1978 Other Porsche Models Fuel system

PORSCHE78

MEMBER
1978 PORSCHE
4 CYL
2WD
MANUAL
18,800 MILES

Hello, I had been having problems starting my 1978 porsche 924. I use to had to pump the Gas pedal to get start the car started when ever the engine was cold. Usually, the car would be easy to start up after I just drove it. Right after the car had a recent oil and fuel filter change, I was unable to get the car started. The mechanic checked it on a Diagoisis Machine and eveything works with the Fuel pump, and fuel injectors. He said he was getting good fuel pressure to the other cylenders but there was little fuel pressure to the #2 cylender. He said we needed to replace a fuel injector line. Which we did, and the car did not Start. We found gas leakage believed to be due to the Fuel Accumulator, which needs to be under pressure. My Mechanic doesn't know what part is leaking, whether it be the fuel accumulator or the Fuel distrubutor or if the Fuel acummulator is the fuel distrubutor. What does these parts do? Other parts include the Cold start valve (What does this part do?) Fuel level Sending unit (what does this part do?), Fuel pump check valve (what does this part do?) Fuel Sender (what does this part do?) Oxygen sensor (What does this part do) Thermo Time switch (What does this part do?) If you can answer all of my question, I will be glad to donate and maybe even donate more later with other questions.

1 Reply

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Hello
Thanks for the donation.

The fuel accumulator is a component in the fuel system that is used to prevent vapor lock. The vapor goes into the accumulator then recondenses back as liquid and is then sent back through the system as fuel.

A fuel distributor is a component that includes a plug connection which serves to provide electrical contact for the fuel injection valves comprising a socket and a plug. The plug connection that is located directly on the valve connection neck, in a region between two sealing elements, that seal off a connection between the fuel distributor and the fuel injection valve, so that the fuel-carrying region is sealed off from the guide conduit, which in turn is sealed off from external influences such as splashing water. Thus, even the plug connections located in the region of the guide conduit are protected. The fuel distributor is especially suitable for fuel injection systems of mixture-compressing internal combustion engines with externally supplied ignition.

The purpose of the cold start valve is to inject fuel into the intake air stream when the engine is cold (and the starter operating) in order to richen the fuel/air mixture for easier starting.

The fuel level sending unit is an electrical rheostat that is mounted either as a part of the fuel pump assembly or as an independent unit which sends signals to computer telling it the level of the fuel.

The fuel pump check valve allows the flow of fluid from the reservoir into the pumping chamber. The fuel pump check valve is constructed such that when a combination of both liquid and vapor is present in the pumping chamber, the liquid and vapor is allowed to flow from the pumping chamber back into the reservoir; but when the pumping chamber is filled only with liquid, the check valve prohibits flow from the pumping chamber into the reservoir.

The fuel sender, also known as the fuel sending unit, controls your fuel gauge readings.

The oxygen sensor (located on the exhaust system) analyses the gases going out the exhaust and tells the computer what is going on. Information such as whether to add fuel, take away fuel or if there's a problem in the exhaust or fuel system is sent to the computer.

The thermo-time switch consists of a contact to ground for the cold start valve and a bimetallic strip surrounded by a heater winding. When the engine is cold and the key is turned to "start, " the bimetallic strip contacts the ground contact and allows the cold start injector to inject fuel. When the key is turned to "on, " that powers the heating element inside the thermo-time switch. As the heater warms the bimetallic strip, it eventually bends away and stops grounding the cold start valve.

Hope this helps.
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