any reason why it wont start when cold?
 

hey guys, is there any reason why the car wont start when it's chilly out? I'm talking -10C or colder..

it cranks and cranks and cranks.. all day long.. it just doesn't fire up.

I've got a battery in there now.. made for an '03 mustang, and has (i believe) 700CCA's (at least 650, but I think 700.. i'll check tomorrow)....

I'm still thinking battery issue though..
both battery terminals are brand spanking new, and the main engine ground is in good shape...

strange. how about fuel delivery? is it possible the cold temp sensor(s) aren't working and it is too lean to start that cold?

no idea.. it's possible i suppose.. how would I test? (And where are the sensors you're talking about?)
i know if it sits in the sun and warms up, even a couple degrees, it'll start right up and run like a champ.

you have one at the front of the engine, just below the cylinder head at cylinder one. also, there is a thermal switch that works from the heat of the coolant at the rear of the engine.

Exactly where is that switch at the rear of the engine? And why, if there is one, would it cause a cold non start problem?

lol ok then socal... what do YOU think? ;)

I'm interested in how others perceive the intricacies of these cars.

I would check the adjustment for the speed/reference sensors and the DME engine temp sensor. Other than the DME engine temp sensor there is the air temp sensor in the AFS that would affect cold weather cold starting. The air temp sensor has very little effect while the engine temp sensor would have a greater effect.

When the engine is cold the mixture is richened (DME engine temp sensor and AFS air temp sensor) and the idle control valve is wide open to raise the idle rpms. With all other inputs and controls working the engine should start. Now what other inputs and sensors could be affected by extreme cold.

Hint: Plastic and aluminum shrink when exposed to extreme cold. What sensor has a clearance adjustment that can be critical? Besides there is a factory bulletin out on the 944S for cold climate running problems on the same sensor adjustment.

its a vacuum switch that lives inside the coolant tube that comes out of the rear coolant passage at the back of the cylinder head. i *think* it has something to do with emissions. i am intimately acquainted with this little bastard, being that i broke them during both of my cylinder head removals. the last just sheared off at the base with very little effort on my part, i was being careful, it was just old.

how would it affect cold starting? i don't know, just brainstorming...

I know what you're saying.. but could 5 or so degrees really make *that* much of a difference between 'no start', and 'starts like new' ?

I mean... obviously it does... but i'm talking in relation to expansion and contraction causing the sensor clearance to be out of spec..

um... DME?

Nynor, That is the "switch" to pull the fumes out of the charcoal canister. Very little change in idle speed.

Cold no starts can be the sensor clearance or just one of the connectors shrinking enough to pull a broken wire apart.

More details: Does the engine start but stumble along for a while then clear up?

right. like i said, just throwing it out there. have a nice easter!

when the car starts normally (ie. when not 'cold'), it starts right up and idles at 950... no stumble at all.

when it's cold and *does* decide to start, the idle is a little low.. 875 to 900... but goes up to 950 after it warms up a bit.

Have you replaced the DME Relay since you got the car? If the problem reoccurs again, remove the DME relay and tap it a few times and/or warm it up before reinstalling it the car may start right up.

I doubt that we will see any more -10C weather in the GTA this year, so if this problem only occurs when it is -10C or colder then you may have to revisit this next winter. In the mean time, if you haven't replaced the DME relay I recommend that you do so as they have been known to cause starting problems.

i'll give it a shot Mark, thanks.. I know the relay is at least 5 years old..

what number is it? Wilk's page with the relay/fuse identification chart is gone...

On my '86 it is Relay G5 located in the Fuse / Relay box under the hood. Your car is an "83 I'm not sure if the relay is in the same place but if you check label on your relay box it will say DME or Fuel Pump relay. I'm not sure if the relays for the early / late cars are the same you will have to look it up. Four years ago I bought one for my '86 from Downtown Porsche in TO for $25CA, The new release of the relay for my car has a 993 number... nice to know the relay is used in the newer cars as well.

*************************************************
Since I'm digging up the speed & reference sensor part numbers for someone else, I'll include the info here as well just in case you or someone else need it.

Reference sensor 944/968 Bosch # 0 261 210 003 (this is marked on the sensor) is the same as BMW part # 12 14 1 708 618 and 12 14 1 710 668 (the difference is the length of the cable).


OEM (Bosche) Number for the 944 sensor is F6010-12761 List $128CA
An OEM (Bosche) Number for the BMW sensor is F6010-12760 List $94CA
Substantial price difference for the same part...

You can research the F6010 numbers on several websites and / or local German car shop can find the sensor using the F6010 number.

On an '83 the DME relay is on the panel in the drivers side footwell. it's on the top row, slightly behing the additional fuse block, and I THINK it's the second from the left. If it's like mine it has 'DME' written on it.

pretty sure this is where it was on my '83, with DME on the butt end of it.

cool.. thanks guys..
i know where the relay panel is.. i'll check the relay the next time i have an issue starting..

mine did rough cold starts
recently the fan thermo switch gave up
replaced it , now it starts "clickvroom"
my starter hardly has to turn over more then once...