ben7 Posted June 9, 2003 Share Posted June 9, 2003 I know there’s been a million posts on this one, but please bear with me. Read the recent thread (couple of weeks or so ago) that recommended the relay solution to the problem. I printed out the installation instructions, passed them to my local auto electrician. Relay installed, problem solved … or so I thought. Took my car to the garage to fill it up with petrol, switched off engine and spent the next 50 minutes waiting for the car to cool down before it would start again. In desperation, I have put rubber fuel hose over any exposed wire to try and insulate it. I have a catalytic heat shield from a Fiesta bolted between the starter motor and the manifold. Each of the branches of the manifold has been individually wrapped as well. Although the problem is marginally better post relay, it still hasn't fixed it. It is a dry-sumped 1.8 k with battery master switch. The new starter motor is the Magnetron type (wasn’t he the king baddy in Transformers???) complete with heat shield over the solenoid. Please help, because at the moment I can’t even take the car to the pub for fear of it not starting again. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 9, 2003 Leadership Team Share Posted June 9, 2003 The "extra relay" starter mod has not been known to fail yet - therefore possibly something amiss with the installation, or your electricians interpretation of what needs doing. How far is the new relay from the starter motor - it should ideally be placed forward of the battery to keep the runs short? Stu. Link to comment Share on other sites More sharing options...
Chris W Posted June 9, 2003 Share Posted June 9, 2003 There are two ways of wiring the additional relay. The original posts meant that the relay inside the MFRU was still in circuit, its contacts being in series with the new relay's contacts albeit only switching a low current. I suggested an alternative way of wiring it which completely bypasses the MFRU relay (search the archives - just checked, sh*t they're not working still). Anyway the MFRU relay is usually the cause of these problems and if it is really corroded, it may not even operate the new relay reliably if it is still in circuit possibly causing your problem. It may be of cause that the auto electrician balls'd it totally up and just didn't wire it up properly at all. After all some of these guys are not the sharpest pin in the box. Worth checking either way. If you're anywhere near me, I'm happy to sort it out for you. Chris 1.8K SV 140hp see it here Edited by - Chris W on 9 Jun 2003 18:02:20 Link to comment Share on other sites More sharing options...
tillson Posted June 9, 2003 Share Posted June 9, 2003 Could someone be kind enough to e-mail or post the relay installation instructions? The search facility does not appear to be working. Cheers Tom thomas.tillson@ntlworld.com Link to comment Share on other sites More sharing options...
Tony Whitley Posted June 9, 2003 Share Posted June 9, 2003 I bookmarked it here Tony M1 7 SMW 1.4SS Lotus colours with cycle wings. No longer featuring the imprint of a Jeep on the nsr wing but still at 7 Workshop Link to comment Share on other sites More sharing options...
Paul Richards. Posted June 9, 2003 Share Posted June 9, 2003 Sorry to hear that the relay hasn't cured your problem. I suffered from a similar hot starting problem and know just how frustrating it can be. I almost felt like selling the car. Fortunately for me the relay was the complete cure and I'm surprised it hasn't worked for you. There have been other threads on fixing starters and it now points to one of the "other" faults. Unfortunately I have been unable to search for the thread, but I seem to recall that one was the cracking of the soldered joint which provides the main feed to the solenoid. Hopefully someone will expand on this for you. No doubt your auto electrician can carry out some tests to confirm. Paul R. C7PPR K series that starts when hot!! Link to comment Share on other sites More sharing options...
Julian Thompson Posted June 9, 2003 Share Posted June 9, 2003 Obviously the if the multifunction unit relay isn't faulty then something else is wrong. I would suggest you whip the solenoid off; one fault which is common is that the connection between the little lucar terminal on the outside and the coil of the solenoid fails and becomes desoldered or snapped. Easy fix though. Link to comment Share on other sites More sharing options...
Mrs Kipper Posted June 10, 2003 Share Posted June 10, 2003 I know it's no help but I fitted one of Paul's solenoid kits earlier in the year (very easy - even I managed it) and have had bsolutely no starter problems since then The car was getting embarassing as nearly every time I turned off the engine when it was reasonably warm - it wouldn't start. Usually in a petrol station with a queue of people behind. I have now done a few sprints this year (with double drives) when the car does get very hot and - bingo - no problems. I would recommend Paul's fix to anyone with a K. The best money you'll ever spend on your car and a very cheap way to get peace of mind. Kipper Fun is not a straight line. Link to comment Share on other sites More sharing options...
ben7 Posted June 10, 2003 Author Share Posted June 10, 2003 Ah yes the getting stuck in a petrol station scenario - I know it only too well! I particularly enjoy it when you've been waxing lyrical about your car to a couple of punters for the last 5 minutes. ❗ Kipper, you mention 'Paul's solenoid kit'. Is this the relay solution, the soldering/joint fix mentioned or is it something entirely different? I'm also going to take the car to another garage for them to look at. I'll ask them check to see if the relay was installed correctly, check the corrosion on the MFRU relay together with the starter soldering/joints. If you can think of anything else, please let me know. By the way Caterham Cars deny that there has ever been a hot start problem with the k series engine. 😳 Thanks, Ben Link to comment Share on other sites More sharing options...
