TheManAlive Posted June 20, 2009 Share Posted June 20, 2009 The car packed up last weekend (I did a string about it whilst sitting by the side of the road waiting) with some electrical problems. CAr is now back in the garage and I have been playing with it to see what the problem is, but am getting nowhere. The problem seemed to start when the speedo died whilst driving - the needle dropped to zero, but I still had a light to the digital mile readings (though I know I drove over a mile with the problem and the number never changed). Pulled over, went to start the car and engine turns over but does not catch. I have now had a look and its the instruments fuse (a 7.5) that keeps blowing as soon as I turn the ignition key to its final point (before pressing the starter button). I have checked the earths and they all seem ok. I have had a look under the dash (very undignified position with legs waving in the air) and can't see anything amiss. Caterham are coming to pick the car up next week and I was wondering if anyone had any ideas to save me a couple hundred quid! Grateful for your thoughts. Link to comment Share on other sites More sharing options...
Myles Posted June 20, 2009 Share Posted June 20, 2009 Well, for want of something better to do, you could disconnect all of the instruments (one by one if you've got plenty of fuses 😬) and see if that makes any difference. 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 I have loads of fuses (just stripped halfords of them!!) so will give it a try. I'll unplug the lot and see if it starts. Electrics are an enigma to me (I was chuffed with myself that I was able to read the diagrams and work out which fuse it was that was blowing!) and I can't understand why losing the instruments should prevent me from starting the engine. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 20, 2009 Share Posted June 20, 2009 In the manual for my car (2002), the 10Ainstrument fuse is shared with the cockpit heater fan. Is the fan switched on, so comes on when you turn the ignition on ? Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 Should have said, its a 2008 roadsport. The manual says a 7.5 for the instruments (third in from the right). The heater works fine, as do the lights (including those to the instruments), hazards, fog, wipers etc etc. I've tried disconnecting all the instruments - same thing happens. As I put the key into the final position, use the dongle to deactivate the immobiliser, there is an audible click (though no sound of the fuel pump) and the fuse blows. I don't even have to turn the car over for it to blow the fuse. What does the immobiliser allow power to once it disconnects? If I understand this correctly, the fault must lie somewhere after the immobiliser. I remember normally when the immobiliser deactivates the instruments would flicker before you started the engine. Grrrr. This is so annoying - its probably something fairly simple and I just can't find it. Link to comment Share on other sites More sharing options...
tbird Posted June 20, 2009 Share Posted June 20, 2009 Hi I am fairly new to 7s but seem to recall reading somewhere that the imobiliser is designed to blow a main fuse if it is tampered with/disabled, maybe a relay which defaults to earth when power removed, could this be the answer, as I say I am a newbie but someone with way more knowledge will be along in a minute Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 20, 2009 Share Posted June 20, 2009 On the old Rover immobiliser, you have to switch off the immobiliser before you turn the ignition on. Is it the same on your new one ... not that it should blow the fuse !! Link to comment Share on other sites More sharing options...
