Djet running way too rich... Still! Options

[emerygt350]

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.

I believe there were no differences between the early 2.0 ECU and the 1.7. they just cheated with a spacer in the MPS and a richer head temp sensor. They cheaped out as best they could that first year of the 2.0.

[JamesM]

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.

I believe there were no differences between the early 2.0 ECU and the 1.7. they just cheated with a spacer in the MPS and a richer head temp sensor. They cheaped out as best they could that first year of the 2.0.

ECU is the same in 73 for 1.7s and 2.0s but everything else is different. MPS differences are more than just a spacer ring.

As stated:
#1 make sure all your parts are correct, should have yellow (or possibly black) injectors. 037 ECU, 049 MPS (041,042 could get you by though)(NOT 043, or 037)

#2 make sure all your parts are adjusted and tested to spec

I find the majority of rich mixture issues are due to the MPS, followed by the head temp sensor. Most other faults cause a lean condition. If you are running the 037 MPS that has a good chance of explaining why you are rich. If you are running the proper MPS but it has been previously opened that might also explain the issue as you have no idea what has been done to the diaphragm or how it has been adjusted.

There really isnt that much involved to diagnose this issue, only roadblock is verifying proper MPS operations as you pretty much need a known good one on hand even if you have an inductance meter to test one electronically. If everything else is passing basic bench tests, chances are its most likely the MPS.

[emerygt350]

My point was, he could borrow my ECU.

[JamesM]

My point was, he could borrow my ECU.

If you want to rule it out they should be the same. I generally try and disrupt that connection as little as possible and in my experience ECU is usually the last thing to fail and the few i have seen with issues fail either not firing one of the injector banks or not powering the fuel pump. Intermittent over rich flood condition, my bets are MPS or CHT.

if the CHT wire losses continuity/gains infinite resistance the systems goes puke rich to the point of stalling.

If the MPS looses vacuum intermittently it goes WOT rich. I have seen this happen with diaphragm cracks that dont always show up with bench vacuum tests.

[914_teener]

I'm with Jeff. This is a common failure mode of the MPS.

If I were you I'd have it look at. If you feel you don't have the skills just send it to Jeff.


I had this exact problem.....would hold vacuum to an extent but was as it turned out a cracked diaphragm.

BTDT.

[rjames]

The ECU is the easiest thing to test first. Move to the MPS afterwards.

[emerygt350]

The intermittent cht is an interesting idea but it seems like something that would go while driving. Jiggle test?

The sitting and losing it makes me think more on the lines of broken logic control in the ECU. Some combination of signals resulting in pig rich when it shouldn't. Mps of course is the major suspect. If you do want to try my extra ECU, just let me know. One more thing you could exclude before tackling the MPS.

[ClayPerrine]

For years the rule of thumb was "The ECU never breaks. It is the last thing you suspect or change." But 50 + years have passed, and they are starting to break from vibration and old age.

This sounds like an intermittent ECU issue to me.

[JeffBowlsby]

While the idea of swapping in 'known good' parts like the ECU is noble, I have seen some 'known good' ECUs be functionally defective in some mode even though they seem to work OK. No harm in trying the swap as a first step as it may get one closer to any issue and solution. But that process is not definitive.

I have the equipment to test the ECUs, D-Jet or LJet, but I don't do repairs. Or send it to an ECU repair shop for their analysis and any needed repair. Verify functionality of every ECU function and take the guess work out of the equation.

[emerygt350]

If cost is no issue, definitely send it out for testing. I would start with jiggling that cht wire while the car is running, that should run 0 dollars and 2 minutes time. Double check the MPS, you may catch it in a failed state. You could check the resistance as well. If neither of those turn up anything and you want to try my ECU, let me know. If that does nothing, I would say Chris's kit might be smart. If nothing else, your mps will be ready for another 50 years and tunable without disassembly.

[emerygt350]

Just a quick mention on the TPS, although I really don't think it could cause this, even in a failed state, but the car will run perfectly fine with it unplugged, so you may want to just try unplugging it and see what happens.

[ClayPerrine]

While the idea of swapping in 'known good' parts like the ECU is noble, I have seen some 'known good' ECUs be functionally defective in some mode even though they seem to work OK. No harm in trying the swap as a first step as it may get one closer to any issue and solution. But that process is not definitive.

