collective percussive load of this system type. That's common to all the electronic systems and not just this one.
You'll see spikes when running but they are unlikely to impact system function, just generally noisy.
 

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For a quick-&-dirty function test, set the plug gap on the "missing" bank to no more than 25 thou and try a run to see if there's any response you can recognize like that.

If the bank has generally one or more missing cylinders it will send oxygen rich output (as it's unburnt) to that O2 sensor, the ECU has a response to too much oxygen in that it adds fuel to burn the oxygen it views as excess !! Which would be incorrect in this case. The ECU (unlike current systems) has no idea whatsoever if a cylinder is misfiring.

The gap test above effectively gives more chance of firing a competent spark with reduced voltage resource and may show you the way initially on this one.
 

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Discussion Starter · #20 ·
I'll give that a try. Also, a couple other ideas:

1: This is my engine block ground from the coil. I get continuity to the hood mount ground, and the battery ground, so it's not NOT grounded. But I do get maybe resistance, 2Ω maybe... I'm wondering: does this ground from the coil contribute to spark strength? If so, perhaps a new ribbon all around, and clean shiny contacts would be smart.
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2: I read a very interesting snippet in the engine section of the service manual. Trouble shooting EVERYthing, it ends up at the brake servo vacuum line as a check point as it can affect engine performance greatly. I havne't found exactly where it is, but it should be an easy check under the brake pedal and out the firewall. I would guess it's VERY old since I haven't replaced it. So, just another thought.

And, really, these things could possibly all add up.
 
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