This kind of knowledge storage is awesome, but a little scary. I wonder what will happen in the long run. Will this all be lost since it wasn't on paper ...

i guess its here now on this website.
lasts as long as the website? which has been around for a while.
which ---is a kind of new book?

van's pursuit of cold start issues also provoked the dig into 74 1.8 L jets.
we kind of got to the bottom of it, for 74 at least, - thats in the history/originality section now.

certainly more here on this website than there is out there in the published paper world. ......and some of whats out there in books can be seen to be inaccurate information as time goes by and more detail surfaces. not the fault of those writers, they just did not have access to a broad enough sample of the cars out there to notice things or see much in things.

guess the L jet cars were in the shadow of the earlier D jets and also the concentration on the 2.0L 4s as the desirable variant?

EDIT
ps - thats why its worth $30 usd in fin. support a year.
not many technical subscriptions at that rate offering this kind of value for money?

flum·moxed
/ˈfləməkst/
adjective
adjective: flummoxed
bewildered or perplexed.
"he became flummoxed when his 914 continued to struggle on cold weather starts”

So, tonight’s attempt required several seconds of cranking, then slowly lumbered to life at a very low RPM. It required two touches of throttle to keep it running in the first minute or so. But then it started to steadily climb out of the hole, which is a new behavior . I just don’t get it! I’ve only got another month of actual cold weather and so I really want to crack this!

So far this quest has uncovered a litany of issues; most of them attributable to improper maintenance. And most importantly, performance when warm has substantially improved. But I am convinced that the cold weather start struggle has multiple causes. Unfortunately, the only thing left for me now is to dig into the engine.

there is only the AFM left to go?

it could be in there.

mine almost does what you describe.
but it does not struggle to life.
it springs into life (for about 10 seconds) and then subsides into the hole.
which it then digs itself out of as per yours.
it takes around two minutes to get up over the edge of the hole.

and then when its warm it runs just dandy.
as it always has.

apart from that hunting thing on a low tank of fuel.
but i am right hand drive which has its own unique problems of my own making.
but i have a full theory/explanation for that now which i shall go into after i reinstall my rebuilt original fuel pump and reroute a couple of fuel lines down there near the fuel pump.


starbear cleaned out his afm. he wrote me a pm about how it mortified him doing it.
he knows how to do it.
his does not seem to suffer this fall into a hole problem like ours?

Any of you 1.8people have an O2 sensor installed?

Not that I’m aware of, though after 48 years still learning about these little contraptions.

no.

ie lamda sensor in the exhaust?

even the 75s with cats didn't have one.
no feed back loop in these early L jets.
they are called open systems.
don't think they went to closed loop L jet until very early 80s.


it does however take an input from the AFM at start up in two ways.
there is an air temp sensor in there.
and while the AAV is open its going to be drawing additional air and moving the AFM flap open slightly.

i figure that if the stamped circuit in the AFM is worn slightly or dirty right at that first part it could be affecting things. ie it gets extra fuel at start up by virtue of almost simple clockwork. aav is open, that pulls AFM flap open a small amount and signals to the ECU that the flap is open give it more fuel. and if its getting no air temp input properly that might be upsetting things too. ie no signal to the ECU that incoming air is cold. all its getting is a signal from the CHT - and its not enough? i'd have to think about it more.

its a possibility. van has been through everything else.
CHT, AAV, new injectors, he has done it all. timed it. tuned it.

once the car is warm it does not need that extra bit of air and fuel so it is content to idle through the idle port in the AFM? and does not need the extra air and flap open at all.
and you rarely (ie never) drive the car at 1200 revs so you never notice that bit of wear or dirt on the AFM?

a thought. can't think of anything else.
and mine is very similar.
everything is hunky dory when its warm.

“Everything is hunky-dory when it’s warm.” Kind of like us ‘mature’ folks, eh?

No, I mean for knowing your afr. I have one in my djet engine to help me tune it. If you had one you could see if it is a fuel ratio issue at cold start. Too rich? Too lean? Helps figure out what is going wrong.

