trophy160 Posted July 7, 2015 Share Posted July 7, 2015 Some background - My Mk6 has been converted to conventional (non reverse flow) rad fans, so sucks in at the front and vents through the beehives. The problem I have is that is starts and runs fine for a few miles, but if I come to a standstill the engine may then stall, or even if I stop the engine which has been running perfectly up to the point that I stop it, I cannot restart the engine for an hour or so until it cools down. Yes I know I could convert back to reverse flow, but this is a fair cost and effort to do (as I don't have the parts) and I'm not 100% convinced that it will solve the problem. I have been working on the assumption that the fuel line or carb was getting a vapour lock so I fitted a secondary electric fuel pump to push the fuel through - problem not fixed. Today I propped open a beehive and drove the vehicle a couple of miles before stopping, as usual it would not restart. Now the relevant points are: the engine bay and carb was not that hot, so I really don't think it was boiling fuel in the carb (one of my theories) the electric pump was not ticking away, so I believe there was fuel in the the lines, in fact when I loosened the banjo on the carb there was some pressure in the lines and I got a squirt of fuel the water temp gauge was reading normal temperature and nothing was boiling over From this I conclude that it is perhaps not a fuelling problem. Next thoughts are (a) the ignition condenser or (b) the ignition coil are breaking down when they get hot. So any thoughts, could this be an electrical problem when it gets hot? any easy quick tests that I can apply at the side of the road, so there will only be me there meaning I can't crank the engine and have my head in the engine bay at the same time so limited as to what I can easily do. Nic ps I've only got just over a month to resolve this if I'm to get to Combined Ops at Headcorn this year. Quote Link to comment Share on other sites More sharing options...
Degsy Posted July 7, 2015 Share Posted July 7, 2015 I had a similar problem with my weasel and suspected the coil or condenser which it could well be. However I finally traced the problem to the radio suppressor attached to the coil, removed same and problem cured. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 7, 2015 Author Share Posted July 7, 2015 That's intersting and I'd not considered it, so your problem was also heat related and presumably would do it every time you used the vehicle? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 7, 2015 Share Posted July 7, 2015 Next thoughts are (a) the ignition condenser or (b) the ignition coil are breaking down when they get hot. So any thoughts, could this be an electrical problem when it gets hot? any easy quick tests that I can apply at the side of the road It is very likely that either of these could be effected by heat. Check that the ventilation pipes to the distributor are not blocked. If you bring the capacitor & coil to WPR I can test them for you. These need to be tested at the sort of voltages they work at, so 300v on the capacitor & I can test the coil for leakage at 5,000v. When the coil is cold this must be quite high because as the coil warms up its insulation can deteriorate significantly. I had a coil with a leakage of 25 megohms that just about functioned but when hot reduced to 2 megohms & became non-functional. It took nearly an hour for it to cool sufficiently to be able to produce a spark again. I have just purchased a new coil & that has a cold leakage of 40 gigohms, so that gives some latitude for when it becomes hot. Quote Link to comment Share on other sites More sharing options...
FEC Posted July 7, 2015 Share Posted July 7, 2015 So any thoughts, could this be an electrical problem when it gets hot? any easy quick tests that I can apply at the side of the road, so there will only be me there meaning I can't crank the engine and have my head in the engine bay at the same time so limited as to what I can easily do. Hi Are you sure it is heat related. I say this because I had a Stalwart doing similar stunts when in motion. I thought the same as you and trolled through the same usual culprits. I fell upon the problem when broken down on a traffic junction. It would fire a number of times while cranking, but this was intermittent. I pulled the distributor cap off and by chance spotted a shard of the centre electrode sitting on the breaker plate. it had enough mass to short the ignition when halting and turning corners. Probably not but worth a look? Quote Link to comment Share on other sites More sharing options...
