928 Fuel System Issue
01-23-2016, 06:46 PM
#1
2nd Gear
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928 Fuel System Issue
I have a 1985 928. Recently I have replaced the fuel tank, sending unit, fuel pump and Catalytic converter. I have also run Seafoam engine cleaner through the tank.
However, when I attempt to drive it and push on the gas, the car will start to die. Once I let off the gas the idle comes back. I am trying to figure out what the next likely candidate for repairs are.
When I start it, the car will idle, but I have to wait for a few minutes before pushing the gas. If I push the gas, a lot of the time the car will start to die out. Once it has warmed up the less likely it will to stall out in idle.
I can drive the car, but have to let it idle up to 15-20 mph, and can push on the gas slightly to get it to 30-35. My mechanic has said he has driven the car, and it has run well, but dying out will come intermittently.
Again, any help from someone who has gone through this would be appreciated. I don't want to keep throwing parts at it.
However, when I attempt to drive it and push on the gas, the car will start to die. Once I let off the gas the idle comes back. I am trying to figure out what the next likely candidate for repairs are.
When I start it, the car will idle, but I have to wait for a few minutes before pushing the gas. If I push the gas, a lot of the time the car will start to die out. Once it has warmed up the less likely it will to stall out in idle.
I can drive the car, but have to let it idle up to 15-20 mph, and can push on the gas slightly to get it to 30-35. My mechanic has said he has driven the car, and it has run well, but dying out will come intermittently.
Again, any help from someone who has gone through this would be appreciated. I don't want to keep throwing parts at it.
01-23-2016, 06:54 PM
#2
Captain Obvious
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Take it to someone that knows more than this mechanic. Need to put fuel pressure gauge on it to see what is happening and go from there.
01-23-2016, 11:32 PM
#4
Rennlist Member
Symptom is of lack of fuel , and you dont mention replacing the Filter! If it is still bad with a new filter check the fuel pressure at the engine, and the delivery rate. You should see 2.3-2.7bar pressure (2.5 with relay bridged, 2.0 at idle running), and delivery of 1350ml/30 secs. This assumes you have L or LH system. Test delivery at the return line joint in the engine bay, carefully, with an extinguisher handy!
When my CIS car had high control pressure it did the same as you describe.
jp 83 Euro S AT 56k
When my CIS car had high control pressure it did the same as you describe.
jp 83 Euro S AT 56k
01-24-2016, 07:19 AM
#6
You can call me Otis
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I have a 1985 928. Recently I have replaced the fuel tank, sending unit, fuel pump and Catalytic converter. I have also run Seafoam engine cleaner through the tank.
However, when I attempt to drive it and push on the gas, the car will start to die. Once I let off the gas the idle comes back. I am trying to figure out what the next likely candidate for repairs are.
When I start it, the car will idle, but I have to wait for a few minutes before pushing the gas. If I push the gas, a lot of the time the car will start to die out. Once it has warmed up the less likely it will to stall out in idle.
I can drive the car, but have to let it idle up to 15-20 mph, and can push on the gas slightly to get it to 30-35. My mechanic has said he has driven the car, and it has run well, but dying out will come intermittently.
Again, any help from someone who has gone through this would be appreciated. I don't want to keep throwing parts at it.
However, when I attempt to drive it and push on the gas, the car will start to die. Once I let off the gas the idle comes back. I am trying to figure out what the next likely candidate for repairs are.
When I start it, the car will idle, but I have to wait for a few minutes before pushing the gas. If I push the gas, a lot of the time the car will start to die out. Once it has warmed up the less likely it will to stall out in idle.
I can drive the car, but have to let it idle up to 15-20 mph, and can push on the gas slightly to get it to 30-35. My mechanic has said he has driven the car, and it has run well, but dying out will come intermittently.
Again, any help from someone who has gone through this would be appreciated. I don't want to keep throwing parts at it.
So it seems it may be running lean, so the 02 sensor may be in question, vacuum leaks could be a problem.
The ICV (idle control valve) is a common fail item, and the vacuum lines connected to it fail.
The fuel pressure regulator could be bad.
I would first check check for vacuum leaks, then the fuel supply chain.
You are either getting too much air, or not enough fuel.
01-24-2016, 10:47 AM
#7
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I would also suggest checking the output of the Temp II sensor on the top of the coolant crossover. There are two identical temperature sensors in the housing, one for the ignition and one for the injection. Check the resistance of each pin to ground - not pin to pin.
The resistance at specified engine temps should be:
32 deg F - 4.4 to 6.8 kOhms
60 - 85 deg F - 1.4 to 3.6 kOhms
104 deg F - 0.9 to 1.3 kOhms
140 deg F - 480 to 720 Ohms
176 deg F - 250 to 390 Ohms
The resistance at specified engine temps should be:
32 deg F - 4.4 to 6.8 kOhms
60 - 85 deg F - 1.4 to 3.6 kOhms
104 deg F - 0.9 to 1.3 kOhms
140 deg F - 480 to 720 Ohms
176 deg F - 250 to 390 Ohms