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Posted by: Halfnelson Jul 23 2021, 06:51 AM

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

Posted by: rfinegan Jul 23 2021, 07:35 AM

Try adjusting the Idle mixture knob on the ECU. I think this is for setting via CO meter reading but will get you in the ball park click or two at a time and you idle will change( speed/hunting) The base line setting is bout 22 clicks or so..if I remember correctly

Posted by: jrmdir Jul 23 2021, 08:19 AM

Welcome to the D-Jet rich mixture madness. I'm going through the same issue with my '73 1.7. Only to my limited knowledge about this car, I don't think it had a lean history that was compensated for. So far I've found a number of reasons for running rich, including disintegrated MPS diaphragm, high fuel pressure and (possibly) leaking cold start injector. Next I'm going to check the cylinder head temp sensor.

There are a number of great threads on this. Here's one that has tons of info:
https://members.rennlist.com/pbanders/DJetParts.htm (easier to search Google than here - and you most ofthen still get to 914World threads as a result.)

If your car was running lean over time and you're looking for ways that the PO might have tried to enrichen it, check out the wiring from the cylinder head temp sensor to the ECU. On our 1.7's there should be no in-line resistor, which, as I understand it was added by the factory for either the 1.8s or 2.0s - to "fool" the ECU into delivering more fuel without reprogramming the 1.7 ECU. There is some mention of 1.7 owners adding this themselves thinking it would add power (not!)

Good luck - report back if/when you get this resolved, it may be something I've yet to find in my quest.

Ron

Posted by: dr914@autoatlanta.com Jul 23 2021, 08:46 AM

SUPER rich could be blocked fuel return, bad valve, or defective head temp sensor. REAL rich could be pad pressure sensor

Posted by: ctc911ctc Jul 23 2021, 09:43 AM

That is a beautiful car!

Posted by: Olympic 914 Jul 23 2021, 11:11 AM

Pull a vacuum on your MPS
Make sure your diaphragm isn't cracked

Posted by: rjames Jul 23 2021, 12:02 PM

See if it's been opened before, too. If it holds vacuum but has been opened up (rivets replaced with screws), it may need calibrating for your engine.
Also make sure the ECU and MPS match & are correct models for your car.

Posted by: Dave_Darling Jul 24 2021, 01:05 AM

Step 1: Check the ignition system. Yes, seriously. Make sure the timing and dwell are in spec, and that you're getting a nice fat white happy spark.

It's amazing how many "FI problems" (and "carb problems"!) are actually caused by ignition system issues.

Step 2: Check the valve adjustments. Valves that are out of whack can cause odd-seeming problems. For instance, an intake valve that doesn't close all the way can cause a very rich mixture. (Don't ask how I know that.)

Then move on to testing the parts of the FI system.

--DD

Posted by: Halfnelson Jul 24 2021, 07:44 AM

Many thanks for all the suggestions - plenty to work our way through on Monday and I'll report back. Had a read through other similar threads - one that said CHT sensors don't often go bad - is it more likely a case of bad connections?

Posted by: jrmdir Jul 24 2021, 10:05 AM

Hi Halfnelson: Hope this doesn't amount to hijacking your thread but since we seem to be in the same boat maybe my experience so far is of interest. (I had no knowledge in this area a month ago so take my advice with a grain of salt.) But the huge body of work on this forum has been very educational!

As advised above, I did start with valves and ignition. PO had replaced all spark related parts and I reset the dwell and timing to spec. I also installed a fuel pressure gauge and lowered it to just under 30 PSI. Next I pulled the throttle body and checked cleaned and adjusted the TPS contact tracks.

Next up, the MPS and sure enough, mine held no vacuum at all. So I replaced the perished diaphragm using TR's kit. Successfully but still in question (see below)

Next I removed and tested the Aux Air Valve - it worked but I decided to leave it off and plug the manifold outlet. Ditto with the Decel Valve. Unlike more modern FI systems with mass air flow meters, a downstream vacuum leak on d-Jet shouldn't cause a lean condition. The MPS will note the pressure drop and add more fuel. BUT, this should be in proportion to the "extra" air so it shouldn't be richer. I think:) Anyway, based on what I read it was OK to disconnect these for a while to reduce the number of variables. I may hook them up again later.

Then, to eliminate doubt re: defective Thermo switch or leaking cold start injector, I got a 3' length of fuel hose and completely bypassed the injector.

Finally, (and I should have done this earlier,) I pulled the ECU connector and performed all of the circuit tests described in the rennlist bpanders link above. Was hoping for a smoking gun test result but everything checked out. (Although I'm still questioning CHT reading of 2,250 ohms @ 78 degrees F. Seems a bit high to me.