Myles Posted June 20, 2009 Share Posted June 20, 2009 The old Rover immobiliser doesn't stop much working really - you can still crank the engine etc. I've got the Emerald ECU and my understanding is that it just cuts the sparks (and possibly injectors) - but that's it. ...but you've narrowed it down to the act of pinging the immob rather than the act of turning the key to the final position, yes? So, presumably, if you turn the key and don't fire the immob - you should still be able to turn the lights, indicators etc. on? Does the 2008 immob have a dashboard telltale by the way? The old Rover jobby has a small LED on the dash. 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester Racing 7s Ecosse™ 🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻 Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 20, 2009 Share Posted June 20, 2009 Rover kills the fuel pump. Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 Myles, the immobilser has a red led on the dash. When i turn the ignition, it rapidly blinks to say its on. then i normally use the dongle and it stops flashing, allowing me to start the engine. Now, though, its dis-abling the immobiliser that fries the fuse. Even after the fuse has been blown, lights and everything else works fine. tbird - I dont understand what you mean. Is there a switch or something I need to look for to reset the imobilsor? ps thanks for everyone's help. I would really like to cure this myself. Edited by - TheManAlive on 20 Jun 2009 19:20:04 Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 OK, I got it wrong. Its not the imobilser that does it, its actually turning the key to the final position that fries the fuse. When I turn the key there is a click and the fuse has gone. So, change of question, that does turning the key put power to? Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 20, 2009 Share Posted June 20, 2009 Do you mean the spring-loaded position that cranks the starter ? Or the last one before then ? ... oops - re-read your post, it's the final one so you can start on the red button. There must be a short somewhere on something connected to the ignition. Did this start after you did anything, or out of the blue ? Look at the wiring to the fuel pump, if you can't hear that running - maybe a dodgy connection, or loose strands of wire grounding on something ? How does the modern dongle switch off the immobiliser ? Do you press a button, or hold it near something ? Does it make a difference if you do this before turning the ignition on ? Edited by - Stationary M25 Traveller on 20 Jun 2009 19:38:07 Edited by - Stationary M25 Traveller on 20 Jun 2009 19:40:44 Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 Yeah, its the final one,not the spring loaded one. It started on my first blat after having a new dif put in by caterham. Everything was running fun, the the speedo died for a few seconds then came back. Carried on driving and then the speedo totally went (the needle that is). Pulled over and was stuck :( The dongle needs to be waved in front of a loop of wire that circles the key block when you turn the key to the final position. Works well normally. OK, silly question, where should I be looking for wires to the fuel pump? Will it be the wires that run under the wooden plank in the boot? I dont remember doing anything with the fuel pump or the wires when I built the car. If it was a short on the fuel pump, though, why would it blow the instruments fuse? (again, thanks for all the advice) Edited by - TheManAlive on 20 Jun 2009 19:49:31 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 20, 2009 Share Posted June 20, 2009 New tack ..... look for whiskers of wire on the cables that run to the ignition switch, to see if any floating free, to short on something. Also - are any connectors touching the next one (uninsulated) ? The ignition obviously sends power to the starter button ... again look for strands of cable outside the connectors on the starter button. If nothing visible, try removing the feed cable from the ignition switch to the starter button and see if fuse stays healthy when you turn the ignition on. If you don't know which wire does what on the starter button, take them both off, and try with each one. It will probably be something silly under the dash. Link to comment Share on other sites More sharing options...
TheManAlive Posted June 20, 2009 Author Share Posted June 20, 2009 OK, been back under the dash board (is there a dignified way to do that that avoids feet pointing up in the air!!) and had a look at the ignition. Pull the plastic cover off and all looks fine. Nothing touching, nothing frayed. Tried the ignition button, no joy still blew the fuse. Only got 3 fuses left!! Link to comment Share on other sites More sharing options...
tbird Posted June 21, 2009 Share Posted June 21, 2009 Tma hi, sorry couldnt be more specific, I have recently bought a CSR and this has a Sterling Excel immobiliser fitted (Toad Powerkey) I suspect yours is similar, I remember reading somewhere (and I am Bu66ered if I can find where) that it immobilises Fuel pump and starter motor, but it also has a circuit built in so that if it is tampered with/disconnected it has a fail to earth relay that earths out a main fuse which causes it to blow, thats all I can remember at the moment and as I say I cant find the source, sorry I will try and find the reference again tomorrow, good luck in meantime, BTW have you tried ringing CC techs to see if what is happening could be caused by the immobiliser, I am begining to doubt myself now If you have a meter you could check both sides of fuse holder to earth with ignition off, that may start to narrow search a little Tim Link to comment Share on other sites More sharing options...
Normans_Ghost Posted June 21, 2009 Share Posted June 21, 2009 Jack up the rear and have a good look at the wires that come out of the tunnel and over the diff. Has the loom been trapped when the diff was put back. Sounds like the wires may have been trapped but taken time to cut through to earth. Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here You and your seven toThe French Blatting Company Limited Link to comment Share on other sites More sharing options...
