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As you may know the changeover from leaded to unleaded has been bad for the FWD. It starts ok, and runs fine for a little while, but then becomes utterly gutless and sounds like a milk churn full of spanners rolling down a flight of stairs. However, a change back to leaded solves the problem instantly.

 

So we have tried:

mixing unleaded with paraffin

Fitting an external fuel pipe in case the petrol was getting too hot

Changing the jet on the carb.

 

None of this has worked. The next suggestion is to adjust the timing. Now as the thing runs fine with leaded, is it feasible that the timing would need to be changed for unleaded? Chapter 8 ("Troubles and remedies") of the manual for the Motor Supply Train (pub 1918) would suggest that this is a good remedy for the symptoms we are suffering. What are the thoughts of this most knowledgable band of brothers?

 

Tim (too)

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Adjusting the timing might solve your problem, a lot of older vehicles needed adjusting when unleaded started to come in.

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None of this has worked. The next suggestion is to adjust the timing. Now as the thing runs fine with leaded, is it feasible that the timing would need to be changed for unleaded? Chapter 8 ("Troubles and remedies") of the manual for the Motor Supply Train (pub 1918) would suggest that this is a good remedy for the symptoms we are suffering. What are the thoughts of this most knowledgable band of brothers?

 

Tim (too)

 

 

Tim,

 

I would think the inconsistencies of petrol in WW1 period would have caused the same problems, in fact I do believe that lead may not have been present in motor spirit at that time. You 1918 book sound like it takes this into account.

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Tim,

 

My understanding is that for low compression engines, lead shouldn't make any real difference (it helps stop pinking). In any event, as RF says, lead additives came in during the 1920s.

 

This may of interest more generally: http://www.quillertriumph.co.uk/Quiller/Unleaded/federation%20info.htm

 

Tim, which octane rating of unleaded do you use? have you tried high and low?

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Yes you are all quite right. The lorry was still in use up until the 1970's, therfore the engine must have been adjusted to take leaded petrol into consideration. Now we have lost leaded it needs readjusting again (or a supply of leaded petrol). Going back to the manual, it states (and please excuse me if i have given too much information, but it makes interesting reading):

 

Diagnosing troubles of automobile engines.

 

To manage successfully an internal combustion engine, especially one that works under a variety of conditions, often very severe, as the automobile engine – it is first of all necessary for the operator to make good use of his reasoning facilities.

 

The symptoms of derangement, when taken singly, are often such as may be caused by any one of several possible defects. In nearly every case the defect, whatever it may be, will produce several symptoms, a careful study of which will lead to the elimination of causes that do not tally with all the symptoms as for instance causes affecting all cylinders when only one or two are misbehaving, or vica versa. When the user has reached this point, generally a short further investigation of the points at which trouble of that particular sort is most likely to occur will lead him to the discovery of the true cause. The cause of loss of power, due to such faults as a lose battery connection, a sticking inlet valve, or a bit of dirt in the carburettor, will at once be recognised in its true character by the experienced operator. The only way to attain final proficiency in these things is by extended experience of the particular engine in hand; but on the other hand there is no excuse for the aimless groping of many inexperienced users, who will often send needlessly for a tow, or will pull an engine to pieces in their search for some simple fault that might be located by intelligent diagnosis. (You heard it here first – I am “an aimless inexperienced groper”).

 

 

Reasons for failure of engine to develop full power.

 

A failure of the engine to develop its full power should not be confused with frictional resistance in the transmission system or dragging brakes. The chief reasons for this trouble in the engine itself are:

 

1). Back pressure on account of choked muffler. Opening the muffler cut out or relief valve will at once indicate whether or not this is a cause of the trouble.

 

2). Lubrication insufficient, especially in the cylinder

 

3). Overheating.

 

4). Compression leaks at the valves, around the piston, or through a porous cylinder wall or a loose cylinder plug.

 

5). Particles of carbon or other dirt under a valve.

