Need rubbish starting help...?

[tartan_rob]

[]
I have had this problem with the car since Dec '14 (I think); I did some welding over x-mas '14 and forgot to dissconnect the battery - this may or may not be resonsible for the issues...

The car was running okay before welding but the next time I tried starting her was Feb '15, she was lumpy, hard to start, struggling to idle, struggling to rev etc before dying. A Porsche trained mechanic mate has been over her with a fine toothcomb but we can't find anything wrong. In the absence of obvious faults we sent the ECU off to BBA-REMAN who confirmed it was faulty. They also confirmed that they were unable to replace the failed component or to bodge a fix.

golfprorich has kindly provided me with the loan of a known good ECU in order to see if that was the issue. The car is better than before but still lumpy, very poor running, struggles to idle or rev and there is no way you could drive her, I can't get her to run long enough to engage a gear.

I am really at the stage of having her cut up unless I can get her going. Does anyone have any advice or support they can offer or even someone in Wiltshire know where I can take her to try and get fixed?

I have committed a lot of time to get her into the shape she is and don't want to let the angle grinder get the better of me.

Thanks in advance,
Rob

 

[zcacogp]

Ooooh dear, vague 'it doesn't work very well' symptoms.

However it runs, so there will be a signal from the flywheel sensor (although possibly a poor one) and presumably a spark of some kind. How old are the plugs and leads and rotor arm and distributor? How old is the fuel?

You need to do some old-fashioned fault-finding. Measure the spark across the plugs (a spark gap tester is a great tool for this - they look like this).

Measure fuel rail pressure as well. I'll bet that one or other of these will get you to the cause of the problem.


Oli.

 

[tartan_rob]

Thanks Oli. The plugs, leads, DR, rotor arm, coilpack, ignition amplifier, ICV, Flywheel sensor, DME temp sensor and FPR are all new. I have a re-con'd MAF and I have cleaned the injectors and they now have an excellent spray pattern.

The fuel is about 6months old...the concern is that within the space of 6weeks (no running in-between) she went from running (albeit requiring a tune up) to running horrendously.

I have youtube'd the issues https://www.youtube.com/watch?v=CdryWmzBjU4

Anyone know of any good specialists in Wiltshire that fancy a challenge?

 

[tartan_rob]

and new TPS

 

[bmnelsc]

Hi - assuming you did "The plugs, leads, DR, rotor arm, coilpack, ignition amplifier, ICV, Flywheel sensor, DME temp sensor and FPR are all new. I have a re-con'd MAF and I have cleaned the injectors and they now have an excellent spray pattern." after your welding then I'd guess you should be checking the TPS as tartan_rob suggests (IIRC for the S and S2 these signal only closed or wide open throttle) which might give you poor results if the ECU thinks the throttle is closed all the time. Otherwise you may have a vacuum leak somewhere which could cause the fuel to lean out to nothing as RPM increases. As you have tried a known good ECU with little success, perhaps a step through of the DME test plan will point you to a faulty signal (so maybe a bad wire/connection from one of your components) or prove that everything is working as it should.

Good luck - I'm sure this gremlin can be conquered with patience and a methodical approach.

 

[Frenchy]

A faulty TPS would usually have the car running rich which would start okay when cold but cut out when warm due to overfuelling, worth cleaning the main earth points up whilst you are at it.

 

[zcacogp]

Sounds like you have either been doing a semi-restoration or simply changing bits and hoping that they will solve the problem.

Having watched the video I'd think it's fuel related too. Try spraying something combustible into the air intake when it's trying to run to see whether that changes things. You can use carb cleaner or even deodorant - anything to burn in the engine and provide an alternative fuel source. If spraying something into the engine while it is spluttering makes it run better then it will show that your problem is lack of fuel, and you can work from there.


Oli.

 

[Gordon Attar]

Is the Earth strap in good condition!?

 

[tartan_rob]

The earthing strap mounting points have been cleaned but they were good anyway. As for fueling, it maybe just that, she seems to be running rich. The TPS was changed and reset as per the Porsche factory manual.

I bought the car as she was running (with an MOT). The inside was a real mess and the body needed some work. So I stripped her back to the bare metal and started from scratch with new carpet sets, new interior etc. The engine needed some TLC but it ran, I overhauled it over the winter 2013 with new, gaskets/seals, new camchain + tensioners, re-conditined hydraulic tappets, new OPV, new oil lines etc....that kind of thing. The mechanical timing is good and was checked by Porsche.

She was running fine until the welding...! I did not run her immediately after welding but between switching her off and she was fine and trying to run her a few months later (with little success), all that was done was welding.

Someone mentioned dual fuel pumps and that one may have failed...? Any truth in that?

 

[peanut]

have you fitted a 3x wire jumper in place of your DME relay yet ?

The 3x wire jumper should eliminate the DME relay and associated circuitry being the cause of the problem as it forces the fuel pump ,injectors, sensor supply ,ignition and power to the ECU
If there is no difference with the 3x wire jumper fitted it will actually give you a lot of information.
I suspect that the welding is coincidental, (3x months is a long time to leave an old Porche without starting and running it,) having said that is it possible that your welding could have melted the loom ? maybe the 12v fuel pump supply ?

 

[white944]

x2 for the 3 wire relay jump. Will eliminate loads of potential faults in one go.

 

[tartan_rob]

I'll have a go tomorrow. If the wiring tithe pump is fried it won't tell me anything though will it?

Have ordered red a fuel pressure gauge as well. What fuel pressure should I be seeing?

 

[tartan_rob]

So I 'hotwired' the DME, removed and checked the spray pattern on the fuel injectors to find two caps loose I refitted the whole lot and the car runs better than before but still misfiring - not running right.

The fuel pressure was spot on; 3.8bar fuel pump running. roughly 3.0bar car running.

She sounds like poor firing and some backfiring also.

 

[tartan_rob]

Thoughts?

 

[PSH]

i doubt it's the welding?...in fact when welding it's better to leave the battery connected to act as a sponge..mind you it's best to use an anti surge device across it the terminals too...all my welding was done last weekend with the battery connected but the ECU removed from the car. Have you tried fresh fuel, i don't recall seeing any mention of the fuel? Backfiring is usually a timing issue...this could be as simple as the rotor arm being loose. I had this myself recently...plugs sparked fine when testing but due to the rotor arm having moved the car naturally had no chance of starting...what I'm saying is don't forget to check the simple things.. I did and had the car recovered to my home, only to be able to fix it in a few minutes the next morning when I had got my head in gear...well it had been a late night before...

Pete

 

[tartan_rob]

So I finally got her running. The plugs were manky from misfiring so I got a new set and noticed #2 and #4 plugs were fouling up really quickly. Did some really basic tracking to find that the plug leads for #2 and #4 were round the wrong way on the distributor cap. Doh.

Anyway, the leads between the plugs and distributor cap were all tangled up and crossing over each other so I have re-routed and sorted out other small issues and job done. She is back together and running.

She is still a little rich but the MAF has been re-built and not set-up for Idle emissions yet....next job, MoT...

Rich - I'll get your ECU back in the post to you this week, thanks.