[s-cars] By-passing the CPS

[Vincent Frégeac]

I kind of expected this. There's no easy way out with the S-Bitch. So
apparently, sleeping is optional is week-end or I'm stuck with a rental for
two weeks (no, I won't bring the car to any mechanic, too many bad
experiences, not the mechanic's fault, it's just the S-Bitch that apparently
doesn't like anyone else to touch her intimates).

Thanks for the info.



Vincent.

-----Message d'origine-----
De : Joshua van Tol [mailto:josh at spiny.com] 
Envoyé : 11 mai 2007 18:29
À : Vincent Frégeac
Objet : Re: [s-cars] By-passing the CPS

Actually, the CPS is used to establish cam phasing so that the  
correct cylinder can be fired. Without the CPS, the ECU doesn't have  
enough info to know which coil to fire first.  Once this information  
is known, the car can continue to run without the CPS.

A better way to diagnose the cam position sensor would be by using  
the built in diagnostics (trouble codes) or by using an oscilloscope  
on the CPS signal wire to see if it's working.

To make a long story short, you're not going to able to jury rig this  
one.
On May 11, 2007, at 5:03 PM, Vincent Frégeac wrote:

> I’ve read somewhere that the role of the CPS is to tell the ECU the  
> starter
> is actually cranking the engine so it’s OK to activate the fuel pump
> (something you don’t really need a buried in 8h of work sensor to  
> realize).
> Then, the engine speed sensor takes the relay and tells the ECU to  
> keep the
> fuel pump running. This brought two questions to my mind:
>
> -          Would a check light on the fuel pump wires be a good way  
> to tell
> if the CPS is the problem, at least for the warm-start problem I’m  
> having?
> If the fuel pump does not receive the expected ~12V when the  
> starter crank
> the hot, not starting engine, but does when the engine is cold,  
> it’s a CPS
> problem. If it’s receiving 12V when the engine is hot, look elsewhere.
>
> -          Would a wire from the starter solenoid wire to the fuel  
> pump,
> with a diode on the existing fuel pump positive wire to avoid  
> frying the
> ECU, be a good way to get rid of the CPS problem until I have time  
> to go
> through the timing belt and CPS, which is not exactly the case  
> right now,
> except if I start considering sleeping time as optional?
>
> I can’t see any logical reason this wouldn’t work but before I fry  
> the ECU
> with my somewhat tired logic, I though pinging the list wisdom  
> would be
> safer.
>
>
>
> -          Optional question: Why in the hell did they use two  
> engine speed
> sensors, which means two reason to fail on us, when one would do  
> the job? I
> mean, when the ECU would realize that the crankshaft is turning but  
> not the
> camshaft because of a broken timing belt, it’s way too late to save  
> the
> valves and pistons anyway, and the engine would have probably  
> stopped by
> himself by loss of any compression, or intake or exhaust or whatever.

See my explanation above as to the function of the cps. It's not  
redundant, even though it seems like it is. If the CPS could be made  
VERY accurate, it could replace the TDC sensor on the crank, but  
because of slop in the timing belt, and possibly other reasons, it  
can't be that accurate, so they use two sensors, one to find out TDC,  
and one (the cps) to see if it's TDC for cylinder #1.

>
>
>
> TIA for your help on bringing reality check to my poor beaten up  
> logic.
>
>
>
>
>
>
>
> Vincent
>
> ’96 S-Bitch keeping me busy and frustrated
>
> ’81 Fiat Spider 2000 I would’nt qualify in fear my post would be  
> rated 18+
>
>
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