4 hours of repair and $500 later ...

Brett Dikeman brett at cloud9.net
Sun Jun 5 14:14:14 EDT 2005

On Jun 5, 2005, at 12:41 PM, Cat ^. .^ ~ wrote:

> Okay, the fule pump works if he by passes the fuel pump relay . . .
> but now he cannot get spark, my hbby says.

You put a known-working relay into the car, so it's not the relay.   
 From bypassing the relay, you know it's not the wiring to the pump  
or the pump itself.  Now we learn there's no spark.  Spark is  
controlled by the ECU triggering the output stage.

[Addressing the list] Why didn't anybody ask her to check whether or  
not the relay is getting power from the ECU, before sending her  
shopping for a new relay?  The mother of all $#@!ups is making  
assumptions.  You all haven't learned from your mistakes, either-  
you're now assuming ignition problems because there's no spark.  Stay  
focused.  Lack of ignition is useful information, but don't get  
distracted from "why is there no fuel pump operation".  See below.

> Does the fuel pump relay have anything to do with the spark ?

No, but if there's no spark (assumption is spark-testing procedure is  
correct) and no power to the fuel pump relay, that means the ECU has  
a sensor failure, or there is something very wrong with basic engine  
function which it has detected (such as a snapped belt or broken  
distributor gear.  Rotating the engine by hand or cranking it with  
the distributor off will tell you either, and I believe the gear is  
metal on the 10v engines, so it's unlikely to be that?)

Wiring trouble is possible, but unlikely to be simultaneously  
affecting both the ignition and fuel pump system(s); the simultaneous  
'failure' is too coincidental, so I'm tempted to rule out a problem  
with the coil, ignition stage, etc.  However, both the fuel pump  
relay and the ignition power output stage can be checked for proper  
ground and power/signal if there is doubt.

Either the ECU:
-does not think the engine is spinning/cannot get timing (flywheel  
sensor; I forget, is the MC-2 a "skip a tooth for TDC" or is there a  
TDC pin and second sensor?)
-can't figure out the cycle (ie, distributor hall effect sensor.  The  
ECU may know where the crankshaft is, but it doesn't know which half  
of the 4-cycle process it's on for that particular cylinder, ie intake 
+compression or power+exhaust, until it knows cam position...which it  
gets from the distributor.)
-thinks some other really important sensor is broken*

*the temperature sensor on the 20vt (I don't know about the MC-2)  
will cause a no-start if it's determined by the ECU to be bad or  
disconnected.  I'm not sure whether failed knock sensors will result  
in a no-start, but I'm fairly certain the intake air temp sensor will  
not, and I can't think of any other engine sensors).

Crank the engine for 15 seconds, do NOT shut off the ignition...and  
pull the codes.  Most of the things that cause no-start conditions  
are reported by the ECU if they're true.

Wastegates really don't fail.  The membrane can, but there's a reason  
the wastegate itself is NLA; nobody ever bought them, because they  
don't fail.  Regardless, it won't cause a no-start condition, so it  
is irrelevant at the moment.

Faye, if your husband is troubleshooting this himself, he needs to  
start on the "no start" troubleshooting chart in the Bentley, and NOT  
like fuel pressure can't be checked by most people given that CIS  
fuel pressure gauges are rare, the Bentley tends to be a little  
"replace-happy", and if you're stuck with limited tools/light/time  
like on the side of the road, you do what you can.  Otherwise, you  
really need to avoid skipping over steps or ignoring stated  
prerequisite conditions.  I've tried to avoid listing suggestions or  
ideas without -my- assumptions, but the Bentley is obviously more  
professional and thorough.  My memory of the 10v engines is also  
quite fuzzy, it's been 6-8 years since I owned one.

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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