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John Rowney
Experienced User
Username: johnrowney

Post Number: 109
Registered: 02-2015
Posted on Tuesday, 16 August, 2022 - 14:41:   Edit PostDelete PostView Post/Check IP

My 1978 Corniche DRH32489 runs very well except occasionally when stopping for a while eg at traffic lights. The Solex 4A1 carburettor has been rebuilt, new gaskets and needle and seat installed, and every nut and screw tensioned as per the manual - I even use a bicycle tension wrench for the 10 in-lb tension on the 8 screws. Most times everything continues as normal, but on rare occasions the revs drop, the generator light comes on and the car starts to run rough when the car is stationary.
Usually having the foot on the brake and applying a little bit more throttle, the revs come up, the gen light goes out as expected and generally the problem disappears (until the next time).

Does anyone have any thoughts on how this happens? It is very frustrating as most of the time everything is perfect, just on the odd occasion. I imagine there is a logical way of tracking down what the problem is, but with the complicated nature of the Solex, it is beyond my feeble brain at this stage.

Any suggestions are most welcome.
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Mark Herbstreit
Frequent User
Username: mark_herbstreit

Post Number: 238
Registered: 05-2005
Posted on Tuesday, 16 August, 2022 - 17:43:   Edit PostDelete PostView Post/Check IP

Hi John,
My only theory is the 12v feed is randomly dropping off the choke. I have yet to confirm if the 12v is required and constant even after warm up on my Camargue. It has been on my to do list for quite a while now!
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John Rowney
Experienced User
Username: johnrowney

Post Number: 113
Registered: 02-2015
Posted on Monday, 22 August, 2022 - 16:54:   Edit PostDelete PostView Post/Check IP

Hi Mark.
I am going to drive the Corniche tomorrow to do a few errands. I will pull off the 12V feed and see what happens. Fingers crossed I don't stall in the Gold Coast traffic jams! I'll let you know.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 114
Registered: 02-2015
Posted on Tuesday, 23 August, 2022 - 15:37:   Edit PostDelete PostView Post/Check IP

I took the Corniche for a few small trips today. Firstly with everything connected - guess what? Everything ran well and not a problem with low idle. After lunch, I disconnected the 12 V supply to the choke, and went for a spin with lots of traffic lights and stops. Everything again ran perfectly. What we can definitely say is that it looks like losing the 12 V supply to the choke is not a problem. The hot coolant must do its trick and it really doesn't matter if the 12 V supply is interrupted.
More head scratching is required.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 117
Registered: 02-2015
Posted on Wednesday, 07 September, 2022 - 11:12:   Edit PostDelete PostView Post/Check IP

Yesterday I did a few little trips. A couple of times the Corniche dropped revs on stopping, ran rough and the gen light came on. On one occasion I was able to lift the bonnet and check underneath, but things came good and revs went back to normal. Very frustrating. I am keeping the car at home for a while so I am using it as my regular driver for a few days to see if I can pick anything up when it gives a problem.
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Mark Tennison
New User
Username: fixstuff

Post Number: 43
Registered: 11-2020
Posted on Friday, 30 September, 2022 - 20:23:   Edit PostDelete PostView Post/Check IP

Could it be your AC compressor kicking-in putting load on engine at low rpm could cause the engine to stumble ?
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 823
Registered: 05-2016
Posted on Saturday, 01 October, 2022 - 08:29:   Edit PostDelete PostView Post/Check IP

I'm not familiar with the Solex 4A1 carb but the symptoms you describe could point to a partially clogged idle jet (assuming the carb has one). I had a similar problem back in the 70s with a small piece of crud in the idle jet on a basic Solex carb in a Triumph Herald.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 122
Registered: 02-2015
Posted on Saturday, 01 October, 2022 - 15:04:   Edit PostDelete PostView Post/Check IP

Mark: Thanks, I will turn off the AC when it happens next. I have some thoughts that I have done this in the past with no change. However, I will try and keep my mind on the job and really take note if the AC has an impact.


