fuel delivery problem?

[drew@scirocco.cs.uoguelph.ca (Drew MacPherson)]

Actually, diesels do require a _bit_ of fuel pressure to get the fuel into 
the cylinders.  Most diesel injectors have breakpoints in the 1600 - 2100 
PSI range - a bit beyond the range of even the relatively high pressure 
CIS fuel injection system... :)

VW diesel injection pumps have transfer pumps built into them that draw
the fuel from the tank through the filter at low pressure (15 psi IIRC) 
where the main pump mechanism attains the pressure required to blast the 
fuel into the compressed air in the combustion chamber.

Drew

On Fri, 27 Dec 2002, Eric S wrote:

> Rick, your dead wrong on diesels.  They require no pressure.  The pump
> is stuck to the motor, and litterally does suck fuel from the tank.  
> Many VW diesel owners have problems with air getting into the lines from
> leaks in the line coming from the tank to the engine, or the fuel filter
> flange leaking air into the system.
> 
> --
> Eric
> Northglenn, CO
> 
> 81 Scirocco S (*TDI* swap and complete restoration in holding pattern)
> 81 Rabbit Truck LX Diesel (Waiting for BAE Turbo Install)
> 83 Scirocco Wolfsburg
> 91 Cabriolet (2.0 Crossflow 8v swap and mechanical rebuild in progress)
> 
> 
> --- "Rick Alexander" <ralexander03@snet.net> wrote:
> >Ryan,
> >
> >This engine can't "suck" fuel neither can a diesel. They need pressure. In
> >the case of the diesel, when they run on it's because they are worn out and
> >are being fed crank case oil. But that is a very wasted engine.
> >
> >Go with Dave's lead and look for a cracked intake boot. That's probably what
> >it is.
> >
> >Rick Alexander
> >
> >----- Original Message -----
> >From: "Ryan Ruggles" <ryanruggles@uniserve.com>
> >To: <scirocco-l@scirocco.org>
> >Sent: Friday, December 27, 2002 1:43 PM
> >Subject: fuel delivery problem?
> >
> >
> >> Details: 1.8L JH, CIS injection in a 82 rabbit.
> >>
> >> Problem(s):
> >>
> >> Almost every time I hammer the throttle, the engine starts to rocks back
> >and
> >> forth and idle goes way down
> >>
> >> It is like it's running on 3 cylinders but it can't be an electric problem
> >>
> >> When I drive it in this condition it sputters until about 2000 rpmn and
> >then
> >> smooths out but as soon as I come to a stop again the engine rocks back
> >and
> >> forth (along with the car ;( ) and the idle is really lumpy.
> >>
> >> It used to go away after I shit it off for a few seconds but it has been
> >> running like shit for a couple of days now.
> >>
> >> Things I have done to try to figure out the problem:
> >>
> >> 1)  Changed fuel filter
> >> 2)  Changed fuel pump  (there is only one)
> >> 3)  New injectors
> >>
> >> Things that are suspect:
> >>
> >> 1) Fuel line from fuel pump to accumulator is rusty ( maybe partially
> >> collapsed internally?)
> >>
> >> 2)  The accumulator is as rusty as Micheal Jordan's dribbling skills ;)
> >> (maybe it's not doing it's job and the engine is trying to get more fuel
> >> than it is being supplied?)
> >>
> >> 3)  Fuel pump relay: if it worked intermittently would the engine be able
> >to
> >> mechanically suck gas for a short period of time maybe creating an air
> >lock
> >> situation?  I know this can be the case in some diesels...
> >>
> >>
> >> If anyone has any suggestions I'd totally appreciate it.
> >>
> >> Cheers,
> >>
> >> Ryan
> >> 82' Rabbit
> >> 87 Scirocco 1.8L 16V  now in the form of a 1.5 foot square cubed
> >> 84 Scirooco 1.8L 8V    RIP
> >>
> >>
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> >>
> >
> >
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