Symptoms Bad Fuel Pressure Regulator m117
 

Hey everyone,

I'm just wondering, what might be some symptoms of a bad fuel pressure reg?

On this 560SEL it has trouble with power under operating temp and if you stomp on the accelerator, the throttle takes a bit to respond to the demand. However if you accelerate slowly it will climb in rpm fine.

The vent line at the regulator is broken, I can feel a woosh of air coming out the back of the regulator. This makes me thing the diaphragm is broken and the unit is not maintaining the needed pressure of 6.5 Bar (I think thats the number)

I dont have any CIS gauges to put on the system so I can't be 100% sure of the pressure. It just seems to want to stall out occasionally. I think this is due to too much fuel, as I recall reading that the FPR is more of a dampener than a "regulator"..

Let me know what you gents think....

You've got to draw a bead on the fuel pressure.

It could be low pressure (fuel pump) or high pressure (regulator).

Jim

CIS.E parts
 

[QUOTE=JamesDean;2669353]Hey everyone,

I'm just wondering, what might be some symptoms of a bad fuel pressure reg?

On this 560SEL it has trouble with power under operating temp and if you stomp on the accelerator, the throttle takes a bit to respond to the demand. However if you accelerate slowly it will climb in rpm fine.

The vent line at the regulator is broken, I can feel a woosh of air coming out the back of the regulator. This makes me thing the diaphragm is broken and the unit is not maintaining the needed pressure of 6.5 Bar (I think thats the number)

I dont have any CIS gauges to put on the system so I can't be 100% sure of the pressure. It just seems to want to stall out occasionally. I think this is due to too much fuel, as I recall reading that the FPR is more of a dampener than a "regulator"..

Most likely your assessment of a malfunctioning regulator is correct.There should be no pressure on the vacuum side of the regulator .
Based on experience with same year vintage i may mention worn-out components requiring replacement are; fuel pump and relay ,OVP relay, fuel accumulator ,fuel regulator and all the fuses with the brass tipped ones . Otherwise the reliability issue remains due to these ageing components
regards.