Petrol engine won't run / start?

jamie N

jamie N

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1936 side valve engine, fuel OK to carburettor, sparks at plugs. Engine ran OK for 20 seconds a couple of times, but nothing since. Have checked that the fuels still OK; have checked that the sparks are still there; the advance/retard (I know..!) is in the original position, but still the engine won't run. Any ideas?
When turning over it 'sort of' backfires, and it's possible that fuel comes from the carb air inlet, indicating the float isn't right. Does anyone have any further ideas? We did have to put emery paper across the points to get a spark which was a journey back into the past!
 
Fresh fuel, a bit of EZ start perhaps?

Check valve clearances, but if it DID run, it sounds basically OK...
 
Hi

The backfire is likely to indicate that you need to retard the ignition. I recall on old bikes that we set the retard / advance so that starting cold was with the lever in the fully retarded pos'n and fully advanced when running hot and fast.
 
If the engine ran for 20 seconds, that would be about the same amount of time it would take for the carb bowl to empty. Make sure the float valve is not sticking up in the body - the floats may be operating and going down, but the valve may get stuck.
I am guessing that a carb od that age would have a tickler button. Push that until fuel flows out. If it doesn't flow - the valve is stuck.

Moving on from there, change the condenser if you can see any blue or purple around the points contacts.
The points should be set with a folded Rizla paper to give around fifteen thou gap.
Double up the Rizla again and check the spark plug gap - 25 thou. Ensure the ceramic electrode head is not cracked.
Check the springiness of the points, do they clamp shut or a bit lazy when sprung open?
Also with an engine of that age, I am going to assume that you have a mag-dyno supplying the electrics. Would need to know which make/model you have, as they set differently. Check the contacts inside that, and ensure it is not arcing out inside.
Further assumptions made include it might have a distributor cap - check all the HT and LT connections are good, check carefully for cracks in any of the Bakelite caps around the whole system - leakage path for high tension.


What engine is it?
 
Also make sure the plug leads are on the correct cylinders (assuming more than one cylinder). If it is an Albin there is a knack to setting the timing right on the magneto. Don't remember the details - just the hanging upside down to reach the back of the engine while somebody else is reading out the instructions in the manual.
 
If it ran before and doesn't now and backfires(ish) it points to weak mixture. Either stuck needle valve as suggested or crud in the main jet. (or loose carb!)
 
Many thanks for all of the above. Here's the sit-rep as of 'Beer O' Clock': the whole day was spent at the engine. I took the carb off and disassembled it. The float valve does operate perfectly, there didn't seem to be any blocked jets, or grime in the carb etc.etc, All in all, the carb does seem to work. The only thing of note was that the choke was connected back to front as it were, but that was easily resolved. I changed the plugs for a slightly longer pair which also sparked magnificently in air; I did change the plug leads around 'just in case', but to no avail. The starter motor had also 'reached the end of it's life' I should also say, thus most of this was being done by the starting handle for added joy! The points were taken off and set to the specs in the manual, a small amount of emery being used to further enhance the sparks. There's fuel in the head after cranking, the sparks seem to be sparking, thus it must be the timing. I removed the points/magneto assembly, and set them by the manual, with no change at all. No backfiring even!
I do realise that it's probably the timing/HT leads, so off I went to 3 motor factors in search of new HT leads. (This is more worthy of a rant in the Lounge by the way). Halfords told me that they don't stock HT leads. Unipart said they don't do this type of HT leads, "only leads for named motors". When I explained that the HT leads don't know which motor they're for, the chap glazed over in confusion. The 3rd factor said that he didn't know if they had any leads like mine as they were all in boxes. When asked if we could look into some of these boxes, he took offence and looked at his watch, "It's quarter to five!".
We'll crack on tomorrow, with tracing a replacement starter motor, and then it'll all work perfectly. (It being beer O' Clock +3 now).
Cheers :encouragement:
Forgot to mention the engine's a Volvo/Penta C10. 1936 design, 880cc, 10hp, side valve twin. Bronze Solex carb and plenty of very pretty piping.
880 cc and 10hp! What will they think of next.....!
 
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The 20 seconds it ran for- was this the first time in a long time?

When you hand crank- plenty of compression? ( I'm asking to eliminate stuck rings)

BTW- the Rizla feeler gauge trick is NOT with a double or quadruple fag paper- use the cardboard of the packet to give you c.12thou on the points and 25thou on the plugs

Second BTW- you should not clean gaps with emery, sandpaper is used ( don't ask me why- not sure I ever knew!)

