@L-Jet914
@Van B
@clayperrine
Having an issue at initial startup idle - runs rough and low rpm. Ok after sitting about 6 minutes or driving about half a block. Got some data:
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+ 1.8; stock FI
+ For test, I let it run in driveway until normal idle reached by itself - about 6 min. Didn’t rev throttle.
+ Normally settles in after driving just half a block or so. Otherwise, runs great!
+ If I reset the idle screw to get a good rpm at the start, then I end up with a final idle of 1400+ rpm.
+ Vacuum lines all secure and tight.

Questions for group-think is:
1. AAR? (Bench tests ok, though old so opens/closes about 80% in each direction)
2. CHT? (Haven’t yet checked resistance)
3. Adjust idle TB air screw to get 950+ rpm at start, then counter adjust AFM to lean static A/F and counter that at idle by richen AFM idle screw A/F in hopes to reduce final idle rpm (too much “beating around the idle bush?”)?
4. Just Old & tired? (Not unlike me; tough to get started but once up and moving get along just fine.)

Other option is to just leave well enough alone and get it on the road half a block and keep going.

congratulatons!

you have suceeded in duplicating how mine has been for 4 years since its reactivation.


very close to exactly the same thing. a weak start.
but it runs and keeps itself running and finally gets to a steady idle.
takes about 4-5 minutes.
but i never let it do it most of the time because its not great to cold start that way.
so most of the time i start it with its backside sticking out the garage door and the engine lid up and apply a bit of throttle directly to the TB to hold it at about 1400k for about 2 minutes and then let it do its thing. get the oil up and circulating.

my bet is on #1. as @Van B has already sternly warned in years previous.
he seemed to solve his with attention to a "hot rodded" AAV from a beemer.
pretty close match. looks the same as our AAV. seems to have the right amount of opening.

although in your case its interesting that it did not do it with the old AFM.
?

i checked my CHT back four years ago when i recommissioned and it seemed to be functioning. so i don't think its that in my case, and probably not in yours.

it would be tempting to think its #4.

i do recall reading some posts about weak cold starts on L jets a few years back.
probably on the samba or shop talk whatever.
seems the old vw L jets do have a reputation for it.
not an uncommon problem.

i'm not presently fussing mine as its a bit like yours.
seems absolutely fine once she is warm and happy with itself and has shaken the chill out of its bones.

one thing i have noticed is its mighty rich on start up.
esp now in winter. you can really see it blowing the black fuel smoke out the exhaust for the first minute or so. but its quickly gone. but it sure is rich on the cold weather start up to begin with. its not like that in summer. so i can say for sure its reacting to cold weather. whether its reacting exactly as it was factory fresh half a century ago who can say. could have something to do with the weak start. a lot of fuel. and not enough air.

Tested CHT. 1975 ohms at 78F. Pretty much spot on, so not the CHT.
Will do an AAR bypass and see what that does. Depending on result may get that AAR that Van suggested back in May 2022.
Yes, odd that it didn’t do this with the old AFM.

Would be interesting to see if that higher flow AAR would be the ticket. A 2056 is probably gonna need more air on startup, I don’t know if it would make enough difference.

I’d almost lean towards a hand throttle like the sixes had, substituting for what my foot does...

having slept on that remark i made - well,
we know your AFM temp sensor was kaput on previous.
and it actually didn't run well when hot and humid above 70F.
and presumably it actually probably wasn't sending a correct signal below 70F either?
but somehow the engine defaulted or the ECU did and you had some sort of flukey set up cold that was sweet running off the CHT.

i think now you have something that is close to factory and correct.
and lo and behold its not getting enough air for the fuel its sending in cold with the correct temp sensor inputs from both sensors.

its pretty much the same as mine.
and if i recall correctly pretty much the same as the symptoms van could not make himself ignore.

thinking about it i am pretty sure its the AAV, pretty much what i think is the aged villain with mine as well.

