Subject: [DML] Digest Number 471
Date: Saturday, March 24, 2001 5:25 AM
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There are 4 messages in this issue.
Topics in this digest:
1. need to adjust mixture levels?
2. Fuel System Explained.
3. Re: Thermo Time Switch
4. Re: need to adjust mixture levels?
From: "Mike Griese" <roscsyl_at_dml_millcomm.com>
Date: Fri, 23 Mar 2001 20:34:05 EST
Subject: need to adjust mixture levels?
still having troubles starting. my dad and i would like to get the car out
of the garage and into the driveway. i tried starting it today and my dad
said there is black smoke coming out of the pipes and my garage is starting
to reek of way too rich exhaust. we would like to adjust the mixture. it is
the allen screw at the base of the fuel distributer, correct?
which way is lean, and which way to rich? is it very sensitive? i do not
want to start adusting stuff without knowing how much i am doing it!
i would like to do this tomorrow morning. therefore, if you have info on
this, please email me privately so i do not need to wait for the list to get
1982 DeLorean DMC-12 VIN#11596
Fargo, ND 58102
[Non-text portions of this message have been removed]
Date: Sat, 24 Mar 2001 02:11:14 -0000
Subject: Fuel System Explained.
Over the past couple of days the subject of the fuel system has been
a sizeable topic. Even if you have th workshop manual, it can be
difficult to understand the componets involved due to the authors
wording, and the mechanical/electronic aspects of the system. So
hopefully this will help everyone understand thier cars better.
The system is called the BOSCH K-Jetronic fuel injection system.
Commonly known as a CIS, or Continuous Injection System because the
fuel injectors never close when the system is active. It is also
known as a Mechanical System because it can operate independant of
any electronic components. The system is driven by fuel pressure. The
System was designed in the early to mid 70's. A good reliable system,
but when it hit the market strict emissions regulations appeared. So
the LAMBDA System was created to enable the system pass EPA testing
via fine tuning.
Mechanical Components and their Functions.
Fuel Deliverly Section:
This is where fuel that will be pumped into the system collects. It
resembles a large cup. To keep the baffle from collapsing, two
sections of wire are installed. Located within the baffle is a filer
screen to keep particles large enough to damage the fuel pump out of
the system. The baffle itself also does this to a certain extent.
Something else to note is that the rubber hose that connects to the
return line is supposed to be clipped in place to pour directly into
the baffle. That way when fuel in the tank is very low, it can still
gather enough fuel to keep the intake submurged and keep the car
Pretty straight thru. It's job consists of two tasks: 1. Supply fuel
to the fuel system. 2. Maintain the proper fuel pressure to keep all
meachanical components working. It also has a check valve installed
to prevent fuel from flowing backwards into the tank.
It's purpose is to maintain the high pressure within the fuel system
when the pump is turned off. The enables quick starting of the engine
rather then waiting for the system to build up pressure. An emergency
overflow hose is connected between the accumulator and the return
line. This hose catches any overflow from within the accumulator
incase it fails, and directs it into the gas tank rather then letting
it spill onto the ground.
Filters out anything that could possibly clog the fuel injectors, or
any delicate parts of the fuel system from here back.
Fuel Management Section:
The purpose of the fuel distributor is to not only route gasoline to
the injectors and the other components that help manage fuel. But it
utilizes feed back from some of these components to measure out just
how much fuel the injectors will supply into the engine. It is a
simple method, but it does use small, delicate parts.
There are two chambers, and upper and a lower. Both are seperated by
a diaphram. Fuel in the upper chamber will flow to the injectors.
Some of the fuel in the lower chambers will flow to the upper
chamber, but the remainder will be returned to the gas tank. In the
upper chamber, there is an intake that opens against the diaphram. If
pressure in the lower chamber is reduced, then the diaphram will bend
down. When the diaphram moves down, more fuel is allowed into the
intake, and thus the injectors. Pressure is reduced in the lower
chamber by allowing more gasoline to return to the tank. There is one
of these diaphram chambers for each injector.
Primary Pressure Regulator.
This item is located inside of the Fuel Distributor. It's job is to
determine what the pressure of the fuel system will be when the
system runs under normal conditions. Has the ability to increase or
decrease pressure by determining how much fuel is allowed to return
to the gas tank. Set by the factory and/or mechanic. Contains no
movable parts, and is probably only adjusted when a new distributor
Air Flow Sensor.
Measures the amount of air that enters into the engine in order to
keep the air/fuel mixture the same. The more that air enters the
engine, the more the air will push down on the plate accordingly. The
plate is connected to a lever that will push up on a plunger located
in the center of the fuel distributor. When moved upwards, this
plunger will in turn allow more fuel to flow from the lower chambers
in to the upper ones, and some to the Primary Pressure Regulator and
the Control Pressure Regulator. The Air Flow Sensor doesn't enrich
the fuel system, it simply keeps the air/fuel mixture the same. The
air/fuel mixture can be adjusted by way of a hex screw. Under normal
conditions, adjustment should rarely, if ever be nessisary.
