jonny986s Posted November 30, 2022 Report Share Posted November 30, 2022 Hi , I have a 2002 Boxster S which has been running great. The other day i did a 50 mile run, parked up and 10 minutes later attempted to head out briefly to the shops - it was struggling to tick over/ start and would stall, despite a strong starter motor/ batt etc. It felt like an electronic/ ecu issue. I managed to get it revving/ ticking over just and attempted the 2 mile run to the shops, 200yrds down the road it stalled completely and just would not start again, I had to leave it on the side of the road for the night. It would crank over but no start at all this time. Some Googling that evening suggested that other many people had experienced similar stalling with hot engines describing exactly the same symptoms i had experienced. That the problem was observed only when hot and typically was a remedied by replacing the crankshaft position sensor. I went down in the morning to the cold car and it started perfectly, driving it back to my garage. I felt confident i knew what was needed to be done I sourced a new CPS convinced that this was going to solve the issue. Next day, from cold i started the engine no problem briefly (with the old sensor) then went about to change out change for a new CPS. After changing for the new part (and making sure it was secured in the connector properly) I tried to start. It would crank but it did not fire at all. I literally changed an old sensor for new and its even worse. What on earth is going on? The worst case scenario i felt is that it would make no difference and I would still have problems when hot, not that it would fail completely I am at a loss for ideas here and a bit stumped. I will switch back to the original part tomorrow to check that the old part works. The part i bought was a brand new Bosch part - its almost as if the new part is faulty Any suggestions? This has completely thrown me. As an aside i just bought a BlueDriver OBD sensor, which shows zero fault codes Quote Link to comment Share on other sites More sharing options...
TROOPER88 Posted November 30, 2022 Report Share Posted November 30, 2022 Sounds like fuel pump relay Quote Link to comment Share on other sites More sharing options...
jonogt6 Posted November 30, 2022 Report Share Posted November 30, 2022 I had an almost identical problem early this year. One day was running and starting fine and then the next day it would barely start and then not run. Turned out it was the MAF sensor that had failed suddenly. You could check this easily by unplugging your MAF...if it starts and runs OK you may have narrowed it down. Quote Link to comment Share on other sites More sharing options...
Bradders59 Posted December 1, 2022 Report Share Posted December 1, 2022 Might the coolant temperature sensor be a possibility ? Quote Link to comment Share on other sites More sharing options...
Sup8man7 Posted December 4, 2022 Report Share Posted December 4, 2022 Had similar issue recently, and turned out to be the fuel sender unit. One of the feeds that connects to the fuel pump had broken off in the tank. There's a couple of videos online to test if it's the fuel pump relay as Trooper88 suggests, as well as testing for fuel pressure if you have the equipment. Quote Link to comment Share on other sites More sharing options...
jonny986s Posted December 4, 2022 Author Report Share Posted December 4, 2022 Some diagnostics later... The fuel pump relay seems to work (on the bench with a 12v supply) i changed for a new one anyway - still no start, Cranks but doesnt catch. I jumpered the two relay pins to start the fuel pump, nothing. with ignition of and in 1st position. Also tried to disconnect the MAF, but this made no difference. The fact that jumping the relay didnt cause pump to run, suggests it could be this. No idea what else i can try. Out of interest how hard is changing fuel pump yourself.? Im happy to drain tank myself - after changing the unit do you have to do any priming or clearing air from the line? I changed the rubber seal on the sender a few months back (as i had gas smell) seems not too bad in there though also always the risk of pipes/ wires disturbing the float Does everything i mention suggest the pump?? Quote Link to comment Share on other sites More sharing options...
TROOPER88 Posted December 5, 2022 Report Share Posted December 5, 2022 Fuel pump is easy. Ensure you have the correct sender unit as there are two types. Don't worry about draining the tank, you will. be fine. You do not need to prime or purge the pump either. The pump simply fits on the base of the tank with a bayonet fitting, be careful not to twist the float and wiring when installing the new one. Paul Quote Link to comment Share on other sites More sharing options...
jonny986s Posted December 5, 2022 Author Report Share Posted December 5, 2022 Thanks all for advice on this - going to change pump later this week/ weekend. Just to confirm, i'm not planing to change the fuel sender as believe thats okay - just the pump is the likely candidate i understand https://www.pelicanparts.com/More_Info/99662013200.htm?pn=996-620-132-00-M82&SVSVSI=0787 Quote Link to comment Share on other sites More sharing options...
Sup8man7 Posted December 5, 2022 Report Share Posted December 5, 2022 I suspected mine was the pump until we removed the sender and found the broken connector but it very much sounds the pump is likely. Hope it solves it! Quote Link to comment Share on other sites More sharing options...
TROOPER88 Posted December 5, 2022 Report Share Posted December 5, 2022 3 hours ago, jonny986s said: Thanks all for advice on this - going to change pump later this week/ weekend. Just to confirm, i'm not planing to change the fuel sender as believe thats okay - just the pump is the likely candidate i understand https://www.pelicanparts.com/More_Info/99662013200.htm?pn=996-620-132-00-M82&SVSVSI=0787 If you are buying second hand from the likes of Douglas Valley, the pump and sender are usually sold as one piece Quote Link to comment Share on other sites More sharing options...
