History: We bought this '73 2.0 last summer. It ran ok at the time, though on cold start-up it would choke if we gave it throttle before it had a chance to warm up for a few minutes. We dropped the drivetrain in the fall to do a bunch of general cleanup on the engine and trans, including:

• replaced all fuel lines in the engine compartment
• replaced all the hoses
• cleaned electrical connectors including all engine compartment relay panel
• replaced plugs, points, rotor, and maybe dist. cap and plug wires (will need to look back at notes)
• adjusted valves
• I don't think I adjusted static timing, so that's a pretty big miss - need to do that

Today: We finally got everything back together and started the car but it was running really rich, so much so that we could barely keep it running. After we shut it off it wouldn't start again. It would spin fine, but not even a hint of firing. Things we've done:

• pulled one plug and it was wet. Cranked engine with the plug on the fan housing and got a good spark.
• verified plug wires were in the correct firing order
• disconnected the thermo switch to prevent the CSV from firing - still no start
• waited a few hours but still no start.

So first, I think it's so badly flooded that we need to wait a day and/or pull the plugs so that the cylinders dry out.

Second, I'm guessing that replacing the hoses fixed a bunch of air leaks, which some PO had compensated for by richening the mixture. I could very well be wrong, just a guess.

I've read a good amount and have a basic understanding of the D-jet system, but I'm looking for pointers about where I should start in fixing this. If I'm right about the flooding we should be able to get it started. Then what do we need to start checking to address the rich running?

Rich - from your previous thread, did you find and connect the CHT (TS2) to the proper sensor? The symptoms are pretty much textbook bad/disconnected CHT. Do you know how to verify that your CHT is good and the connection to the ECU is good?

Other options are blown MPS, fuel pressure too high, stuck fuel injector or CSV.

Sorry, I forgot to give you a shout yesterday

test the vacuum of the MPS

then the range of the CHT

both of these can fail in a very rich condition

also you may want to pull the injectors and test them... one could be leaking/open causing a very rich condition.... but usually that would only flood the offending cylinder.... where as the MPS or CHT would effect all cylinders

MPS was my first thought. See if it holds a vacuum.

Guys,
Thanks, great info.

I'd read the car won't run without the CHT sensor connected and working, so I'd measured the resistance. It was 1034 ohms between the pigtail and the negative battery terminal at 85F ambient. The engine had run for a couple of minutes within the previous hour, as well. That seems to be in the right ballpark per Brad's info, right? If there's more I need to do there let me know. I've not checked the connection from the CHT sensor to the ECU (Rob, we're confident we got the same wire plugged onto the CHT sensor that we took off some months ago. And no worries -- my evening filled up, as it turns out.)

We'll check the vacuum on the MPS per Brad's page. Might take a couple of days to get it done.

My co-owner (the car's at his house) pulled all the plugs and said all of them were wet with gas. That means it's something systemic rather than injectors. Could be the CSV, though, so that will be on the to-be-checked list.

So, MPS vacuum test and CSV leakage are the first two things to check. I'll be back as we get results.

That CHT number doesn't seem out of whack in general. Definitely need to make sure you have good continuity from the lead to the ECU - a lot of times these wires get brittle and kink and crack. The wire may look ok but still have a break.

I have a spare MPS that holds a vacuum and is tuned to 2.0 specs if you need a quick swap (also have a spare CHT if you want to try that).

You could eliminate the CSV as the cause just by pulling that fuel line and plugging the fuel rail.

Lastly, it's pretty easy to verify fuel pressure and make sure that hasn't spiked for some reason.

Otherwise, I think you are on the right track.

How's the fuel pressure? A kinked return line, or hooking up the fuel pressure regulator backwards, will result in very high fuel pressure. Which means a rich mixture.

--DD

Good point about brittle wires. It seems the FI harness is particularly prone to that on this car. I'll check the wire from the CHT sensor to the ECU. I assume I need to unplug the ECU for that. Any tricks to unplugging? The connector is pretty big and I'm concerned it's fragile.

Will check the fuel pressure and pressure regulator connections. I seem to recall reading that the fixture on the fuel rail is the easiest spot to check that.

Rob, appreciate the offer of the loaner parts. I'll let you know if or when we get to that point.

Thanks all

Getting the ECU connector off can be a small challenge. The connector and harness is a tight fit, and you need to slide that cover off after removing the screws. Once you slide the cover off, there's a plastic piece that acts as a handle that can be used to carefully remove the connector from the ECU board. Once you do it a couple of times it makes sense.

Before you do that, though, it's probably easier to remove the fuel line at the fuel rail (to test the CSV) and then check fuel pressure.

Point taken.

My buddy checked the MPS vacuum today and found: "It does not hold suction. When vacuumed to 20 " Hg it dropped to 15 in 5 seconds and continued to go down. I put hose clamps on both ends of the hose to check again--same result."

Sounds like the MPS has a terminal vacuum leak. Unless I've read everything wrong, this explains the rich running (though we'll continue to check other things).

What's the best solution for the MPS, have it repaired or try to find a good replacement? If repair, who's recommended? The MPS is part #0 280 100 043.

You can get lucky with a used MPS on the cheap from the right seller (they exist, just vacuum test it first). Or you can call on someone like Tangerine Racing who can provide you a quality refurbished unit.

Hey Rich - that MPS is not serviceable. It may not be the cause of all your problems, but that's definitely one you want to fix. Your options now are:

1. Try to find a serviceable 043. They are pretty pricey if confirmed to be working.

2. Repair this one using the Tangerine Racing kit and then get it "tuned" to 043 specs. This requires an inductance meter and a little practice, and I can help if needed.

Tangerine Racing MPS Diaphragm Repair kit: http://www.tangerineracing.com/engine.htm

Thanks again, guys. Looks like the Tangerine Racing kit is the ticket. I'll update in a couple of days.

Today's update:

Turns out the MPS leak isn't as bad as I thought. It leaks, but slow enough so that it can function.

The real culprit turned out to be the CSV. I pulled it out and as soon as I turned the key on there was a gush of fuel. I clamped the fuel line to the CSV and the car ran fine. New replacements are a little (!) pricey. Can these be rebuilt? From what I've read the CSV is only operational at or below the setpoint of the thermo switch, which is O(32F). So it's not critical for me (and, I suspect, not for most owners).

Also checked the CHT sensor again, which read 1534 ohms at 73F ambient. Set the dwell to 49 degrees, and timing was spot on at 27 degrees BTDC at 3500rpms. The fuel pressure might have been a tad off, but it's now right at 2 bar/29 psi.

Thanks a lot to Rob (BeatNavy) who went above and beyond to lend me his spare MPS for testing. And thanks to everyone who offered advice -- it was spot on.

Click to view attachment

So the CSV was the guilty party on this one. Good info.


Correct - these aren't super critical. You can run fine without it while keeping an eye out for a serviceable one that's reasonably priced. Not sure if they can be rebuilt or not.

I sent an email to the WitchHunter folks and asked about rebuilding. They said they could do their (thorough) cleaning but did not respond about rebuilding. I'd conclude from that that they're not rebuildable.

You probably don't need the CSV if you don't live in a particularly cold climate (or drive in the cold).

Yeah, thanks, got that. My personal preference is to keep it complete and correct. Not obsessively, but that's the direction I default to.