 

6). Valves not properly timed.

 

7). Mixture too rich or too lean.

 

8). Ignition spark weak on account of weak battery.

 

9). Water entering cylinder from water jacket.

 

10). Timer slipped on shaft causing late spark.

 

As it works fine with leaded but not unleaded we can narrow it down to just items 6 or 7. As we have tried the adjusting the mixture the problem looks to be a timing issue. Any thoughts or other good ideas?

 

Tim (too)

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If it's any help, my Ford WOT2 manual lists a change to the main jet on the carb when using leaded petrol, the change being dated Dec 1943. The jet was 140 for pre-war unleaded and 145 for wartime leaded petrol.

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no excuse for the aimless groping

 

As it works fine with leaded but not unleaded we can narrow it down to just items 6 or 7. As we have tried the adjusting the mixture the problem looks to be a timing issue. Any thoughts or other good ideas?

 

 

 

 

Tim,

 

I like that "groping" phrase......a lot of that goes on :-D

 

You mention valves, check the clearances are correct because any variation effects valve timing, also breaker points gap if not right will effect ignition timing, assuming it is a magneto or distributor ( or is it a trembler coil ignition?)

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How about trying some of those Unleaded Octane boosters that are sold. They are available in Halfords. The old leaded petrol was a higher octane rating than the present unleaded. Another idea is trying super unleaded.

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Groping and tremblers, that brings a number of images to mind.......none of them related to timing or ignition:cool2:

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How about trying some of those Unleaded Octane boosters that are sold. They are available in Halfords. The old leaded petrol was a higher octane rating than the present unleaded. Another idea is trying super unleaded.

 

I wouldn't have thought that either of these options would be necessary when you consider the octane rating of the fuel that this engine was originally manufactured to run on.

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Yes you are all quite right. The lorry was still in use up until the 1970's, therfore the engine must have been adjusted to take leaded petrol into consideration. Now we have lost leaded it needs readjusting again (or a supply of leaded petrol). Going back to the manual, it states (and please excuse me if i have given too much information, but it makes interesting reading):

 

Diagnosing troubles of automobile engines.

 

To manage successfully an internal combustion engine, especially one that works under a variety of conditions, often very severe, as the automobile engine – it is first of all necessary for the operator to make good use of his reasoning facilities.

 

The symptoms of derangement, when taken singly, are often such as may be caused by any one of several possible defects. In nearly every case the defect, whatever it may be, will produce several symptoms, a careful study of which will lead to the elimination of causes that do not tally with all the symptoms as for instance causes affecting all cylinders when only one or two are misbehaving, or vica versa. When the user has reached this point, generally a short further investigation of the points at which trouble of that particular sort is most likely to occur will lead him to the discovery of the true cause. The cause of loss of power, due to such faults as a lose battery connection, a sticking inlet valve, or a bit of dirt in the carburettor, will at once be recognised in its true character by the experienced operator. The only way to attain final proficiency in these things is by extended experience of the particular engine in hand; but on the other hand there is no excuse for the aimless groping of many inexperienced users, who will often send needlessly for a tow, or will pull an engine to pieces in their search for some simple fault that might be located by intelligent diagnosis. (You heard it here first – I am “an aimless inexperienced groper”).

 

 

Reasons for failure of engine to develop full power.

 

A failure of the engine to develop its full power should not be confused with frictional resistance in the transmission system or dragging brakes. The chief reasons for this trouble in the engine itself are:

 

1). Back pressure on account of choked muffler. Opening the muffler cut out or relief valve will at once indicate whether or not this is a cause of the trouble.

 

2). Lubrication insufficient, especially in the cylinder

 

3). Overheating.

 

4). Compression leaks at the valves, around the piston, or through a porous cylinder wall or a loose cylinder plug.

 

5). Particles of carbon or other dirt under a valve.

 

6). Valves not properly timed.

 

7). Mixture too rich or too lean.