Tony B Posted July 7, 2015 Share Posted July 7, 2015 Simple heat gaurds, cut sections of tin fitted around vunerable points can help a lot and are cheap and easy. You can get various goos that coat manifolds to keep the heat in, but they can be pricy. Other thought is an electronic ignition, not the cheapest option, but cure a multitude of problems. Fuel could be gassing, check the fuel lines are not running near anything hot. Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted July 7, 2015 Share Posted July 7, 2015 Nic, I have seen RFC Saracens fitted with original fans and many of them have had heat/ fuel problems. When I say heat, I mean it is being forced back past the gearbox and in the area of the fuel tank and pipes causing vapour locks. The airflow will not evacuate through the beehives easily. If you look at a conventional Saracen you will see ducts around the top rear of engine bay, these are no longer on a RFC type. All you need to do to revert to RFC is change the fans and fit the shroud back on the front of the vehicle. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 7, 2015 Author Share Posted July 7, 2015 Hi Richard, I appreciate the point you are making and this morning I spoke to Richard Banister about buying one of his reverse flow cooling conversion kits. However........ Before making the decision to buy and fit this I conducted a fairly controlled road test today. As I say I propped open a beehive and this really did allow the engine bay to vent and stay pretty cool I also have the vents open inside the vehicle which do allow air to vent from the rear of the gearbox. I drove less than two miles when I stopped the vehicle which was running smoothly. As usual it would not restart, I immediately was able to confirm that there was fuel at the carb and there were no vapour locks in the line. The carb was only warm to the touch I simply cannot believe that vapour locks/boiling fuel in the carb could have been a problem today. I am however convinced that the problem in in some way heat related as by allowing everything to cool off resolves the problem. I'm not saying that my cooling configuration will not cause problems on a hot day and a 'long' journey, but today the temperature of the engine etc was just not that hot. Not sure what the cost of a condenser and coil is, but my thoughts are that it might be worth me swapping those out first before I change fans and re-instate the cowl. Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted July 7, 2015 Share Posted July 7, 2015 Hi Richard, I appreciate the point you are making and this morning I spoke to Richard Banister about buying one of his reverse flow cooling conversion kits. However........ Before making the decision to buy and fit this I conducted a fairly controlled road test today. As I say I propped open a beehive and this really did allow the engine bay to vent and stay pretty cool I also have the vents open inside the vehicle which do allow air to vent from the rear of the gearbox. I drove less than two miles when I stopped the vehicle which was running smoothly. As usual it would not restart, I immediately was able to confirm that there was fuel at the carb and there were no vapour locks in the line. The carb was only warm to the touch I simply cannot believe that vapour locks/boiling fuel in the carb could have been a problem today. I am however convinced that the problem in in some way heat related as by allowing everything to cool off resolves the problem. I'm not saying that my cooling configuration will not cause problems on a hot day and a 'long' journey, but today the temperature of the engine etc was just not that hot. Not sure what the cost of a condenser and coil is, but my thoughts are that it might be worth me swapping those out first before I change fans and re-instate the cowl. Hi Nic, Your points noted. In all your problems with this in last year or so, have you changed coil or condenser yet? Think that would have been my first move, but the RFC change around would have aroused suspicions as it is non-standard and could have been a possible issue. regards, Richard Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 7, 2015 Author Share Posted July 7, 2015 Hi Richard, no not changed them yet. I think until today I had really assumed that the problem was fuel starvation due to the points you make and was focused on ways to mitigate, ie adding in an additional electric fuel pump. I can imagine that I will end up changing the fans and replacing the cowl, but perhaps do the other things first ad they are pretty quick to do Nic Quote Link to comment Share on other sites More sharing options...
CMP-Phil Posted July 7, 2015 Share Posted July 7, 2015 Hi Nic Do you have an IR thermometer? I have found them to be very useful in diagnosing over heating or heat related problems. As other people have mentioned there are a number of electrical components that can be heat sensitive and cause the ignition system to break down. Using an IR Gun Thermometer look at the temperatures of those components are they getting hotter than surround components? Also can you rig up a spark plug on a lead to plug into the coil when the engine will not start to see what kind of a spark you are getting? Last thought, has this problem existed for more than one tank of fuel? Here in the US the first thing to suspect or change is the fuel, amazing how many times that solves the problem. Cheers Phil Please keep us posted on what you try and what the problem is in the end. Quote Link to comment Share on other sites More sharing options...