Fuel Enrichment Secion:
Control Pressure Regulator.
The Control Pressure Regulator can lower fuel pressure within the
fuel distributor to enrich the fuel mixture. In other words it can
change the air/fuel mixture by allowing more fuel then normal into
the injectors automaticly, yet the amount of air that enters into the
engine stays the same. Two important things to note about about the
Control Pressure Regulator is that any enrichment it performs for the
fuel system is only temporary. And the Control Pressure Regulator
only lowers the presure for the fuel system, it does not raise it
above what is set but the Primary Pressure Regulator. The way that
the CPR works is simple. Think of the chambers in the fuel
distributor. When the diapram moves down, more fuel flows thru. But
this time the fuel comes from the distributor. And instead of fuel
going off to the injectors, it goes to the Primary Pressure Regulator
to be returned to the tank. The result is pressure is lowered in the
lower chambers of the distributor to allow more fuel into the
injectors. But now in the CPR there are 2 diaphrams with 4 chambers.
The 1st diaphram has a bimetal armature attached to it. This diaphram
divides the 1st and 2nd chambers. The 2nd chamber is open to the
outside air. The two bottom chambers are connected to vaccums.
The CPR only enriches the fuel mixture for two reasons:
1. Cold Engine. It's a fact, when metal is hot, it expands. And when
it is cold, it contracts. Your engine is no exception. And when the
motor is cold, the cylinders will naturally constrict against the
pistons. This causes more friction then normal inside the engine. So
to be able to run properly with this extra friction involved, more
fuel is needed to give the pistons a little more power. When below a
specific temp, the bimetal arm will bend down pulling the diaphram
with it. This will activate the Cold Pressure regulator. Once the
engine has warmed up, the extra fuel is no longer needed, and the CPR
will deactivate. There is no long term benefit from the extra fuel.
The engine will just burn it off decreasing you gas milage. There is
also an electric heater in the unit which will warm the bimetal arm
with in a certain amount of time since the unit relys on radiant
temperature of the engine.
2. If you need to acellerate quickly you hit the throttle. This
increases the vaccum in the intake manifold. The lower 3rd & 4th
chambers of the CPR are connected via a hose to the manifold by way
of the Thermal Vacum Control Valve that is split by a "T" fitting.
But the side which connects to the upper of the two chambers is
fitted with a delay valve. When an increased vaccum is applied to the
CPR, the pressure in the lower chamber decreases first pulling the
diaphram down. A spring connects the lower diaphram to the upper one,
and will increase the fuel flow. As this ocurrs the Delay Valve is
slowly decreasing the pressure in the upper chamber. Once the
pressures in both chambers are equal, the diaphrams will return to
their normal positions. The purpose of the Thermal Vaccum Control
Valve in this circuit is to only allow this enrichment to occur once
the engine has reached a specific temperature.
Cold Start Valve.
Just as with the Control Pressure Regulator, your engine needs extra
fuel to run properly when cold. But it also needs even more fuel to
initaily start when cold. That's where the Cold Start Valve comes in.
When the engine is below a certain temperature, the CSV will activate.
Thermo Time Switch.
A bimetal arm inside of the Thermo Time Switch will ground itself to
complete the electrical circuit for the Cold Start Valve to open. But
unlike the CPR, the Thermo Time Switch reads engine temperature
directly from the engine coolant. Located in the TTS is a heater. So,
if within a certain amount of time the engine does not start, the
bimetal arm will heat up enough to bend and break the circuit to
close the valve. If the valve stays open too long, it can pose a
possible fire hazard. Which is why the use of a "Hot Start Relay" is
not always reccomended except for in extreme situaions. It should
also be noted that circuit is only active when the ignition key is in
the Start position (marked as "III" on the ignition itself).
Fuel Injection Section:
The end of the line for fuel. From here it is sprayed into the engine
to be burned. Here is the differance between EFI and CIS. In the K-
Jetronic application the fuel injectors will only open when the
pressure behind them has reached a specific level. So, once this
level is achieved, the injectors do not close. Hence they
Continuously Inject. On a EFI system the injectors will only open
when they have recieved an electrical signal to do so. more precise,
but as a mechanic explained it to me, CIS is better in the long run
because EFI injectors will wear out and eventually fail. But with the
life span of most cars, that's why it isn't a concern.
Cold Start Valve.
It's purpose has already been explained above. But is is listed here
as well since it does deliver fuel to the engine. An interesting not
about it is that it recieves it's fuel before any gasoline goes to
the fuel distributor.
As mentioned above, the K-Jetronic system is purely mechanical, and
requires no solid state electronics of any kind for proper and
reliable operation. BUT, on it's own it does NOT meet EPA standards.
