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Discussion Starter #1
Hello, I am struggling with a Silver Shadow LRA12965. Sorry for the long, rambling narrative below. This does come from pouring over other posts and printing out manuals from RROCA.

Having agreed to help a friend has me searching for this forums opinions and expertise. Long story short, the previous custodian is not available with information. Supposedly, the car had seized the water pump and thrown the fan blade through the radiator but otherwise was in good condition. A lot of recent repairs were either not recent or done poorly. When I took possession of the car, it was immediately evident that it had not been stored well, smelled badly and had to be scrubbed hard inside and out before rolling it in my garage. The car shows 34,000 miles that appear to be original. The HD8 SU carburetors were allegedly rebuilt recently as was the braking system.

Having remedied the cooling system and some other items, mostly cosmetic, the car runs poorly. The car will start easily and run. I will do my best to provide information that I believe to be true, and tasks from reading other past forum posts.

Some time, an electronic ignition, Crane XR3000 was installed using the original distributor. The timing is currently set at 12 degrees advanced @ 800 rpm with the distributor vacuum advance plugged, instead of the 5 degrees the manual states.
I have drained fuel from the tank and added 15 gallons of higher octane, non-ethanol fuel. Replaced the main original fuel filter before the dual SU fuel pumps. I put a fuel pressure gauge at the exit of the pump and with the key on, shows 4 psi.
Have hooked a vacuum gauge to a hose that leads to the vacuum retard tap mounted near the passenger-side carb. Gauge reads 19-20 hg at start up on high idle (1700 rpm), raises to 22 when it finally idles down to about 700 rpm.
The dashpots have oil. I have pulled the dashpots, visually inspected the needles and adjusted the float seats to 2.5 turns in from flush with the bridge. The volume screws were at 3 turns out, I put them to 1.5 per the book. I cannot seem to figure out the correct way to adjust the idle to these carbs together or separately. I also need to understand the fast idle linkage. I will.


This all said, this is how the car is behaving. Typically, from cold, 2-3 pumps of the pedal, car starts up and runs on high idle at about 1,700 rpms and seems to stay there longer than it should. After about 20 seconds, I will try to stab the pedal to bring the idle down. At that point it might drop to 1300-1200. I have to wait a couple minutes before the choke plate opens fully and still have to fight to get this car to idle down.

Once the car is finally to an idle of 700-800, it will not take the throttle, it will bog & hesitate, even backfire through the tail pipe at a rapid acceleration. With the car warmed up and choke blade open, I can get the engine to accelerate if I hold my hand over the intake or shoot carb cleaner inside. This is telling me that the car is lean? I cannot find a vacuum leak. I have attempted to drive this car around the block and can just barely get back home and up the grade of my driveway. (it does seem like if I had a perfectly flat 5 mile air strip, I could little by little add acceleration to eventually cruising speed.)

Last bit of information, I did unhook the hose on either side of the weaking device, but plugged all 4 sides. In perspective, I should have probably only plugged the line to the fuel valve and left the others open to vent? What is the correct way to disable the weakening system to test? I have also checked for vacuum on both sides of the retard tap and only read hg on one side of it. There is no vacuum appearing to the distributor which looks to tee to a vacuum switch at the driver’s side carb. Back to the manuals.

Thanks for any direction.
Chad
 

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This is unlikely but maybe the coil is incorrectly wired. If the positive and negative terminal wires are interchanged it can cause some of the lack of power and backfiring symptoms you describe. The cam that operates the choke butterfly may be sticking too, it should be clean and only very lightly oiled with a light weight oil e.g., a drop of ATF. I oiled my choke cam with engine oil and after a while it became sticky as in your case so I sprayed it with carb cleaner and it has been working fine since.
 

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Hi Chad

The first thing I would do is set the ignition to 5 degrees btdc as per the manual. My car is also a "series 1" (SRX18501) and I know it would run very badly at 12 degrees btdc. 12 degrees is the setting for the lower compression series 2 cars.

Geoff
 

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Discussion Starter #4
Shadow,
Where is this choke cam located? It does seem like each time I clean the fast idle linkage area with carb cleaner, the choke seems to step down quicker. Also, could you describe to me how these cars should start, warm up, and how soon to be at operating idle? What is your procedure before you drive down the road? I will print out the installation instructions from Crane and double check the coil/ballast wiring.

