Date registered: May 2014
Vehicle: 1988 300CE
Mentioned: 35 Post(s)
Quoted: 511 Post(s)
Okay Anthony, let’s see what we got:
You say your “pump DOES come on when turning the ignition”
Does the fuel pump also come on when the car can not be restarted (with the engine still warm)
The tests I recommended in my last post refer to that situation only!
So, if not done so yet, first find out whether the fuel pump comes on when you or your daughter vainly try to restart the engine. Then we know whether there is a problem with the FPR (fuel pump relay) or not. Show your daughter what it should sound like when turning the key to ignition (not to crank), so that she knows how to check that next time!
Your plan to do a spark test has the same meaning as what I suggested, when I said: check voltage between terminal 1 and 2 of the diagnostic socket during cranking. If you don’t see voltage between 6 and 12 volts, respectively if you don’t see sparks at your spark plug: It’s the CPS (crankshaft position sensor)! (or - less likely - the EZL)
Checking the voltage at the diagnostic socket is just a lot easier to do than a spark test.
And again: It only makes sence to do that, when the car can not be restarted.
You wonder: "Could it also be tank purge valve or EHA on the fuel distributor? If its that, doesn't this need to be tuned to the car or is it a simple swap?"
Forget the fuel pressure regulator and the tank purge valve and at the moment also the EHA!
Generally, after replacing the EHA only the basic setting of the KE-Jetronic (or as many misleadingly call it “the air/fuel mixture”) needs to be checked and possibly readjusted.
You ask: “Does the sitting an hour allow the car to cool or gas to vaporize?”
That’s indeed a justified question. Because there is another suspect, the fuel pump’s check valve.
If that is leaky, then you have reduced or even no more holding pressure in the system after the engine is switched off or stalls. That plus the heat of the engine (under the closed hood), which when no more cold fuel is pumped through the system heats up the fuel lines between the injectors and the fuel distributor causes “vapor locks”.
And as well as a faulty FPR or a faulty CPS, that, caused by a faulty fuel pump check valve (or any other leak, like for instance in the accumulator) can result in exactly the same problem that your daughter’s car shows. But checking the FPR and the CPS is a lot easier then checking the check valve.
So, if the FPR and the CPS should prove to be okay, then it’s very probably the check valve!