Jim Bond Posted December 7, 2022 Report Share Posted December 7, 2022 Had the same issue and tried the same solutions and discovered that supermarket petrol was the problem. Use shell / BP and have never had the problem since. Quote Link to comment Share on other sites More sharing options...
the baron Posted December 7, 2022 Report Share Posted December 7, 2022 My guess is the MAF, try unplugging and see how it runs Quote Link to comment Share on other sites More sharing options...
½cwt Posted December 7, 2022 Report Share Posted December 7, 2022 (edited) 5 hours ago, the baron said: My guess is the MAF, try unplugging and see how it runs OP has already said this made no difference... As my teachers used to say, RTQ. 😉 Edited December 7, 2022 by ½cwt Quote Link to comment Share on other sites More sharing options...
map Posted December 7, 2022 Report Share Posted December 7, 2022 If the suggestions above don’t remedy the problem consider replacing the throttle pedal sensor. I had problems like these and eventually they disappeared when I replaced it with one from a breaker. If these go rogue the car’s diagnostics do not report the failure/errors. Quote Link to comment Share on other sites More sharing options...
BBB Posted December 7, 2022 Report Share Posted December 7, 2022 3 hours ago, ½cwt said: OP has already said this made no difference... As my teachers used to say, RTQ. 😉 Or as we say now, RTFQ Quote Link to comment Share on other sites More sharing options...
the baron Posted December 8, 2022 Report Share Posted December 8, 2022 On 12/7/2022 at 6:00 PM, ½cwt said: OP has already said this made no difference... As my teachers used to say, RTQ. 😉 I should really learn to read all the posts before I comment, I will go and stand in the naughty corner🤓 Quote Link to comment Share on other sites More sharing options...
jonny986s Posted December 12, 2022 Author Report Share Posted December 12, 2022 Some success, I just replaced the fuel pump and it starts!. Although the tickover revs are pumping between 600 and 800 at a rate of 1 second i would say, doesnt sound right but at least its running. Its been standing, unstarted, for a couple of weeks now, maybe needs time to get fuel into the system, though i have given it 10/15 minutes. I just powered up the old pump and it seems to work so that has thrown me a bit too. The only thing i have left to do now is maybe use some MAF cleaner on that sensor. All very weird as had been running great. It really seemed like a sensor had gone down and that the ecu was not happy. Any thoughts on the pumping tick over revs? Quote Link to comment Share on other sites More sharing options...
jonny986s Posted December 12, 2022 Author Report Share Posted December 12, 2022 Just cleaned the MAF, made no difference but running engine with it disconnected i dont notice pumping. I guess that means a faulty MAF? All very odd, didnt have pumping before As an aside, I have a blue reader which is showing no codes. I bought it to check codes but assumed iut could sort out the airbag lamp that came on after an ind gatage did a overall check for me. How do i clear an airbag light? Quote Link to comment Share on other sites More sharing options...
Paul P Posted December 12, 2022 Report Share Posted December 12, 2022 8 hours ago, jonny986s said: As an aside, I have a blue reader which is showing no codes. I bought it to check codes but assumed iut could sort out the airbag lamp that came on after an ind gatage did a overall check for me. How do i clear an airbag light? You need a reader with some "smarts" - cheap and cheerful ones do generic powertrain codes ( check engine light) and little else - the popular one is the icarsoft v1/v2 POR ( or their multi brand versions) - BUT - folks have reported mixed results with those units and 9x6 AIRBAGS (no 1st hand experience - but I have cleared an airbag code using Porsche PIWIS that apparently an icarsoft unit had been unable to do, but that was only anecdotal. ) The Foxwell NT 530 does seem to work fine for Airbags on 9x6 as well as supporting a number of other car systems and has good reviews and allows some coding - but you are spending a couple of hundred quid - likely a decent investment for long term ownership but maybe too much for a "quick reset" Whereabouts are you - there's a map top of the technical questions section with locations of various folks who have access to some of the diag tools available - if you are in striking distance of North Kent - happy to help if I can. Quote Link to comment Share on other sites More sharing options...
Boxstclever Posted December 12, 2022 Report Share Posted December 12, 2022 Could be throttle body. You might be lucky with a clean if it's a bit gunked up it can cause idle hunting, but the non starting may point to more sinister issues with the electronic module. Need to get it plugged in to be sure. If it is that, they can be sent away for rebuild/refurb which is considerably cheaper than replacement. Quote Link to comment Share on other sites More sharing options...
½cwt Posted December 12, 2022 Report Share Posted December 12, 2022 If it runs poorly with MAF and OK without MAF connected, I think you have your fault. Why would a faulty.or gunked up throttle body start to behave when the MAF is disconnected. Make sure you get correct MAF, early cars end .124.00, later .125.00 or 01 or 02. I have as salvage one in mine that has been going well for over 3 years, genuine Porsche/Bosch. They cost about £35 from Douglas Valley so you can afford to do 3 or 4 before getting to Bosch or Porsche new cost. You need a small Torx security bit with a hollow tip to get it out. Quote Link to comment Share on other sites More sharing options...
Boxstclever Posted December 14, 2022 Report Share Posted December 14, 2022 Apologies, missed the bit about "no pumping" when MAF disconnected. Ignore me! Quote Link to comment Share on other sites More sharing options...
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