TheManAlive Posted June 21, 2009 Author Share Posted June 21, 2009 I had the wooden plank in the boot our last night and the wires looked ok. Will have a closer look around the diff today as that would make sense. Thanks for all the help. I have three more fuses left to try with!! Had her up on strands and had a good look around the diff. Nothing looks pinched and all looks fine. Ho hum. Edited by - TheManAlive on 21 Jun 2009 11:23:38 Link to comment Share on other sites More sharing options...
tbird Posted June 21, 2009 Share Posted June 21, 2009 Any joy measuring fuse holder (without fuse fitted) both sides resistance to earth, this would pretty much tell you if you have a trapped wire as there would be a permanent v low resistance to earth, maybe safest to have battery disconnected although from what you have said, keys out of ignition would also be ok keep hunting you will find the problem Link to comment Share on other sites More sharing options...
TheManAlive Posted June 21, 2009 Author Share Posted June 21, 2009 Tbird, dont know how to do that 😳 I have a meter but really dont know what I am doing with it or what I am looking for. A quick question for anyone near their car. If you take out the fuse for the instruments, does your car start? I still find it odd that you cant start the car jsut due to the lack of instruments. Link to comment Share on other sites More sharing options...
TheManAlive Posted June 21, 2009 Author Share Posted June 21, 2009 Ok, a bit of googlinh during the rather dull GP I worked out how to use the meter. I unplugged the battery then tested by putting the probes in both connectors for the fuse socket and it came out at 92 thingys. When I tested some of the other sockets they were 0. Does that mean there is an earth wrong somewhere?? Link to comment Share on other sites More sharing options...
tbird Posted June 21, 2009 Share Posted June 21, 2009 first have a look at your battery leads one of them will be connected directly to the engine or Chassis, normaly the negative terminal. with battery disconnectedthis will be your earth point, get someone to help if possible and hold one meter lead firmly on the lead, set meter to lowest Ohms range and press other probe onto the engine somewhere, you should get a low reading, Idealy less than 1 ohm, you may have to use the point of the meter probe quite firmly to get through any gunk, once you have confirmed what that low reading is, anything more than a couple of ohms and you dont have a very good connection, you can repeat between the battery lead and each side of the fuse holder (with fuse removed) if you get a low reading, again less than a couple of ohms on one side or the other then you probably have a short to earth somewhere, if both sides are greater than say 10 ohms the wiring is probably ok, BTW you said that some of the fuse sockets were 0 ohms, was this with fuse in or out, I would be a bit concerned if you are getting 0 ohms accross a fuse holder with fuse removed Tim Edited by - tbird on 21 Jun 2009 18:44:24 Link to comment Share on other sites More sharing options...
BadBob Posted June 21, 2009 Share Posted June 21, 2009 Hello, This is a long shot but I had exactly the same symptoms in my 2008 Roadsport last year. In my case it turned out to be the speed sensor on the off-side rear wheel which had shorted where the wire enters the sensor. The wires get a lot of flex as the wheel moves and so I guess are vulnerable. Worth a look, there's a plug connection on the chassis wide you can undo. I fitted the new one with a lot of precautions against a recurrence. Rob Link to comment Share on other sites More sharing options...
TheManAlive Posted June 21, 2009 Author Share Posted June 21, 2009 😬 BadBob You Sir are a legend!! You've just had me running up and down the garden like an idiot in celebration! I unplugged the speedo and turned the key, heard the glorious sound of the the fuel pump whir and then started her! You've saved me a load of money I couldn't afford, so thanks very much. I guess its a short in the speedo sensor that is causing the problem (which if I am honest was what I first thought it could be, but I never tried unplugging it 😔 wot a muppet I am!) Thanks to everyone for their help. I'll be cancelling the pick up by caterham tomorrow morning! 😬 😬 😬 POBC prevails again (and I am really really chuffed). No speedo, but hell, still might go for a blatet! Link to comment Share on other sites More sharing options...
tbird Posted June 21, 2009 Share Posted June 21, 2009 Hooraah another Cat back on the road 8 lives left Link to comment Share on other sites More sharing options...
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