Dounraey,
I have backed the timing to 5 degrees advanced and it runs even worse, with even less power and more hesitation, making me think this car is very lean.

Perhaps I have a bad vacuum leak I haven't discovered yet. Perhaps I should read up on how to go about checking the float levels as well. I probably should trust nothing at this point.
 

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Did you remove the spark plugs and look at their condition?

This will give valuable insight to how the engine is working and what the possible cause it.

Need to determine if it is fuel or ignition related - unless it is something very strange such as timing, compression, which is very unlikely.

My understanding is that weak condition is either fuel or ignition related (I'm currently going through a similar issue with my '76 Corniche - see my post).

The only thing that would concern me I'd that you said the carburetors were recently re-built, and from what you are saying everything was done poorly - so it is possible something may be wrong there.

Did you check the needle and jet, is the piston free? Make sure all the parts are the correct ones (in my case I was missing a needle guide).

Also, 4 PSI is a bit on the low side, measure fuel pressure at the carburetor unions, for both pressure and flow (120/125 liters per minute or 20/25 GPH).

Good luck and keep us posted!

Post pictures as well, helps in the diagnosis and makes it more involving for all :)



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Dounraey,
I have backed the timing to 5 degrees advanced and it runs even worse, with even less power and more hesitation, making me think this car is very lean.

Perhaps I have a bad vacuum leak I haven't discovered yet. Perhaps I should read up on how to go about checking the float levels as well. I probably should trust nothing at this point.

I suspect there are several factors at play here, but another thing I would check is that the bob weights in the distributor have not seized. This would explain why you need to set the timing so advanced.
 

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You cannot plug the hoses from the carb that go to the weakener. Just pull the hoses off the float bowl vents and leave them open to the atmosphere. They must be vented or it will not run. Both vent hoses off float bowls isolates the weakener and anti diesel solenoids from the equation.
12 degrees advance should run fine.
Brakleen only to wash oil and dirt off of fast idle cam. It should not be oiled with anything. Intended to work dry. Any oil attracts dirt and then they stick.
4 psi perfectly fine from an SU pump. Volume is more important.
Those are not the float seats you turned 2.5 turns, they are the jets and adjusting them varies the mixture. Screwing the jet adjusting screws clockwise, (down) enriches the mixture. Counterclockwise (up) leans it. the lower the jet appears in relation to the bridge the richer it is. Try screwing down another turn clockwise and try it.
Higher octane not needed.
Those Crane ignition modules are very sensitive to the key being left on without the car running. As little as 10 or 15 minutes will fry it. Test that it is still switching the coil to fire by attaching a test light to the + terminal of coil and ground. The light should flash 4 times per 1 RPM if the module is triggering the coil.
2 or 3 stabs of gas pedal not needed, these carbs have no accelerator pumps. Only one pump is needed to set the choke and fast idle cam.
Fast idle will not drop down automatically, you have to stab the pedal as it warms up.
 

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Bring the jets up to level to the bridge and then 1.5 / 2 turns down.

There is a couple of vacuum take offs, make sure they are all sound.
Make sure the float chambers fixings have the correct red cut away washers fitted.

Check that the fuel pumps are delivering quantity, Check the filters in the carbs and above the rear axle.

Remove the electrical feeds from each end of the pumps and apply the feeds separately to ensure both ends are working independently.

I feel it will be a back to basics exercise but 'learning on the job' is a tedious and VERY difficult task.

Here is my take on lubricate the linkages. This seems to be very controversial but have a think on it and choose your own solution.
I was always taught that you must NEVER lubricate the choke fast idle cam (Which everybody agrees with). But I was taught you must lubricate the cam spindle. It is imperative to have friction between the CAM and the FAST IDLE ADJUSTING SCREW. If you lubricate the cam it will slip down too early. That is bad!

It is important that that the cam and the other linkages move freely, including all the linkage ball joints. So a few drops of oil are important. Clean it off at the annual service, add some PAS oil to it, that's it for another year. I have never had a choke stick with thin oil on it, I have had plenty stick when completely dry.

As it was explained to me by the Hythe Road Service centre, at some point the instruction to not lubricate the cam has been taken to mean don't lubricate the spindles either.

What I find is that a clean, dry spindle may be fine on a car which is in daily or frequent use, but any less than that and you end up having to kick the choke a good few times (Or open the bonnet and finger the cam to get it from it's maximum stop) to get it off max fast idle.

