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Strange Hot Re-Start Condition, Motronic 1.8[900/95] posted by Tom Irwin on
Friday, 13 August 1999, at 9:52 a.m.
Here's a strange one...
95 960, 117k, ordinarily when you crank the engine, it will crank w/o ignition for what sounds like 3 or 4 revolutions. At this point there is enough rotational speed to support ignition and the spark is switched on and the engine starts. Am I close to correct?
Now on HOT restart, frequently the engine will ATTEMPT to start within the first 1/2 to 1 revolution, before it is rotating fast enough to support ignition.
What it should sound like is:
"(key twist)..crank- crank- crank- crank...pop...Vrooom!"
What it's doing now on HOT restart is this:
"(key twist)..crank....pop..boom..boom..boom shaka- laka- laka- ...sputter..fizz...Ppheeewww!!
One's natural tendency is to release the key twist once you hear the ignition pop. What I have to do now is hold the key in the start position until the engine has actually cranked 3-4 times, regardless of whether or not it SOUNDS like it has started.
One quick brain fart is that the crank speed sensor may be sending errant info to the Motronic brain.
But then again, the condition did improve somewhat after I did my intake/PCV clean out last week so any thoughts are appreciated.
Tom
Tom Irwin 95 960, 94 940 Los Angeles, CA
Re: Strange Hot Re-Start Condition, Motronic 1.8[900/95] posted by abe crombie on
Friday, 13 August 1999, at 10:22 a.m.
If the oil leak at rear of eng is fouling the cam sensor with oil then it will not give signals and the default for cam sensor takes over and the ignition is quicker to begin coil firing since in default it doesn't need to know firing order. The default is to do "wasted spark" where the coils for both cylinders that are paired on crank will be fired. The downside is that the default also gives very little timing advance as the knock sensor system relies on knowing firing order and without knock sensors as a safeguard against too much advance the safe thing is to give too little.(safe really means safe from EPA penalties for excessive emissions)
Re: Strange Hot Re-Start Condition, Motronic 1.8[900/95] posted by Tom Irwin on
Friday, 13 August 1999, at 11:24 a.m.
Hi Abe:
Wow, that's quite a bit to digest. Thank you for the info. The question I'm wondering about now is, did I ruin the cam sensor? Or can it be cleaned up and used again?
Also, I've been having fits trying to get the right tool to press that seal in. I gave up and fabricated one of my own based on actual dims of the seal and a fuzzy picture in the Volvo Service Manual.
My tool is esentially a section of nylon round stock 1.5"L x 36mmID x 39mmOD with a steel backing plate bonded to the backside with a hole in it to accept a pressing screw of unknown spec.
Does this sound about right? I am going to try and do this job this afternoon, especially in light of what you've just told me. Suppose I get the old seal out and then my tool won't work. Any advice? Should I take out the heater hoses in the way? Jack the tail of the trans up for clearance at the firewall?
Thanks again Abe!
Tom
--Tom Irwin 95 960, 94 940 Los Angeles, CA
Re: Strange Hot Re-Start Condition, Motronic 1.8[900/95] posted by abe crombie on
Friday, 13 August 1999, at 10:45 p.m.
The cam sensor is not designed to be wet with oil and I've seen halls sensors in distributors on the older models that used them for ignition have troubles if dist is full of oil (the hall sensor is the same thing as the cam position sensor just it's purpose and location is different).
Clean it up when you do leak repair and see if it is cured.