Fuel Distributor

 
The Bosch Fuel Distributor P/N102807 is the primary fuel distribution device on the DeLorean engine. The Fuel Distributor meters the fuel based on engine demand (air flow), temperature, load, and emissions tuning. It also distributes the fuel to the 6 pressure-activated fuel injectors. Fuel flow is continuous, as opposed to being pulsed on and off as in modern Electronic systems. Fuel is always flowing from all injectors at all times when the engine is running. For proper engine operation the fuel must be in the correct proportion to air intake (i.e. fuel mixture) and must be even across all 6 injectors.
 
Almost all fuel injection problems have their genesis in fuel contamination due to long term storage or lack of use. (See also Gasoline Discussion).  The way to avoid fuel system troubles is to use the car regularly and often, or empty the tank and system completely for storage longer than three months.
 
Diagnostics:
A failed fuel distributor can cause several different issues:
  1. Fuel dumping; i.e., an extremely rich condition. This is often first noticed, if the car even runs at all, as a glowing red-hot catalytic converter, liquid fuel coming out of the tail pipes, or thick white  or black exhaust smoke.
  2. Unequal fuel delivery to the injectors. This will be seen as an engine that runs unevenly, often mistaken for a misfire/missing spark on one or more cylinders.  
  3. Insufficient fuel delivery to the injectors. This will be seen as an engine that may actually idle ok but will be very low on power under acceleration.
 
Conditions "2" and "3" can also be caused by bad/plugged fuel injectors, so troubleshooting of fuel problems can be confusing and lead to replacement of multiple parts at the same time.  
 
Repairs:
The Fuel Distributor on the DeLorean is a sealed unit. Although it appears that it can be taken apart, in reality that will almost certainly make the unit irreparable.  It is extremely difficult to re-seal as the two halves are sealed without gasketing, but a sealant would gum up the internal parts. There are numerous small parts inside that can not be interchanged per-port, as they were calibrated during initial manufacturing of the unit. If the Fuel Distributor has failed, it must be sent in for core exchange for a rebuild unit. Units that have been field-disassembled or have had repairs attempted may not be useful as cores.  DO NOT fill the ports on the fuel distributor with solvent (aka carb cleaner) in an attempt to clean it out. This will quickly dissolve the internal rubber parts, making eventual repair more difficult.
 
There are two repairs that may be attempted in the field:
 
1 - One of the few maintenance procedures possible is to free the center plunger in case it is frozen in its channel.  This will not necessarily fix the problem, but may only change the symptoms. A stuck plunger is typically observed as an air input metering flap that is either frozen in the closed position, or never develops any pressure with the engine running, and the very rich condition mentioned above.
 
With the fuel distributor removed from the engine, pull on the plunger with needle-nosed pliers. The plunger is VERY hard so this will not damage it. If the plunger does not come out with some effort, STOP and get another fuel distributor. If the plunger does come out, clean it up with solvent, use some cotton swabs to clean out the passage (DO NOT pour solvent into the unit!) and reassemble. CAUTION: dropping the plunger on a concrete floor will damage it and it will no longer move freely in the bore. Be careful!
 
2 - The fuel distributor regulates operating fuel pressure via a built-in needle and seat/spring plunger arrangement known as the Primary Fuel Pressure Regulator. The common failure is a tearing of the O-ring during service attempt, or due to using the wrong depth hollow bolt on the frequency valve line connection. Operational failure is rare.  The symptom of failure is the system's inability to hold fuel pressure for more than a few seconds after the engine is turned off. This may be mistaken for a failed fuel accumulator. Refer to "Hot Start Issues" for more detailed discussion of this failure.
 
This internal pressure regulator is accessible from the outside of the fuel distributor with the fuel distributor still installed on the car. The internal mechanism can be removed and the smaller o-ring inspected and replaced. Be sure to contact DMC for information on this repair, as it is very important to use the correct fuel-resistant o-ring in this application.
 
Rewritten DAS 6/22/2016

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