Degsy Posted July 7, 2015 Share Posted July 7, 2015 That's intersting and I'd not considered it, so your problem was also heat related and presumably would do it every time you used the vehicle? Correct, started first time when cold but would not restart when up to running temperature, once cooled down would start again perfectly. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 7, 2015 Share Posted July 7, 2015 Hi Nic Do you have an IR thermometer? I have found them to be very useful in diagnosing over heating or heat related problems. As other people have mentioned there are a number of electrical components that can be heat sensitive and cause the ignition system to break down. Using an IR Gun Thermometer look at the temperatures of those components are they getting hotter than surround components? Also can you rig up a spark plug on a lead to plug into the coil when the engine will not start to see what kind of a spark you are getting? Last thought, has this problem existed for more than one tank of fuel? Here in the US the first thing to suspect or change is the fuel, amazing how many times that solves the problem. Cheers Phil Please keep us posted on what you try and what the problem is in the end. Phil that sounds a good idea but with my IR gun I was unable to get any sensible readings on the shiny aluminium of the coil. Getting a spark that you can see on a plug can be misleading. The spark gap is of course very small & you may not be getting a spark in the engine due to compression & the gas density. So a spark in air for a healthy coil should be at least 1cm. Quote Link to comment Share on other sites More sharing options...
CMP-Phil Posted July 7, 2015 Share Posted July 7, 2015 Yup IR guns don't like shiny surface, masking tape helps kill that problem. Yes, spark plug spark in open air is different then under compression but the try visual and sound of spark when engine is cold to hot. Your observation though that a no compression spark may look OK is spot on, is a weak spark finding another path when hot? Any indication of trying to cross when hot? Cheers Phil Quote Link to comment Share on other sites More sharing options...
FoolsHumor Posted July 8, 2015 Share Posted July 8, 2015 I seem to have quite a lot of old things that do not run from time to time. If I have nothing when cranking the engine I give the air intake a very light dusting of starting fluid (ether) . If it runs briefly it tells me it was missing fuel but has spark. Be sure to use only minimal amounts of starting fluid. Engine parts turned to shrapnel are disheartening.I have also had considerable trouble with older vehicles and condensers dying. I seem to remember Clive warning that many new old stock condensers are already bad due to age. There was a thread here or on the Ferret Forum where someone had a number for a Chrysler condenser that was the correct size and cap value to work as a direct replacement.You might also consider cooling the ignition coil with some water when it refuses to start, to see if the cooler temps bring it back to life. That used to work on early Ford ECM's that were very heat sensitive.If any of the much wiser individuals here suggest you not try some of the above suggestions, follow their lead. These are just random thoughts from an old guy who has old tired vehicles.Regards,Bob Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 8, 2015 Author Share Posted July 8, 2015 Hi Nic Do you have an IR thermometer? I have found them to be very useful in diagnosing over heating or heat related problems. As other people have mentioned there are a number of electrical components that can be heat sensitive and cause the ignition system to break down. Using an IR Gun Thermometer look at the temperatures of those components are they getting hotter than surround components? Also can you rig up a spark plug on a lead to plug into the coil when the engine will not start to see what kind of a spark you are getting? Last thought, has this problem existed for more than one tank of fuel? Here in the US the first thing to suspect or change is the fuel, amazing how many times that solves the problem. Cheers Phil Please keep us posted on what you try and what the problem is in the end. Hi Phil, IR thermometer is a good idea, I do have one which I'll need to check out first but it could yield some interesting info. The spark idea is a good one, but difficult to implement when there is only one person. I think the fuel should be OK as I put fresh in this year and also when it's running, it runs really well. I've got to resolve this issue as I have spent two hard years restoring it cosmetically inside and out and sitting in the garage is not what I want it to be