Djet running way too rich... Still! Options

[Halfnelson]

Had a previous thread starting in 2022 about my 73 1.7 standard D-Jet running way too rich and flooding to the point where it wouldn't start. It's been an ongoing issue. I've had a go. 2 garages have had a go. I'm at the point where I'm beginning to lose hope.

A recap. Bought the car 2021, had a problem with intermittent flooding. So far have:
Checked MPS - holding vacuum.
Replaced CHT sensor and tested. Working when flooded.
Replaced fuel pump and tested pressure.
Replaced all vacuum hoses and tested for leaks.
Valves set and rechecked.
New 123 distributor.
New injectors.

Each time I think I've cracked it and it runs and drives - sometimes for a month or so. Then I'll go to start it and it'll flood again to the point where it contaminates the oil. I feel like I've never managed to get to the bottom of the problem. Just keep replacing parts. Thinking maybe a return line that intermittently blocks? I'm kind of at a loss.

[emerygt350]

Have you removed the cold start valve from the equation?

Does it run rich or is the flooding happening when the car is off?

[Halfnelson]

Have you removed the cold start valve from the equation?

Does it run rich or is the flooding happening when the car is off?

Yes, cold start valve has been bypassed. Car runs ok, put it away. Go to start it from cold a few days later and it just doesn't fire up. If I keep trying then it just floods the engine with petrol to the point it comes out of the exhaust.

[JeffBowlsby]

The MPS holding vacuum is not a definitive test. I've seen several MPS that hold vacuum and yet the diaphragm is fractured, sometime completely. I would open that MPS up to verify the diaphragm condition and replace the diaphragm if its torn.

[Halfnelson]

The MPS holding vacuum is not a definitive test. I've seen several MPS that hold vacuum and yet the diaphragm is fractured, sometime completely. I would open that MPS up to verify the diaphragm condition and replace the diaphragm if its torn.

Thanks Jeff, Is there a way to check without breaking the unit open? If I do I guess it would then need recalibrating?

[Halfnelson]

The MPS holding vacuum is not a definitive test. I've seen several MPS that hold vacuum and yet the diaphragm is fractured, sometime completely. I would open that MPS up to verify the diaphragm condition and replace the diaphragm if its torn.

Thanks Jeff, Is there a way to check without breaking the unit open? If I do I guess it would then need recalibrating?

Also would that present as an intermittent issue as it has had a few runs where it's seemed to be fine?

[emerygt350]

It could. Just depends on how it is cracked. I know guys have borrowed mps before. Maybe somebody could lend you the right model and you could do a quick swap to see if that is actually the problem.

[JeffBowlsby]

The MPS holding vacuum is not a definitive test. I've seen several MPS that hold vacuum and yet the diaphragm is fractured, sometime completely. I would open that MPS up to verify the diaphragm condition and replace the diaphragm if its torn.

Thanks Jeff, Is there a way to check without breaking the unit open? If I do I guess it would then need recalibrating?

A visual diaphragm check requires opening it for inspection.

If you are very careful, and use a micrometer to set the inner screws to a new diaphragm (the Chris Foley method) you may not need to calibrate it. Potentially be prepared to open it more than once to fine tune. This method an avoid needing to remove the epoxy plug and WOT stop. Its delicate work, but possible.

[JeffBowlsby]

Also would that present as an intermittent issue as it has had a few runs where it's seemed to be fine?

Thats exactly how it would behave.

[Halfnelson]

Also would that present as an intermittent issue as it has had a few runs where it's seemed to be fine?

Thats exactly how it would behave.

Thanks Jeff, I’ll have a read up on the process to see if it’s in my skill set.

[emerygt350]

If you get the rebuild kit from Chris it is super easy and inexpensive. The more difficult part is tuning it. I agree with Jeff, if you are super careful about recording where the inner, outer, and full stop is when you disassemble, you 'should' be able to put it back. If you get a cheap lcr and vacuum pump you could measure the inductance and make sure they are the same when you reassemble. No guarantees of course. The physical repair is super easy.

[emerygt350]

I wonder about the ECU... They rarely go but perhaps this is one of those moments? Do you know the number on it?

[rjames]

I wonder about the ECU... They rarely go but perhaps this is one of those moments? Do you know the number on it?

I agree with emerygt350 in suggesting the ECU. In fact I had to replace mine because it was doing the exact same thing as yours. It would drive fine for hours and then out of the blue go full rich and stall. I chased my tail for months because I bought into the 'ECUs rarely fail' myth. I had to go through 3 ECUs (including a truly NOS ECU) before finding one that worked properly.

Try and find a known good ECU to test before opening up the MPS.

[rjames]

double post

[emerygt350]

I have a known working extra 037 from my 73 2.0. I believe they are the same units the 1.7 used that year.

[StarBear]

If you get the rebuild kit from Chris it is super easy and inexpensive. The more difficult part is tuning it. I agree with Jeff, if you are super careful about recording where the inner, outer, and full stop is when you disassemble, you 'should' be able to put it back. If you get a cheap lcr and vacuum pump you could measure the inductance and make sure they are the same when you reassemble. No guarantees of course. The physical repair is super easy.

@wonkipop @Van B @L-Jet914
Hence, our L-Jets. (IMG:style_emoticons/default/beerchug.gif) Trade-off: our vacuum senisitivity for D-Jet MPS sensitivity. (IMG:style_emoticons/default/beer.gif)

[FlacaProductions]

What MPS do you currently have? I believe a 73 1.7 should be an 049.

From my notes, @emerygt350 - the 037 is for an early 73 2.0.

[914_teener]

What MPS do you currently have? I believe a 73 1.7 should be an 049.

From my notes, @emerygt350 - the 037 is for an early 73 2.0.

There you go. First task, make sure your parts are correct for the displacement.

[Ishley]

It sounds a lot like you're having ignition and spark issues. I chased a lot of issues before I realized I had a spark plug wire issue that would intermittently cause misses.... and my car would run very rich. Chasing down problems and checking plugs etc.... I would move the suspect wire... and then it would run fine... for a while. Sometimes if you're lucky... it's the simple things.

Another issue I had earlier... was the seating of the 123 Distributor. The my unit came with a spacer ring... which I added... and I found that to be a problem. Once I removed it... it seats better and is really locked in place.

Also... with the 123 Distributor.... make sure the two wires that are connected to 914 harness are making solid connections.

What are your plugs gapped to? Too small/big and you can have misfire issues... The 123 with the right coil should give you a healthy fat spark. Do you replace your plugs after a rich running cycle? They could be fouling over and over... and slight misfires will appear as rich.

Is your coil good? Do you have the correct one for the 123 distributor?

Another issue could be the Throttle position sensor. It underneath the throttle valve. There is an adjustment procedure that needs to be right. If the adjustment screws are not holding it firmly in place.... you can get weird issues. This can be replaced too.... at the very least make sure your injector harness is solidly connected to the TPS.

Do you have a fuel pressure gauge installed in the engine bay? I would recommend it and make sure you have a consistent rate of fuel. Easy install and worth knowing where your pressure is at.

The MPS rebuild could be your issue... I did mine... but in my opinion....you're are moving into a complex area with this... and the tuning afterwards can be complicated and is really best done with a Wideband O2 sensor installed in your exhaust and an Air Fuel Ratio Gauge that is wired to a dash gauge for monitoring. I would make sure everything else is working right first before I jumped into this.

Check and recheck all the easy stuff with your Ignition system. Your clearly getting fuel.

[FlacaProductions]

Agreed on MPS tuning - that's a whole different game. I was thinking that maybe a quick swap to another unit might help rule it in/out.