1976 Silver Shadow Starting Problems - Rolls-Royce and Bentley Forums
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post #1 of 32 (permalink) Old 07-13-2010, 09:19 AM Thread Starter
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1976 Silver Shadow Starting Problems

Working on this car for the first time for a friend. Got the manual off of one of the links I found on here.

Background:

Car ran and drove before being parked for around 9 months. A fresh battery was put in and it cranks over fine.

Problem:

Car cranks but does not fire. Since I am not familiar with these cars, I have a couple of questions. Is there anything specificially that these cars are finiky with? For example, do the carbs gunk up fast or is there something else that messes up when it sits for too long? Just want to make sure I check all the easy things before I pull the carbs off for a cleaning. Thanks in advance

1975 Silver Shadow
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post #2 of 32 (permalink) Old 07-13-2010, 09:38 AM
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The original Opus ignition system is known to be a weak spot. Definitely check to see that you have spark.

The car has three fuel filters, one Crosland 444 (now made of unobtainium) in a canister under the car on the right and two smaller filters at the inlet to the carbs. Any of these might be clogged.

Also, it is entirely possible that the fuel pump has finally failed. These cars have dual SU fuel pumps and can function if only one is working. It is not infrequently the case that one has long ago given up the ghost and it's only when the second one goes that anyone knows there's a problem. If a fuel pump is working you should hear the distinctive ticking sound when the key is turned to "Run" but before you crank the engine at the "Start" position. I should add the caveat that I'm presuming your car has the "more typical" fuel pump configuration. There were also Pierburg rotary vein pumps used in certain markets.

I don't know that anything in the list above is easy, per se, but it's better to check before tearing the carbs apart. If you do get to that stage do yourself a favor and buy the rebuild kits before you even start so that you can just do this as part of the process. If you download the file I maintain on the "Finding a Good Service Shop" thread you'll find a section dedicated to SU Carb resources.

As to what can be finicky about these cars, the list is virtually endless, particularly for those that are not driven regularly and have lots of deferred maintenance.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #3 of 32 (permalink) Old 07-13-2010, 10:58 PM Thread Starter
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Thanks for the reply. Very helpful info. I was informed today the car is a 1975 not a 76 but if my history is correct there is no major difference...

After browsing through the manual after reading your reply, I have a couple questions. Keep in mind I have not had the opportunity to see the car again in person so some of these maybe a little silly.

1. Where are the fuel pumps located? Are they in the engine bay? The manual doesn't give a schematic of where they are.

2. Does one fuel pump feed one carburetor? For ex. one fuel pump feeds right carb, and one fuel pump feeds left?

3. Fuel filters were mentioned. You mentioned the first filter is no unavailable. If that is clogged, is it possible to remove it and just run two filters at the carbs?

4. Are there fuel pump relays or fueses stashed away in a fuse block somewhere?

Again thanks for the help, the last thing I want to do is tear the carbs apart.

1975 Silver Shadow
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post #4 of 32 (permalink) Old 07-14-2010, 12:52 AM
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Quote:
1. Where are the fuel pumps located? Are they in the engine bay? The manual doesn't give a schematic of where they are.
The fuel pumps are under the car, on the right, in front of the rear axle.

Quote:
2. Does one fuel pump feed one carburetor? For ex. one fuel pump feeds right carb, and one fuel pump feeds left?
No. There is a single fuel line between the pumps and the engine bay.

Quote:
3. Fuel filters were mentioned. You mentioned the first filter is no unavailable. If that is clogged, is it possible to remove it and just run two filters at the carbs?
No. The main fuel filter is the primary. The two carburettor filters are only to protect against anything that might have been missed by the main filter. The main filter is under the car and the cover can be removed and the filter examined and cleaned (in petrol).

Quote:
4. Are there fuel pump relays or fueses stashed away in a fuse block somewhere?
The same fuse is used for the fuel pumps and the ignition. Thus if the ignition works, the fuel pump fuse is OK. I don't believe there is any relay for the fuel pumps.
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post #5 of 32 (permalink) Old 07-14-2010, 08:58 AM
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lordphi has given you good information.

I the ignition and fuel pumps are on fuse 12 in the original Shadow series cars (see PDF pg 5, Chapter M, Workshop manual).

One relatively easy way to determine if you have spark, but not fuel, is to detach your air intake line from the "center tube" that joins the section between it and the carburetors. Give a light spray or two of starting fluid then try to start the car. If it sputters or, like mine did, runs perfectly for a couple of seconds then dies you know you've got spark but no fuel.