We have a CO adjustment screw; that’s all though doubt many of us have a meter.
How does the O2 sensor provide a useful monitoring info? Ties into a meter reading somehow? An interesting idea….

Knowing it is too rich or too lean can point you to the issue (if it's fuel related). Also as the car warms and starts to run well you can see if the afr is changing appropriately. Just more data points.

It would be a very handy diagnostic tool for sure. I don't want a gauge/dash setup but I would like to have one that could run as a stand alone with a probe or with a bosch wide band sensor. When I built the exhaust for my 996, I installed extra bungs just so I could have that option down the line. that car only has narrow band sensors so the data from them is not real helpful.

Regarding the 914 and @StarBear 's question, it would have much less usefulness for tuning and without another car with a confirmed functioning cold starting feature to compare against on the same day with the same temps, it would be tough to know what the numbers mean. I mean technically, I would see the values, but how much enrichment am I looking for, ya know?

its way dumber than that @Emerygt350 .

you can adjust things after the engine is warm.
the CO screw does all that.
and you could additionally measure O levels with a probe.
but......may not help for the warm up.

from what i have read the warm up enrichment is controlled by 3 things.

1. CHT. Van has already put in a new one.

2. intake air temp sensor in AFM.

3. movement of the stator flap in the AFM (which would be drawn slightly open by the AAV being open).

#2 influences and modifies the signal sent by #3 to the ECU. so that intake air temp sensor has an effect on the signal generated by the stator flap and the ECU can recognise the engine is cold and even further to that it is drawing in cold air. logic tells me that is what sends it into the cold start regime. part of the input is the CHT. but there is also input to say stator flap is slightly open (AAV pulls it open but as a piece of "clockwork"). and the ECU recognises those two additional inputs, stator flap and cold intake air. ie it can also distinguish that the stator flap is open in a cold air situation. together all three switch a circuit(s)in the ECU that is the full cold start regime?

how you can adjust that alone is i think not possible.
you can adjust CO at warm idle and you can adjust CO generally i think at ECU further.
i'd have to check up on our ECUs for 1.8s again. but that is not going to help at warm up as its got an internal "routine" so to speak inbuilt in the ECU if you could call it that.

so i think an air temp sensor in AFM or the printed circuit the stator flap sweeps over could be a culprit. it would be in that section of the first part of the stator flaps movement. the open AAV would not be pulling the stator flap very far open at warm up.
but if its not getting the correct electrical signal generated by that first part of the AAV flap movement it is definitely going to affect enrichment. it might be worn or have residue built up on it.

there is some proceedure to clean that printed circuit in there.
i've come across it here on this website.
how to open up the AFM and do that.

as to the temp sensor in there.
somewhere i have an L jet tech manual that tells you how to test it.
but.....having said that it then says that if it is defective it cannot be repaired.
however - as we know 914 owners seem to be capable of rebuilding just about anything at this stage that previously were regarded as unfixable and to be thrown away.

------

down at the workshop i can get hold of an exhaust gas analyser.
a real old piece of equipment. we use it to tune all the old cars.
but there is something that needs fixing on it at present.
we have been borrowing one from the mechanics across the road.

i'd have to leave the 14 down there overnight and then do a cold start fire up.
i think that would give me the values you are talking about emery?
whats going on at cold start in terms of the air fuel ratio.


-------

i've got a good CHT i have tested.
i've got good injectors that work perfectly.
i've got a good cold start injector and temp switch that works perfectly.
i've got an AAR that opens but i suspect may close too quick.

and a similar set of symptoms to vans car at cold start.
and a similar set of components i know to be close to as good as the ones van has in now.
(i'm guessing if i was in maryland or cold cold north america mine would really fall in a deep hole too for the first couple of minutes just like vans).

and i'm think with mine when i get it into the workshop for the fuel pump fiddle that i will see if i can do the tests on the AFR and maybe even open it up and clean it if necessary.
i can test the temp sensor too, but what i can do about it i don't know if its not right.

