D-Jet hell

[Tony Bryant]

> Date:          Wed, 08 Oct 1997 21:14:50 -0400
> From:          Peter Lindberg <plindb1 at gl.umbc.edu>
> To:            diy_efi at coulomb.eng.ohio-state.edu
> Subject:       D-Jet hell
> Reply-to:      diy_efi at coulomb.eng.ohio-state.edu

> The D-Jet system in my '71 Volvo has been very reliable and (relatively)
> decent running, but the engine is very lacking in low rpm power.  This
> engine (B20E) is not known for being particularly 'torquey' to begin
> with, but I'm sure something's not quite right.
> 
> I've done the basic resistance test with all of the electronic
> components.  I recently replaced the injector seals, and gave a complete
> ignition tune-up and valve adjustment.  When I was replacing the
> injector seals, I examined the spray patterns of the injectors, but did
> not do a flow test.  
> 
> I know the spray quality affects low end power, because the injectors
> are triggered in pairs.  Are there any other possibilities besides the
> injectors?  What can I do, other than buying a new set of injectors
> ($250) or having them 'serviced' -- which I'm not sure I trust --
> ($120).
> 
> Is there any DIY way of renewing the injectors?  I've tried several
> brands of the pour-in-the-gas-tank cleaners, none of them seemed to do
> anything.  I thought maybe forcing solvent backward through the injector
> with compressed air might do something. . . 
> 
> any tips, ideas, suggestions?
> 
> By the way, another D-jet question:  Can the manifold vaccume sensor
> sense manifold pressure as well as vaccume, or could it be modified to
> do so?
> 
> Peter Lindberg
> 


Suggestions:

DJets (at least in Jaguars) are known for having leaky vaccuum 
sensors, suck on it and see if it holds a vaccum. Also check you fuel 
pressure. Check ECU grounding. Check operation of thermo-time switch

I've cleaned leaky injectors before by clamping them in reverse to 
the pressured fuel rail using some 3/8" fuel line and applying power 
repeatedly to it until they stop leaking.

Caveats:

1) Pull the plastic cap off the spray end of the injector for a more 
solid clamping (its still prone to popping off)

2) Run LONG wires to the injector and switch the wire from a 
relatively remote vapour free location.

3) DONT apply 12V to low impedence injectors for more than a fraction
of a second. A 4-5 Ohm resistor in series would be fine though.

4) You probably need to hard wire the fuel pump to get it to stay on 
with the engine not running

have fun..








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