Larry: I hadn't thought of crud in the jets (there are two). I have had the Solex completely overhauled a couple of years ago, so it should be OK, although you never know. I have never taken the idle screws out, the adjustment is not that easy to get to. Maybe a re-read of the manual might help me.


Many thanks to both of you for your suggestions. I won't be driving the car for a couple of weeks since we are going away for a while. I have put your suggestions in my diary to attend to when I get back and I will take the Solex part of the manual with me on the holiday. I will post any outcome afterwards.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 824
Registered: 05-2016
Posted on Sunday, 02 October, 2022 - 21:17:   Edit PostDelete PostView Post/Check IP

Hi John, Normally when the engine is at idle the fuel is supplied through the carb idle jet but as soon as you press the accelerator the fuel then goes through the main jet. Revving it won't clear an idle jet because it is bypassed once you press the accelerator pedal. The only way to clear it is by removing the jet and blowing it clean. If you find crud there it might be time to replace the fuel filters.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 124
Registered: 02-2015
Posted on Friday, 28 October, 2022 - 22:42:   Edit PostDelete PostView Post/Check IP

Larry: Many thanks for your thoughts, and also to Phil Sproston who rang a few weeks ago with lots of suggestions.
I was away for a while recently, but I got back this week to trying to sort things out again. My first thing was to remove the idle jet screws and clean them. I took the screws out and squirted carby cleaner in the passage and blew everything out with compressed air.
I had two wonderful days driving the Corniche around the Gold Coast with the hood down, and DRH32489 simply purred without a murmur.
However, yesterday when I was enjoying the rather hot sun on a trip to Coolangatta, she stopped completely at the lights before turning into Marine Parade - much to the annoyance of the traffic behind.
Anyway, she started eventually and then I spent the rest of the time on returning to the shed petrified that she would stall again. With judicious braking and accelerator manipulation, I managed to keep going relatively well.
Until... a moronic woman backed her 4WC suddenly out of a parking space in Tugan. A smoking wheel-locking stop to avoid a horrible prang caused DRH32489 to stall again.
I eventually got home, and today I took the Solex carby out of the car, and gave it a thorough clean with carby cleaner and horrific blasts with compressed air. Imagine my surprise when there was quite a few millilitres of water in the effluent from the liquid deposits (mainly carby cleaner).
Anyway, with everything back installed, I went for a spin and all is good (so far).
I will drive DRH 32489 for a few days over the next week or so and report back. Buggered if I know how water got in the system!
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2541
Registered: 09-2004
Posted on Saturday, 29 October, 2022 - 00:46:   Edit PostDelete PostView Post/Check IP

The running of E10 can cause problems if the car is not used for longish periods with fuel separation.
Hope will all be ok now.

If the problem still prosists.

IMO it has all the classic signs of the starting of electronic ignition failure.

Maybe check the ballast amplifier first!
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David Gore
Moderator
Username: david_gore

Post Number: 4130
Registered: 04-2003
Posted on Saturday, 29 October, 2022 - 06:55:   Edit PostDelete PostView Post/Check IP

John,

I have never suggested the use of E10 in RR/B vehicles especially those subject to infrequent use due to past problems such as what you have experienced.

I suggest you run the fuel tank down to safely near empty before refilling it with 95 or 98 RON fuel which is ethanol-free.

If you are of the "belt and braces" segment of the population, I suggest another change of the fuel filter[s] as well afterward as there could be additional pick-up of sediment with the low fuel level in the tank pushing sediment into the fuel pickup in the tank.

If all else fails and sediment blockages are an ongoing problem, the best preventative would be remove the fuel line fittings from the tank and flush the tank with clean fuel to wash-out any remaining sediment.

P.S. are your Solex carburettor[s] fitted with E10 compatible gaskets/seals? If not, you may be having a problem with breakdown of these items from exposure to the E10.

