Frank, thanks for staying on board. I have had the plugs out. They look dry.....and seem to be okay color wise...none of them visually (carbon...oil) startled me..some looked really nice. The plugs have a much smaller electrode (the small diameter wire that the spark jumps from)than I am used to. I have not been able to view the sensor plate when the car is running for the brief period that it does run since I am in the drivers seat. I will have my wife start the car and observe. I have checked the action of the plate while the car is not running....seems smooth no binding. In the 8-14 post you state if dry the control regulator could be stuck closed.....is the control regulator the pressure regulator in the fuel distributor?

Chuck and Frank.....hold open the throttle? there is the air sensor plate and the throttle butterfly.....I know once the car runs...which it does for 20 seconds or so the air sensor plate needs to open...I was assuming it was opening because the car starts and runs for a brief period of time. Can the motor run without the air sensor plate opening? I need to get my butt out of the drivers seat and see what is going on.....Whats interesting is that while the car runs(20 seconds or so)....at a low idle....stepping on the accelerator doesnt seem to do anything. I should make sure the accelerator pedal is opening the throttle butterfly. The throttle is the butterfly the accelerator cable moves not the air sensor plate. Chuck the the air valve doesnt need to come off to determine air valve operation? I had my the air valve off my other 280 years ago..probably after the head was removed...I remember it being stuck and using hot water to test it I was able to get it working again....cleaning and lubrication. I look at where it is located....from on top of the motor and shudder when thinking about if it has to be accessed from underneath the intake manifold. If I could convince myself it is working w/o removal I am interested.

as you can tell I am always solo in the garage. sad state of affairs. I need to make myself a remote starting switch...any ideas?

I think you need to figure out why you can't get the RPMs to come up. That's pretty basic. Usually this is caused by high control pressure. Can you get a reading with the engine running?

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Good to hear that the plugs are dry; that is consistent with lack of fuel, both supply and metering. Small diam. center electrode probably = Bosch Platinum. The sensor plate is not mechanically connected to the throttle plate; it is moved by air flow. If the safety switch is mis-adjusted, too much sensor plate movement will be required to open it than is produced by a low idle. The test is to unplug the safety switch, and then start the engine. That will ensure that the pump runs after the key is released from the start position. Re: lack of throttle response. Assuming that the throttle linkage is intact, if the pump is not running after the key is released, the fuel pressure (from the accumulator) will be too low to pick up the engine. That also suggests that the aux air valve is open.

There is a connecter block on the right wheelhouse where the leads to/from the starter motor join. One of them (about 16 ga.) when jumped to +12v will engage the starter.

Control pressure regulator = warm up regulator

Chuck, about a 1-1/2 weeks ago I checked the system pressure and control pressure by turning key to run position and disconnecting safety switch. The 12V connector was not on the wur. I had just finished a complete tear down and reassembly of the wur. I measured 70psi system and 20-25 psi control pressure. Ambient temp was close to 80° F. I thought that looked good.....dont know what happens when the car starts.

as stated the car starts and idles for maybe 20 seconds....I could have my gauge in place and get a reading before it stalls.

Tonight I am going to put my meter back on the fuel pump. Confirm 8-10V at start position and 12V after motor starts to run and idle. Confirm if air sensor plate opens when engine runs. Reconfirm my system and control pressures preferably with motor running.

Good plan. Also check the movement of the air sensor plate with the pump running by pushing it down.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

rechecked voltage at fuel pump while key in start measured .2/.4Volts. Even after it started and ran for a short period of time .2/.5 Volts. I am starting to be suspicious of the fuel pump. If it is getting ready to fail it might be drawing a whole lot of amps? Does anybody know how many amps the pump should draw? If I take a 4amp 12Volt charger and place it across the fuel pump it does operate. Doesnt sound that great? But it runs.

okay.... I may need to go back and confirm some of my old findings....but I was trying to measure 12V at the fuel pump on the negative terminal. It is normal to see less than
0.5V if potential is checked from the negative terminal of the pump to ground. When I moved the probe over to the positive terminal, voila 9V when key is in start position and 11/12V after key springs back to run position. The air sensor plate is opening when the car runs. Tomorrow night I will check the system and control pressure while the car runs for 20 seconds or so. I tried to check timing but the motor didnt run long enough for a measurement. I will try that again tomorrow night. I tried the throttle valve while it was running but it doesnt appear to help it almost seems like it makes it stall quicker.

Considering that the starter motor only pulls system voltage down to 9V, I am inclined to reject the idea of a high draw of the pump. I do think that there is a point of high resistance in the circuit between the relay socket and the pump. A loose fit of the pins in the socket, and/or corrosion in the sockets can do it. Next would be the connection of the wires to the bottom of the sockets, and then the terminal and post of the pump. Unless there is mechanical damage to the wire harness itself, a fault in the harness is a rather long shot. If necessary, a bypass wire from the 30 socket, run outside the car to the pump, can help isolate the fault.

Early in this thread you did pressure and flow checks. Was the flow check done at the return line fitting of the fuel dist., and with a cold WUR? Checking flow at the return port ensures that the pump is operating against the system pressure (70 psi). A pump may appear to be flowing at spec. against zero pressure, but can be so worn internally that it will not flow at system pressure. Also, is the filter new?

Yes the flow check was done at the fuel return line, see attached image. The car was not running, key was in run, warm up regulator was cold and the safety switch connector was removed. I was surprised I got the flow as well. I think it is time to recheck the pressures while the car runs.

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Frank you were right about rejecting such a high draw from the pump that it would only see .4Volts. As you already know I was checking for voltage on the negative terminal of the pump. I was a bit surprised myself. Well I guess replacing the fpr was not necessary.

I thought this image had been added to the thread.....but here it is. The location of the fuel pump relay is directly above the fuse box located in right side kick panel.

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