Hot Starting Problem

[Cater_Racer]

Our S2 has a hot starting problem.

The battery is a new gel race one, but the problem existed with the earlier new standard lead acid battery.

Ok the leads are a bit under size, (got to connect thru a race cut-off isolator), but when the car is cold or just warm, it turns over slowly and starts! From cold it always starts in two seconds from turning the key.

When its HOT , ie at the driver change pits stop, will it start....................No!

We ended up bumping it down the pit lane again yesterday, lost 2 minutes in the pits, that's two (59 second) laps at Brands.

So what's the answer? is fuel evaporation? or injectors or DMA ?

Any ideas?

 

[edh]

Try the DME temp sensor (it's only a £10 Bosch part anyway..)

http://www.123spareparts.co.uk/cgi-...pag_goto_page=0&pag_select_items_per_page=10&

If it's failing it will run very rich. Mine was struggling to re-start when hot - needed loads of throttle to keep it alive, swapping this sorted it. there is a test procedure on clarks garage, but for £10 it was easier to replace.

 

[homesea]

Is this the same part for a turbo?

 

[Cater_Racer]

Thanks Ed I'll certainly give it a try, as you say at a tenner its a no-brainer.

 

[edh]

ORIGINAL: homesea

Is this the same part for a turbo?

"This item is suitable for 457 vehicles. >>>"

yes - looks like all 944's and 924S

 

[peanut]

it might be worth attaching a fuel pressure gauge to the test point on the fuel rail and monitor the pressure when you switch off hot. (leak down test)
I believe the fuel system should maintain at least half pressure at 20 minutes .

If the fuel system is holding pressure then check that you have a spark when you attempt a hot restart.
If no spark I would try fitting a 3xway bypass in place of the DME relay and see if it then starts hot.

If the car then starts it will have narrowed down where the the problem lies considerably

 

[homesea]

Nice one cheers, guess I could of just read that[]

 

[zcacogp]

Gerry,

Sorry to have heard about your problem yesterday.

Thinking about it, I think the logical route to go is the age old testing for fuel and sparks. My gut feeling is that it is fuel, but certainly test for hot sparks (plug out, rest it on the block and crank to see whether there is a spark.)

If it is fuel, your are into things like EDH's sensor (which is a great start), and Peanut's fuel pressure rail test is a good one, to see whether it holds fuel pressure when turned off. This requires fairly specialist kit, so you may do better paying someone else to do the test for you (I don't know how comprehensive your workshop is.) I do know that the suspect part in cases of bad fuelling is often the fuel pressure regulator, and there seemed to be a spate of them failing on this forum about 18 months ago. However I'm hazy on what that actually does, although someone else will be along soon to explain it.

For what it's worth, it sounds not dissimilar to a problem I had with my S2 in very hot weather in France a couple of years ago. That make hot starting very hard, although it was in high ambient temperatures (so unlike Brands yesterday!) The cure for this seemed to be to remove the cover from the fuel fail - I happened upon this in desperation, but assume therefore that it was fuel vaporisation. As a long shot, it may be worth removing the cover and seeing whether this helps ...


Oli.

 

[Neil Haughey]

Definitely check ignition, drop out when hot is likely either the coil or crank angle sensor (or its wiring). I had a terrible problem with my car where it would cut out after a while on track and then wouldn't restart, left to cool for 1/2 an hour and it started on the button.

It does sound like a fuelling problem though given that you are managing to get the car going again and it lasts a 40 minute race.

 

[Cater_Racer]

Thanks Neil & Oli, I'm sure it's the fuel evaporation thing, because it always does start eventually and goes well once going.

Tom thinks it's definitely the ignition, but he's an engines designer with automotive engineering degree, I'm a accountant, so I must be right!

 

[edh]

Fuel pressure gauge is pretty cheap - get one off ebay with the right connector for the fuel rail (M12?) That will show you if the pressure drops off very quickly when stopped.

DME relay is worth investigating as well - always worth carrying a spare one

 

[zcacogp]

... in which case then try removing the fuel rail cover and see if that makes any difference, and if not then work methodically though the standard tests. Including (amongst others) sparks and fuel rail pressure. You'll get there in the end, it's just a matter of time and logic.

Given it's not road-registered, how do you test it when away from the track?

ORIGINAL: Cater_Racer
Tom thinks it's definitely the ignition, but he's an engines designer with automotive engineering degree, I'm the guy with the cash, so I must be right!

Bit of an edit there for you Gerry ... []


Oli.

 

[Diver944]

I'm watching this thread with interest as my S2 has just started to display the beginnings of this problem. It starts from cold no problem at all, but if I stop for just a few minutes and then try to restart (like when you've just popped into a shop) it has to turn over for a long time and needs coaxing with a bit of throttle. Leave it for 10-15 minutes and it starts fine again.

