scph

I have a 87 S. It does not want to start when cold. It turns over but does not fire. The tach is jumping when its spinning over. When it finally starts it runs fine the rest of the day. It seems to start fine as long as it has a little temperature in it. I have replaced the DME relay and checked the maf with the help of Clarks garage page. Any ideas guys?

944Newb

temp sensor? first check in and around the connector for the sensor. i dont know the resistance values for these cars as im not very familiar with them. To test them check resistance cold and hot, you'll find out if its a neg or pos temperature coefficient that way too..

If its bad the car will think its already warm when your trying to start it, and will not be as fuel enriched as it should.

Could also be other possibilities too but you have to start somewhere

scph

Thanks. I will check that tomorrow. I will let you know my findings.

PerceptionProblem

I'm having a similar problem. My 85.5 n/a will turn over, then halt. a second turn it will fire right up. I'm thinking it might have to do with misfiring though. I'll keep The List posted as to what I find out. Good luck friend!

River

Yup.

Change out your dme temp sensor. Aka, fuel injection sensor. It's the best $20 you'll ever spend to keep things running smooth when it's cold and in general.

Also think about changing the coolant sensor on the block while you're in the area too.

Also, cold weather and Porsches do not mix for the older ones. So make sure your grounds are clean, all your vacuum lines are fine, sensor connectors are clean. If fuel pump is old, consider changing it out. They'll act up more when it's cold out.

Rule of thumb, do the free stuff first, then the easy cheap stuff, then work your way around.

I have a dollar on the sensor first

scph

Was warm enough today so started the car and drove her up the hill and put her in the shop. Ohmed the plug for the temp sensor at the dme. Checked good when warm. Tomorrow I will check it when cold and report back. Here is hoping.

River

Hoping is good, sometimes it's all we have


At least there is a good checklist to go thru. I'm from the school of replacing things when they're old. (i.e. you should replace your O2 sensor at 60k ish, so, might as well replace things like a temp sensore/coolant sensor at the same time).

Lot of heat cooking those electronic bits over the years...

reminds me, this season might be the last for the battery. Remember cold is makes things bite it, lol! (they don't call it cold crank amps for nada!)

Grandpa#3

X10 on what River said about the temp sensor. Go to the link below and you will find a great write-up all about it and pictures.

http://www.944online.com/cgi-bin/for...num=1294677445

Cheers,
Larry

scph

Well I won the contest from Lithium Pros for the lithium battery. It arrived yesterday. But it is going in the turbo car. lol. So one of them gets a new battery anyway.

scph

I ohmed it at the dme plug warm yesterday and cold today. The temp sensor ohmed perfect yet the car would not start cold. Once it started it would start no problem. Ggggrrrrrrrr

ZR8ED

Sounds like a fueling issue. Either the temp sensor (sounds like a no there) lack of fuel pressure at initial startup (leak down and/or regulator issue) Weak fuel pump, poor power/ground for the fuel pump. Just trying to get some ideas flowing here.

Sure you have spark/good spark?

River

I'd go with fuel pressure regulator next. That thing can cause a plethora of issues from symptoms like no start, cold start, shakes, etc.

One little part that can cause so much grief. Cheap fix. And if that's not it, peace of mind that it should be changed out every 60k or so

944Ross

Just because the temp sensor itself is good, doesn't mean the signal is getting to the DME. Check its signal at the pins on the DME. I just had my intake off and the bundle of wires that includes the temp sender wires was being cut by the ISV base. The protective sheath was cut nearly all the way thru.

scph

Thanks Ross. That is where I checked it. I am going to get a new fuel pressure regulator just for the peace of mind.

Sentinelist

Are you sure you have a good battery? Gauges do funny things with dead batteries when cranking or running. Elsewhere on the 'spark' side, I just replaced my whole system. Battery, coil, distributor, rotor, plugs, wires.

On the fuel side, check the fuel filter, FPR and maybe even injectors if you get desperate. I'd go with the above and sort out DME sensor stuff first though. DME relay too, though that would be less averse to cold. Check the computer box for any broken solder leads.