Check that you've got power on both sides of the fuse using a multimeter. Touch the positive lead to one side of the fuse and the other to ground, then do the same on the other side of the fuse. You should have 12V on both sides (or mighty close to 12V).

If that checks out, go on to checking the power at each of the pumps (the technique is the same, positive lead to power input and negative lead to ground). Again, you should have something around 12V. You will need to slide the rubber end caps off to get to the power connection at each end. If the wiring is original Crewe used wire that was white with a pink stripe.

These cars can (and often do) run with only one of the two dual pumps operating. You won't have a "failure to proceed" unless both pumps fail. I think my car was doing that for years. If you're really ambitious, you can install a discreetly hidden SPDT switch that will allow you to isolate one pump from the other to test them individually, but that's another story.

It is entirely possible, and has been done many times, to splice a more typical disposable style gas filter into the line. I would not operate the car without this and both the carb filters in place. By the way, the Crosland 444 can be obtained from HVAC supply shops in the UK, as it is also used as the filter for oil furnaces. It's just a pain to locate a supplier who still has stock. There are also aftermarket options to replace the canister filter that's on the car that still have easy replacement part availability. The one thing you don't want to do is to throw away any of the Crewe Original parts you might remove. Who knows what future owner might want to "go back to original" and not having these parts can often kill a sale.

Rebuild kits for SU carbs and fuel pumps can be sourced from Burlen in the UK. Also Victoria British here in the US can source rebuild kits for the fuel pump. Our cars use precisely the same kit as an MGB (although I would reuse the diaphragm spring that is already in the car if there's any doubt about the spring pressure being the same). The part number from Victoria for a pump rebuild kit is 3-2058 (and you'd need two). As of last week a new pump from Burlen (an SU AZX 1405 series pump) was about $265 with shipping. Two rebuild kits from Victoria British are a bit under $150 with shipping.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #6 of 32 (permalink) Old 07-14-2010, 09:15 AM Thread Starter
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Thanks for the replies from the both of you. I will go ahead with the trouble shoot as you guys suggest. I believe I am headed over there on friday to start working on it.

How is clearance under the car? Do I need to bring a jack. I'm not a huge dude, probably a 40 inch chest haha. Also I looked at your RR technical reference pdf and the jacking information link doesn't seem to work anymore. Is jacking this thing up that specific? or can I get by with picking a standard spot?

1975 Silver Shadow
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post #7 of 32 (permalink) Old 07-14-2010, 10:01 AM
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Clearance under the car is very, very minimal. There's no way I can fit under there without the car being jacked up quite a bit and placed on jack stands or being put up on ramps or a lift.

The jacking points on these cars are very specific. If you have downloaded the resources file from the "Finding a Good Service Shop" thread, I just checked and both of those editions of Tee-One topics are at the same URLs as they've always been. A copy and paste of the URLs took me straight to these issues of Tee-One Topics. If that's not working then just go to http://rrtechnical.info then to the Tee-One Topics section and look for issues number 38 and 45.

You can do a great deal of damage to the car, and yourself, if you're not careful about using the correct jacking points and jack stands that can handle the weight of these cars. I use a set of 3-Ton jack stands and a 2.5 ton hydraulic jack. Never, ever, ever, ever, get under these cars (or any car, for that matter) with only the jack for support!! Also, it really is essential to make yourself a set of sill blocks if you're going to use jack stands with these cars. For mine I didn't need the little center cut out shown in the picture.

Good luck.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #8 of 32 (permalink) Old 07-15-2010, 09:51 PM Thread Starter
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Quote:
Originally Posted by guyslp
Clearance under the car is very, very minimal. There's no way I can fit under there without the car being jacked up quite a bit and placed on jack stands or being put up on ramps or a lift.

The jacking points on these cars are very specific. If you have downloaded the resources file from the "Finding a Good Service Shop" thread, I just checked and both of those editions of Tee-One topics are at the same URLs as they've always been. A copy and paste of the URLs took me straight to these issues of Tee-One Topics. If that's not working then just go to http://rrtechnical.info then to the Tee-One Topics section and look for issues number 38 and 45.

You can do a great deal of damage to the car, and yourself, if you're not careful about using the correct jacking points and jack stands that can handle the weight of these cars. I use a set of 3-Ton jack stands and a 2.5 ton hydraulic jack. Never, ever, ever, ever, get under these cars (or any car, for that matter) with only the jack for support!! Also, it really is essential to make yourself a set of sill blocks if you're going to use jack stands with these cars. For mine I didn't need the little center cut out shown in the picture.

