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

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.

can you keep it running with toots of starting fluid? If not it is flooding, if so, something like the head temp sensor or pressure sensor

Check dizzy FI contacts for dirt and grease.

Start the car cold. Adjust idle to about 1600rpm. Wait two minutes and see what happens. report back, please.

This is what I did this morning.

tried to check ohms on cht. I must not know how to do it properly but after wiggling the wire I did get some readings. I got 1300 ohms cold. Maybe it was 400 ohms not quite sure. The next thing was to check vacuum on the mps with the hose and without hose. I could get 15 inches of mercury on both ways and no leak down after 5 min. When I started the engine yesterday I did not have the cold start valve hooked up (the 5th injector) since I removed the hose for the fuel pressure gauge. Today I did have it hooked up. The other main thing I did was replace the mps wiring connection with another connector from a FI wiring harness.

The car started great and ran around 1300 rpm for about 2 minutes. It then started to go down in rpms. I then shot some starting fluid into the air filter box and it jump back up in rpms. I did this 3 more times do to the rpms going low and then it stayed at about 800 rpms for over 10 minutes until I turned off the car. I waited a few minutes and started it back up and it stayed at 800 rpms. I let it sit for 30 minutes and then started it up. I started to get the really low rpms going so I shot some more starting fluid in the air filter box and it held idle at 800 rpm.
At any time during this testing I could hit the throttle and it responded great.

So I think it is a lean issue going on. I will check the fuel lines for kinks. Could it be the cht? Should I check for vacuum leaks. I do need it to keep the revs up to 800 rpm without having to resort to using starting fluid.

I will post some video on how the motor is working this evening.

By the way the alternator is working fine now. Maybe it was because the engine hasn't been started in over a year and it is finally running again.

Buck

Well it certainly sounds more like a fuel starvation issue. If the car has sat for long periods of time, it may be worth inspecting and replacing all fuel lines, checking for clogged sock in tank, clogged filter, and for kinks somewhere. I'd still consider sending injectors out for servicing.

If the CHT, or wire lead from CHT to ECU, is shorted to ground (e.g., against case), it will significantly lean out the mixture. It's still worth checking it cold and hot, from sensor to ground. And inspecting the wire for shorts through wiring harness to ECU.

Normally the alternator will not actually start charging until the engine gets well above 1000 RPM.

Vaccum leak somewhere and maybe even a couple of issues.


First, the CHT depends on a ground connection to work and if no ground is there the car will not run. Over time and since it is alum to steel it oxidizes. Remove the CHT and clean the threads thoroughly reinstall and make sure the single lead that goes to the FI harness is firmly seated.

Sounds from your description that you have a fuel restriction or a vaccum leak or possibly both. Check ALL the vaccum connections visually and then try to isolate them with a Stethoscope or by spraying the connection with the starting fluid.....be careful. I prefer the former and then a visual. Pull vaccum on the dizzy dashpot as well if you have a stock dizzy. Check the AAR as well for functionality and if it is closing completely. You can bench test this by a simple 12v source and then a flashlight to spy the valve if it is closing. It's just a 12v thermister.

Check the sock in the fuel tank with a flashlight and or pull it and replace it if it appears rusted or collapsed. Then as already mentioned pull the steering rack cover underneath and inspect the fuel lines underneath the tank for kinks and or deterioration.

Rob has good points here as well. Vacuum leaks are ALWAYS worth looking for if the lines are suspect at all. D-Jet won't run right with vacuum leaks.

Remove the fuel filler cap and test.

How do I test? I have replaced the gasket on the filler cap. I also took off the cap when it was running and that was enough to lower the rpms. I have ordered a new cht and I will spend some time looking for vacuum leaks. I will probably spray carb cleaner around hoses to see if anything is affected.

The fuel lines, filler sock, and filter are all new.

Buck