As I say, think about it and make your own decision.

The choke is designed to work best by dipping the accelerator, starting the engine, and then once running smoothly (up to 10 seconds usually) giving it one blip (to get if off maximum fast idle) and then driving off. It is important not to sit there and leave the car warming up until you can get the choke off and then driving off. The choke is too severe for that and you will end up with sooted up plugs and puddles of soot on the floor - or on any walls, cars, items in close proximity.

Good luck with the project.
 

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Discussion Starter #10
Thank You for all the direction here. I have made 2 lists, ignition and fuel. I will start with ignition first. I have read here more than once that 90% of carb issues are actually ignition.
I will report back.
 

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Hi OilChanger, The choke idle cam is located on the side of the air intake between the top of the A-Bank carb and the distributor cap (slightly closer to the carb). There's a nut on the outside of the air intake which is attached to the the end of the choke butterfly spindle. The cam operating lever (about 3 inches long - from memory) is attached to the spindle by this nut and the lever drops down to a lower cam. When the choke is fully closed on cold start the cam at the bottom should be at 45 degrees and move back to 90 degrees when the choke butterfly is open on warming up. The length of time it takes for the choke to open depends on the ambient temperature. There's another electrical device that reads the ambient temperature and controls the choke operation, it's on the bulkhead behind or below the heater air intake tube, 2 wires go from it to a device on top of the air intake above the choke cam. I don't have access to my car at the moment as it is in for a re-paint but from memory it should take about 30 seconds for the choke to start opening but the ambient temperature will affect the time taken. If the accelerator pedal is given a slight kick it will open sooner and the revs will drop unless the choke cam is sticking.
 

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Discussion Starter #13
Shadow, got it. Sorry, for some reason I thought there was an additional internal mechanism. I will pay attention to it. Thanks.
 

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Discussion Starter #14
So, I am reporting on my unsuccessful evening.


  • Bentley 8, Pulled several random plugs, look fairly recent BPR5ES NGK. Understandably not beautiful based on the way the car runs, not oil fouled.
  • Jim Walters, I put a test light on the + side of the coil while running and it was blinking in a blur.
  • Shadow, It appears that the coil wiring is correct, however, it does appear to utilize the original Lucas silver coil and a block ballast resistor. I need to look further into this, I though an electronic ignition did not “want” ballast resistors. I also don’t know if the OEM coil has internal resistance as well.
  • I have attempted to measure vacuum from the retard tap to the distributor advance and get a zero reading. I do have full vacuum on the other side of the “tap”. At what point does this tap open and what is it’s purpose? I would imagine at start up, it should be open at full vacuum and only close at cruise? Maybe it is faulty? I see that it also "tees" to a valve on the "B" side carb throttle arm?
  • After spraying the choke cam and fast idle linkage with cleaner several times, the car quits at final kickdown. I will describe the current warm up observations as now I am moving to the fuel side.
  • Pumped the pedal once, started and quit. Pumped twice more, started and jumped up onto high idle @2200. Let 10 seconds go by, stabbed it, dropped to 1800. 30 seconds, stabbed again, 1100. Took a few minutes and attempts to get it to come down and it then quit and did not want to stay running even after holding the pedal at partial throttle. Few minutes later, it started and ran. I have already turned the jet adjusting screws in an additional full turn per Jim Turner. I also adjusted the mixture screws out to 3 turns total.
  • I took a few pictures of both throttle arms to show that both are not touching a stop. Pictures are after the car was running and stopped. They appear the same when the car is cold. Perhaps my whole issue is a very bad linkage adjustment issue?
  • While the car was running, I pulled the hoses to the float bowls. The rpms rose.
  • Paul Yorke, I see red washers at both bowl taps. I have established fuel pressure @ 4psi with key on, how does one establish quantity? Stopwatch and a bucket?

That is all I got for now. I have some trick tools coming for the weekend for synch and balance. Hopefully, I will be able to use them before this car self destructs…
If this triggers any other thoughts from expertise. Pile it on.



Thank You Gents.