 

8). Ignition spark weak on account of weak battery.

 

9). Water entering cylinder from water jacket.

 

10). Timer slipped on shaft causing late spark.

 

As it works fine with leaded but not unleaded we can narrow it down to just items 6 or 7. As we have tried the adjusting the mixture the problem looks to be a timing issue. Any thoughts or other good ideas?

 

Tim (too)

 

When unleaded fuel first came in; manufacturers recommended retarding the ignition timing (A few degrees) due to the different combustion characteristics of the fuel. I take it you have valves and seats suitable for unleaded fuel, as the lead content also provides a lubricant for the valve seat to reduce wear?

 

Have you tried using a lead substitute in the fuel as this could help. Another alternative would be to use a fuel catalyst, either an in line one or a bag of pellets in the fuel tank. (WW2 technology)

 

I suspect that modern fuel is of too high a quality for an engine such a yours and if all else fails then I would you give it what it wants, which is obviously leaded fuel. If it runs ok on this, then there isn't anything wrong with the engine settings such as valve timing.

 

I hope this has been of some help to you. Good luck, Will.

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Tim,

 

On another forum, an owner of a Bedford RL, Green Goddess to be precise, reckoned that it ran better on stale petrol (6 months old), in other words, when some of the more volatile ingridients had evaporated off. I have also noticed this, so perhaps fresh petrol is to be avoided, keep a can to one side for a while. :confused:

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And I thought a lot of vehicles of that era had timing adjustable at the wheel or certainly on the dash to allow for the variation in fuel supply.

 

If it really does return to O.K. instantly you switch back to leaded it can only be the octane difference, nothing to do with valve timing or lubrication of valves and seats. Therefore I would imagine tweaking the timing of the spark should do the trick.

 

Failing finding data in a book to suggest settings. Can't you run the engine and adjust the timing back and forth whilst running to see if there's an improvement in performance. I've set timing by ear a few times even on V8's to get up and running when no other equipment has been to hand.

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Tim,

 

On another forum, an owner of a Bedford RL, Green Goddess to be precise, reckoned that it ran better on stale petrol (6 months old), in other words, when some of the more volatile ingridients had evaporated off. I have also noticed this, so perhaps fresh petrol is to be avoided, keep a can to one side for a while. :confused:

 

I've heard the modern unleaded stuff is bad for old fuel lines and many rubber seals.

Not something that'd cause your problems Tim as the damage would be permanent but something to bear in mind.

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"it is first of all necessary for the operator to make good use of his reasoning facilities."

this first part I can grasp but the next one is open to question as it could apply to either the engine or the operator

"The symptoms of derangement"

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As you may know the changeover from leaded to unleaded has been bad for the FWD. It starts ok, and runs fine for a little while, but then becomes utterly gutless and sounds like a milk churn full of spanners rolling down a flight of stairs. However, a change back to leaded solves the problem instantly.

 

So we have tried:

mixing unleaded with paraffin

Fitting an external fuel pipe in case the petrol was getting too hot

Changing the jet on the carb.

 

None of this has worked. The next suggestion is to adjust the timing. Now as the thing runs fine with leaded, is it feasible that the timing would need to be changed for unleaded? Chapter 8 ("Troubles and remedies") of the manual for the Motor Supply Train (pub 1918) would suggest that this is a good remedy for the symptoms we are suffering. What are the thoughts of this most knowledgable band of brothers?

 

Tim (too)

 

Tim, that fact that it runs OK for a while and then develops problems may be overheating due to the mixture still burning when the exhaust valves open. This may be caused by the very low compression causing a delay in complete combustion. Is the exhaust manifold getting very hot with unleaded or flames showing at the tailpipe? The lack of power and mechanical noise may be the valves begining to seize and not closing correctly.

