Engine won't run with MPS hooked up

[fastempo]

I have a '73 2.0L, which has been rebuilt motor, abt. 5.0k miles ago, with a lighter flywheel and a hotter cam than orig. I recently sent out the Pressure Sensor (MPS) to be rebuilt at Jetronics in Livermoore, CA. Now when I have it back, as soon as I attach the vacuum hose the engine quits and will not restart. Oh sometimes when I cycle the fuel pump several times, before ignition, the engine will run for abt 10 secs. Without the pressure sensor vacuum hose hooked up it runs quite well, although you have to apply throttle very carefully or it will backfire badly.

Can anyone help, please.

[Dave at Pelican Parts]

If the hose is disconnected, the engine will run very rich as the FI will think there is lots of air going into it. If it runs at all that way, chances are that it is very lean when the MPS is plugged in correctly.

Check for fuel pressure; should be 29 PSI when the pump is on.

I know one guy whose 914 would idle for ever, but only if he left the fuel pump unplugged. The MPS was either unplugged or blown (forget which), and the rich mixture from the MPS seeing atmospheric pressure just about compensated for the very low fuel pressure from gravity feed. It was very odd...

Could be other stuff, but fuel pressure is the only one that comes to mind for a lean mixture. Oh, wait--the head temp sensor could be shorted to ground too.

--DD

[fastempo]

Thanks Dave;

I will check both of those items, i.e. "The fuel pressure (just got the Tee and the gauge)"

and, "Verify that the head temp-II sensor is not grounded,
shorted out.

If, as you said, the engine is running very lean without the MPS's "at idle lean-out input"-
How do I richen the mixture, so that the input from MPS can be tolerated.
Turn the plastic top knob on the ECU??

[Dave at Pelican Parts]

The knob only controls the idle mixture. Its range of adjustment is limited, so I doubt you can get it lean enough to work correctly.

Read through http://members.rennlist.com/pbanders for just about everything currently known about D-jet fuel injection.

--DD

[fastempo]

Thanks Dave!
I SET THE FUEL PRESSURE AT 30 psi, and I set the throttle valve at "one notch past zero ohms", and I opened up the back of the pressure sensor, and turned the set screw CCW to full rich, and now the motor runs with the p.s. vacuum hose hooked up, and it idles quite nicely at abt 950 to 850 rpm. But when I go to drive the car it seems to have very little power and backfires alot in air intake as well as in muffler, which is very bad I know. Any more suggestions,
thanks UW

[fastempo]

ps I think maybe th press. sens. is still bad after it supposedly was rebuilt. And shouldn't I be using a ...00037 rather than the ...00043 pressure sensor. My '73 chassi number puts me just past the the halfway numbers for production in that year (abt 14500, of the 27300 or so built)

[Bleyseng]

A 73 2.0L requires a 037 MPS which is setup quite richer than a 043 plus the right CHT with 270 resistor. The banging and spitting when running is that you are still too lean. You can adjust the MPS by ear by having a friend try to hold 2500rpms and you adjust the MPS for best running by ear. Or get a LM1 or 2 and hook up the O2 sensor to set the afr at 14 to one at 2500rpms with a slight load.