Help - Djet running way too rich Options

[Halfnelson]

Help - my new to me 1973 1.7 Djet came running really sweet, but almost immediately developed the 'hunting tick-over' of lean running / air leak. We replaced all the vacuum pipes, found one of the inlet gaskets had a very slight leak. Seems somewhere along the line things have been tweaked to compensate for the leaks so that now they're cured, the car is running super rich. Having had a L-jet for years the Djet is new to me so any advice on where to start first would be much appreciated. Thanks Chris

[Rand]

What was the difference in idle when you pulled the hose off at the MPS? Just give me that.

[rjames]

What was the difference in idle when you pulled the hose off at the MPS? Just give me that.

Would it even run? IIRC, pulling the hose off would just cause it to go super lean, so if it ran I guess it would tell you that something else in the system is causing an uber rich condition, but it wouldn't rule out the MPS as a contributor.
If it doesn't run, what would that tell us?

If it's an intermittent issue or doesn't happen until the car warms up a little (I'm still not clear if that is the case here) then it's probably not the MPS. I haven't run across intermittent issues, or issues that happen only when the engine is cold or only when warm that ended up being the MPS. Seems like when it's the MPS that's the problem, the symptoms there all the time.

[Rand]

What was the difference in idle when you pulled the hose off at the MPS? Just give me that.

Would it even run? IIRC, pulling the hose off would just cause it to go super lean, so if it ran I guess it would tell you that something else in the system is causing an uber rich condition, but it wouldn't rule out the MPS as a contributor.
If it doesn't run, what would that tell us?

If it's an intermittent issue or doesn't happen until the car warms up a little (I'm still not clear if that is the case here) then it's probably not the MPS. I haven't run across intermittent issues, or issues that happen only when the engine is cold or only when warm that ended up being the MPS. Seems like when it's the MPS that's the problem, the symptoms there all the time.

Pulling the MPS hose does NOT cause lean, it causes full RICH. True, it should not run, it should immediately choke and die. I wasn't necessarily suggesting the MPS as the problem, but ANY time Djet runs rich, check the MPS because a bad diaphragm or leaky hose/connection is a common cause of running rich! I can't think of another test that takes two seconds that tells so much about fuel mixture. IF it didn't change, it would have absolutely been MPS (or not) in 2 seconds! Always do the quick tests to quickly rule things out in early troubleshooting!

[rjames]

What was the difference in idle when you pulled the hose off at the MPS? Just give me that.

Would it even run? IIRC, pulling the hose off would just cause it to go super lean, so if it ran I guess it would tell you that something else in the system is causing an uber rich condition, but it wouldn't rule out the MPS as a contributor.
If it doesn't run, what would that tell us?

If it's an intermittent issue or doesn't happen until the car warms up a little (I'm still not clear if that is the case here) then it's probably not the MPS. I haven't run across intermittent issues, or issues that happen only when the engine is cold or only when warm that ended up being the MPS. Seems like when it's the MPS that's the problem, the symptoms there all the time.

Pulling the MPS hose does NOT cause lean, it causes full RICH. True, it should not run, it should immediately choke and die. I wasn't necessarily suggesting the MPS as the problem, but ANY time Djet runs rich, check the MPS because it's so easy (and a bad diaphragm will absolutely cause rich running). I can't think of another test that takes two seconds that tells so much about fuel mixture. IF it didn't change, it would have absolutely been MPS in 2 seconds! Always do the quick tests to quickly rule things out in early troubleshooting!

Yup- I had it backwards. After all the DJet and MPS troubleshooting I’ve done in the last two years I don’t know how I got that one wrong! (IMG:style_emoticons/default/unsure.gif)