wardpaa Posted June 22, 2016 Report Share Posted June 22, 2016 30 years of motoring and I've never had a non starter. Buy a Porsche and voila ! Battery at 12.8V so I d thought I'd check the fuel pump relay. Car cranks. No errors. Where is it on a 987 ? All of the how to's are for the 986, which has the relay box in the boot at the LH rear of the car. Mine has only a couple of relays in the rear boot, so where is the other relay board ? Link to comment Share on other sites More sharing options...
wardpaa Posted June 22, 2016 Author Report Share Posted June 22, 2016 Found it in the end. Traced the fault to an intermittent fuel pump. Link to comment Share on other sites More sharing options...
Andy Mac Posted June 22, 2016 Report Share Posted June 22, 2016 Ah good work ?? Link to comment Share on other sites More sharing options...
mrbikerdood Posted June 22, 2016 Report Share Posted June 22, 2016 BoooooM....there it is! hope you got sorted?! Link to comment Share on other sites More sharing options...
wardpaa Posted June 22, 2016 Author Report Share Posted June 22, 2016 I had tried a fast charge on the car battery, which is a good one year old Bosch unit. Also disconnected the battery for 20 mins. The relay board is a real pain in the azz to remove. You have to undo the 3 screws which secure the carpet surround trim to the fuse board, then unclip the relay board above it and tilt it out. The relay for the fuel pump is number 8 and is only operated when a signal from the crank position sensor is received by the ECU, so on cranking the relay should operate an d supply the pump. I also removed and bench tested the relay to confirm it was not faulty and tried swapping it with another identical one on the same relay board. So on to the pump itself. Removing the battery, siren and the battery tray reveals the top of the fuel tank sender and power to the pump. With the plug removed, Resistance to the pump measured just over 1 ohm with my DVM confirming the motor was not open circuit. Using a small motor cycle battery I connected to the pump and you can hear it power up. I left it running for about 10 seconds. Now I'm confused as the battery is OK, the crank sensor is OK, the fuel pump fuse is OK, the relay is OK and now the pump is OK. I connected everything back again, turned the key and it fired up ! DOH ! Conclusion is that I may have a dodgy pump. Link to comment Share on other sites More sharing options...
RickLS7 Posted June 23, 2016 Report Share Posted June 23, 2016 You're not the only one, this guy was equally frustrated:http://www.renntech.org/forums/topic/43985-intermittent-issue-cranks-but-wont-start/ Link to comment Share on other sites More sharing options...
Daniel Joseph Posted June 23, 2016 Report Share Posted June 23, 2016 Sometimes the complex electronics can be too clever for their own good! The only time in six years my 987 failed to start was caused by a failed engine temperature sender. For a couple of weeks beforehand, the temperature gauge would suddenly fall to zero when driving along then, after a few minutes, return to the normal reading. I put it on my "things to do" list, but then the car simply refused to start one day. Fortunately, It was at home at the time, so Green Flag trailered it to my local indy. He phoned me an hour later to let me know that it was the temperature sender failure that caused the problem. Without an ambient temperature reading at startup, the ECU assumes that the outside temperature is super cold and, to protect the engine, disables the ignition so it will turn over but not start. The replacement cost, including fitting, was just £118, so a happy outcome. ☺ Link to comment Share on other sites More sharing options...
wardpaa Posted June 23, 2016 Author Report Share Posted June 23, 2016 Yes I saw that the poster on the Rennlist forums had both the pump and the coolant temp sensor changed, both failing at different moments. Design 911 have a pump for £250 in VAT and its annoying that although it started after I powered the pump up using an external supply before putting back together, It did not conclude 100% that the pump was to blame. On the other hand if I take the risk and ignore it until it fails, I might be in the middle of nowhere. Link to comment Share on other sites More sharing options...
PaulQ Posted June 23, 2016 Report Share Posted June 23, 2016 If you do decide to buy a pump, its worth shopping around for the best prices. I ended up paying around £170 from Buycarparts for a VDO/Seimens one for my 986. Link to comment Share on other sites More sharing options...
wardpaa Posted June 23, 2016 Author Report Share Posted June 23, 2016 Saw the VDO one Paul but it looked like the later one after 2008. Mine is a 2002 to 2004, 2005 to 2007 pump. I will take another look Link to comment Share on other sites More sharing options...
PaulQ Posted June 23, 2016 Report Share Posted June 23, 2016 I think its p/n 99662013200 for your car. http://www.buycarparts.co.uk/search?keyword=99662013200 Link to comment Share on other sites More sharing options...
wardpaa Posted June 23, 2016 Author Report Share Posted June 23, 2016 A Genuine porsche part is 996 620 131 02, which is the revised part of the original 996 620 132 00. £195 + VAT. Link to comment Share on other sites More sharing options...
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