| Author | Message | ||
     Mike Aldridge Yet to post message Username: speckledjim Post Number: 1 Registered: 04-2024 |
Hi All, My first post here, about my first Rolls-Royce. I'm afraid that in terms of information flow I'm not going to be able to provide anywhere as much as I'm going to ask for, but you seem a particularly friendly and helpful bunch! 1974 Silver Shadow - SRH18920 Stalls when hot, usually after a brief period of low-power, fluffy misfiring, refusing to take revs/load. Things I've looked at/changed: Main fuel filter: sparkling clean Air filter: like new Coil - changed for a new one Condenser - changed for a new one Fan coupling - changed for good used example I am pretty sure it's heat-related - it always starts and drives well when cold. Also, I'm getting the sound of boiling coolant, although there is plenty in there and no indication of a leak. OK - Any help and advice is very gratefully received, thank you! | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 2351 Registered: 05-2012 |
The symptoms you describe could well be caused by fuel vaporization in the float chambers/fuel lines. It is a known problem in these cars. In fact Flying Spares have a kit to help mitigate this. I would investigate the sound of boiling coolant first. The coolant should not be boiling. Check the thermostat is opening properly and there are no obstructions in the rad. Is the water pump circulating coolant efficiently. A very hot engine will definitely exacerbate the problem of fuel vaporization. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 3371 Registered: 06-2009 |
The coolant definitely should not be boiling, even at low to no pressure if it's a 50/50 mix unless the engine is running very, very hot indeed, which isn't likely. Also, are you sure that what you're hearing boiling is coolant? I ask because Geoff is right that if you have a very hot engine compartment that can cause boiling of the fuel in the float bowls. Unless something is really off, boiling of any sort should not be audible in the engine compartment. Brian | ||
| Mike Aldridge New User Username: speckledjim Post Number: 2 Registered: 04-2024 |
Thanks. After turning the car off once it's idled a while (or after it stalls) I can hear the pops of a boiling fluid, and feel the vibration in the hoses, so I'm 90% sure that's what's happening. I'll test the fluid (which is topped up and quite a bright green) and inspect and test the thermostat. The fan is now spinning nicely on its replacement coupling and no leaks apparent around the water pump, so does that indicate that the water pump is probably ok? | ||
| Graham Phillips Frequent User Username: playtime Post Number: 576 Registered: 03-2019 |
G'day everyone,.... As to the boiling coolant,... Is the valve in the radiator sealing allowing the system to pressurize properly? This stops boiling by raising the boiling point. If its fuel,.... Is the fuel pump providing enough pressure? If its just coping it my not fill the float bowl and LOW fuel in the bowl will boil easy. Graham. | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 852 Registered: 11-2017 |
One of the main causes of "vapor lock" with fuel, is low fuel in the tank. | ||
| Christian S. Hansen Prolific User Username: enquiring_mind Post Number: 1060 Registered: 04-2015 |
I suggest that your attention should be directed to the cause of the overheating as that seems to be the proximate cause of the secondary ignition issue. Your problem seems to be in line with the same issue I have with a 1967 MPW coupe, that is excessive coolant heat. I replaced the radiator to no avail. I am suspecting that the bypass cut off system is inoperative and a source of the problem as this would allow the coolant to simply recirculate through the engine and never really circulate through the radiator thus causing the overheating. Unfortunately due to age and an illness, I have not played with any of my collection for years and have never really resolved the issue. Your issue seems to be quite similar however and I make you aware of the possibility. The test procedure that I never got around to would have been to plug off the coolant recirculating channel which would force all coolant to go through the radiator. The preliminary warm up time would of course be considerably longer but that would simply be acceptable in lieu of the overheating issue. Just saying. Good Luck! | ||
| Mike Aldridge New User Username: speckledjim Post Number: 3 Registered: 04-2024 |
Thanks all. I've gone to the car to start to work through these ideas this evening and now the blessed thing won't start. The fuel pump doesn't seem to be priming in ignition position 2. It turns over strongly but not a glimmer of catching. Great fun, this, isn't it. It is, isn't it? | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 3372 Registered: 06-2009 |
Mike, Are you hearing the characteristic ticking of the dual SU pump priming the carbs by filling the bowls prior to turning the key to the start position? That's how I knew that my pump had "bitten the dust" some years back. I also never even attempt to start the car after turning the key to the Run position until that priming ticking has stopped. Brian | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2588 Registered: 09-2004 |
A few clicks is sufficient for starting. Beware of a car that has not been used for some time. With to-days horrid petrol that has a tendency to stick the float needles open allowing the pump to click continuously causing a dangerous puddle under the car. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2589 Registered: 09-2004 |
Original question=== Stalls when hot, usually after a brief period of low-power, fluffy misfiring, refusing to take revs/load. Do check the coil ballast they can cause the symptoms you describe. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 2352 Registered: 05-2012 |
I use Brian's method. In fact I wait until the fuel pump stops clicking before starting the engine. Of course, if the clicking doesn't stop after a few seconds you know there's a problem with a sticking float needle. Better to find there's a problem before driving the car than driving with a flooding float chamber. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 2353 Registered: 05-2012 |
And if you hear no clicking you know to investigate. Beats running out of gas a short distance down the road as the floats run dry. These are heavy cars to push. Listening out for the fuel pump is a great diagnostic test before starting the engine. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2590 Registered: 09-2004 |
Geoff, unless the car is used all the time, floats will be full and no pump clicking.  | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 3374 Registered: 06-2009 |
Geoff, Worked for me for decades, and as you noted, the clicking should not persist for "minutes" but subside within 15-20 seconds if the car has not been used in a while. I would, of course, have no clicking if I'd used the car and parked it recently. But if I'm starting it after a few days to weeks or months of inactivity, the clicking was guaranteed and a reliable indicator of the car being ready to start was waiting for it to stop. Of course, on LRK37110, which is a US spec 1979 Silver Wraith II with a Pierburg rotary vane pump, and a "return to tank" setup once the float bowls are full, I just wait about 15 seconds after turning the key to the run position before turning it to the start position. You hear the Pierburg pump start whirring the moment the key is in the run position, and it's priming the carbs. It just doesn't turn off. Brian | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2591 Registered: 09-2004 |
Interesting running a rotary pump.What pressure does it run at? have you fitted a fuel pressure regulator as well? | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 3375 Registered: 06-2009 |
Patrick, I have no idea what pressure it runs at as far as having taken any measurements. The Pierburg rotary vane pump is what came fitted from Crewe for the US spec cars in 1979 and it's shown in the workshop and spare parts manuals. The fuel system in LRK37110 is stock and unchanged from how it came from Crewe, so if a fuel pressure regulator is needed, it should be in the system somewhere already. I haven't taken a careful look at the spare parts manual for this system as it has not, as yet, needed attention. Brian |