So now I'm down to one question that perhaps the group here can help us with:

In rebuilding the MPS, reestablishing the height of the center plunger involves an imprecise measurement. So this could be the issue. There is mention of uncovering the adjustment screw and then calibrating the MPS. But Mr Anders says this requires special equipment. It seems like this adjustment could easily impact the rich/lean situation. Has anyone tackled this calibration without test equipment?

Again, sorry if this is a hijack but hope our shared experience helps someone now or in the future.

Good luck!

Ron

Posted by: rjames Jul 24 2021, 10:19 AM

Calibrating the MPS correctly requires being able to know what the AFR is at idle, part load and WOT.
It could be said that fully dialing it in requires an inductance meter, but it isn’t necessary to get the car running well.

Fix/replace faulty FI components, don’t just bypass them. They are there for a reason. For example, removing the decel valve will shorten the life of the MPS diaphragm.

Posted by: brant Jul 24 2021, 01:09 PM

Posted by: jrmdir Jul 24 2021, 02:14 PM

Thanks for the feedback. Just to be clear, I'm in no way advocating permanently removing components. This car is still in the ER as far as drivability so I wanted to rule out things before buying parts. My decel valve is toast - stuck shut - so "bypassing" it was more because I took it off to get to the MPS and didn't feel the need to bolt it back on just for appearances. Easier to plug the line. I will spring for a new one once I can get this car on the road long enough to actually have a deceleration event

I removed the AAR to test it and found that the unobtainable (AFAIK) rubber "Y" pipe between the manifold and AAR was also toast. Again, easier to cap the manifold nipple until I can find a way to re-plumb. Probably run a straight hose from manifold to AAR and find another vacuum source for the small hose that is supposed to operate the devel valve.

Finally, chasing a rich mixture it's advised to make sure the cold start valve isn't leaking or being opened when not needed. I.E. colder than 40 degrees while starting. So, to me, bypassing in this case was a no brainer. Since there has been no improvement I'll reconnect it at some point.

Thanks once more for the great knowledge base that makes up this forum. Without support like this I'd probably have already given up.

Ron

Posted by: Dave_Darling Jul 24 2021, 07:20 PM

Also worth checking the fuel pressure. Should be right about 29 PSI while the fuel pump is running. Higher means a richer mixture, as more fuel is being pushed through the injector valve per millisecond that the valve is open.

--DD

Posted by: r_towle Jul 24 2021, 09:39 PM

Clean the inner parts in the distributor.
The advance plates stick in the wrong position after 40+ years.
Remove, clean, re-grease.
Costs 0.05 cents

Posted by: Halfnelson Aug 11 2021, 08:45 AM

Thanks for everyone's feedback on this. I've finally got an update on things. After a couple of false dawns I'm hoping we've nailed the issue. Total work included:
Checking MPS - OK
New fuel lines, filter and fuel pump
Sorting the ignition as the spark was weak - so new coil etc
Going through all wiring and fuses
New CHT sender
New plugs for injectors

My guess is multiple small faults adding up to a lot of head scratching when we thought the problem was solved... only for it not to be.

Done a few local trips including a car show at the weekend. Fingers crossed now for a longer test drive.

Posted by: Rand Aug 11 2021, 06:30 PM

I would have bet MPS. How was it tested?

A simple test: With car running, pull the hose off the MPS (at the mps end) and tell us what happens to the RPMs.
(Actually, that's a good checkup for all of us DJet users to do every couple years.)

Posted by: Halfnelson Aug 20 2021, 07:53 AM

OK - so not sorted after all.

After about half a dozen test drives with stops, restarts, refuelling etc went down the road to today, car stalled at junction and refused to restart. Strong petrol smell. Disconnected injectors and it would at least try and start but still lots of fuel still coming out of the exhaust so recovered home.

What's adding all the excess fuel with the injectors disconnected? Could the cold start injector be faulty?

Posted by: Bartlett 914 Aug 20 2021, 07:58 AM

I would suspect an intermittent CHT or simply a poor connection with it

Posted by: Halfnelson Aug 20 2021, 09:34 AM

Thanks Mark - have replaced the CHT but will test that again and also check the connection.

Posted by: rjames Aug 20 2021, 09:35 AM

I had a similar situation and it turned out to be a bad ECU. After 15-30 minutes of driving, the car would run super rich.

