Date: Fri, 3 Jul 1998 00:38:39 -0600
Reply-To: kenstich <kenstich@BEWELLNET.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: kenstich <kenstich@BEWELLNET.COM>
Organization: Central Intelligence
Subject: Re: FI Weirdness -- please help
Content-Type: text/plain; charset=us-ascii
Sean,
Well - I've done some troubleshooting on my 80 Vanagon with similar AFC injection.
got schematics - got a digital multimeter (DMM) ??
1) You are getting constant fuel pump power from relay pin 88d - bummer -
gmbulley's response is correct in that a short from power input pin 88y to 86d
would activate the fuel pump continuously (88y is battery power - hot all the
time) - check that first - Another failure mode that would have the same
symptom is a short from the negative side of the relay coil - pin 88c to
ground - the + side of the coil is continuously hot from the battery as gm
says - the negative side of the relay coil normally grounds through a circuit
in the ECU to activate the fuel pump relay - a short to ground in this circuit
would have the same effect. (battery disconnected - test isolation from 85 to
chassis - should be high resistance) if its shorted, disconnect the relay
connector and retest from both the relay 85 and then the connector 85. (The
short to power that gmbulley mentioned or the short to ground splained above
could either be in the harness or internal to the relay - both explain a
continuously running fuel pump)
I'm having a problem with #1 though - if the fuel pump is running continuously
- why doesn't the engine run ??? - it should - you know - the pump makes fuel
pressure - with a continuously running pump, the engine doesn;t just die - Eh
???? - thats why I've included #2 & #3 below.
2) I've seen the exact same symptoms in my 80 Vanagon with similar AFC
injection when there is a large vaccum leak - take a real good look at all the
lines coming off the intake plenum - plug the line to the brake booster
temporarily - pinch off other vaccum lines to eliminate them. Bosch designed
in a failsafe so that if the engine dies, the fuel pump shuts off - via switch
contacts in the air flow sensor - this vaccum leak scenario does NOT explain
the continuously running pump however - but instead would cause the ECU to
turn off the fuel pump relay
3) Why do I have this sneaking suspicion that you are losing injector power ??
You say that the pump is continuously running regardless of ignition switch
position - Just for giggles, check ignition voltage at the coil with a test
light or meter whilst cranking it up per your description - remote starter
switch is very handy here.
4) Maybe then check injector power at one of the injectors - put a meter or
test light on a disconnected injector connector power pin and crank it -
should see continuous injector power when cranking/running (the ECU
intermittently grounds the injector solenoid coil negative terminal to
pulse-activate the injectors)
5) Put a fuel pressure gauge on the test port tap on the fuel distribution
ring - fuel pressure is critical - should see 29-36psi - fuel pressure -
doesn't fit the symptoms very well though.
6) Have a beer - you'll need it after all this - Miller time (OK - Sam Adams
maybe - try the Honey Porter or cream stout - mmmmmmm good)
My pin numbers are from my Vanagon schematic - I believe that they are the
same as your 75/78, but have no way to check this.
Hunch/scenario - the engine starts to run with fuel provided by the cold start
valve, but when the thermo-time switch cuts off the cold start valve power,
its all over cause the injectors aren't getting any power.
Hunch/scenario#2 - since you've just reconnected everything since reinstalling
- really check the connections to the coil - very easy to screw up - did you
tag the wires ??? You've checked the connections to the single point ground on
the block - Right ???
Best of luck
Ken Stich
================================================================================================
Sean Bartnik wrote:
>
> Hey all,
> I copied this note to Vanagon.com because I know one of the FI experts
> on the list, Tom Young, is there.
>
> We are still trying to start Steve Dolan's '73 Bus with '78 FI engine.
> It has not started since it was re-installed in the Bus, though it
> certainly tries.
>
> Here's what we have found. We presume at least part of the problem to
> be electrical and in the FI wiring.
>
> When we turn the key to start, the engine cranks normally. It may catch
> and run for a second or two and then will die. However, when it dies,
> the fuel pump will strangely stay running. EVEN WHEN THE KEY IS TURNED
> TO "OFF" AND EVEN WHEN THE KEY IS REMOVED from the ignition lock. Note
> that the pump will not start running when the key is "on." The starter
> must operate first, then once the starter has operated, the fuel pump
> will remain on regardless of ignition switch position until the battery
> is disconnected.
>
> We found while trying to figure this out:
> The fuel pump will also quit if the AFM plug is unplugged (with the
> ignition key off) and the same result is obtained if the ECU plug is
> unplugged. We expect there is some sort of power feedback loop running
> thru the double relay, though we are having a bit of trouble finding out
> where it's coming from. Note that there is some somewhat flakey wiring
> on the fuel pump side of the double relay wiring harness. We will take
> that down next time and inspect for short circuits, etc. That's a
> distinct possibility. Other options include a possibly bad ECU. We
> have both an AFM and ECU to swap in and test with.
>
> We found that all wiring appears to be in the right place. The wiring
> to the starter is all good and all other FI wiring appears to be OK.
> I know this is really weird but if anyone has anything helpful we'd
> appreciate it. The thing I'm most curious about is why we have power in
> the system even with the key off and removed.
>
> Thanks
>
> Sean Bartnik
> Fairfax, Virginia
> ============================
> '81 Vanagon L Westfalia
> '74 Karmann Ghia convertible
>
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