Re: [T3] excessive fuel consumption

["dubdriver" <reeves32@home.com>]

Well I checked the voltage.....right at 14.5.  The pressure sensor holds a
vacuum just fine.  The line is connected to the manifold correctly and the
pinching it will immediately shut the engine down.  I'm going to clamp off
the cold start fuel line next and drive it awhile and see what that does....
Oh.  checked the trip meter and the thing is spot on, so it's not a false
reading.

----- Original Message -----
From: "Jim Adney" <jadney@vwtype3.org>
To: <type3@vwtype3.org>
Sent: Thursday, April 19, 2001 8:52 AM
Subject: RE: [T3] excessive fuel consumption


> On 18 Apr 2001, at 19:28, Leon Martinez B. wrote:
>
> > The excessive fuel cosumption of your efi
> > system can be caused by vacume leaks, even
> > around missing or cracked injector seals.
>
> I'm gonna have to respectfully disagree with this. On the D-jetronic
> FI ONLY, MOST vacuum leaks cause no problems at all, except
> that they may cause a higher than normal idle speed.
>
> Leaks at the outer ends of the air runners will cause that cylinder
> to run LEAN, which is not good, but is not rich.
>
> Leaks near the center of the system, near the air distributor, will
> cause no effect except a high idle.
>
> Only leaks IN the pressure sensor will cause the engine to run rich.
> Of course running with the pressure sensor hose disconnected (on
> either end!) is the biggest leak you can have, and is certainly a
> possibility in this case.
>
> In all cases, the effect will vary with the size of the leak.
>
> > Check for all vacume leaks everywhere and place clamps on the
> > intake runners to the manifold.
>
> I see these ALL the time and I always take them off because they
> just tear up those hoses. Sometimes the engine assembly was
> done poorly and the tubes don't line up right. In these cases you
> are much better off loosening the air distributor bolts and the
> manifold bolts and let these parts all line themselves up. Then
> retighten in a stress-free condition. Sometimes rotating the hoses
> around the tubes will allow them to get into a position where they
> seal better. In general, if you can get the tubes to line up well and
> the engine to idle acceptably, then just letting those hoses relax
> into place WITHOUT CLAMPS will result in their seating and
> sealing better and better with time.
>
> > Make sure your pressure sensor holds vacume for a minute (I suck
> > with clean clamped hose to the sensor)
>
> A good suggestion. It doesn't have to be for a minute, of course,
> but you want to be able to suck on the PS and verify that you don't
> just keep getting air.
>
> The thing to understand is that the later FI systems are
> fundamentally different from our D-jetronic systems. Vacuum leaks
> cause big problems for all the later systems, but this is NOT true
> for the D-jetronic. If your mechanic is giving you a big line about
> vacuum leaks, he's most likely well trained in modern FI systems
> and just assuming that this is true of your system, too.
> Unfortunately, this is wrong, but this assumption is very common.
>
> Finding someone who really understands the type 3 D-jet system
> these days is hard, and misinformation is rampant.
>
> -
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> USA
>
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