i think i once reported i got a freak fast start out of mine last year. it was a super cold day down here when it did it. at least super cold for australia. my theory is that the AAV despite being cleaned and serviced and checked has in fact got a corrosion ridge in it that stops if from fully opening when it stone cold. the little turning disc i think sticks at a point it formed during its 15 year lay off. i think what happened on the suoer cold day is that the coil inside super shrunk and it pulled itself open past its usual resting point.
and then......did a factory spec style cold start. its only happened once!
the rest of the time it does what you describe yours doing. i think the problem is the new AFM with its functional temp sensor is signalling the cold start enrichment backing up the CHT so the ECU is giving it the juice, but the AAV is not giving it the air.
so its basically kind of on the verge of flooding.

next time you cold start it - do it with the engine lid open. give it a tiny bit of throttle while standing on the side of the car and look at whats coming out the tailpipe for the first half minute or so. if you see visible black smoke then its rich like its supposed to be at cold start but inadequate air. by giving it revs to about 1400-1500 you will see the smoke clearly as the revs push it out of the engine.

@StarBear

looking carefully at those A/F read outs you posted.
yes thats exactly mine.
and at about the same time interval. revs and all.
except i am just guessing my A/F ratio. but i know it the old school way.
its got black smoke for that first 30 seconds to a minute.
lots of fuel. not enough air.
but the revs reported match mine to a T.


it will be the AAV.
now that you are getting proper enrichment for a fast warm up.
needs that air to match the fuel.

Thanks for the vote of confidence @wonkipop

@StarBear I found the bypass to be useless because it just flowed ALL the air and sent the idle to the moon!

The thing about these aux air valves is that they are simple mechanical devices. So function degrades vs outright failure.

Update:
Spent a lot of time on #3 - got things leaned out nicely yet countered the AFM idle screw to keep the same 13.3 A/F. Same results. So looking more like the AAV. Out of curiosity, took a hair drier and blew cold air into intake horn to simulate more AAV (or super cheap turbo!). Didn’t work; no change.

BTW, the dwell is within spec but at the edge at 50degrees; could being at the edge of 47+-3 degrees make enough difference? Again, runs and drives fine after warm up. Same results with warm start.

No black or sooty look or smell when hand revving the throttle to 3000 rpm.

Thinking of ordering that bmw unit Van has suggested.

of course its your summer.
and its winter here. mine only tends to blow the black visible smoke on a cold start down here in winter. but not in summer. so i guess you might not get any since its summer for you.

tells me my temp sensors are working at least.
its gone after 30 seconds or so.
its all that juice the cold start valve threw in as well as a bit of extra enrichment.
its actually damn frosty down here at the moment. unusually so.
but "heat wave" by your white winter standards.

at least its not humid in summer here. dry as a dead dingo's d__k in this neck of antarctica.

thats what i do.
poke the cars arse out the garage and just stand there with my hand on the TB with an eye on the tacho and just hold it at 1400 for a minute or two.
then i let it idle on its own.
during which i cast a paranoid eye over the fuel lines looking for leaks.
the joys of a 914 and the blazing fire in the back of the imagination.

after 5 minutes i then depart on whatever mission i am on with the car.
if i had a hand throttle like a six i could wander off and dust the shelves or something.

....but then the car might burn down.

Ok, thought I’d throw some stuff in this thread for kicks…

@wonkipop

First off, if you still have those factory fuel lines, do your peace of mind a favor and replace them with the stainless versions; while the nylon sections in the tunnel on my car were ok, back in the engine compartment they were quite brittle and I actually broke one intentionally when replacing them so see how much effort was needed to do so. Not a whole lot. I got the stainless lines from Tangerine ten or eleven years ago when I changed my engine after it blew at one of Chris’s rallies. @ejm Ed was there (isn’t he everywhere??) Very easy with the engine out but I understand it’s doable with it in.

@starbear

You say you think your AAR is only functioning at about 80%. That could be a difference maker on a 1.8, maybe see if you can beg/borrow/buy a known functional unit from the classifieds? I’d be willing to send you mine as an experiment over the winter after driving season if that helps. Have you tried soaking/working the unit to get it to fully open and close? Apologies if you have, I may have missed it if’n you did.

Another thing I saw was that the AAR housing can be rotated slightly to allow a little more opening, I did that but unfortunately I didn’t notice any difference.

