Cutting out

[alwigley]

Could do with a little more info..... Does it happen from cold, or just when warmed up ? How long before you can restart ? Is the cut-out sudden, or does the engine start to stumble then eventually cut-out ? Do you have a very low idle speed, or is the idle affected by turning on auxillary electrics such as headlights ? Does she start OK, or do you have problems starting ? Let us know, and we can probably give you some decent pointers, although fuel injection problems can be painful to identify on these cars..... took me weeks to figure out a no-idle problem on mine, all down to a £15 sensor []

 

[will87r]

It happens from cold, and doesnt change no matter how warm the engine is. It cuts out suddenly, just like it was switched off. You have to wait about 30 seconds before a sucessful restart. It starts grand, and easily. Is it possible theres a relay that overheats? fuel pump relay? where is it? ignition coil?

 

[will87r]

I Tried a search on here, but couldnt find anything
My car runs for a while, say 2 mins to 60 seconds, Then cuts out. I have just replaced the fuel pump with brand new as the old one used to make a squeeling noise before cutting out. This has had no effect on the symptoms.
I have blew through the filter backwards, and it came out clean, and seems free flowing.
The engine cuts out faster if reved?
Im Stumped

Thanks for any help

 

[AntB]

Speed reference sensors. My 2.7 lux did the same

 

[will87r]

What are these? how do the affect the car? and where are they? Thanks

 

[AntB]

I believe that they are the sensors that measure the speed of the engine and also the position. there are two - one on the top cam and one on the bottom crank (I think).. These then report back to the ecu that supplies the correct fuel for the speed and position reference of the engine. Thats the way I believe it anyway... I had mine diagnosed and changed (both) at a porsche indi. I believe they are located under the cam belt cover.. HTH Anthony

 

[bertelli_1]

The sensors are both on the bellhousing next to eachother. They are generally a pain to change. I'd be checking for fuel pressure when it fails, this will at least tell you whether the fault is fuel or electrics.

 

[alwigley]

Sounds electrical rather than fuel related to me - fuel related tends to cause the engine to surge or falter before dying, whereas electrical faults cut out immediately. According to the Bosch manual, you need an oscilloscope to test the speed and reference mark sensors which are located on the bell housing between the engine and the firewall (as mentioned earlier), and very few of us have access to one...... I would suggest that you carefully check all the connections first of all, before you consider replacing parts - get hold of a copy of the 'troubleshooting DME' section of the workshop manual, and work your way through with a multimeter. Does not sound like a fault with the DME relay, as I they pretty much just fail, and does not sound like ignition components as breaks in leads etc., normally cause cut-out one the engine has warmed, and will not restart until the engine has cooled sufficiently. The engine/DME temperature sensor seems to be pretty critical on these cars as they seem to provide key data to the DME and failure of this can cause all manner of wierd problems. Couple of hours patient testing with a multimeter and a few jumper leads should help at least rule out the good components, and narrow the problem down.

 

[avante101]

I just had a very similar problem a couple of weeks ago. See post on here called 'Intermitant Cutting Out'. I tested speed sensors, changed DME, etc and was starting to consider getting rid of the car. Using clarkes website I narrowed it down to fuel pressure regulator. I changed the FPR and it has cured the problem. £55ish from Porscheshop

 

[Mike_Pollock]

I'd be looking at fuel pressure regulator too, it sounds like it is not maintaining pressure. Mike

 

[pauljmcnulty]

Getting very common, FPR is often the culprit. I think it's time to carry a spare with the DME re[8|]lay in the glovebox.

 

[peanut]

Do you get a spark at the coil/plugs when cranking the engine when it won't start ? You should check that you still have fuel pressure after the engine cuts out . That will either eliminate or pinpoint the problem being due to the fuel delivery system. You should have at least 2.0 Bar pressure after 20 minutes from memory. If you are losing fuel pressure it could be due to either the FPR or the non return valve in your new pump. First of all I would remove the DME relay and fit a 3x way bypass cable as per instructions on Clarkes garage workshop manual site. ie terminal 30, 87 & 87b This will make your fuel pump run continuously and will bypass your crank sensors and temp sensors and ECU . It is very unlikey to be your crank sensor which would normally either work or not. It is only a coil of wire around a magnet .Far more likely to be loss of fuel pressure or loss of spark I should have thought. p.s. don't be tempted to add a fuel system cleaner to your tank. All that will achieve is loosen all the crap in your fuel pipes and carry it down to your injector rail where it will block the extremly fine filters in the injectors.

 

[will87r]

Yes, the fuel pressure regulator sounds like a likely culprit alrite, given that it cuts out under any load. Now which is the fuel pressure regulator? there appear to be 2 on the fuel rail on mine, which iv never seen before, one at the front, and one at the back? There is also what appears to be a fuel pressure regulator on the right hand suspension turret what on earth is this for? Thanks for all your help guys

 

[peanut]

one is the FPR fuel pressure regulator the other is the FPD fuel pressure damper which damps any occilations in fuel pressure. The FPR will have a pipe coming from it which returns excess fuel to the fuel tank when over-pressured. I've got a S2 so I can't tell you which is which on your car without seeing them sorry. You haven't answered any of the other questions that i asked !. without a systematic approach to testing you'll end up buying stuff you don't need and possibly making the situaton worse. It doesn't necessarily follow that the FPR is at fault if you have a under -pressure situation. Fuel flow is electronically controlled by the ECU and you need to check a host of other stuff before assuming your FPR is faulty.

 

[will87r]

Sorry Peanut was in a rush, yes there is spark when it wont start and i did the jumperwire test, she stops while the pump is still running. I need to track down a pressure guage, is there a best place to test? Thanks

 

[peanut]

yes you can test on the rail itself .There is a large nut which is the test point. When you undo the nut make sure that the 3xway jumper is removed and the engine is stone cold . There is potentially 2.5 Bar pressure of fuel in the rail so put a towel over the nut and make sure you are wearing safety glasses. When the nut comes off make sure you don't lose the huge ball bearing inside which is the seal. Use a length of ordinary garden hose and push onto the spigot and put the other end onto your fuel pressure guage. (I bought one on Ebay for £7.50) You might not need jubilee clips depending on how tight the hose fits. Use the 3 x way bypass to get the pump running continuously and watch the guage. It should be around 2.5 Bar from memory . When it reaches that you should hear the FPR release excess fuel and pressure back to the fuel tank but the pressure should stay around 2.5 Bar Next remove the bypass and monitor the pressure over 20 minutes. It should only drop to around 2 Bar from memory . Whilst you do that remove the guage (take care to reduce pressure obviously ) and put the hose into a clear plastic 2 ltr cokebottle . Connect the 3x way bypass again for 15 seconds only. measure the fuel with the Wife's best measuring jug and multiply by 4x and you have the flow rate of your pump in lts per minute .

 

[Mike_Pollock]

measure the fuel with the Wife's best measuring jug and multiply by 4x and you have the flow rate of your pump in lts per minute .

You're a braver man than me! Mike

 

[peanut]

ORIGINAL: A9XXC

measure the fuel with the Wife's best measuring jug and multiply by 4x and you have the flow rate of your pump in lts per minute .

You're a braver man than me! Mike

if er indoors knew what had been put into her measuring jug over the years i'd be a dead man walking.[]

 

[GC8]

Im going to venture a guess (without reading the whole thread): fuel pressure regulator. If it fails the pressure goes up from 2.5/3 atmospheres up to 8+, flooding the cylinders. A new one costs about £35 and is a relatively cheap part to change as part of the diagnostic process. Simon