okay so in the on going effort to figure out why my car won't start when its hot, I changed out the FPR and looked at the Plugs and changed those as well since I had just ordered a new set for my 30K tune up. Anyways after changing the FPR car still wouldn't start. It turns over but won't fire. Looking at the plugs they have black carbon deposit on them. So it could be one of two things. first one being running to rich causing the car to stall out, second one being a weak spark. The car will start sometimes and drive great but when I shut it off and try to start it again it won't start again till morning. So tell me what do I have?

 

So the plug in the picture is a brand new plug?

-Darwin

 

No they are about 18 months old. But still they should be a nice golden brown and not black like that.

 

very hard to read a plug from pictures......

the black ring on the base (end of the threads, not on the electrode) is from oil leaking into the cc. past the rings or valve guides, pretty normal for almost 30 yr old car.

the electrode looks a bit dark, but in normal range (see caveat above). doesn't appear to be part of your hot start problem IMHO.

 

This could be wrong. My car can suck some mean oil into the combustion chamber - however it comes from some worn *** turbo seals.

 

The problem could very well be electrical. It could be either heat raising resistance somewhere, or heat causing a crack in the wire to expand and open (breaking circuit).

Next time the car gets hot, check for spark. If there is no spark, there is a sensor or wire somewhere that's giving you problems. The electrical gremlin can also cause fuel issues. I have seen a case where the heat causes the DME relay to stop functioning properly, so the fuel pump stops pumping. So when it's hot again also check to see if the fuel pump runs, or you can bypass the DME relay with a jumper to see if that fixes anything.

When it gets hot, and you try to start it, do you see the rpm needle bounce slightly? If it does not, you have a speed/ref sensor problem. I've seen some speed and reference sensors become heat sensitive as they fail (the sensor part is fine but the wire connector part of it is what becomes damaged from heat and only works when cold).

 

Agreed. Very difficult to read a plug from pictures alone, but they don't look too bad.

You can clean off the carbon by taking a propane torch to them and heating the electrode until it just turns red. Let it cool and reinstall.

 

Well I but in new plugs yesterday and when I started it up I now have really bad spark knock it sounds like plus it smells like the car is running lean.

 

So earlier i was thinking ignition system, but since it was just running that doesn't make much sense.

There is a check valve after the fuel pump that might be bad, and also an injector leaking will cause no start when hot. the problem is fuel pressure is not kept up in the lines after shutdown the way it should be. it's worth a try, i've not had this problem so let us know what works.

thanx