Volvo saw this, and thus the LAMBDA emissions system was born! The
LAMBDA gives the K-Jetronic system more precise control over itself
with out any major modifications. It is a "bolt-on" component, not an
intergrated one. EPA emissions cover not only how much CO, H-C's, and
other toxins are expelled out of the engine, but also gas milage.
LAMBDA Emission Control Unit (ECU).
The heart of the system. This computer monitors by way of a oxygen
sensor how well fuel is being burned inside of the engine. It also
can take over the all mechanical duties of the Control Pressure
Regulator. The ECU executes it's functions be controlling the
pressure of the fuel system. This is accomplished by allowing fuel to
return to the gas tank.
What the ECU uses in order to control the pressure in the fuel lines.
The Frequency Valve functions by cycling on and off, or rather
opening and closing. When open it allows more fuel to return to the
gas tank, thus decreasing pressure in the lower chambers of the fuel
distributor. The faster the cycle of the frequency valve, the more
fuel it allows to flow thru. The cycle it self is determined by the
Also commonly known as the oxygen sensor. This little device reports
back to the ECU how much oxygen is in the exhaust gases. The more
oxygen it detects, the more fuel pressure is reduced, and vice-versa.
For proper operation, the probe must reach a specific temperature
first. If no signal from the probe is detected by the ECU, then will
run in a preset mode if the thermal probe has not been tripped.
A thermal switch that is tripped if the engine coolant is below a
specific temperature. Will activate the ECU to run in a "Warm Up"
When the throtle is full open, a microswitch is tripped telling the
ECU to run in a rich mode. Creates a fuel spike same as the CPR does.
I hope this helps everyone understand thier fuel system better as in
how it works. I also hope this helps as a trouble shooting guide as
in if something is not working properly, you'll be able to find the
problem much quicker by way of detecting what isn't doing it's job.
You can also see that while I described the detail of how everything
works, I did leave out specific data as to pressures, temperatures,
etc... This is because this write up should not be used alone in
trouble shooting. There is no substitute for the workshop manual, and
there is certainly no reason that any DeLorean owner should not own a
The reason I created this write up was to give a better understanding
of the fuel system. The DeLorean workshop manual does a good job, but
it uses more advanced terms then most folks are used to. Is has ok
diagrams, but if you don't understand the wording, they don't always
make sense. The Volvo 760 Haynes manual has some good pictures, but
is way too vague in it's explinations. Plus it doesn't cover all
aspects of the K-Jetronic system. It also has in my opinion a very
poor trouble shooting guide. The DeLorean t.s. section is much more
complete. The BOSCH handbook uses easy to understand terms, but lacks
any good descriptions of the DeLorean application.
This write up combined with the workshop manual descriptions and
diagrams should make things much easier to understand.
After reading this, hopefully everyone is more comfortable in dealing
with their fuel system. Even if you yourself do not do the actual
work on it, you can give your mechanic more direction as to what you
One more thing. If you elect to perform any repairs on your fuel
system, particuarly the injectors and the distributor, make sure of
NEVER, EVER UNDER ANY CIRCUMSTANCES REUSE ANY OF THE COPPER SEALS
THAT CONNECT THE FUEL HOSES! ALWAYS USE NEW SEALS!!!!!!
The seals are "crush-fit". In otherwords, they seal themselves by the
banjo fittings and bolts crushing down into the copper. If resued,
leaks can develop and cause engine fires. If ever in doubt, take you
car either to a DeLorean service center, to to an "early" Volvo
specialist. They will know the car, and they will know better about
Date: Sat, 24 Mar 2001 02:25:20 -0000
Subject: Re: Thermo Time Switch
It sounds like the warm up ciruit is not functioning correctly. If
the car cranks immediately, that means the cold start valve and the
thermo time switch are fine. Try this: Have someone hold the
microswitch on the throttle spool in while you start the car. Hold
the switch in to see if the engine will run. Other then that, it does
indeen sound like you might have a bad conrol pressure regulator.
--- In dmcnews_at_dml_y..., "Rob van der Veer" <rob.van.der.veer_at_dml_d...> wrote:
> Thank you Robert, it starts to make sense now, but I'm still not
> I'm having problems with cold starting. Warm starts are perfect. At
> first crank, the engine starts very eager, but after 2 or three
> engine starts stalling en after 15 seconds or so, it stops
Date: Sat, 24 Mar 2001 03:39:25 -0000
From: "Mike Griese" <roscsyl_at_dml_millcomm.com>
Subject: Re: need to adjust mixture levels?
Andy - I wouldn't mess with the idle mixture until you
understand why your fuel pressure is so high. Otherwise
once you do fix the fuel pressure problem you'll have to
readjust the mixture.
--- In dmcnews_at_dml_y..., Soma576_at_dml_a... wrote:
> Hello All,
> still having troubles starting. my dad and i would like to get the
> of the garage and into the driveway. i tried starting it today and
> said there is black smoke coming out of the pipes and my garage is
> to reek of way too rich exhaust. we would like to adjust the
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