AdamQ

I need to plunder the wisdom of Blatchat over a problem that's got me somewhat foxed. I have a Sprite with an A series engine. It was going well about 8 months ago. I resurrected it recently (following the changes in the MoT regs meaning that it didn't need one). I now have a misfire on 1 and 4 at anything below about 3000 RPM. Above that, all cylinders fire. This has been diagnosed by removing plug leads with the engine running: <3000 RPM - removing 1 or 4 HT lead makes no difference, removing 2 or 3 does; above 3000 RPM - removing any of the HT leads makes a difference. The battery appears to be healthy (Powervamp Clubsport) - it starts the engine fine and there's 12.5V there with the engine running and the alternator disconnected, ~14.2V with the alternator connected. I've also tried running it with it connected to another car with jump leads with that car held at about 3000 RPM - same problems. At tickover, there's a healthy spark from 1 and 4 with a plug earthed on the block. Today I replaced the entire ignition system - new distributor, cap, rotor arm, coil, HT leads and I swapped the plugs from 2 and 3 with those from 1 and 4 (all plugs new about 2 hours running ago). Still the same problem. I've removed the fuel line at the carbs (twin DCOEs) and have drained off about a gallon of (possibly stale) fuel, having filled up with 5 gallons of fresh fuel. The timing hasn't been touched since she was running fine last year. I've checked and double-checked that I haven't mixed up the HT leads in my messing about. The ignition was a Lumenition electronic system and as of today is a Powerspark electronic system. One possibly relevant observation is that the non-firing plugs appear oily rather than petrolly when removed - could this be a problem related to idle jets and Siamese ports - or am I getting a little too elaborate in my analysis here? Compression on all cylinders is 125 - 130 psi. I've also had the rocker cover off to check that side of things and all appears to be in order - valves all opening and closing fully (i.e. when cold there's the few thou of clearance required (as borne out by the compression figures)). I'm at something of a loss. I appear to have compression, a spark and some timing that's not too far off - that only leaves fuel to my simplistic way of thinking, but 2 and 3 are firing beautifully ... Thought, ideas and suggestions welcome ... And apologies for the exuberance of my verbosity ...

Somewhere on here somebody once gave an approximate figure for the effect in degrees on toe-in/toe-out of one rotation of the track rod but I'm struggling to find it - does anybody happen to know what it is? I suppose a bit of research into thread pitches followed by some sums would yield the figure, but ... Thanks, Adam

Hi Tom, It's RAL 1028, 'Melon Yellow' ...

Pictures as promised - the replacement mount from eBay followed by the 'same' item from the Caterham parts site.

Here's the link as requested: https://www.ebay.co.uk/itm/Jaguar-MK2-V8-E-Type-S1-S2-XK-Engine-Mounting-C18556/182432679129?hash=item2a79d5c4d9:g:d70AAOSwt5hYh329 I'll add a picture later to try to illustrate what I was talking about above ...

It seems all engine mounts are not created equal. Having hunted high and low for the old engine mounts, I've fitted them and the vibration is gone. In fitting them, I looked carefully at the original mounts and the replacements I'd used. There's a big difference in the thickness of the rubber between the bit the large mount bolt goes into and the base of the mount that bolts to the chassis: ~10 mm on the originals versus ~2 mm on the replacements. The minimal rubber and consequent lack of compliance in the replacements in the region described would appear to be the problem. FWIW ... Adam

Hi Andrew, That was something I came across in the archives and have checked, but all in order - top of mount to top of chassis rail is 80 mm and bolt is 63 mm.

I completed a nut-and-bolt rebuild of my 1999 Seven a while ago. Since then, I've been suffering from a lot of vibration through the steering wheel (numb fingers after 30 minutes or so driving) which wasn't there before the rebuild. Having checked all the usual suspects (worn or incorrectly installed bushes, primaries in contact with steering column, overlength mount bolts and a host of other things), I've just removed the big long engine mount bolts, put the weight of the engine on a jack and raised it a few mm. The vibration disappeared completely. The rebuild included new mounts off eBay (C18556 Jaguar E-Type items). Would I be correct in assuming that not all mounts are created equal? Naturally (or maybe not) I went for the cheapest UK items I could find. I've done a brief search of the archives on the Vibra-Technics mounts (£113 a pair ...!) - are there any strong opinions on the worth of these? Given that all was well with standard mounts before I replaced them, logic suggests taking a gamble on another - better quality - set of 'standard' mounts ...