 

Mike

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Hi Tim, have been reading all the helpfull coments about your timing etc. I phoned your father and suggested that as your engine was produced well before leaded petrol was in supply that the ignition timing would need altering, much as others have posted on here. I should have known that you can do this manually from the steering column, Dad instructed me to carry on and put a reply on here regardless, He also had a good laugh when I told him that I was Blackpowder and I have been writing about MPV, he obviously had enjoyed the site. May see you at Honiton Hill Rally, John.

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Tim, I know that there will be a lot of argument, but try a Brocquet catalyst, either in line or in the tank. I've had a lot of success with the same one, moved from car to car over the years. Out of intrest, what date is the manual you've quoted from?

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Hi Chaps!

 

I have just spent the weekend in Devon trying to get the thing to go properly but with little success. This is the story so far:

 

As I recall (and no doubt Tim will be able to correct me!) After some initial fiddling and messing, we finally got the lorry to go well on leaded four-star after we first rebuilt it. For two years or so, it was fine and behaved as one might expect. The change to LRP didn't faze it and we were fine. Then, we were forced to go over to unleaded at which point (possibly coincidental) it became gutless and would not pull at all. Removal of the engine covers allowed a real wall of heat out and the fuel could be seen boiling in the float chamber (the float chamber is made of glass). We tried various ratios of paraffin mixed in but it never came back to its old self. At one of the local rallies, we plumbed in a separate tank of leaded fuel and then ran it around the field. It popped and banged terribly on unleaded but immediately recovered when we changed over to leaded and decayed again when we changed back. We have therefore reached the conclusion that fuel does have something to do with the problem.

 

When Fathers car was converted over, they retarded the ignition. The timing on the lorry is manually adjustable from 5° retarded to 25° advanced so I retarded the ignition whilst it was running but achieved no noticeable effect.

 

This weekend, I drained the tank and filled it with new fuel. I then carefully sealed the manifold joints and we ran it. The caburettor was immediately seen to start icing. We set off down the road and the performance was quite acceptable for a while. After about half a mile, as it all warmed up, the power began to decay noticeably and the lorry began to surge. In other words, it pulled well for a few revolutions and then died back and then the same again. With the icing carb and the surging, I diagnosed a lean mixture (do you agree?) and fitted a larger high speed jet. This got us home but was no real improvement.

 

On Sunday morning, I put the original jets back and rigged up a separate fuel line outside the engine bay in order that the fuel was not heated. Another test run had it running pretty rough but the performance did not decay. From this, I think that fuel vapourisation may also be a part of the problem. I seem to recall that unleaded is more volatile than the old four star. Is this correct?

 

At this point I took some advice and tried advancing the magneto one notch. We set off for another test run but it was awful. Continuous backfiring through the silencer (which we blew to pieces!) and total loss of power. I then returned the timing to what it had been but it was then even worse. At first, it would run on only one cylinder. Then it idled fine but as soon as any load came on, it suffered multiple mis-fires and could not move itself. After fooling around with it for a couple of hours, we towed it home with the Land Rover. It is currently parked outside as it requires power to move it into the shed.

 

I originally thought fuel was the problem but am now beginning to think the magneto might be weak. The mis-firing under load could be an indication of this. Next time we go out, I intend to fit our spare mag but in the mean time, I would be very pleased to hear your views.

 

The knowledge is out there!

 

Cheers!

 

Steve

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Steve,

 

You are correct about the fuel being more volatile. Would it be possible to fit an insulator gasket between the carb and manifold? Also wrap the fuel lines adjacent ot the engine in asbestos string (I know H&S, did it to my Bedford 20 years ago to cure evaporation problems).

 

Have you been in contact with any veteran car owners, as some of them may be experiencing this?

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Hi Steve, what's the chances of the problems being your plugs not coping with the differences in fuel?

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Have you got (if it uses one) a head gasket or valve problem? Only when the Champ went on the road for the first time Lots of running problem no power when hot and two split silencers due to a blown head gasket.

