Cynic-al Posted April 30, 2012 Share Posted April 30, 2012 Sequence of events; Landy starter was playing up due to solenoid so I swapped it and the car fired up fine. I hadn't run it for a while so decided to leave it running to get it warm and pump a bit of oil around. Wedged the throttle slightly with a stick to pick the revs up and turned a few things on to put a bit of a load on. Came back about 20 mins later and it had cut out. A bit unusual but turned the key to try fire it again but it wouldn't. I noticed the fuel pump wasn't running so went to look for a fault around the relay and noticed it was clicking in and out all the time. Took the relay out and tested the line from the megasquirt and sure enough it was pulsing the pump. Had a look online and it seems the pulsing is an indicator of a setting conflict. Brought the computer down, plugged it in, turned the ignition on, all the gauges on megatune looked fine and hte fuel pump didn't seem to be pulsing anymore so I decided to give it another try. After cranking for maybe 10 seconds the megasquirt lost communication with the pc and hasn't reconnected since. There is power and earth to the board and I can't see any obvious signs of dry joints or damaged components, any other tests I can do to try narrow the fault? All help appreciated Quote Link to comment Share on other sites More sharing options...
zoltan Posted April 30, 2012 Share Posted April 30, 2012 Have you got a serial port on the PC or are you runnning a USB/Serial adaptor? Battery voltage OK? Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted April 30, 2012 Author Share Posted April 30, 2012 Comms is via usb converter which has been problem free upto now. Battery voltage is around 12.5v static and 10.5v to 11v when cranking at the ECU Quote Link to comment Share on other sites More sharing options...
stuck Posted April 30, 2012 Share Posted April 30, 2012 ^^^ battery ok? My 110 wouldn't start on Saturday, cranked over a bit sluggishly but I could hear the fuel pump relay chattering in between cranks. Gave her a jump start and fired ok. Edit, sorry must have posted at the same time as your response. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted April 30, 2012 Author Share Posted April 30, 2012 seems to crank ok and not sure why it won't talk but no harm in trying with a jump pack on too, appreciate the input Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted April 30, 2012 Share Posted April 30, 2012 Could also be fouled plugs if your WUE is off... Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted April 30, 2012 Author Share Posted April 30, 2012 I think first I need to sort out why it's not talking to the pc or priming the fuel pump like it usually would. I suspect hardware rather than software at this stage, don't know what others think? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted April 30, 2012 Share Posted April 30, 2012 If it's had a spike or something while saving the settings it could have corrupted the firmware, fist thing I'd do is re-flash the firmware. Quote Link to comment Share on other sites More sharing options...
zardos Posted April 30, 2012 Share Posted April 30, 2012 I found that my problem with no comms to the ECU was a bad connection between 37 way plug and socket (I have always thought this was a bit of a naff connector to use) How did you measure power and earth? measured actually on the pcb or just to the 37 way plug? Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 1, 2012 Author Share Posted May 1, 2012 Think I did voltage on board but will check again, will look into flashing firmware Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 1, 2012 Author Share Posted May 1, 2012 No joy flashing it, get the message expecting " response, getting "" Not sure what that means exactly apart from its not worked! Going to order a 37pin connector tomorrow and a 12v power supply so I can power it with no sensors attached and communicate from my desktop rather than the laptop with the usb adaptor. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 1, 2012 Share Posted May 1, 2012 Al - PM me your address, I've got tonnes of the connectors kicking round, I'll post you one. Might even solder a wire or two on for ya too Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 2, 2012 Author Share Posted May 2, 2012 Thankyou very much, appreciated Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 11, 2012 Author Share Posted May 11, 2012 Is there a tolerance on the 5v regulator? I'm getting about 4.4v with a 12.0v supply? So far i've followed the build instructions on mega manual and passed; -Power tests (apart from voltage quiery above) -Communication tests (in terms of getting an echo by looping pins 12 & 13 of the 40 pin socket -There seems to be an exposed track on the board (see photo below) but there is 12v both sides. It won't talk to the PC, it won't flash the firmware regardless of the boot jumper position and options selected. It's powered from a mains 12v adaptor and plugged into the desktop without a usb adaptor and the above tests with hyperterminal show the signal is getting as far as the 40-pin socket. The tests later in the manual seem to require a connection to the PC. Ideas? Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 11, 2012 Author Share Posted May 11, 2012 Starting to think its a power supply issue, I have 4.4v between the middle pin and left pin and 4.4v between the middle pin and right pin and its jumping down as low as 4.0v sometimes. One side of that should be 12v right? Maybe a broken track or short somewhere or a failed component? Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 11, 2012 Share Posted May 11, 2012 It should be 5v with a very small variance - but it'd probably still run at 4.4v so I'd be looking at what might be causing it to drop that far. Shorted track/bad component maybe. The exposed track in the photo looks like it's overheated - where does it go? My instinct would be to follow it. edit: I'd also be looking at the fat black wire running north in the photo - a pin could have rubbed through the insulation. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 11, 2012 Author Share Posted May 11, 2012 The damaged track runs from the 12v live in pin on the db37 to a selection of components. I will try follow where it goes more closely and inspect the black (earth) cable. Thanks for the ideas Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 12, 2012 Author Share Posted May 12, 2012 So found damage to the cable as suggested, there was a grey dust around the imprint so i'm guessing its been shorting. Also found another damaged track on the board under some diodes. I'm thinking it must have been a short now as the battery was flat when I came to start the car which although unusual at the time I put down to the length of time it had been stood. The voltage at the regulator is now around 3.6 and I don't know whats pulling the voltage down. Not sure now if I should just write off the board? Looking at the wiring diagram what draws live off the board so I can check for faults on the car? +5v for the TPS +12v ish for the coolant temp sensor +12v ish for the air temp sensor Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 13, 2012 Share Posted May 13, 2012 Well looks like you've found the problem, or at least some of it. The burnt track can be repaired, looking at it it looks like it's just burnt the lacquer off the PCB so you may just get away with giving it a coat of something and fixing the fault. The MS power distribution is fairly robust, if you look at the input circuit and follow it from +12v in, there is protection before it's used for anything, then there's protection after the 5v regulator as well. It's difficult to see from that what's shorted to what. You often find once you remove the fault the polyfuses etc. reset and it comes back to life. Main thing to do is start from the 12v pin, preferably off the car using just 12v and ground, check that track's got continuity, then follow the circuit through, eventually you should get to checking you've got 5v coming out of the regulator, then on the other side of the polyfuse, etc. The MS will run (off the car) from a 9v battery quite happily. Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted May 13, 2012 Share Posted May 13, 2012 Are the PCB's multi layer boards? If so it maybe that one of the tracks inside the board have over heated and burnt out. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 14, 2012 Share Posted May 14, 2012 They are multi-layer yes, I have been looking for the internal layout for a faulty abused board I've got here but they don't seem to have published it for the V3 ones I'd start with the basics though, the V3 boards were designed to be fairly idiot-proof so there's plenty of protection on there, if something is dragging the 5v down it shouldn't be hard to hunt. Could unplug the CPU as a start, it's unlikely to be that but at least with it out you can poke round with a bit more impunity. The V3 build instructions in the MegaManual give you all the tests in about the right order, so I'd work through those and see what you see. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 14, 2012 Author Share Posted May 14, 2012 I haven't been able to find a diagram either which is somewhat annoying. I did the tests upto the point where you needed communication and the voltage issue was the only thing that stood out. I will repair the tracks and take it from there, thanks all. Better buy a magnifying glass Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 14, 2012 Share Posted May 14, 2012 TBH you can do most of it from the circuit diagram rather than PCB track drawing. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 14, 2012 Author Share Posted May 14, 2012 Ok so using the diagra below i've traced the fault as far as D10. Side 'A' has 12v, side 'C' has the floating 3-5v. This is also one of the components bridging the damaged track. With the power off the diode has flow in both directions. I'm going to pull it out and see if it still has flow in both directions. If it does I guess its faulty, otherwise I guess its something thats shorting this component like the damaged track. Either way taking the component out should help me see the fault... fingers crossed Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted May 14, 2012 Author Share Posted May 14, 2012 Well d10 replaced, the broken track cut out and replaced with a piece of wire and it's killed d10 straight away again. The search will have to continue again tomorrow... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.