P.P.S I hate E10 fuel from past knowledge of owners using E10 fuel in various vehicles from different manufacturers made before the introduction of E10 fuel experiencing problems similar to you.
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Patrick Ryan
Grand Master
Username: patrick_r

Post Number: 2359
Registered: 04-2016
Posted on Saturday, 29 October, 2022 - 08:16:   Edit PostDelete PostView Post/Check IP

David,
You are spot on.
There is a huge misunderstanding of ethanol based fuels.

As I have mentioned here many times, there is a huge difference between manufacturers specifications of;
“E10 compatible”
“Designed for E10”

We can discuss this if anyone is interested.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 125
Registered: 02-2015
Posted on Saturday, 29 October, 2022 - 09:50:   Edit PostDelete PostView Post/Check IP

I can discount the impact of E10 since I always run the Corniche on 98 Octane unleaded. The petrol spec for this car is 97 RON, and I have never used E10. In Queensland there is always non-E10 available at all petrol stations, unlike some other states.
I had planned to replace the filter after next week and I will also look at cleaning out the tank.

I did find some teflon-type gunk about a year ago in the carby after the NRMA in NSW checked the strainer on the carby due to another issue. I thought that there might have been a bit more of this gunk in the fuel passages. This teflon gunk was deposited when the NRMA assisted after a large piece the O-ring between the air cleaner and the carburettor lodged in the one of the carburettor throats (due to a mechanic (not me!) incorrectly installing the air filter and accidently cut the O-ring in two!!!)

Many thanks for all the suggestions - in a couple of weeks I will have worked through each suggestion one by one, so that hopefully I will fix the problem and know exactly what the cause is.
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Trevor Hodgekinson
Frequent User
Username: wm20

Post Number: 290
Registered: 11-2006
Posted on Wednesday, 02 November, 2022 - 09:11:   Edit PostDelete PostView Post/Check IP

With all of the rain we have had this year, water in your fuel is not a surprise particularly if the tank is not kept full when the car is not being used.

The moisture in the air condenses to water overnight then drops to the bottom of the tank where it gets picked up when you corner, go up or down steep hills etc.

You man need o drain the fuel tank.

Excesive water will cause the problems you are having ( along with 100 other things )

Try to capture the fuel in the filter when you change it then tip it out & see what is there.

.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2542
Registered: 09-2004
Posted on Thursday, 03 November, 2022 - 05:53:   Edit PostDelete PostView Post/Check IP

You are lucky to be able to obtain fuel without E5 and E10 (Ethanol), in the Uk just the two ethanol types. E5 is now ethanol super unleaded.
Time to start flying again and run 100 avgas in some of my classics.


Thank goodness for LPG on the Shadow.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 126
Registered: 02-2015
Posted on Friday, 04 November, 2022 - 15:09:   Edit PostDelete PostView Post/Check IP

Today I drained some fuel from the tank. There was a couple of fine black sediment particles, but no water.
I then replaced the fuel filter. This was previously replaced in October 2016. There was an amount of fine black sediment collected in the bottom of the filter bowl, but no water.

The car is running well, so I will persevere for a few more days before taking the Solex out again if the rough idling recurs.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 127
Registered: 02-2015
Posted on Tuesday, 08 November, 2022 - 05:49:   Edit PostDelete PostView Post/Check IP

I ran the Corniche for a couple of days, usually without incident. However, after some time, about once every 10 stops in traffic, the car would run rough. Ugh!

Yesterday, I pulled the Solex 4A1 carby out. There was no water and everything was clean. I reckon the water I found the previous time I took the carby out was from the coolant running through the heater/bimetallic element.
I put it back in and didn't finish the job as a mate called in and we had a beer.
This morning I woke up at 1 am and started thinking again. I have been running the idle screws at three and a half turns out to keep the idle speed up a bit versus the recommended one and a half turns to two turns out. Then I thought what if one of the Anti Run On Valves was playing up? This would stop the fuel to one of the primary throats at idle and cause my problem.