I have the equipment to test the ECUs, D-Jet or LJet, but I don't do repairs. Or send it to an ECU repair shop for their analysis and any needed repair. Verify functionality of every ECU function and take the guess work out of the equation.

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But the downside to bench testing and ECU is that is is not subjected to engine heat and vibration when you do this. So intermittent connection issues won't show up.

If there is a break in the CHT circuit, the ECU is designed to go full rich. So a solder joint inside the ECU in the CHT circuit, broken due to vibration or heat, could cause a intermittent flooding condition.

Another could be an old wire in the CHT circuit the harness that is old and brittle. Vibration causes it to move enough to break the circuit, and it goes full rich.

Or the connector between the CHT and the harness is corroded or making a bad connection.

The last two can be resolved with a new harness. The ones Jeff makes are excellent and resolve a LOT of running issues with D-Jet, or even L-Jet. So if you have not bought one of the new harnesses, I would suggest it.

Jeff. You can send my sales commission to me via paypal. (IMG:style_emoticons/default/biggrin.gif)

[dr914@autoatlanta.com]

substitution is your friend. That is what we do here to save time and frustration. MANY also send us their components for testing on another 914

[Halfnelson]

Thanks so much for the suggestions. I’ve been through the list of part numbers and can confirm they are correct for a 73 1.7 so no parts have been mismatched previously. The MPS hasn’t previously been opened and I had hoped the 123 would mate sure the spark was good and consistent but I’ll double check this and leads (which should also have been new).

Thanks so much for the kind offer of a loan of an ecu and if I was stateside I would gladly take you up on it, but I’m in the UK. I’ll try and source ecu and mps to swap and see.

If it does come to rebuilding mps is there a specialist who can do this?

[Halfnelson]

I’m not sure if this is relevant but when it does flood, if I unplug the injectors, turn the engine over, after a few cranks it’ll fire up and run for a few seconds on the fuel already in the system, then die. If I plug in the injectors then it’ll fire up and run. However it’s flooded so badly that the oil now smells of fuel.

[ClayPerrine]

I’m not sure if this is relevant but when it does flood, if I unplug the injectors, turn the engine over, after a few cranks it’ll fire up and run for a few seconds on the fuel already in the system, then die. If I plug in the injectors then it’ll fire up and run. However it’s flooded so badly that the oil now smells of fuel.

That really sounds like the CHT is open circuiting. I would find a good CHT (not the junk aftermarket ones currently available) and replace it. It is approximately $25.00 US, so it is a cheap investment to try to fix it.

And change the oil soon.

Good luck!

[emerygt350]

Ahh, Cornwall, just noticed that.

Can you describe exactly when this is happening?
1) Do the cylinders fill while it is sitting or is this only once you try to restart the car?

2) does it run rich when it is running but not flooded?

[Halfnelson]

Although the cht has been changed and I’ve tested it a couple of times, once when running ok, once when it wouldn’t start, I have an another new one to swap in. I’m also going to test it from ecu plug 23 to see if it’s something in the wire.

Re rich running, I think the car is running too rich generally. I swapped out the plugs and they were black and sooty. I guess it could be flooding when I turn the engine off? Hadn’t thought of that. It sometimes stands for a week or two and then I go to start it and it doesn’t even try to fire, it just cranks with no attempt to fire up, not even a splutter.

When it does fire it fires first crank… like the moment I turn the key from the pump priming to the starter.

[ClayPerrine]

Although the cht has been changed and I’ve tested it a couple of times, once when running ok, once when it wouldn’t start, I have an another new one to swap in. I’m also going to test it from ecu plug 23 to see if it’s something in the wire.

Where and when did you get the CHT? The current batch of aftermarket ones are having issues....

http://www.914world.com/bbs2/index.php?showtopic=360631

Hope that helps.

[technicalninja]

What he's describing appears to be fuel fouling BEFORE he tries to start it.
Sounds like it doesn't even bark or cough for him.
He's WET!

And it's intermittent...
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Next time it doesn't start I'd pull a plug IMMEDIATELY and check for wet.
If the plug was dry enough to fire I'd verify spark next.

Does it run a vacuum referenced FP regulator?
If so, check the vacuum line for evidence of fuel
That's almost NEVER intermittent, but it doesn't take long to verify.

I'm interested in what it turns out to be.

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