I've used electrical shrink-wrap.

I've found the 'spanner' for changing discs on an angle grinder works well ... FWIW ... Adam

Hi Jonathan, I've got the diagram from the 05.2012 assembly guide that you kindly sent me a while ago. What I'd really like is a 'conventional' version of that - i.e. one that shows each wire - I'm also not convinced it's complete - e.g. I have a BN wire which I think might be for oil temperature but I can't see it on the engine harness diagram. Also, the R400 engine harness diagram in particular in the manual appears to be a scan and, by way of sod's law, always seems to lack clarity in any given area in which I'm interested - but that's a minor gripe really and I'll snap out of Victor Meldrew mode now ... Adam

Hi Charles, Many thanks for that. Extrapolating what you say suggests that the gauges for the 'new' senders are different to the gauges for the 'old' senders in that they expect a pulse signal rather than a steady voltage feed - is that correct do you happen to know? I'm using an old-style sender with an old-style gauge, but also have a new-style gauge - as soon as the battery arrives, I'll do some experimenting. Your words 'I’ve yet to fully document this' interest me considerably - does your documenting happen to include a 'conventional' wiring diagram for the more recent cars? I can't resist asking as such a thing would be of immense use in my opinion ... Thanks again, Adam

I'm using an old-style oil pressure sender on a recent loom (simply because I had a new and unused spare sitting in a box). As far as I remember, the white and brown wire used to go from the sender directly to the gauge via the grey plug. On recent cars, according to the wiring diagram, it appears to go to the tacho and thence to the gauge, changing from white and brown to white and green at the tacho. I can't check with the ignition on as I'm waiting for the battery to arrive, but with the ignition off there doesn't appear to be continuity between the wires. Does anybody know what goes on within the tacho with the two connections? Is there some sort of warning light function? Or a buzzer or something? A simple solution (famous last words) would be to extract the wires from the tacho plug and join them together, but I guess I'm just curious as to why there's been this change ... Plus I don't want to mess anything else up or create any other problems.

I've used metric lowered brackets on an Imperial (1999) car - I basically had to after CC supplied a metric nosecone (without the cut-outs for the 'standard' brackets) to the paint shop and we found out too late. The brackets (and nosecone) both fit fine. I read somewhere that the CSR brackets are the ones you need for an Imperial car, but they were out of stock so I went with the other lowered brackets and, as I say, all was well. I had to drill a hole in the each of the top front wishbone mounts for the wires, but that was it as far as I remember. I hope that helps ... Adam

Getting the individual wires out of the connectors is fairly easy: take the yellow insert out of the connector and then use one of those small watchmaker screwdrivers from the insert side to push the locking tag out slightly and then pull the wire out from the back (I've found it often works best to push the wire in a bit before levering out the locking tag and pulling the wire). They just push back in and click into place (I think they'll only click properly one way round, but it's probably worth noting which way up the connectors are inserted into the connecting block). To get the wires out through the bracket tube is usually simple enough - just stagger them so that they follow each other through the tube and pull the appropriate wires from the headlight end. Getting them back through the tubing of the new bracket is an altogether different matter. It can be done - lubrication, a 'pilot' wire to pull the wires through and all sorts of ingenious methods are used. In my experience it either takes five minutes or three hours - never anything in between. I'd be inclined to order some new connectors and rubber seal thingies and chop the connectors off the wires - that makes threading the wires through the bracket tube a whole lot easier. FWIW ... Adam

Hi James, Many thanks indeed for your comprehensive response. That all makes a whole heap of good sense. I've converted the values as above and all looks good. My ECU has the facility to allow for injector opening time (as a function of battery voltage) and that's 1.13 ms at 12 V and 0.94 ms at 13 V so that would appear to be about right. Fingers crossed ... Thanks again, Adam

I have an ECU that uses Volumetric Efficiency (VE) rather than Pulse Width (PW) to control fuelling. I have suitable maps from other ECUs (thank you to kind people on here) that contain PW figures. I obviously need to convert PW to VE (as a starting point at least) and that is my question - how? The ECU manual gives (for Alpha-N fuelling): PW = INJ_CONST * VE(tps,rpm) * AirDensity * Corrections + AccEnrich + InjOpeningTime where INJ_CONST is "a constant for the given size of injectors, engine’s displacement, pressure 100kPa, temperatures of the intake air 21°C, VE 100%, time of injectors’ opening required to obtain the stoichiometric mixture (Lambda = 1)" The engine is a 2.0 Duratec and the injectors are Bosch 0280 156 095 items which are, I believe, 315 cc/min (242.5 g/min). I've Googled away and have searched the ECU forum, but have found nothing definitive (or anything that gives realistic figures - my first check gave a VE of 349% which seems somewhat unlikely). Any assistance would be much appreciated. Adam

