'75 2.0L d-jet woes Starts off at 900 rpm for 2 min and dies, Is there a sequence to analyze problem? Options

[buck toenges]

Have a 75 D-jet 2.0L in earlier 72 car. Have later model main chassis wiring harness and 75 engine (fI wiring harness with the over rev limit switch. The switch is not hooked up). Car starts right away and idles at 900 rpm. I can rev the engine easily. After 1-2 minutes the engine dies. after that I can start engine it will rev to about 1000 rpm then die. This repeats as I start engine. I have to wait overnight to get the engine to start at 900 rpm and stay that way for 1-2 minutes. I have looked up d-jet stuff like Brad Anders' site and other posts to figure out what to do next.
Is there a sequence that would make the checkout easier?

This is what I have found so far as to sequence:

1)Fuel pressure at FI rail I have done this and it reads about 28-29 lbs during starting, running, and restarting.
2) check points condition and dwell 45-50 degrees Haven't done this yet but points and dist cap look new.
3) check cht ohm readings before starting and after running. Haven't done this yet but I do know I need to check it with cht not connected to harness
4) check air intake temp sensor resistance readings. Haven't done yet
5) mps check for vacuum and check terminal wires resistance. I know that one of the wires was disconnected from plastic connector. I did repair that.
6) trigger points/advance plates

Are there any other checks or sequence of checks that could help me correct the problem? I am trying to attack this problem in a rational sequence. It might be the ecu, maybe the old cracked FI harness, or maybe the distributor. I haven't seen any posts that talk about the rpms starting at 900 rpm then dying after 1-2 minutes. I have seen posts about rpms starting at 1500 rpms then idlying down before dying. I don't know if the aar needs checked or not.
Are there other things to check OR not to check?
One final thing. My gen light does not go out. I am going to jump D+ and DF to see if battery is getting charged. Just saying this just in case this might effect my symptoms.

Thanks,
Buck

[BeatNavy]

Buck - if you're just trying to solve this specific problem of the engine dying after a minute or two, I'd focus on fuel delivery -- you're either getting too much and it's flooding out or not enough, and it's starving. At some point, though, ALL the other tune-up checks and FI sensor checks and tests are valuable, as they will a) eliminate variables, and b) get your car running right.

But to the immediate problem at hand. The root cause is probably NOT:

1. ECU - they don't fail that often.
2. T1 (Ambient Air Temp, or Intake) Sensor - they don't have a large effect.
3. Trigger points / advance plates - they can cause funny issues, but probably won't give the symptom you are describing.
4. Points and dwell - those should be verified, but that's probably not the root cause of the engine dying.

I would focus on the following:

1. Definitely verify the continuity AND the readings of the CHT, from sensor to ECU. The sensor might be fine, but there may be a break in the wiring harness, or even just a wire frayed or kinked enough to increase resistance significantly. I'd probably go ahead and replace it soon, too. Old ones fail, often, and then you get symptoms similar to what you are describing.

2. You've checked fuel pressure. How about the fuel lines, filter, and tank? It's possible you have blocked lines or filter. Maybe they allow just enough fuel to seep through overnight to start the car but not enough to sustain delivery necessary for engine to stay running.

3. Bite the bullet and send the injectors out to Mr. Injector to get them checked and serviced. If they are leaking, you can get flooding.

4. Try to determine why your charging light won't go out - it could simply be the engine never gets RPM's up high enough to excite the charging system. But it could also not be providing enough to provide strong spark.

5. Validate MPS holds vacuum. Not sure a blown diaphragm will cause engine to flood in and of itself, but it could contribute.

6. Disconnect fuel line to Cold Start Valve, just to eliminate as a variable.

Problem with old fuel and FI systems is that there are lots of variables involved, either causing too much or too little fuel to be delivered. What other symptoms are you seeing that might suggest either flooding, starvation, or maybe lack of spark? If you crank the engine after it dies do you smell fuel? Do you get a spark when you crank after the engine dies?

Others will have more and probably better suggestions.

[914_teener]

Buck - if you're just trying to solve this specific problem of the engine dying after a minute or two, I'd focus on fuel delivery -- you're either getting too much and it's flooding out or not enough, and it's starving. At some point, though, ALL the other tune-up checks and FI sensor checks and tests are valuable, as they will a) eliminate variables, and b) get your car running right.

But to the immediate problem at hand. The root cause is probably NOT:

1. ECU - they don't fail that often.
2. T1 (Ambient Air Temp, or Intake) Sensor - they don't have a large effect.
3. Trigger points / advance plates - they can cause funny issues, but probably won't give the symptom you are describing.
4. Points and dwell - those should be verified, but that's probably not the root cause of the engine dying.

I would focus on the following:

1. Definitely verify the continuity AND the readings of the CHT, from sensor to ECU. The sensor might be fine, but there may be a break in the wiring harness, or even just a wire frayed or kinked enough to increase resistance significantly. I'd probably go ahead and replace it soon, too. Old ones fail, often, and then you get symptoms similar to what you are describing.

2. You've checked fuel pressure. How about the fuel lines, filter, and tank? It's possible you have blocked lines or filter. Maybe they allow just enough fuel to seep through overnight to start the car but not enough to sustain delivery necessary for engine to stay running.

3. Bite the bullet and send the injectors out to Mr. Injector to get them checked and serviced. If they are leaking, you can get flooding.

4. Try to determine why your charging light won't go out - it could simply be the engine never gets RPM's up high enough to excite the charging system. But it could also not be providing enough to provide strong spark.

5. Validate MPS holds vacuum. Not sure a blown diaphragm will cause engine to flood in and of itself, but it could contribute.

6. Disconnect fuel line to Cold Start Valve, just to eliminate as a variable.

Problem with old fuel and FI systems is that there are lots of variables involved, either causing too much or too little fuel to be delivered. What other symptoms are you seeing that might suggest either flooding, starvation, or maybe lack of spark? If you crank the engine after it dies do you smell fuel? Do you get a spark when you crank after the engine dies?

Others will have more and probably better suggestions.

+1 with what Rob said and;

Check under the steering rack cover if you have worked on the fuel tank for kinked lines.

Static check for vacuum leak in the MPS.

One time I had a cracked diaphragm in one that mimicked these same symptoms.

One thing is for sure...you are getting spark.