Intermittent Starting Issue - 95 - 993 - Page 2 - Porsche General - PistonHeads UK

Hello, My Jan. 95 993 manual has an intermittent starting problem. It cranks but sometimes won't start. When it starts there seems to be a single 'clack' type of sound. I don't have a key fob. I use the blade in the dash to disarm the alarm/imob. Plugs and starter motor were replaced last year. As was the DME and crank sensor. HT leads and dizzy caps are being replaced soon. I understand that other culprits may include : Battery/terminals Fuses fuel pump fuse) Ignition/switch Fuel pump Fuel filter Lack of fuel pressure DME ECU Earth strap Voltage issue (too much being sent to the fuel pump) Immobilizer/alarm/ key issue Pulse sender Have I missed anything? Thank you :-)

Can we break this down a little further please? Did the issue appear before the changes you list above? For the absolute avoidance of doubt, the engine is pre-varioram? 1 - if it cranks it's not the H&P immobiliser (from memory) 2 - if it cranks but starts occasionally then it could well be the DME relay. These have been known to fail 'out of the box' as the issue is the solder joints crack over time, and that could even be the case with a newly bought relay. 3 - the ignition switch fail is a 9x6 issue I believe? In your position, if the battery earth strap is original I'd buy a new one. I'd also buy the solid state DME relay made in America. Then you can discount those as the issue, and they are worth doing anyway. What starter motor did you get (ETA by this I mean OEM 993 or the 996 Turbo version - both will fit), and did you get a new starter-motor-to-chassis earth strap at the same time? (but if it cranks strongly, it won't be the starter motor) After the above, yes IMO you are looking for a fuelling issue; but very rare reported. What fuel have you been using? Fill it with ESSO E5 and see if that helps. Edited by Orangecurry on Monday 7th August 19:43

Remember having a similar problem on my old 3.2. Intermittent problem was driving as mad! DME was replaced and found out it was the reference and speed sensor that needing replacing. G

I haven't heard of there being an issue with the 993 ignition switch - but it is quite well known for the 986 and 996... is what I meant. Anecdotal evidence only, but E10 fuel is not great for older fueling systems, and I don't mean attacking the hoses... just in general. For the few extra quid involved for low miles? usage, I'd use E5 (superunleaded) and ESSO at the moment probably has the lowest ethanol percentage. A clack after the engine has started? When in the sequence of parts-replaced did that emerge? Edited by Orangecurry on Monday 7th August 20:09

[quote=Orangecurry]I haven't heard of there being an issue with the 993 ignition switch - but it is quite well known for the 986 and 996... is what I meant. - ah I see - thanks A clack after the engine has started? When in the sequence of parts-replaced did that emerge? In truth I don't know when the clack started because I can't hear it from the drivers seat. Around 18 months or so ago someone standing near it when I started it told me that they can hear quite a loud sound as it starts. Just like a rather loud clack or mechanical slap type of sound. It only happens once when it starts. It's miffed my local indy. It went to my indy because it wouldn't start at all once. Turned out to be the crank sensor Someone else suggested it may be linked to too much voltage being sent to the starter.

Thanks for your very helpful and quick response OC. The starting issue was present before the new starter, DME, crank sensor last year. It worked fine afterward for a while but now the issue is back it seems. - Yes Pre Vario - Agreed on the DME - I've not used a soldering iron before so may need to try the solid-type DME relay - Not sure what you mean ''re 9x6 issue'' for ignition. - The earth strap is original I believe - Bosch Starter Motor for 993 C2 - (no new earth strap). Cranks strongly - I use standard fuel I don't know if it's related but the single 'clack' sound upon startup has baffled a few people. One said it sounded like piston slap then changed his mind. Edited by Solarized on Monday 7th August 20:01 Edited by Solarized on Monday 7th August 21:07

If your Indy doesn't know what it is, what chance do we imaginary beings on your computer have? So it's not the starter motor not disengaging when it should?

Orangecurry said: If your Indy doesn't know what it is, what chance do we imaginary beings on your computer have? So it's not the starter motor not disengaging when it should? Well you guys are an invaluable source of Porsche experience and wisdom! I don't know if its the starter not disengaging or not.....however I've just found some info online about something similar (main earth strap) that sounds interesting --- This person had a new Bosch starter fitted in 2019, car's done fewer than 2k miles and got a non-starting/clicking noise from the engine bay--- response ---Also, have your battery checked on a device that can measure available starting-demand amperage as well as static and running voltage. Conceivably the same test could be administered at the starter end of the starter supply cables revealing any amperage drop from a suspect cable or ground strap. Also, the solenoid that makes the clicking sound is the outboard part of the starter to which the electrical cables are attached to. It can be the source of your non-start as the electromagnet and switch internal to it triggers the starter motor once the Bendix gear it inserts into the ring gear on the flywheel is fully seated. If it doesn't fully insert the gear or the electrical switch internal to it doesn't make contact all one will hear is clicking. It can be purchased as a separate part. Unfortunately reman part durability is highly variable. See the section on Remanufactured Parts in this document: https://993servicerepair.blogspot.co...sdom-page.h...