Hi James, Thanks for the reply - I've sent you a message. Regards, Adam

Would anybody happen to have a map for the above - pretty much standard Caterham 420 spec. 2.0 Duratec? Which ECU it comes from really doesn't matter as long as it's legible in some way or another. TIA, Adam

Caterham do a tailor-made set of heat-shielding for the engine bay and transmission tunnel. Others have used various DIY insulation products from B&Q or wherever, including foil-backed polystyrene (only 3 or 4 mm thick) and thicker foil-backed bubblewrap-type stuff. Lining the tunnel is obviously infinitely easier with the gearbox (and therefore engine) removed - I think that was the advantage of the foil-backed polystyrene - it can be applied underneath the carpet (if you have carpet) in the cockpit so no need to remove the engine and gearbox. Wrapping the primaries seems to be a slightly contentious subject - my simplistic understanding is that wrapping the primaries hinders heat dissipation from the head. In my (subjective) experience, it made little or no difference to footwell temperature. One school of thought is that rather than blocking the heat, it needs to be given somewhere to go, i.e. some sort of flow route through the tunnel needs to be created. To this end, I perforated my handbrake and exhaust gaiters. The amount of heat coming up through them was significant, but, again, I can't claim it made a massive difference to footwell temperature - though there might have been some slight improvement. ISTR reading somewhere of somebody who'd opened up the top rear end of the tunnel top and I think that was moderately successful. I hope that helps a little bit.

I've had about three or four sessions there over the years and I'd recommend him highly - all very professional, he did a good job (as far as I am qualified to tell - I was certainly very happy with the results), and in addition to all that he's a very pleasant chap. If I hadn't moved a bit further from him, I'd use him without hesitation every time. HTH, Adam

Yes, the original LED appears unchanged in brightness - if it is dimmer, it's only marginal and still perfectly functional, but I think it's unaffected. Agreed about documenting a fix - and a fix it certainly is ... I should be able to work it out (or I could just experiment), but, out of interest, will the diode stop the radiator fan keeping the engine running for those extra few seconds? I found it slightly disconcerting the first time it happened, but it's never bothered me since.

Andrew, that's superb - many thanks indeed - all installed and normal service has been resumed ... There were four diodes in the box with a second-hand ECU I bought recently (I wondered what they were ...!) and one of those has done the job. And boy am I glad I took the trouble to put rivnuts rather than rivets around the scuttle - I am no longer the contortionist I never was! And thanks for the detailed explanations of what's going on - like so many things, it all makes perfect sense when somebody who fully understands these things explains them - all interesting and informative stuff ... Adam

Erm ... Not quite sure how to put this ... Perhaps best summed up by: HELLLLLLP!!!! I have wired the resistor in parallel with the LED by connecting it to the same NY wire as the LED is connected to and to one of the G wires that feeds the switches. I've double-checked that I've used the correct wires using a multimeter. All seems good - ignition light shines brightly with ignition on and there's a healthy 14.4V across the battery with the engine running (at which time the ignition light is out). The problem comes when I try to turn the engine off. Usually I press the button that turns the ignition on and off and all is as it should be. Now, when I turn the ignition off the instruments all die but the engine carries on running. Hmmmmmm I thought, well I've got a BMS so I might as well use it. No effect - engine continues to purr merrily away. I eventually killed it by disconnecting the green wire from the resistor. I dare say that with a cold towel around my head and a bit of ruthlessly applied logic, I could eventually work out what's going on, but it seems so much easier to ask the clever men of Blatchat who know all there is to be knowed ... I presume the resistor is preventing a circuit from being broken when the ignition is turned off and that the engine is simply running from the output from the alternator when the battery is disconnected. I guess I ought to add that it's a 1999 car with the ignition light external to the tachometer, not integrated, and that it has a latching ignition button and a momentary starter button. The BMS is one of the cheap and cheerful ones with solely two big connections for the battery cables. TIA as they say ... Adam