MarkInstance Posted June 10, 2003 Share Posted June 10, 2003 Ben, I bought my car used from Caterham 3 months ago. It had the hot starting problem from the day I picked it up. Yes it was always when in a petrol station, out side a pub etc that it let me down. I called Caterham about the problem and they knew all about it and said it was very common. I then booked the car in and they changed the starter motor. If anything this made the problem worse. I then did the Paul Richards fix and had no problems since. I am not sure that I did the wiring in quite the same way as paul as buy the time I came to do the fix the search was down and I could not find the instructions. This is what I did:- 1) Used 30 amp Wire. 2) Took the Positive from the large wire from the mater switch to the solenoid. Put this to the + side of the relay. 3) Put the little lucar terminal on the switching terminal of the relay 4) Connected the power output of the relay to the lucar ternimal on the solenoid 5) Connected the earth to the battery.. This seems to work fine and as far as I can tell will ensure that the master switch will still work correctly. This will not bypass the MFU though. Not sure what to do about that! Mark Link to comment Share on other sites More sharing options...
Mrs Kipper Posted June 11, 2003 Share Posted June 11, 2003 Ben Paul's fix is the relay, which, if I remember (I am not at home so I can't refer to the instructions) takes a feed directly from the battery through the relay to the solenoid of the starter motor. Therefore, when you press the starter button you get full whack from the battery straight to the solenoid without any power loss through yards of other wire. I have a battery master switch fitted and an immobiliser and neither have these have been effected or needed any special rewiring. Try it, it works 😬 Kipper Fun is not a straight line. Link to comment Share on other sites More sharing options...
Risky Posted June 11, 2003 Share Posted June 11, 2003 The 'Paul Richards' relay fix is in this months Low Flying. Risky Saving up for Supersport R conversion Link to comment Share on other sites More sharing options...
Chris W Posted June 11, 2003 Share Posted June 11, 2003 Kipper Your description of the relay circuit and its missing out yards of other wiring is not the reason it works. The length of wiring the current goes through after the mod is the same. The reason it works is that there appears to be a problem with the small starting relay in the MFRU which gets easily pitted and burnt carrying the current to the solenoid. This means it cannot deliver enough current to the solenoid, hence the click only. Depending on how you wire in the new additional bigger relay it either totally bypasses the MFRU relay (recommended method) or the MFRU relay is used to supply only the very small current to operate the new additional relay. Pitted contacts on the MFRU relay will have virtually no effect at small currents (unless they're REALLY bad). The new additional relay has contacts which are designed to take higher currents without burning and therefore the previous starting problem goes away. cheers Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Jason Plato Posted June 11, 2003 Share Posted June 11, 2003 however - if the post on the solenoid is cracked or damaged to the degree that it is a break in the circuit , the starter will still not work . tested and proven on my solenoid ...... Dave Link to comment Share on other sites More sharing options...
Chris W Posted June 11, 2003 Share Posted June 11, 2003 That goes without saying Dave. The relay mod is only for where the problem is the MFRU relay. Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Tony Whitley Posted June 14, 2003 Share Posted June 14, 2003 I too fitted a relay, using the Luke Beaumont improvement to Chris W's improvement to Paul Richards method here. This seemed to have cured the problem but on the first hot day I got the dreaded click. Fortunately it happened at James Whiting's and he suggested cooling it with an air line and that did the trick (thanks James). I killed a load of brain cells earlier today reading all the threads and decided that the relay set-up is essentially the same as Paul has written up in Low Fying so my thought turned to the solenoid itself (I have the Magneton starter motor with the solenoid underneath). Why wouldn't it work when it got hot? There was no sign of bad connections or anything so took it off and stripped it down (warning: this is not rocket science but it's not for the mechanically faint-hearted) and came up with the theory that it fails when it's hot because of differential expansion of the metal of the can and the plunger (to use the technical terms ) reducing the clearance so that the plunger can't move. Whether or not that's valid, I cleaned it up with wire wool and smeared with a little high temperature grease then reassembled it, cleaning the terminals and protecting them with vaseline. I have to wait to be sure of the result, but I took the car for a run to warm it up and it re-started fine. A further test was to leave it for a while in the sunshine to let the heat soak through. Still OK. The weatherman was promising a hotter day tomorrow so I'll have to try it again then... Tony M1 7 SMW 1.4SS Lotus colours with cycle wings. Back on the road Link to comment Share on other sites More sharing options...