I still question your rebuilt MPS. You said you tested it, but just verifying that it holds vacuum isn't enough. You need the tools to adjust it (tangerine racing) and an AFR meter to dial it in. If the rich running your experiencing is intermittent, than you can probably check the MPS off of your list. But if it's always rich and swapping the ECU out doesn't change anything, then I suspect your MPS needs calibrating.

@http://www.914world.com/bbs2/index.php?showuser=25544 At the very least you need the tools to adjust the MPS and and an AFR meter to set the MPS correctly.

Posted by: Halfnelson Aug 20 2021, 09:54 AM

Thanks Robert - the MPS hasn't been rebuilt, still the original and holds vacuum - or at least was. Will double back and recheck.

How did you diagnose that it was the ECU? There seem to so many potential culprits and I had hoped these were already ticked off the list.

Posted by: rjames Aug 20 2021, 10:15 AM

My mistake- I thought your MPS had been opened up.
I figured out it my ECU was bad after testing all of my other components and eventually swapping it with a known good ECU. See if you can find someone who will let you borrow theirs. You're lucky in that there seems to be a ton of used 1.7 ECUs for sale at any given time. 2.0 ECUs can be hard to find.

Posted by: Rand Aug 20 2021, 12:58 PM

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

Posted by: rjames Aug 20 2021, 02:23 PM

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.

Posted by: emerygt350 Aug 20 2021, 04:44 PM

Just out of curiosity, have you checked which injectors are in there? Mine came with 1 1.7 injector and on a 2.0 that means one really lean cylinder. Some fool might have put 2.0 injectors in yours.

Posted by: Halfnelson Aug 23 2021, 07:57 AM

OK - I'd never even considered the injectors could be wrong but...

Posted by: Halfnelson Aug 23 2021, 08:02 AM

Lots of questions spring to mind like how it was even running with the wrong injectors in?

The number seems to end 1120 07 (although I couldn't quite see) - which doesn't look like 2 litre green injectors?

Next step is where can I find either the correct yellow injectors or a new set of compatible alternatives?

Posted by: emerygt350 Aug 23 2021, 06:19 PM

I have 1... And it is yellow.


I bought those new injectors, Standard motor products. The guy that rebuilds injectors tested them and found them to be quality. Not sure what the 1.7 version is labeled as. Fj67 is the 2.0

Posted by: emerygt350 Aug 23 2021, 06:27 PM

The left side is the 2.0

Posted by: steuspeed Aug 23 2021, 10:34 PM

Wrong injectors.. amazing! I bought a set of Standard Motor Products injectors for my 2.0 Outlaw and they sure look nice. Get them if you can't find OEM yellow injectors. RockAuto had the best price I could find.

Posted by: ChrisFoley Aug 24 2021, 09:52 AM

Those look like 1.8L injectors, for L-Jet. Someone had to mess with the wiring harness to use those.

Posted by: emerygt350 Aug 24 2021, 11:23 AM

Wow, the plot thickens.

Posted by: Rand Aug 24 2021, 09:10 PM

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!

Posted by: rjames Aug 24 2021, 09:48 PM

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!

Posted by: Rand Aug 24 2021, 09:52 PM

We've all gotten things wrong. My biggest point, is quick troubleshooting. I've seen people spend hours chasing rabbit trails that could have been ruled out in seconds! It hurts every time.

PS: Checking out your music

Posted by: Halfnelson Aug 25 2021, 09:37 AM

My guess is not 1.8 as they are more of a blue / green IIRC but also the whole shape of the injector plug looks different to the 2.0 and 1.7 injector plugs. Could be someone try to find a suitable alternative or ordered the wrong part? The FJ67's etc aren't available in Europe.

Posted by: emerygt350 Aug 25 2021, 10:09 AM

The one you are looking for is the fj114. 59 dollars on Amazon.

Posted by: Halfnelson Sep 6 2022, 10:10 AM

I'm resurrecting this thread if that's ok so hopefully it'll add some context / back story.

The gist is my 73 1.7 on standard Djet would run ok for a short period of time - then flood. It was an intermittent problem that got so bad petrol is now actually spewing out of the exhaust.

After discovering I had the wrong injectors fitted (way too much fuel being delivered) I had a set of new FJ114. I hoped this would crack it - but after starting and ticking over for a short while... it started to run rough, smoke cough and die. Turning the car over then results in petrol spewing out of the exhaust again.

Short recap of work done includes: all new vacuum lines, CHT sensor replaced, MPS tested, fuel return tested, cold start injector disconnected and bypassed, new fuel pump fitted and fuel pressure tested, new coil fitted.

