[DMCForum] Re: Misfire problems
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[DMCForum] Re: Misfire problems



I have the same type of symptoms with my car, although less 
dramatic.  When the engine is cold it will take a while to get some 
power.  After a couple of farts, it is fine.  
I haven't done the following procedures, so if you do them, do them 
at your own risk.  I took this info from the DMCNEWS homepage.

Author/source: Dave Sontos  dsontos(AT)sybercom.net

Description: There is a tiny hole in the stainless-steel diaphragm 
that separates the lower chambers from the upper chambers of the 
fuel distributor. This hole allows fuel to flow from the lower 
chambers into an area above the control plunger. The Control 
Pressure Regulator controls the pressure in this area, limiting the 
degree to which the control plunger can be lifted for a given amount 
of airflow into the engine. Limiting the movement of the control 
plunger in turn limits the richness of the air-fuel ratio. The 
Control Pressure Regulator achieves this control by bleeding off 
fuel pressure from the control plunger and returning fuel back to 
the fuel tank.

Problem:

Symptoms exhibited by the car included multiple cold starts before 
the engine would idle and then the idle would be rough. Acceleration 
would make the engine cough and sputter and die until several 
minutes till the engine warmed.

Diagnosis:

Attach fuel pressure gauge between fuel distributor center line and 
the Control Pressure Regulator (CPR) with the shut off valve between 
the CPR and the gauge. Attach a fused jumper wire between terminals 
87 and 30 of the RPM Relay connector to energize the fuel pump and 
pressurize the fuel system. The cold engine fuel pressure should 
read around 35-40 psi. Next rotate the gauge valve to the closed 
position. By doing so the CPR will be isolated, thus the pressure 
gauge will show system pressure. System pressure should be around 65 
psi. If the readings do not change when operating the gauge valve 
your CPR is not working.

Fixes:

If your car may have been sitting for a while it is a good 
possibility that debris in the fuel line has plugged up the CPR 
inlet side. Inside the inlet to the CPR is a very fine screen. Dirt 
from a contaminated system will plug up this screen making the CPR 
inoperable. Remove both fuel lines from the top of the CPR and using 
a shop air hose blow air into the outlet side fuel port of the CPR. 
Make sure you wear some sort of eye protection when you do this. The 
air should dislodge the dirt in the inlet side of the CPR. Shine a 
light into the inlet and inspect for dirt. You may need to use a 
small probe to dislodge any remaining dirt here and clear with shop 
air. You should now be able to see the screen at the bottom of the 
inlet hole. Place the ends of both fuel lines from the CPR into a 
one pound coffee can or other suitable container and run the fuel 
pump for a couple of minutes to flush out any remaining dirt from 
the fuel line. Re-attach the fuel lines to the CPR and repeat the 
Diagnosis again to confirm normal operation and check for leaks in 
the fuel system.

The CPR assembly may be completely disassembled for cleaning. When I 
removed mine and opened the two halves I found the inside completely 
filled with some insect infestation. Although I don't believe this 
affected its operation it looked like hell. Inside the CPR is the 
heater and electrical contacts and also the vacuum bellows. Check 
the electrical with a VOM and the vacuum bellows with a hand vacuum 
pump.





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