Chris W Posted June 14, 2003 Share Posted June 14, 2003 Tony Your experiment and subsequent strip down is a great step forward. I think the reason the additional relay helps is that if, as you say, the expansion of the solenoid plunger etc when hot causes it to be tight inside the casing then the solenoid will need more current to force the plunger to move the final bit. The MFRU relay seems to get pitted and burnt very easily so (I postulate) cannot supply the additional current needed to activate the solenoid. The new relay on the other hand has high-current contacts and can pass the additional current that the solenoid is trying to draw without getting pitted and burnt. It always mystified me somewhat as to why this problem was worse with hot engines. I never believed it was due to increased resistance in the wiring. I think you may have finally found the missing link. Chris 1.8K SV 140hp see it here Edited by - Chris W on 14 Jun 2003 17:49:42 Link to comment Share on other sites More sharing options...
jackb_ms Posted June 18, 2003 Share Posted June 18, 2003 It look like i have a completely different hot start problem with my 21. My starter motor will turn but the engine will not start. When it start there is a massive missfire, which clear after a few minute. I took the heat shield off last night and discovered that the small connector to the coil was broken off. Which can explain some mal functionement but not the miss fire Anybody got a spare coil? Or any idea where i could get one? Jack Link to comment Share on other sites More sharing options...
Paul Richards. Posted June 19, 2003 Share Posted June 19, 2003 Chris W. I agree that the problem being cured is the pitted/corroded contacts in the MFU. The cure is the use of a relay which only needs a very small current (which even below par MFU can still provide) to activate the additional solenoid which activates the starter. I originally thought that sticking plunger on solenoid was the problem, but dismissed it after several cleanings and no improvement. What I can't understand is :- 1. Why did my problem only occur when hot? 2. Why was my problem worse when a battery cut off switch (along with associated extra wiring) was included? I've now decided not to worry. It works for me and continues to work, despite high engine and ambient temperatures experienced on recent Le Mans trip. Now 12 months with no hint of failure, when in the past I would have had problems at least weekly. Keep Starting. Paul R. C7PPR K series that starts when hot!! Link to comment Share on other sites More sharing options...
Chris W Posted June 19, 2003 Share Posted June 19, 2003 I have thought about this "hot" problem a lot (sad b*gger). Basically the problem comes down to one thing - the amount of current needed to operate the solenoid. If it receives enough current, it'll work. If it doesn't, it won't. The issues that will cause the solenoid not to receive enough current (broken connectors aside) are three-fold: 1. The solenoid's current requirement increases due to its being hot, expanding and maybe thereby getting "tighter". More current is needed to create the force needed to overcome the additional friction. A previously working system may not be able to supply the additional current. The maximum current available is simply volts applied divided by the circuit resistance. This puts an upper limit on the maximum current able to be supplied. If the current needed, due to the solenoid's demand increasing, exceeds the maximum current available, the solenoid won't function. 2. The solenoid's demands remain the same but the maximum current available decreases due to increased circuit resistance. This increased resistance will come about by the contacts on the starting relay in the MFU getting heavily pitted and thereby adding significant resistance or by increased wiring length (pretty minimal increase). If adding additional wiring tips it over the limit, I would guess first that it's more likely to be a bad connection on that wiring rather than the wiring itself. 3. Both 1. and 2. happen simultaneously. This puts a real strain on total circuit resistance. Even a small increase (like Paul's additional battery cut-off switch wiring) might be enough to push the total resistance over the critical limit if it's already on the brink. Adding the additional relay which has beefier contacts, that are far less susceptible to pitting, removes the basic problem and decreases the total circuit resistance. My own strong view however is that it should always be wired in so as to bypass the MFU relay totally. The assertion that just because the current needed by the new relay to operate is small (true), means the MFU relay can therefore handle this regardless of its pitted condition is an opinion not a fact. It can never be good engineering practice to introduce a second and totally unnecessary point of failure.... and particularly in this case where to exclude the MFU relay actually makes the wiring simpler! That's why, whenever I have done this mod for people (and I have done 4 so far, with another waiting), I always bypass the MFU relay. I thoroughly recommend this mod to everyone and applaud Paul for originally bringing it to our attention. Chris 1.8K SV 140hp see it here Edited by - Chris W on 20 Jun 2003 08:56:56 Link to comment Share on other sites More sharing options...
caterhamnut Posted June 20, 2003 Share Posted June 20, 2003 I shall be fitting the relay in this weekend. Just a quick question - does the article in LowFlying show the system that by-passes the MFU? (don't have it to hand) - if not, what do I have to do to bypass it? (had problems with the MFU so anythingto avoid using it is good!) New site! mycaterham.com here 42,000 in 23 months! Link to comment Share on other sites More sharing options...
Chris W Posted June 20, 2003 Share Posted June 20, 2003 Angus The article in LF does NOT describe how to bypass the MFU relay. Look here at the 9th post (mine) and you will see full instructions on how to bypass it. Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
caterhamnut Posted June 20, 2003 Share Posted June 20, 2003 duh - just thanked you Chris on that old link - but thanks again! New site! mycaterham.com here 42,000 in 23 months! Link to comment Share on other sites More sharing options...
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