This morning I checked in the workshop manual, and, sure enough, one of 3 causes of rough idling is a faulty Anti Run On Valve. The problem now is that Flying Spares and IntroCar are out of the replacement valves.

Can these valves be reconditioned or are they available somewhere else? It seems that a failure of one of these valves would be a good explanation of my intermittent problem - ie an electrical problem affecting the operation of the carburettor.

Any thoughts on how to recondition the valves or a source of new ones would be most welcome.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 128
Registered: 02-2015
Posted on Tuesday, 08 November, 2022 - 08:33:   Edit PostDelete PostView Post/Check IP

I went to the Bentley Heritage Parts website this morning, and it claimed that the Anti Run On Valves were in stock. I had so much difficulty with the site, I don't really know whether they got my query. I will let you know if I get a response.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 825
Registered: 05-2016
Posted on Tuesday, 08 November, 2022 - 10:13:   Edit PostDelete PostView Post/Check IP

The valves can stick, sometimes removing them an squirting a good dose of WD40 into the hose inlet and giving it a shake can unstick it.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 129
Registered: 02-2015
Posted on Tuesday, 08 November, 2022 - 20:50:   Edit PostDelete PostView Post/Check IP

Today I decided to remove the Anti Run On (ARO) Valves. What a pest that I had just re-installed the Solex. To remove the ARO valves, the carby has to be removed from the engine.

Removing a carby twice in two days is a thing reserved for dud mechanics (ie me!).
I took off the carby and removed the ARO valves. They were clean and I worked them backwards and forwards with an independent 12 V supply. Everything worked perfectly. Just for good measure I liberally cleaned them with carby cleaner.

I spoke to Richard Treacy earlier today to see if he had any replacement AROs, but he didn't. He suggested that I run the car without the AROs to see what happened. I am chasing up 8mm bolts with 1.00mm pitch to try and plug the holes left after removing the AROs. A bit tricky, since the holes are at an angle and sealing the fittings might be a problem. Judicious use of small O-rings might do the trick.

I am now suspicious that there might be an intermittent failure of the power to the AROs. The solenoids worked perfectly over at least 50 cycles each. Removing the AROs and seeing what happens might confirm that I have a problem with the power supply.

Any feedback on what I am trying to do would be most welcome.
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John Rowney
Experienced User
Username: johnrowney

Post Number: 130
Registered: 02-2015
Posted on Friday, 11 November, 2022 - 18:39:   Edit PostDelete PostView Post/Check IP

Today I replaced the AROs and fitted a concoction of a bolt, washer, teflon tape and O-rings to seal the hole where the ARO previously existed.
I put everything back in place and there were no leaks. Wow! a bit of success. After starting DRH32489 up, nothing went according to plan!
Unless I had my foot well on the accelerator, the engine would stop instantly.
After many thoughts, I found that I had forgotten to re-install the idling air correction jets. These are little grub screws with a small hole drilled in them. Wouldn't you know it, I dropped one of them and spent half an hour looking for it. Something about 4mm by 2mm and black in colour is rather difficult to find on a black and white floor! Finally, success.
Once I put the grub screws in, everything worked well, except I had to open the stop on the main throttle to keep the revs up. This must be due to the fact that the AVO has a significant restriction with the holes in the business end of the solenoid. Without the AVO, the liquid flow must be significantly higher than normal.

Anyway things are looking good. I have given up for the night and I have drowned my sorrows in a couple of rum-and-cokes. I will tackle the problems again later in the weekend.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 827
Registered: 05-2016
Posted on Friday, 11 November, 2022 - 22:16:   Edit PostDelete PostView Post/Check IP

The joys of classic car ownership, it's rewarding when problems are eventually solved.

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