Good luck.
I completely missed the T-one link on their website. Lots of stuff going on in that page, easily missed. Just downloaded the doc, and looked through it. Jack points are pretty straight forward. I think i will be jacking it up at point number 4 just to get access to the fuel pumps. When they say trolley jack, Im assuming its english for just your everyday hydraulic pump jack?

1975 Silver Shadow
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post #9 of 32 (permalink) Old 07-15-2010, 10:46 PM
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Hello,

After looking at both of the Tee-One Topics issues I referred to I see that even their excellent instructions leave some room for making mistakes when going between "Brit-speak" and U.S. English.

First, in Issue 38, which shows the numbered points you refer to, the ones called "Car Jack and Sill Block Positions," with the front ones being numbered 3 and the rear ones being numbered 4, are referring ONLY to the positions where you may place jack stands using sill blocks. They are not suggesting that you can raise the car with a hydraulic floor jack (trolley jack, the top of which you can see clearly pictured in issue 45 on PDF page 8) at these points. The car will flex horribly if you try that. I would never use a hydraulic bottle jack with these cars for any reason.

There are four points you can use if you wish to jack the car up with a trolley jack, it just depends on which two wheels you want to get up in the air. You center the jack (with a heavy rubber square on the head) directly under the differential (position #6) if you want to raise both back wheels at once [You'll then place your jack stands with sill blocks at both points numbered 4]. Position #1 is used to get both front wheels off of the ground at once [You'll then place your jack stands with sill blocks at both points numbered 3]. If you wish to put up both wheels on one side of the car or the other, you will place the floor jack with a rubber block on its head and a sill block on the sill positioned directly under the little door midway down the side of the car where the regular jack bar is inserted were you using it. You can see this technique clearly in the photo in Issue 45. Once the car is up you would then place one jack stand with a sill block at position #3 and #4 on the side of the car that you just raised up.

If you want to get to the fuel pump my suggestion would be to jack under the differential and put the stands/blocks at positions numbered 4. Otherwise, I'd jack up the right side of the car using the central jacking point (unnumbered in the Issue 38 diagram, but shown under the floor jack in Issue 45) and then put your jack stands/blocks at positions numbered 3 and 4 on that side of the car.

In all cases, give the car several good challenge shoves once you've let it down on the jack stands. I've put my car up on jack stands many times and a lift as well. If you're using a lift then the arms are positioned at both numbers 3 and 4.

As an aside, I've found that tread sample squares you can get from most tire centers when they're throwing them out make excellent rubber block to put on the jack head.

Sorry if this explanation has been a bit overly specific, but I really hope it makes things crystal clear. Good luck and be very, very, very safety conscious!!

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #10 of 32 (permalink) Old 07-20-2010, 11:20 PM Thread Starter
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Thanks for everyone's help so far. Went over and worked on it today.


Luckily I didnt have to jack up the car at all. I barely squeezed under there and it worked out perfect. Here is my trouble shoot.


1. Took air cleaner boot off and sprayed some starter fluid into the intake. Cranked it over and it sputtered a little bit. Got spark.

2. Made sure everything was quiet, went to "key on" position and heard nothing from fuel pumps.

3. Got under the car with the car in the "key on" position and put my test light to the positive terminals of the pumps. Have 12v going to the pumps at both pumps. Also checked the ground and it was good as well.

4. Removed downstream fuel line, the fuel line after the pump going to the motor and cranked the car. No fuel was pumped out into my bottle. This leads me to believe the fuel pumps are bad.

5. Removed the fuel pumps from the car and hooked it straight to a battery and still nothing.

Is it safe to say that the problem is the fuel pumps being bad? Did I miss anything in my diagnosis?

Also I come back with a couple more questions. I noticed there was a small round cylinder hooked to a wire that looks like it goes to the positive terminal of one of the pumps. I read the manual and it looks like its the radio interference module or something? Did I ID that correctly? Does it indeed connect to the positive side of one of the pumps?

Last question I have is, if the fuel pumps are indeed bad, how involved is the rebuild? How is the quality? Am I better off getting a new set of pumps and bolting them on? Or is the rebuild pretty straight forward and will last longer then a year. Thanks again for all the help so far, this project is going alot smoother then I ever thought.

1975 Silver Shadow
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