Keep us posted-
 
You said it was a magneto- suggest you clean the earth brush and try it without surpressor caps if you have them fitted. They tend to increase the resistance flowing in the secondary coil -- should your magneto armature be a bit old with suspect insulation it could track else where not at the plugs when under load- making the plug gap smaller could also help. Do the plugs come out wet after trying to start? If they are wet it points to an electrical problem-- sparks or timing.
 
have you tried putting some oil into each bore to give a false compression to give it a chance to fire up
If you don't get it running there is a chance you'll wash the bores with petrol
The carb sounds like a 30mhg solex the needle valve should have a washer thickness between 1.2 mm to 1.4mm
be sure to have flame trap gauze over the carb intake, you risk fire if there's just an open inlet

cheers
mick
 
jamie N said:
Forgot to mention the engine's a Volvo/Penta C10. 1936 design, 880cc, 10hp, side valve twin. Bronze Solex carb and plenty of very pretty piping.
880 cc and 10hp! What will they think of next.....!
Click to expand...

It is actually an Albin badged as a Volvo (nothing new!). Does the magneto have a little lever to alter the advance retard? Seem to remember when I looked after one years ago that getting that set right was important.
 
Do the plugs come out wet after trying to start? If they are wet it points to an electrical problem-- sparks or timing.
Yup, they do come out wet, but I don't believe it's due to the needle valve being stuck open, but as you say, no ignition through timing (maybe).

The carb sounds like a 30mhg solex the needle valve should have a washer thickness between 1.2 mm to 1.4mm
be sure to have flame trap gauze over the carb intake, you risk fire if there's just an open inlet
Very close! It's a Solex 26 NV906, with 4 layers of wire gauze in place. I've never seen this before.

It is actually an Albin badged as a Volvo (nothing new!). Does the magneto have a little lever to alter the advance retard? Seem to remember when I looked after one years ago that getting that set right was important.
I altered the advance retard lever, and also the housing that it's mounted on to further the adjustment, perhaps by +/- 45degs. Not a bit of difference.

Todays plan is to get the starter motor either replaced or repaired. I've a bit of luck also as SWMBO is deserting me this weekend for Edinburgh, which will encourage straighter thinking perhaps?
Many thanks again for all the advice on this. I'll keep posting about it until it's cured and the engine's running, then I'm sure that all contributors will be trying to pay a percentage in the cost of repairing the starter motor as we're all SO involved in it? :D
 
Make sure the exhaust is clear - I once had a Vire 6 with similar symptoms - after a couple of years struggling found out the rubber bellow silencer hidden away in the lazarette was the wrong way round- it had a non-return flap in it !
Stupidly simple but worth a check.
 
That's a VERY good fault to find! Progress is halted right now as I've had to dismantle the starter motor, and am now waiting on springs for the brushes to arrive. Unfortunately, they're due to arrive on Wednesday, when I'm due to go to Germany for 10 days! Many of the Auto-Factors that I've been to visit in trying to get these springs, and new HT leads also, have shown themselves to be utterly unhelpful and lazy. Unless one's able to specify what 'car' it's for, thus enabling them to find the shelf that it's located on from the computer, they're not interested. I did ask one shop if we could perhaps look into a box to see if I could perhaps adapt it. The guy was quite shocked.
Only one shop was at all helpful, but didn't have the bits I need, he did say that almost no-one these days would do this type of work. He was impressed with the spec of the engine, in being able to get only 10hp out of an 880 cc engine!
 
Jamie
Wasting a lot of time in a motor factors. Find an auto electrician.
David Riach Unit 5, 8 Harbour RoadIV1 1SY Inverness 01463 714277


A.S Wells
141/24 Station SquareIV1 1LD Inverness 01463719453

If they're any good they'll have all the bits in stock - especially wire plug lead.

ps it isn't 10 bhp, it's 10 fiscal (or tax) hp

One way of calculating it
was
The RAC (British) formula for calculating tax horsepower:

\text{RAC h.p.}=\frac{D^2\times n}{2.5}

where

D is the diameter (or bore) of the cylinder in inches
n is the number of cylinders

:)
 
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Getting bits is almost impossible from motor factors these days.Lucas actually used to be pretty good when it came to springs and brushes.
however if you look had enough on Google you can usually find the supplier of your dreams.
Recently I was having an issue with brake shoes for an old trailer and low and behold I found an aftermarket brake company in Leeds with an online by measurement cross reference catalogue.
More to the point I recall a few years ago finding an auto electrician quite happy to restore a wipac mag.
Then there are the carburettor stockists who collect defunct carbs from whom I got a carb for the old Coventry victor I used to have.
 
Might be worth considering a coil conversion.Use the existing points, but rewire for a 12v coil, or two. OK, it needs a battery to power it. But it has been a very sucessful mod to other two stroke twins from ancient times. Nothing to beat a nice fat spark..
 
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