@Van B

Do you plan on acquiring one of those fancy BMW AAR’s? Some of us are sitting on the edge of our seats with bated breath and all like that Would be most interesting to see your results if’n you do…

Lastly, if you’ve all considered a 123 at all, I know it’s a pricey decision, but it made a huge difference in how my engine runs. I was really on the fence about it as it as a substantial $$ investment for me but I couldn’t be happier with it. No, I have no affiliation…


I get the desire to work this out, it’s really satisfying to have the car run as it should. I remember when I got the car with it’s original Djet, I could stick my hand through the window and start it, it would idle at about 1200rpm for about a minute and then drop down to normal idle. Was a beautiful thing


@wonkipop One last thing, that’s a pretty funny description of the humidity situation there’s an Aussie down the street I may have to throw that out to…

@Porschef
Yep; bench testing my spare as we chat.
In freezer about 20 minutes; seems fully to 80% open. Rechecking.
Room temp at 74F; about half (?) open
On 12V converter; fully closed in less than 3 minutes.
Will swap it out later today and report.

BTW, Van did install that larger BMW AAR and reported it worked great. Thread back in March 2022 followed by event PMs to confirm unit and source. Also a slightly smaller one about our current size for the more cost-conscious.

@ejm
Ed; any wisdom you can add to this LJet idle issue?
Great to see you again at the Gathering. Glad you could make it!

Up until 2020, when Betty's car got hit, I was looking at making a computer controlled idle air setup for the L-Jet on her car. It would replace the decel valve and would read the RPM from the negative side of the coil, and use a raspberry PI and an stepper IAC to maintain a 1K idle at all times. So if the RPM dropped, it would open more. If it got too high, it would close. I would also have to tap the throttle switch on the throttle body to tell it to hold position when the engine was off idle.

But I have bigger problems with that car right now.

Cool, interested to see your results. I didn’t see that he’d gotten that AAR valve, I’ll have to check it out, thanks

Clay, that sounds very sophisticated. Hope Betty’s car is back together soon…

nah mate.
i hand made mild steel main fuel lines right through the tunnel.
rhd. those nice yank ss kits don't fit at the top end.
bastard of a job.

the black nylon fume line in mine is still in outstanding condition.
even in the engine bay. went over that one to make sure it was ok.
don't think much fuel can end up in it but with condensation it might.
the treacherous section would be the bit after the firewall under the engine.
was stil a ok.
its a low mile car.

everything is brand spanking new from tank to injectors.
but i still suffer paranoia.

i can still remember the horror of attempting to start this car in the original owners garage in wisconsin 35 years ago and we shot fuel out of 2 injectors that hit the roof of his garage.

there are many variations on the dead dingo's....
dong, dick, etc on and on. old school lingo. describes dessication of items lying around in the desert dust.
but not many young people speak australian anymore.
its very international. i blame the internet. and they all grow up in the city these days.
i noticed recently that V Bottas the F1 driver has got himself an aus girlfriend. she gave him a mullet haircut. classic.

@wonkipop I am sure Chris Foley would make you a set of custom stainless fuel lines to fit a RHD conversion.

Now if y'all drove on the RIGHT side of the road like the majority of the world, this wouldn't be a problem.

don't worry i am a fan of being on the right side of the road.
but i am stuck on this prison island.

and i'm not going through that ordeal of lying on my back feeding those lines up that tunnel, ever. again.
i'm driving it now. trying to wear out the very expensive michey skinnies.

Ok, more test results on both the current in-car AAR and spare AAR. Carb cleaned both units and shot a bit of WD40 on both sides of the discs:
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So, looks like the current one is fine, and maybe even better than the spare.

Thus, #1 (AAR) doesn’t seem to be the culprit, unless the initial idle wants to be RICHER than the first test. Seems unlikely?

Just as overkill will also test the in-car electric heater plug connection to confirm voltage there, but not a big determinate factor at summer temps IMHO.