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The following is the Petrol octane ratings prior to WW2:-

 

Petrol - Commercial 68 octane (Pool Petrol), No. 1 grade 75 octane and top grade 80 octane.

 

Modern unleaded is around the 96 octane mark, even higher for the premium grades around 105 octane, so modern fuel is nothing like the stuff designed for vehicles of yore.

 

Here is an excerpt from the Ferguson tractor guys, they used to use a mix called TVO (Tractor Vapourising Oil) no longer available for sale, but it has alot of applications in other older vehicles:-

 

"There must only ever be 2 ingredients in TVO

1. Petrol (unleaded is absolutely fine for a Ferguson tractor) 98 Octane.

2. 28 Second Heating Oil 20 Octane.

 

Aim for an Octane value between 55 and 70.

55 if doing very hard work

70 if doing topping and the like

To give you some idea of the sums:-

1 part petrol and 1 part heating oil comes out at 59 Octane.

2 parts petrol and 1 part heating oil comes out at 72 Octane.

1 part petrol and 2 parts heating oil comes out at 46 Octane.

Petrol on its own is suitable for road runs (with the heat shield removed).

Octane is not the only factor, but it provides a good guide.

Diesel fuel is designed to cause ignition by compression and will encourage pinking. It is not designed to burn in TVO tractors, and no upper cylinder lubricant is required in these tractors, so do not use anything other than petrol and heating oil.

Using fuel which does not burn completely will destroy the lubricating properties of the oil and that (in a Ferguson TE tractor) will result in wear to the cam shaft bushes and then loss of oil pressure from cam shaft bushes. Loss of oil pressure will, then result in damage to the crank shaft."

 

Its referring to a tractor, but its a low compression version of the Standard Triumph car engine that it is using.

 

I have tried it in my Humber, making a mix equating to approx 72 octane, and it ran very nice and smooth, (Smells like a tilley lamp!) this is the equivalent to the old 2 star, and close to the Pool petrol that the B series range of engines was designed to run on.

Croc has a theory that the poor running of numerous Petrol Meadows engines in Scammell Explorers is purely down to modern fuel octane causing vapour locks and atomising/evaporating faster due to the higher spirit in the distillation, i am inclined to agree.

 

It would be prudent to point out that the Customs and Excise dont like you adding non-taxed for the road fuel additives to existing Pump petrol and diesel, and that all tests carried out by myself were at a standstill in my back yard nowhere near a road or anywhere else for a matter of fact....who are you, what you on about, i dont know you do i.......

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Guest catweazle (Banned Member)
evaporating faster due to the higher spirit in the distillation, i am inclined to agree.

This is the main problem without a doubt,i have found fitting an electric pump for back up or full time use with a bleed back to the tank allows fresh cooler petrol to circulate and especially in hot weather in traffic doesnt get vapour locked,first sign of traffic on it goes,i used to get vapour locked after filling up in the garage because the under bonnet temp goes up when you stop.I put pump on purges system of you go,:-D

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This is the main problem without a doubt,i have found fitting an electric pump for back up or full time use with a bleed back to the tank allows fresh cooler petrol to circulate and especially in hot weather in traffic doesnt get vapour locked,first sign of traffic on it goes,i used to get vapour locked after filling up in the garage because the under bonnet temp goes up when you stop.I put pump on purges system of you go,:-D

 

Sounds similar to the system most modern cars run these days. Cycling the petrol back to the tank. I belive most even filter the fuel on it's return as well as pickup through the same filter chamber. I don't know if this is also intended as a method of heat exchange.

 

Sounds like a lot of hassle to have to go to to get a classic MV to run, and not particualrly easy to hide on some.

Think I'd be trying out the fuel mixes myself. You can legally run on fuel oil (red) as long as you declare any road mileage to customs and excise and pay the duty due.

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You can legally run on fuel oil (red) as long as you declare any road mileage to customs and excise and pay the duty due.

 

 

Are you not confusing red diesel with 28 second burning oil which is essentially kerosine?

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