[Gmecm] 93 CHEVY g20 VAN

[Tyler Townsley]

Here is the current setup for the Corvette and XLR, the only ecm control 
mentioned is on the XLR to reduce pressure at idle.

http://service.gm.com/gmtechlink/images/issues/mar04/TLMar04e.html#f1

Tyler

WopOnTour wrote:

> Sorry Phil but it's not the LS1
> I've just looked at the FP wiring schematics for the LS1/LS2 from 
> 1997-2006 and NONE of them have the ECM/PCM controlling the fuel pump 
> voltage in any way. (Other than turning on the relay of course). Go 
> back and look at your GM training manuals or eSI Description and 
> Operation again, it very clearly states what the vacuum compensation 
> on a pressure regulator is actually for. Quite simply it's for 
> LOWERING fuel pressure when vacuum is high, not RAISING it when vacuum 
> is low (at least on a naturally aspirated engine).
> An injector's delivery specification (lb/hr. g/s, cc/min etc) can only 
> be maintained when a consistent pressure differential exists between 
> the internal injector pressure and the point to which it's being 
> delivered.Since the software calibration in the ECM/PCM assumes this 
> injector delivery, it must rely on the regulator to apply the 
> appropriate compensation. Newer systems (like the 2.2 Ecotec in the 
> J-body for instance) don't even have a vacuum source connected to 
> regulator (even though they have a vacuum line) and instead the 
> compensation is handled by reducing injector base pulse width when MAP 
> pressures are low.(Maybe THATs what you meant??)
>
> On the GM dual-point TBI (as this van would have) the regulator gets 
> it's atmospheric reference via a large vent that the regulator 
> diaphragm chamber seals against (a large foam o-ring) when the 
> regulator/injector housing is installed onto the TB. Since this places 
> it OUTSIDE of the airfilter it does not require a "vent" line such as 
> the Tracker or other import TBIs.If this regulators diaphragm 
> ruptures, you would know it in hurry as fuel would be running directly 
> out the back of the TB onto the intake.
>
> So my point being it would be almost impossible for the regulator 
> system in this particular fuel system to result in a rich mixture 
> without a significant and obvious fuel leak. Of course if the return 
> line was somehow restricted... But until Michael.b get back to let us 
> know what his fuel pressure is, it will be of course extremely 
> difficult to come up with ALL of the possibilities that would result 
> in a RICH condition. Considering the fact that I don't recall any 
> failure particularly "chronic" in the TBI system of that era.
> HTH
> WopOnTour
> ----- Original Message ----- From: "Phillip Kuhn" <pmkls1 at yahoo.com>
> To: <gmecm at diy-efi.org>
> Sent: Saturday, December 31, 2005 5:16 PM
> Subject: Re: [Gmecm] 93 CHEVY g20 VAN
>
>
>> Wop on tour,
>> the GM returnless systems that use the pcm to control
>> fuel pressure are the newer systems used on the ls1
>> engine and all of it's derivatives and basically any
>> new engine they use that has a returnless system which
>> the list is pretty long nowadays but it first appeared
>> on the ls1. I do not remember ,however, what type of
>> signal they use but I think it is a pwm type signal.
>> As far as what I wrote about the vaccum reference for
>> a fuel pressure regulator that is exactly what GM
>> trainers tought me  the purpose was. Reguardless of
>> what the purpose of the vaccum signal is it DOES
>> significantly affect fuel pressure and fuel pressure
>> significantly affects fuel mixture. What I am
>> interested in more than anything else at this point
>> though is what is wrong with this guy's van. And back
>> to my original suggestion, fuel pressure regulators
>> are notorious for having the diaphragm rupture and
>> leak raw fuel which on most engines gets sucked
>> directly into the engine causing it to smoke black and
>> die (exactly the symptoms described about this van).
>> Also, somebody else mentioned the IAT sensor going bad
>> which on GM cars when they do they usually read
>> something like 40 degrees below zero and will also
>> cause a significantly rich condition and smoking and
>> wont always set a DTC. So at this point I would like
>> to hear back from the guy that has the van to see if
>> he has found anything yet..............
>>
>>
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