Chad (Oil & Parts Changer)
 

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Hi Chad, My car is a Silver Shadow 11 has electronic ignition and a ballast resistor. I think the fuel supply pressure should be near 7PSI but I'm not certain about that, I recall reading it somewhere so will try to find the info again. If you have dual SU fuel pumps it's possible that one of them isn't working and this might cause a power loss on acceleration. It's easy to check, just disconnect the pumps one at a time (and insulate the wires against possible sparking) and see if this changes the engine performance. These engines will run on one pump but won't respond well under acceleration especially if the working pump isn't great.
 

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Hi Chad, Ignore my previous reference to 7PSI fuel pressure. A test rig is needed to test the pumps output and a paraffin bath is used in the test. The output should be 1.333 pints or .758 litres in 28 seconds according to the manual. If you hear a buzzing noise from either pump it would indicate that a pump diaphragm is weak and needs to be replaced.
 

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Shadow, Perhaps I should have read your post again and section K8 describing the test before jumping to performing my perception of the test, but as I read it now, the bench test with a parraffin bath/portable tank and measuring apparatus doesn't seem any different than on the car with a hose and a bucket. (actually, you need two buckets). So I attached a length of hose from the pump exit to a bucket, and placed another container next to it. Turned the key on, set timer, moved hose to second container. After 28 seconds, moved hose to original bucket and turned key off. (due to very poor coordination of my own, I had to do this a second time). The result was 48.5 US ounces=2.524 Imp pints=1.434 liters? I was able to feel both pumps running, with no buzzing. (I would describe the sound as putt, putt, putt.) I cracked open the main union before the tee to the carburettors and had plenty of fuel there.

I have hopes that I can move on from the fuel pump and declare it sound?

My next thought is to move onto the linkage. It seems odd that both carb arms/bell cranks are so far away from their stops at rest, shown in pictures attached to my previous post.
 

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Hello,

As far as I know the flow should be 120/130 liters per min, so you are a bit under that.

Open the float bowl Chambers and see if fuel is getting to them.

There is a filter at the union, verify that that one is not blocked.

The fact that the engine is starting and running makes me think that it is not ignition related.

Question: Does the engine run strong and fire on all cylinders when it is running?

Would be helpful if you could share a video of the engine starting and running.

At this point, to completely rule out fuel delivery I would get a new pump and feed fuel from an external source.

Open up the chamber and show us the needle and jet. Are all the components there?

I am suspicious of the recent rebuild you mentioned - perhaps to save time you should remove the carburetors and send them to a specialized shop in SU.

Good luck

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Discussion Starter #19
Hello Bentley,
120/130 liters a minute? I have cracked the unions, they are getting fuel. The car starts and runs, all 8 cylinders are getting spark. The car does not seem to miss even in the current state. That said, I have not done a compression test. Other than pulling the dashpots, checking the needles , making sure there is fuel in the seats, the adjustment goes up and down in relation to the bridge, I have not gone farther than that at this point. I suspect the linkage and overall set up which I need to read up on. A step at a time. Time is not an issue and won't be sending carbs to a shop. What fun would that be?
Chad
 

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Shadow, Perhaps I should have read your post again and section K8 describing the test before jumping to performing my perception of the test, but as I read it now, the bench test with a parraffin bath/portable tank and measuring apparatus doesn't seem any different than on the car with a hose and a bucket. (actually, you need two buckets). So I attached a length of hose from the pump exit to a bucket, and placed another container next to it. Turned the key on, set timer, moved hose to second container. After 28 seconds, moved hose to original bucket and turned key off. (due to very poor coordination of my own, I had to do this a second time). The result was 48.5 US ounces=2.524 Imp pints=1.434 liters? I was able to feel both pumps running, with no buzzing. (I would describe the sound as putt, putt, putt.) I cracked open the main union before the tee to the carburettors and had plenty of fuel there.

I have hopes that I can move on from the fuel pump and declare it sound?

My next thought is to move onto the linkage. It seems odd that both carb arms/bell cranks are so far away from their stops at rest, shown in pictures attached to my previous post.
The "putt putt" sound is what you want to hear.
Even if you were to assume that the fuel pump(s) were not working, if the float bowls had fuel in them, the car would run normally until they were emptied.
However, even with the float bowls full of fuel, the car still does not run as it should.
Jim Walters said 4 lbs. pressure is good and his observation should be heeded as such _ time to move on.
Take a look at Jim's web site, his opinion should not be taken lightly.

If you want to check something to do with fuel delivery, look at any plugged filters and that's about it.
 
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