I had a non starting issue 18 months ago with my non varioram 1995 C2. From memory the starter would do its business however the engine never started. I had it towed to my indy who fixed it. My invoice said the following: "Investigate non starting, trace fault to failed crank refrence sensor, remove sensor bracket and cut failed sensor from bracket , renew and set air gap. Test :OK" No idea if this is any help

hopeydaze said: I had a non starting issue 18 months ago with my non varioram 1995 C2. From memory the starter would do its business however the engine never started. I had it towed to my indy who fixed it. My invoice said the following: "Investigate non starting, trace fault to failed crank refrence sensor, remove sensor bracket and cut failed sensor from bracket , renew and set air gap. Test :OK" No idea if this is any help Helpful thank you - when mine didn't start at all it got towed to my indy who, after quite a while and expensive theories, replaced the crank sensor and the car started fine - for a while. Another thing worth noting is that my indy could not access one of the plugs and so that plug was not replaced at the time. It will get replaced with the HT leads, dizzy caps and rotors soon.

...but yours is cranking and not starting.... ? Any clicking (and not cranking EFA) is deffo a failing 'something' in a starter motor.... incl a grounding issue. Edited by Orangecurry on Monday 7th August 22:17

Has the interior of the car got wet at all? Have you checked for any dampness under both seats? Just a thought. Solarized said: Another thing worth noting is that my indy could not access one of the plugs and so that plug was not replaced at the time. Seriously?

Broken head stud?

Yes Well they could access it but it was solid apparently and they were reluctant to attempt to remove it. My other mechanic will have a go at removing it.

There's no dampness that I'm aware of however I will check again.

Ahh right - that is good sense. Was it the one behind the power steering pump? That was the one that allegedly the OPC mechanics never bothered with as they weren't given enough time. Having said that, I've done mine twice now, all 12 obviously, and it really isn't difficult if you have enough joints and extension lengths (and the rest of the remove-to-access-parts come undone) which the OPCs would have, so maybe the above is internet myth. Re the dampness.... did the interior EVER get wet, as that might have put corrosion into the Motronic unit, which could show as intermittent electrical issues. There are also at least two grounding points under the passenger seat, but IIRC they are quite 'high' so shouldn't have sat in water.

OC I suspect it will be that one if that's the usual culprit that's difficult to get to. My carpets feel dry. The car is always garaged and never really taken out in the wet. There's only been a handful of times in the 11 years I've owned it where I've been caught in the rain. It does get washed fairly regularly so not impossible that water ingress may have gone unnoticed. My wee list is getting bigger. It will soon be getting ; HT Leads 1 x awkward plug 2 x dizzy caps & rotors Upper and lower cam covers (both sides) Earth strap When the rear bumper is removed I'm expecting to replace the 4 x bumper supports And I'm considering wrapping the exhaust rather than replacing the expensive and not great exhaust tinware - Anyone get any comments on this? I'll also replace the DME again with the one you mentioned.

Obviously all of those things may need doing, but none are likely to be the issue (apart from the DME relay, and maybe the earth strap). Why are they taking the rear PU off? One thing I forgot to ask was has the car ever died whilst you were driving along? That's also a symptom of a solder-cracked DME relay. I would still find a local old-Porsche indy that has an old-Porsche OBD reader, as that may point to a sensor issue. Edited by Orangecurry on Tuesday 8th August 22:20

No the car has never died while driving. The car started no problem last night but then it does most times and not at others - which is very concerning at the fuel pumps 😳 My mechanic reckoned the bumper may need removed to do the work I listed - maybe it won't? Yes I agree an Indy with the OBD reader is likely the way to go.

Hi. I’ve experienced similar intermittent starting and presumed crank pos sensor or DME Was actually air flow meter which 9M diagnosed immediately & sorted.

jonny finance said: Hi. I’ve experienced similar intermittent starting and presumed crank pos sensor or DME Was actually air flow meter which 9M diagnosed immediately & sorted. Interesting thanks! I'll add air flow meter to the list of possibilities

Also worth checking: Distributor - the belt can fail and leave you with only one ignition circuit working; the clack may also be associated; where the stationary rotor receives firing pulses and directs them to the wrong plug causing pre-ignition or knocking; the rotor is free to rotate and can sometimes align and sometimes not giving strange misfire/hiccup running. A 993 running on one ignition circuit will feel fairly flat - but will still be running. Ignition transformer; there are two, under the passenger seat, they are solid state but have been known to intermittently fail - a hard door slam would make/break the last faulty one I saw. Ignition coil(s); there are two Its not uncommon to have a biild up of issues; I have seen a failed circuit 1 ignition transformer which led to an overloaded ignition coil on circuit 2, both gave a no-spark condition but clearly separate causes.