Testing EFI injectors

[Alan Pritchard]

Hmm, clutching at straws a bit here... don't know anything about alfa's...
you mentioned cold start valve? I was under the belief that efi equipped
cars generally just increased the pulse of the injectors to enrichen on
start.  On my cis coupe I had a broken injector and the car would run ok for
a while, until the 6th injector turned off. Then it would die, so I guess if
you do have an extra injector it maybe worth looking at that.  As for
checking with a multimeter I guess what you would see is a waveform as the
injector pulses, that !might! show up measuring ac voltage and I guess that
value would rise as the injector duty cycle rises.  Would it be feasible to
disconnect one injector at a time (electrically) and see if the situation
changes? Ie you may find your one troublesome injector (if there is one).
Perhaps all injectors are slightly blocked, so upon start when the mixture
is normally richened, there may only be enough fuel to keep the car running,
and as the enrichening backs off the engine will shut down?  I have cleaned
cis injectors before now by putting them in isopropynol, but I do not know
if that will damage your efi units.
Hope some of my random thoughts help.
 

 -----Original Message-----
From: 	Vic Norman [mailto:vicn at icarz.com] 
Sent:	16 December 2003 12:23
To:	quattro at audifans.com
Subject:	Testing EFI injectors

I'm working on a Bosch L-Jetronic (EFI) equipped car that has been sitting
unused for a couple of years. Initial no-start diagnosis was no fuel
pressure. Cleaned out the gas tank and replaced the fuel pump and filter.
Now I have good fuel pressure. When I crank the engine it fires for a few
seconds and then dies - presumably the cold start valve doing its thing. The
obvious diagnosis is that the injectors are gummed up but how do I test
them? By the time I have got the injectors out of the car I have pretty much
torn the intake system to pieces so I can't simply crank the engine and look
at the injector output. I hate to spend several hundred dollars on new
injectors and then find out that they weren't the problem. Is it possible to
dunk the injectors in carb cleaner or some such to clean them?
Also -  is it possible to monitor the signal to the injectors with a basic
voltmeter (I don't have an oscilloscope) and if so, what sort of values
would I expect to see?
Thanks
Vic Norman  1996 A4 2.8 1989 Alfa Spuder Veloce

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