Any further thoughts? Summer fuel? Dwell? Dark forces?

well it idles through a pretty small orifice in the t/b normally.
so an AAV that is only 70% open makes a hell of a difference is what i think.
it may seem like a minor thing but is not?.

i reckon @Van B has cracked it. its got to be a 100% er.

i did end up pulling one off an old late 80s SAAB but once i got into trying to revive it i think it was going to be worse than the original i have so i gave up on that one.
still on the look out down here for suitable candidates whenever i go to pick a part junkyard. which hasn't been a lot this year. chained to the "drawing board" since late jan.

Yes, it’s 100% at cold and 0% at hot so 70-80% at warm 78F seems reasonable for a temp dependent thermo wire. Unless it is a bigger thing as you suggest.

@StarBear did you run it after your lube job?

@Porschef I pulled the trigger on that thing over a year ago and it worked out great for me. Gave a beefy 1400RPM on a cold Maryland morning and took a couple minutes longer to close all the way. It was after I got it running properly that I realized the car was about to fall apart everywhere else lol…

@wonkipop , that’s exactly what I assessed. After weeks of going around and around like Steve. But it was during that process I found a lot of other things like spark plugs that bottomed out on the shoulder of the head recess vs the actual seat, injectors that weren’t making a mist, which meant more cold start issues due to lack of fuel vaporization when cold, and the whole problem with these cheap chinese CHTs

Clay, you’re just a big ole tease!

Van; Yep, just did it. Mostly no affect though time to smooth idle was a bit shorter - maybe 4 min instead of 6.
Of note:
1. I adjusted the TB idle to desired 1000 rpm early in the test. As expected, the idle rose to 1800+ by the end of the period. Tweaked TB idle screw back to 1000rpm, which increased A/F richness so tweaked AFM idle back to desired 13.2.
2. Tested AAR input plug voltage. Bounced all over the place rapidly 1V-14V; could hardly catch a reading it changed so fast. Not a key factor but interesting, maybe.
3. Let sit about 10 min while spraying weeds, then restarted with same rough starting idle.
Not convinced AAR is the issue but can’t define what it is. Summer low RVP gas? Demons?
Van - will pm you with an idea….

@Van B

Fantastic. So it was the BMW unit? Would you mind briefly describing your engine configuration or pointing me to your thread? Thanks

I don’t really drive the car during the winter unless there’s been no road salting. Even then, I’m not a big fan of driving with the top on. But we’ve been having some wacky weather last few years

Glad you got it ciphered

@Porschef . It was a long drawn out thread as 1.8s tend to be with our small sample size who insist on keeping the L-Jet working. But here’s the post: http://www.914world.com/bbs2/index.php?s=&...t&p=2988976

oh that is interesting re point 3.

mine only does the weak idle on a stone cold start.
not a warm start as you are noting.
you have a point. hmmmm.

Ljet is really a decent system, even today, 50 years later. Pretty smart and simple. The last issue I had was the brain crapped out after driving over some rough road under repair. @JimHoyland hooked me up with a spare he had and I was back in business.

Yes, they do go bad…

Update:
No great progress though still tweaking and getting inconsistent reactions. The wild fluctuations on the AAR plug voltage seemed promising lead to pump portion of dual relay but turns out that voltmeter just sensitive to engine spark like the old radios. Used my better newer voltmeter and checked out ok.

Next to try advance adjustments and trying tank of new gas.

Solved!!
After much perseverance, hard detective work, and problem solving processing got to “Flawless”!

Took MUCH tweaking of new second-generation 6-pin AFM, along with tweaking the timing another two nudges to the advance. Maybe (?) after setting timing at the start of all this I bumped the timing backwards a bit before tightening the dizzy clamp?

A/F numbers looking good albeit with little reference targets and no data logging/mapping.

As I’ve noted in the past, who needs senior mind exercise games and software when one has a 914 to keep running!

So, on to the next phase - doing cleanup update in time for the New Hope car show.

Lost in the sauce… that’ll definitely happen. I’ll wait for you to revisit this thread when it turns cold lol..