The question is - a year down the line - what next? And what could be causing such a catastrophic over-fueling - it's not just running rich - there is fuel pissing out

Posted by: JeffBowlsby Sep 6 2022, 10:30 AM

Have you checked your CSV for leakage?

Posted by: rjames Sep 6 2022, 11:19 AM

I spent well over a year troubleshooting a similar issue. The car would run fine for a while, and then out of nowhere, go rich and then stall. Right before I figured out what it was, the amount of time it would run well before stalling decreased.

It turned out to be a bad ECU- the things that rarely fail supposedly. I think it was a heat issue. As the engine bay warmed up something in the ECU would fail and cause an overly rich condition. Figuring it out wasn't easy. I had two other ECUs that I used for testing and both caused the car to flood- including a NOS unit that had never been installed. A 3rd ECU I tried out of desperation fixed the issue, and have had no issues since installing it 2 years ago.

It's an easy thing to rule out if you have another known good ECU you can swap in for testing.

Posted by: JamesM Sep 6 2022, 11:52 AM

You mentioned before that you had disconnected the injectors and were still getting fuel, the cold start injector is the only other source for fuel.

Posted by: Halfnelson Sep 6 2022, 12:57 PM

Thanks for the ideas - yes, we have bypassed the cold start injector.

Posted by: mgphoto Sep 6 2022, 01:00 PM

No it won’t, going on ten years and 40k miles, deaccl valve is a stop gap pollution device pretty much ruins engine braking.

Posted by: emerygt350 Sep 6 2022, 01:01 PM

Yeah, check that cold start valve.

Any chance you can borrow another ECU? (another quick and easy check if it is available).

I have to suspect soemthing catastrophic with something like the csv. Even max rich by the ECU wouldn't cause what you are experiencing. I seriously doubt your brand new injectors are stuck open. as stated above... it's the only other thing bringing fuel. You could block the csv fuel line (super easy) and give it a go.


Not even sure the trigger points or malfunctioning 123dizzy could cause this either.

Posted by: Halfnelson Sep 6 2022, 01:07 PM

The CSV should have been done - but I'll double check as that makes sense. Also, will try and borrow an ECU.

Posted by: mgphoto Sep 6 2022, 01:10 PM

Pull one side of the fuel rail off while the engine is running, note the amount of spray, at idle it should be minimal, if the injectors are just open the ECU is at fault.

Posted by: emerygt350 Sep 6 2022, 01:38 PM

You mean the injectors right? Make sure you put them In coffee cans too. Double check that csv first since it is easy. Have you checked your fuel pressure recently? On the rails?

Posted by: JeffBowlsby Sep 6 2022, 01:53 PM

Two other things to check:

TS2 - cyl head temp sensor. It can fail to dump enough fuel not allowing it to start, perhaps yours is intermittently failing.

MPS - check its ability to hold vacuum. Does it hold up to 18 inHG steady, or is there a vacuum leak? When the diaphragm fractures it fails rich. No vacuum or a rapid vacuum loss will be very rich.

Posted by: rjames Sep 6 2022, 02:24 PM

@http://www.914world.com/bbs2/index.php?showuser=25740 Not true. What he is experiencing is exactly what the bad ECUs I had did, and all were the correct model for my car.

Posted by: emerygt350 Sep 6 2022, 02:40 PM

Gas pouring out of the exhaust?

And speaking of that, make sure you are changing your oil.

Posted by: rjames Sep 6 2022, 03:00 PM

I didn't let it get that far, but it contaminated the oil bad enough pretty quickly.

Posted by: emerygt350 Sep 6 2022, 07:00 PM

I guess there is no reason it couldn't go outside of normal parameters if something fries in the ecu...

Posted by: Lockwodo Sep 7 2022, 04:38 PM

You mentioned checking the CSV "bypass" but I'm not seeing in this string if that was done. If the pressurized fuel line is still connected to the cold start valve and that valve is leaking, that could be the source of the fuel leak into the engine as others have pointed out. You could confirm by pulling the valve out of the manifold and pressurizing the fuel line.

Posted by: emerygt350 Sep 7 2022, 05:30 PM

And with the ignition on as well.

Posted by: 914_teener Sep 7 2022, 07:43 PM

Time Out.

There is a difference between testing and speculation.
Testing is methodical (there's a method) and speculation guessing albeit it MAYBE somewhat educated guessing.

FIRST IS TO Confirm the right parts to the engine. Has this been done?