doing. Nic Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 8, 2015 Author Share Posted July 8, 2015 Lots of good ideas thanks everyone and Clive thanks for the offer of testing my coil and condenser. Since Richard Banister is only a few miles up the road from me I bought a coil and condenser today. Coil is now fitted and hopefully I'll fit the condenser tomorrow and do another road test......I'll post results as soon as I have some Nic Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 8, 2015 Share Posted July 8, 2015 Nic if you are at W&P might be worth bringing the coil & capacitor to test to have a definitive diagnosis. If your capacitor is of recent manufacture you'll probably be fine. But most old stock ones I have tested are defective to some degree. Not defective in the sense they are open or short circuit that can be detected with a multimeter but the insulation has deteriorated so it leaks. So it does not give such an abrupt collapse of the magnetic field when the contact breaker opens, this will reduce the HT output. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 8, 2015 Author Share Posted July 8, 2015 Thanks Clive I'm hoping to get to W&P and will certainly bring the parts if I come. Nic Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 8, 2015 Share Posted July 8, 2015 Nic that would be good. Please bring any other capacitors you want testing. I shall be in Wolf 110 with EMLRA usually fairly close to that enormous Dutch mast which is a very good location marker. Anyone else who wants coils, capacitors, screened cables, sparking plugs etc testing come along with your bits. I am especially keen to gather coils that you might throw away as defective so I can later do post mortems on them & establish the reason for the failure as part of on going research for the good of all. Like trying to determine the lowest tolerable leakage resistance of a cold coil against its leakage after 15 mins of carrying a continuous current. If it then reaches a point of failure to produce a spark, I can produce a value of tolerable cold resistance a coil should have to be to be regarded as reliable. From a breakdown in the Shorland a month ago I know a cold resistance of 22 megohms is too low for it to function when hot. But I need coils of higher resistance to see where the cut in point is for a cold coil to be judged as able to still function when hot. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 10, 2015 Author Share Posted July 10, 2015 New coil and condenser made no difference. Tried running it direct from a jerry can of fresh fuel today to rule out fuel or fuel tank problems - no difference. On the last couple of test runs (my standard 2 mile run) I have been able to restart it, but it runs very roughly, there is no power and it is not drivable, again it is OK once left for an hour or so. Looking like the next step is converting back to reverse flow, so new fans and cowling :-(. Quote Link to comment Share on other sites More sharing options...
Tony B Posted July 10, 2015 Share Posted July 10, 2015 Try some heatsheild first, a lot cheaper and easier. Quote Link to comment Share on other sites More sharing options...
Starfire Posted July 11, 2015 Share Posted July 11, 2015 I don't know of anyone that has a Mk 3 or 6 Saracen that has had the cooling system modified and doesn't have problems with it. In stick form, they all work great. My Mk 5 settles at about 170f and stays there all day. Cheers, Terry Quote Link to comment Share on other sites More sharing options...
Nick Johns Posted July 11, 2015 Share Posted July 11, 2015 (edited) Just a thought, not mentioned previously, had a similar problem with my Dodge, when the temperature rose in traffic it would stutter onto 2/3 cylinders then stop, .. the points had seized on their pivot and were not closing, when engine cooled down points would free up and it would run again fine, have you checked the points still move freely and are closing ok when the engine stops? Edited July 11, 2015 by Nick Johns Quote Link to comment Share on other sites More sharing options...
attleej Posted July 11, 2015 Share Posted July 11, 2015 I had the same thing on a B81 in a Leyland Martian. If I worked it too hard it would run rough. It was the points pivot seizing. It was fair enough because I had a blowing exhaust manifold gasket allowing flames to heat up the distributor! It got so hot the condenser came unsoldered. I got around that by using a Landrover one from my FAMTO box and mounting it on the air cleaner connected with a long bit of wire. I think partially seized pivot is a strong possibility. John Quote Link to comment Share on other sites More sharing options...
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