78 Control Pressures without a pushup valve

[aricaandjustin]

My 78 2.7 engine is stock. It accelerates well but surges (loping)when coasting. I have set up the control pressures- 1 bar cold and 2.8 hot. Plugs are tanned and all injectors working well. I just replaced the fuel filter and wires, points and cap. None of these helped. I feel it is running lean but I cannot find any vacuum leaks...as well idle does not change when I open the oil tank cap. Any help would be appreciated.

I also am loosing my system pressure 7 minutes after I shutdown the engine. I have my pressure tester set up on the line from the FD to the WUR. The tester isolation valve is on the WUR side of the test gauge. When I SD the engine and close the valve the pressure stays up on the gauge. So pressure back to the FD is holding but the WUR is leaking pressure. I see the other line on the WUR goes to the tank return line. So I assume that when the WUR is warmed up it should not leak to tank? (thus releasing my fuel pressure). I also assume that as the bimetallic strip and engine heat cool down that the pressure drains off through the WUR normally but mine seems to leak all the time...

[ossiblue]

Surging tends to be a symptom of overly rich idle. The warm pressure you posted, 2.8 bar, appears to be too low for your car--IIRC, it should be about 3.4 +/- .2 bar. Cold pressure may or may not be in spec, depending on the ambient temps. Setting the warm pressure up a bit may solve your problem.

The failure to hold pressure could be from a faulty fuel accumulator, fuel pump check valve, or the WUR. Connect you gauge to the hose that goes to the inlet of the fuel accumulator, run the fuel pump to pressurize and then turn it off. If pressure holds, the check valve is working. Move to the outlet from the filter and repeat--if pressure holds, the accumulator is good (your accumulator, I believe, has three ports--the one on the bottom connected to the tank return line. A leaking accumulator will bleed pressure through this line back to the tank.) If the previous two tests are good, the the WUR must be at fault. However, be absolutely certain the gauge set up has no leaks at the connections when you test the WUR.