Re: DHOW: Injector testing

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <199811090455.XAA21482@hme0.mailrouter02.sprint.ca> sbigelow@sprint.ca writes:

> A) Pull both the thermo-time switch and the cold start injector (wiring
> intact) submerge thermo-time switch in ice water, ground coil output, and
> crank. (Bentley seems to say no cold start until below 10C) Check for
> spray, and lack of leakdown, and time of spray.

There's a different algorithm at very low temperatures, but you should
get cold start right up to 30C - 40C or so.  I'll see if I can find
the factory figures.  "Cold" is not relative to outside ambient, but
to the engine.  60C is "cold".

> B) Pull the five main injecters, and pressurize with pump. Check for
> leak-down. (It _seems_ to be rich when it gets going) What kind of time
> frame would it show up?

If you have Viton-tipped injectors (Audi part suffix "F" - side of
injector) don't keep them dry for more than an hour.  Any tests done
"dry" are invalid.  I have a little jar of petrol to keep injectors
wet if I have them out for any reason.  For the same reason, any test
has to be with _petrol_, not with air.

The approved technique is to pull the injectors (including the cold
start injector) but leave them attached.  Run the fuel pump using either
a jumper in the relay socket or the onboard diagnostics - see Scott
Mockry's web page for instructions on this at
http://www.teleport.com/~scottmo/ecuf.html

Let the fuel pump run for ten seconds, then switch it off and watch
the ends of the injectors.  _Any_ leakage is a failure for that
injector.

> Anyway I can check the check-valve in the fool pump?

By elimination only.  If everything else checks out, and you still have
leakdown, it's the check valve.

> Do I have a fuel accumulator in this crazy thing? Any way to check that,
> too?

Undo the screw on the end of it (tiny little thing) and see if you
get an eyeful of fuel.

> I dont have a pressure gauge for fuel. (Yet!)

JC Whitney.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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