Let the OP provide results.....I think there is a lot of speculation that throwing partsat the situation is testing and not confirming that a component or system is good. A system is component driven. You need the right components for a 1.7.
First off...is it in fact a 1.7? How do you know that it is? Let’s ASSUME your cam is the stock cam and not another grind. Has the engine ever been rebuilt to your knowledge? You can measure valve lift and degree the cam for duration to be sure.
Make sure all the mechanical systems are within spec. This includes valve function and piston compression specs FIRST. Any failure or out of spec situation here means that you haven't assured that the engine vacuum system mechanically is functional or functioning properly. If not, D-jet won't function properly if at all. You don't have to have the engine running to do this.
Air-Fuel -Spark
Vaccum
If you’ve checked your valves and compression and this is ok then the next thing to check is the actual system for vacuum leaks...everywhere the is vacuum. You mention that you did this, but a smoke test under vacuum is a very definitive test. Instead it reads like you just visually tested the components and not the intake system like the plenum and all the parts installed. This Do a smoke test to make sure there isn't a crack there or anywhere else. There are threads here on how to do it….safely.

As far as the MPS is concerned...I had an instance where the Diaphragm was cracked and only intermittently would leak which did the same thing...dumped fuel like crazy into the manifold and cylinder to the point where the fuel vapor coming out the exhaust like a white fog and gas dripping out of the tip.

So when you do a test on the MPS you should pull it to about 12 HG and test it for leak down overnight. Make SURE you test it for leak down and not just for a minute or two. Any leak down could mean it is only slightly cracked or it is leaking somewhere. You also did not mention if you testing it electrically. All of this procedure is listed on Brad (Paul) Anders website with addition of all the component testing for the D-jet system. We’ll assume you’ve done this and all the D-jet components test good.

Fuel:
It doesn’t appear that you have a fuel delivery issue except from your post, it appear you have a mismatched injectors….maybe. If you’ve had check for components for the 1.7 D-jet you probably would have picked this up already.
Testing for injectors is best left to hydraulic bench and electrical testing for pintel function and is best left to a house that specializes doing it. Its well worth the money and aggravation. Forget baby jars or coffee cans as a test. They will check mostly for flow rate…that it..not worth your time.
Fuel pressure test is essential and easy to do at the test point at the driver side fuel rail. Check also the fuel tank sock and return lines. and all fuel connections for safety, correct type and for cracks while your’re there. Make sure the fuel pressure is to spec and you don’t need the car running to do this.
Testing for a bad CSV is simple. Just bypass the fuel line for it. There is a gasket there…however youv’e done the smoke test already so don’t worry about it. You found no leaks…right?
Spark:

Again we’ll assume you have done a component checks and testing and if good the only check are for there installed function. These are mostly electrical connections such as the ground contacts and wires for the CHT, wires and contact to the head. The test for these are resistance to ground and if either the head thread is dirty and the ground lead to the ECU is not cracked or grounded properly the engine will not run. Period.
The CHT is a thermistor so it is resister to ground but it must ground to provide a signal to the ECU. The full test is to ground the lead and see if the engine will run. Again…if you have tested the harness you know either the CHT is bad or the ECU and if you tested the CHT and the ground points then it HAS to be the ECU. I hate the threads about bad CHT when very rarely do they actually fail.
As already mentioned the dizzy is a big issue, but you should have already confirmed that it is the right dizzy for that displacement and functions properly including the advance and retard vaccum can.

When I fist bought my 73 914 (now almost 20 years ago) I removed the entire top end including all the D-jet parts. I checked them all, cleaned them, and serviced and tested the injectors. I replaced everything that didn’t test or check to spec. It ran flawlessly. In that time I had three failures. The MPS, the ECU and then the dizzy. I replaced the dizzy with a 123 unit and it ran better than it ever did before.

If you do all of the above and mostly in that order your car will be well sorted and provide many years of enjoyment as it did for me. Sometimes I regret selling it but looking back now…years of fun and friends.

Good luck and wrenching.

Posted by: Halfnelson Sep 18 2022, 11:42 AM

Finally got a chance to get to the 914 so can confirm...

Engine is original EB 1.7 unit.
ECU is a 0280000037
MPS is 0280100049

I did a vacuum test on the MPS and it is holding vacuum. Was tested up to 20inHg and left for an hour and was at 18inHg which I assume is OK?

One of the things I did notice was that the ECU as very loose. At some point the garage hadn't re-attached it properly and it was rubbing on the wiring loom which in turn was resting on the cooling shroud. It had rubbed through some off the outer protective sleeve but the wires appeared intact - however some had a weird brown discolouration on them... (Pic attached) perhaps like they had been getting hot? Anyone seen this before?

Cheers

Chris

Posted by: emerygt350 Sep 18 2022, 05:09 PM

Possibly but they look ok.