fuel pump surging, why?? Options

[Tab914]

Another one for you guys...........

Here is the problem I am trying to fix. Whenever the needle in the temp guage gets to about 1/4 the fuel pump starts surging. This causes the idle to start to go up and down in rythm with the fuel pump. Also when under load the car stutters and shudders and kinda wants to choke.

Before the car gets up to that temp. it runs nice and smooth, strong on acceleration and no poping or backfiring on decel or anything. Just sounds great and runs fine. Idle is where it should be and fuel pump does not surge.

Here is what has been done. -Valve adjustement
-Dwell adjustement
-Timing adjustement
-Tested MPC as per proper ohms.
Parts I have changed- coil, plugs, ignition points, trigger points, condenser, rotor, cap and wires.

Questions:- what could make the pump surge like that?
-does it make a difference how the MPC wire goes into it's conector?
-How do I properly check the head temp sensor.
-Could the intake temp. sensor be the cause.

I am at a lost. Feel like I am going in circles. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

Has anyone had this kind of problem??
Desperate for advice. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

Thanks, Dominic.

forgot to add. car is a 1974 2.0 with stock fuel injection.

[Dave_Darling]

Do you mean the MPS? Manifold Pressure Sensor? If so, you have D-jetronic FI, which is an important distinction.

How do you know the fuel pump is surging? That would be an unusual failure mode. Does the fuel pressure go up and down? (Do you have a gauge?)

I would guess that you have a vacuum leak somewhere. Another possibility is that your mixture is going somewhat lean when the engine is at warm idle. A few clicks clockwise on the knob on the ECU may help with that, at least somewhat.

You test the Head Temp Sensor by unplugging it from the harness (the plastic box connector stays on the harness), putting one probe of your ohmmeter on the metal connector on the HTS wire, and the other probe on the cylinder head. Should be 2K-3K when cold, <100 ohms when the engine is at operating temp.

The MPS connector can go in either way; it doesn't matter which way around it is. The two outer pins connect to one coil in the sensor, and the two inner pins connect to the other coil. They don't care which way around they are.

Finally, for all of your D-jetronic informational needs, see:
http://members.rennlist.com/pbanders .