D-Jet Conversion not going as planned., Car starts but will not run. Options

[slapshot]

I am converting back to D-Jet and my car will start but dies right after. It will not rev up applying throttle. I have a 1975 914 2.0. It was running great with Weber 40s prior.

The D-Jet system is from a 1974 2.0. All the parts came in visibly good condition. TPS calibrates good, AAV tested good, Thermo sensor good, air intake temp sensor good, and a new cylinder head temp sensor. The only test that I think is failing is the vacuum test on the MPS. It leaks. Video of testing the MPS.. The MPS has also been rebuilt at some point. The original part # has been removed. There's a good chance it is not calibrated for my car. I have all new vacuum hose and fuel pressure is between 28 and 30.

I don't have any tools to calibrate the MPS. Should I try turning the inner screw on the MPS to see if it helps? Or should I send it to someone to have it rebuild again and recalibrated? If the later do you have any recommendations on who to send it to?

[emerygt350]

I use a boroscope to ensure tdc, but what you did works too. Idle is set at 3400 if I remember correctly (double check that). My car really likes 28.5 but each car is different. Since we have 123s I am not certain that old way of setting idle is really necessary. I find 8ish at idle equals where I want to be all in. However, if your idle is high you are stuck doing the high rpm timing anyway.

I am not familiar with setting the curve in Bluetooth dizzys but I do know there are some suggested curves to start with for d-jet.

If you are getting a miss and your timing is good I would suspect mps tuning at that point. You probably have lean spots at particular vacuum rpm combinations. Do you have afr gauge set up? I found having a vacuum gauge and an afr in the cab allowed me to tune the mps relatively easily in the car.

Oh, and if you have bad spots in your TPS, the whole engine stops (the ECU seems to stop the injectors or something). Like a whole engine miss. It's really disturbing and only tends to happen when you are cruising (that's where the bad spot develops).

[slapshot]

I use a boroscope to ensure tdc, but what you did works too. Idle is set at 3400 if I remember correctly (double check that). My car really likes 28.5 but each car is different. Since we have 123s I am not certain that old way of setting idle is really necessary. I find 8ish at idle equals where I want to be all in. However, if your idle is high you are stuck doing the high rpm timing anyway.

Here's how I set the timing. Set TDC #1, turn the dizzy CCW til the light turns off, then turn it CW til it turns on making sure there is not slack in the rotor. I then set the dizzy on the app @ 20 degrees for all RMPs and set my timing gun to 20 degrees, start the car and turn the dizzy CCW til the timing light is in the "V". Turn timing up to 28 in the app and checked it again at 3000 RPMs. If this is wrong LMK cause it does sounds like the timing is off or maybe MPS calibration is wrong. How about the ECU knob? I've got it 5 click CCW from total CW. I'm still trying different clicks.

I am not familiar with setting the curve in Bluetooth dizzys but I do know there are some suggested curves to start with for d-jet.

See attachment for my curve. This is what worked best for my Webers.

If you are getting a miss and your timing is good I would suspect mps tuning at that point. You probably have lean spots at particular vacuum rpm combinations. Do you have afr gauge set up? I found having a vacuum gauge and an afr in the cab allowed me to tune the mps relatively easily in the car.

I found and fixed another vacuum leak going to the decel valve. I will probably get a rebuilt MPS from a repealable supplier. I don't have an AFR.

Oh, and if you have bad spots in your TPS, the whole engine stops (the ECU seems to stop the injectors or something). Like a whole engine miss. It's really disturbing and only tends to happen when you are cruising (that's where the bad spot develops).

I unplugged the TPS and went for a ride. The engine misses stopped. Before it was like you described where it seemed that the engine would dang near stopped. My body would jerk forward in my seat.

[JamesM]

That's a lot of advance at idle. Likely kicking up you idle speed.

set a flat line at 8 degrees between 500-1200 and see what happens

[emerygt350]

That's a lot of advance at idle. Likely kicking up you idle speed.

set a flat line at 8 degrees between 500-1200 and see what happens

Ahh, yes, I didn't see that. That makes me wonder if they weren't anticipating vacuum retard? That kind of advance down there would add a couple hundred to the old idle for sure. I would start adding timing around 1200 like mentioned above.

[slapshot]

That's a lot of advance at idle. Likely kicking up you idle speed.

set a flat line at 8 degrees between 500-1200 and see what happens

Ahh, yes, I didn't see that. That makes me wonder if they weren't anticipating vacuum retard? That kind of advance down there would add a couple hundred to the old idle for sure. I would start adding timing around 1200 like mentioned above.

I set it to 8 degrees up to 1200 RPMs. It did lower it to about 1000-1050RPMs after warmup.

The engine seems to miss here and there from my ear. Its not a smooth as I think it should run. I took all the plugs out and did a compression test. I didn't have time to do a leak down test on all cylinders. The compression was about 100 on all cylinders. That's what it has always been since I bought it in 11-2022. The engine has about 3000 miles since it was rebuilt by its previous owner.

Plugs 1, 2 and 4 showed lean running with 3 showing normal. I sprayed starting fluid around #3 intake. It didn't change RPMs.

[emerygt350]

That's a lot of advance at idle. Likely kicking up you idle speed.

set a flat line at 8 degrees between 500-1200 and see what happens

Ahh, yes, I didn't see that. That makes me wonder if they weren't anticipating vacuum retard? That kind of advance down there would add a couple hundred to the old idle for sure. I would start adding timing around 1200 like mentioned above.

I set it to 8 degrees up to 1200 RPMs. It did lower it to about 1000-1050RPMs after warmup.

The engine seems to miss here and there from my ear. Its not a smooth as I think it should run. I took all the plugs out and did a compression test. I didn't have time to do a leak down test on all cylinders. The compression was about 100 on all cylinders. That's what it has always been since I bought it in 11-2022. The engine has about 3000 miles since it was rebuilt by its previous owner.

Plugs 1, 2 and 4 showed lean running with 3 showing normal. I sprayed starting fluid around #3 intake. It didn't change RPMs.

I can't remember, are these new injectors? If not some fj67s are cheap and quick.