Trying to help a friend out by doing some troubleshooting while he is out of town, no, really, it’s for a friend not one of my cars. Really. Yes, really.

The backstory on this thing is it’s a 1973 1.7 with its factory fuel injection system, it has the number of electrical issues that ultimately will need to get tidied up but as of right now it will briefly catch every three or four full revolutions of the engine with the starter and then immediately die.

The MPS looked original and I was skeptical that it was in good working order so, lacking a vacuum pump at the moment,, I disconnected it and the engine seemed much more willing to start but didn’t quite catch.

I have a rebuilt MPS from Jeff that I’m going to loan The car’s owner but obviously the fact that it seemed more eager to start without the MPS suggest that the MPS is an issue.

Does anything else come to mind when the car seems to be more eager to start/run without the MPS? My 1.7 ultimately was well behaved and ran great with very little fiddling, so looking for some ideas to pass along here...

I have forwarded the troubleshooting guide on Rennlist...

Thanks!

I was working on one last night that was kinda starting but just wouldn’t. Checked spark and injectors and had spark and fuel but it just wouldn’t run for more than a second. Turned out to be the distributor was not fully seated down. Once we had the distributor engaged properly it fired right up. To check pull the cap and see if the rotor turns by hand. It shouldn’t.

The great thing about D-Jet is that it consists of only a few individual components that work together, and can be easily tested for function discretely. Because they function together a failure of a single component may mask the real problem causing one to go down rabbit trails. So make it easy, just check each item separately until you find the issue. This process eliminates other suspects for peace of mind. For a non-start condition (not for fine tuning), most D-Jet no start issues can be identified by performing a short list of simple tests, each is critical for engine start-up. You need a few important but common tools:

1. For a 1974-76 914 verify that the seatbelt interlock has been bypassed (under the passenger seat). A failed interlock prevents ignition.
2. Visually check to see that each FI electrical component and vacuum hose is correctly and securely (not loosely) attached where it belongs, to the FI harness or its vacuum component.
3. Check FI harness visually that the 3 pairs of ground wires are attached at the top center rear of the engine case, and the harness has no wire breaks, bent or dirty wire terminals. Continuity check each FI harness circuit if anything is suspect. FI harness diagrams are on my wiring harness website (see link in my signature) for free download. This should indicate that circuits are complete.
4. Check for specified TS2 (cyl head temp sensor) cold resistance value with an ohmmeter.
5. Check MPS holds vacuum = 15psi for 15 minutes with a vacuum pump and gauge. Minor, slow leak down is OK.
6. Check TPS visually for worn traces on the circuit 'ladder'. Unplug it if you want.
7. Check trigger points in distributor. Pull the dizzy out if easier and check between the center contact and each if the two outer contacts, for alternating continuity with an ohmmeter, while rotating the shaft. These two coupled switches initiate the injector pulse cycles.
8. While engine is cranking check spark plugs for spark.
9. While engine is cranking, check for specified fuel pressure, using a fuel pressure gauge.
10. With ignition switch on, check for switched 12V power at Pin I of the relay board (where the FI harness connects, male contact at front passenger side).

Other tests can follow if needed:
-Leaky injectors including the cold start valve
-Leaky vacuum connections/gaskets or air plenum
-MPS coil resistance values and calibration
-TS2 warm resistance value
-ECU can be tested with special equipment
-High resistance values in the FI harness circuits
-Ignition coil/wires function
-Ignition timing and dwell
-Valve clearance
-Fuel pump delivery volume

Thank you for the replies, with a special tip of the hat to a very clear and thoughtful response from Jeff.