Hehehehe. I think.

you gotta love @Van B 's enthusiasm for keeping the L jet going and in some kind of version of half a century ago showroom performance.

anyway good stuff getting it settled down @StarBear .

i got to refit my original fuel pump later this year when it warms up a bit.
been staying clear of the workshop in the super cold chilly winter conditions down here.
unusual for this part of australia. anyway i have to do a lot of drawings at moment so sitting by the heater. but real keen to get the 3 port pump back on.
the two port pump i have gives me fuel pressure problems whenever the tank gets low - like to about 1/4 on the guage. unsteady idle. i know whats doing it and the why of it - and its partly to do with right hand drive conversion where i have had to slice 1/2 of the bottom bulb of the tank off and then the feed into the fuel pump which is from the high end of a turbine two port. basically it struggles for fuel whenever the tank drifts down to 1/4 full. hardly a problem of originality. it never had the problem with the original 3 port pump which says something for those old pumps in terms of dealing with the gravity flow to them from the tank. they were actually really good at it compared to newer two port turbine pumps.

ah the fun of the L jets.

@StarBear (and fans of the ol' L jet -"bound to be a classic" ).
was disappearing down another rabbit hole and pulled a cardboard box down with some random dusty 14 literature in it. found this. had it for yonks. forgot it was there.
had this since i bought the car.


most (all) thats in it we already know and have seen as diagrams etc.
but i don't think mr. b @JeffBowlsby has it on his wonderful website.
maybe he does. what they handed out to the service techs when L jet arrived.

a curio of days gone by.
but it does have a page on the brain in it with a diagram i have not seen before.
not that it means a lot in info terms.

i love the way they consign D jet to "history" with there this is the present and this is the NEW diagram pages. the germans. always heading into a brighter future.

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Cool. I will put it up on the site. Any other meaningful pages? I see a cover, 2, 3, 4, 5, 14.

'll do you a full scan jeff and post it up here later when i get time.
i was amazed i had it. completely forget it was there.
came with the car.
apparently the original owners had a friendly relationship with the young tech who worked on the car at capitol porsche audi. he was a young german sent out from VW/Porsche and stayed on in the USA. his name is written in biro in the front of the owners manual. he went on tp be a fairly well known porsche engine rebuilder in northern california and only recently retired from his business. he probably gave the owners this tech training book. its for the service staff to introduce them to L jet.
its still in perfect condition.

Wow! Great find @wonkipop! Can’t wait to see and read it when posted. What a resource!

@StarBear & @JeffBowlsby

for you fans of ancient texts.
doesn't really add any knowledge but its a nice looking little doc.
typically beautiful graphic layout of VW/Porsche.

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Wow, that should've been standard issue with every 1.8!

Very nice, haven’t seen this before. Spelled out so clearly and simply even I can understand it...

Time to get the multi tester, just for kicks.

Thanks Wonk

Along with the Ttrouble-shooting Guide!

So a smoke test to check for vacuum leaks. I had a small crack in the large elbow connecting the AFM to the throttle body. Ran like crap untill it warmed up.

funny you should say that/

now that i have refound it and remembered where it came from,
i think the bloke who had his name scribbled in the front of my glovebox manual thought the same thing? otherwise why was it in the pile of records that came with the car back in 89, remembering i bought it off the husband of the original owner, his deceased wife.
there must have been some shared enthusiasm for it as something new between the owners and the tech guy looking after the brand spanking new tech?

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i think the name scribbled in is this bloke.
the name at the top is the sales guy but the name below, tom martinot.......
the history fits.
he was at capitol porsche audi in dc, your neck of the woods where the car was originally sold and where it roamed the streets once.
and he ended up here?

http://deutschemotorsport.blogspot.com/201...m-martenot.html

i think he might still be alive.
i've got a feeling he is responsible for this ancient text ending up in the pile of papers that came with the car. he handed it across to the owner at some point early on to fill em in?

Thanks for the ancient L-Jet Service Training document. It appears to be an early L-Jet Service and Training Manual with only 300 copies printed.

A later version here: https://bowlsby.net/914/Classic/zMan_1974_1...iningManual.pdf

For convenience, I've improved and compiled the images of @wonkipop 1973 Guide into a consolidated PDF:
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thanks for doing that mate. makes it easy for folks.

a bit more info in your version.

does that mean my yellow one is a rare tome jeff?
can't be many left floating around out there?
might be worth more than the car.

no worries.