Does anyone know if the 3 bar FPR that upgraded Turbos use is the same as the S2 version. I just happen to have a couple of those in the garage

 

[peanut]

ORIGINAL: Cater_Racer

Our S2 has a hot starting problem.


So what's the answer? is fuel evaporation? or injectors or DMA ?

Any ideas?

you need to follow a proper systematic approach to troubleshooting the problem or you're likely to just make the situation worse by changing parts and fiddling with stuff at random. The 944 fuel injection and ignition system is a complex one and requires a thorough understanding in order to fault find.

You've given us too little information to diagnose the fault over the net and to be completly frank you haven't even bothered to acknowledge the advice given or do any of the tests suggested . I wish you luck but I would suggest you either get a Bosche trained technician to check it over or get hold of the Bosch fuel injection and engine management manual
http://www.amazon.co.uk/dp/0837603005
good luck

 

[edh]

ORIGINAL: Diver944

Does anyone know if the 3 bar FPR that upgraded Turbos use is the same as the S2 version. I just happen to have a couple of those in the garage

Don't think so - it's 3.8 bar I think (and expensive).

same symptoms as mine (mine was also running a bit rough, tailpipe blackened) - test the DME temp sender at the DME plug (Clarks Garage) or replace it. You're not going to make things worse by changing it..

How is the fuel consumption? Mine dropped right off - about 200 miles on 2/3 tank, mainly m-way crusing

 

[944 man]

Wherever theres doubt about whether the problem is fuel or ignition related, I always suggest Laser tools ignition lights. They cost about a tenner from Halfords and you fit them inbetween the ignition lead and the spark plug.

Fit them and replicate the conditions, then turn the engine over with the bonnet open and see if the leads light up! If they do then you know that you have a spark, which rules out so much.


Simon

 

[Cater_Racer]

ORIGINAL: peanut


to be completly frank you haven't even bothered to acknowledge the advice given or do any of the tests suggested

Sorry I wasn't up t'ill midnight surfing the web, got too much of a life I guess.

As Oli points out I can't trial anything until I'm next at a track, so I'll try and get some diagnostic bits together for Spa early next month. We can test on the Thursday, so I'll see if I can get the pressure meter Peanut suggested.

The Lazer lights seem a good idea, I've got a temp sensor on order, and I carry a spare DME so I'll report back from Spa.

Fortunately they've changed the race structure at Spa, so we are running two half hour races one on Saturday next on Sunday, with Sunday's grid taken from the finishing positions of the Saturday race.

 

[zcacogp]

Gerry,

Forgive me for saying this, but surely you want to be addressing this fault before you leave for Spa? Can't you run the car up to temperature at home and then see whether it will stop and re-start? Being confident that you have fixed it before leaving the country would be a better position to be in as fixing it may be quite time-consuming. I appreciate that Spa doesn't have the pit stop that Brands did, so hot starting is not as critical, but I'd suggest that fixing this earlier rather than later is a good idea (if nothing else because it may get worse, and turn into a cold-starting issue as well. Which would be a real pain in the bum for you.)


Oli.

 

[peanut]

ORIGINAL: Cater_Racer

ORIGINAL: peanut


to be completly frank you haven't even bothered to acknowledge the advice given or do any of the tests suggested

Sorry I wasn't up t'ill midnight surfing the web, got too much of a life I guess.

As Oli points out I can't trial anything until I'm next at a track, so I'll try and get some diagnostic bits together for Spa early next month. We can test on the Thursday, so I'll see if I can get the pressure meter Peanut suggested.

The Lazer lights seem a good idea, I've got a temp sensor on order, and I carry a spare DME so I'll report back from Spa.

Fortunately they've changed the race structure at Spa, so we are running two half hour races one on Saturday next on Sunday, with Sunday's grid taken from the finishing positions of the Saturday race.

Threads on fuel pressure, flow and leakdown testing are all over this forum. If you had the time you could do a search and save us all some time. I have personally written 3x detailed accounts of how to do it , one this year.!

Any pressure gauge will do the job including a tyre air pressure gauge as long as it reads up to 3Bar . They cost around £10.00 on ebay and you can use some garden hose to connect it up to the fuel rail. There are plenty of links on this forum.

If you cannot find the time to do a simple search or carry out a simple 15 minute test on your car then you've no right asking us to waste our time trying to help you.
Sorry if that offends you but people that waste my time make me angry

 

[Cater_Racer]

Thank you for your valuable time, I am unworthy................Please accept my humblest apologies.