Well, something is up. Knowing couldn't hurt. Pretty much every car wants the same thing as they warm. 10:1 at the start (csv) rapidly leaning to about 12:1 (cht) then a slower rise to 14:1 (at idle). I know at idle wide bands are not great but in both my 84 FI mustang and the 2.0 914 they follow the same pattern. Both run about as good as they can (the mustang probably better than it was ever meant to).

Temp sensors can be tricked with pots and resistors...

good general info - thanks for that emery.
i'll try and get mine on a machine with the exhaust probe and see if i can get some comparative measures. got to get the ford falcon out of the way to make room to leave it down the workshop. not far to go.
it will be a bit cooler here soon in autumn so i can get a better guage on cold starts again.

Manual doesn’t tell me what pins to check for temp sensor 1. The 912E also isn’t helpful because it’s a 7 pin connector.

Without the tester specified in the manual, there are only two resistance checks I can do, and I don’t even know what they mean. But I do know that mine is within spec on both readings.

try this.
its from another L jet manual i have.
unfortunately there is no real separate test it seems for temp sensor 1 distinguishing from potentiometer test. both are same?

Click to view attachment
Click to view attachment
Click to view attachment
Click to view attachment

looks like your info is same as mine.

if you tested it and it is ok that is good news.
means your temp sensor 1 is still ok.

it could be the worn track thing on the inside.
i need to find that thread here about cleaning it.

i'm sure starbear told me he did open his up and this cleaning proceedure.

I pulled the cover and it’s nearly new in there. It’s a rebuilt unit from fuel injection corp.

I mean it, I cannot think of any other system aspect to check. The only roads left are mechanical.
It’s not like I haven’t made steps through all this by finding and addressing substantial issues, but nothing has solved the cold start issue.

I would say these are the numbers of a well tuned engine. I think OE tunes are generally a bit too rich (high 12’s)

is the flap moving freely in the intake plenum chamber.
can you sense any hesitancy from the closed position.

just wondering it if could be sticking and the aav is unable to pull it open at cold start.

sticking with the idea that what triggers the a f r mix is the air flow in L jet.
(yes there is temp input, but its in parallel with the flap being moved).
i mean that is all i can see that triggers the enrichment for cold start up.
those two sensors and what must naturally occur if the AAV opens which is the flap moves in the air flow meter to let in additional air or send the signal that additional air is coming in. if its not getting the signal that additional air is coming in then temp sensor 1 can do all it likes to modify the signal but the signal would be saying no add air is incoming.

or am i thinking this wrong?

am thinking there is one last test you can do.

it should be possible to undo the aircleaner, get the base out of the way and prop the top half so you can see inside to the flap. do a cold start and go have a look and see if its pulling the afm flap open during that first initial part of warm up.

sit there and watch it. see if the AAV is doing its job and pulling that AFM flap open.
and watch to see if it closes right up again when its warm. it should since by then it will be running off the idle passage through the AFM. to my way of thinking it cannot be doing initial warm up through the idle passage alone?

this should not disturb anything or cause any air leaks.
and its the last mechanical test of all components.

if that flap is puling open then its got to be something not getting that signal through to the ECU. or in the ECU itself? because you have crossed everything else off the list?
as far as i can tell anyway!

i admire your commitment to the cold start.

It moves like it’s made of butter. But I don’t see any reason not to lay eyes on it during a start up.

My commitment to this is that I believe a real cold start brings out issues with an engine that may otherwise be masked in more favorable conditions. That’s how the “cold start” became such a classic proof when selling or buying a car.

Just look at all I’ve uncovered during this pursuit:

-Spark plugs that weren’t seated
-Faulty fuel injector
-Incorrect engine timing
-Incorrect setting on decel valve
-Bad thermo time switch
-bad voltage regulator
-wrong charcoal filter pellets (leaking into the intake)
-cracked intake boot
-cracked vacuum lines
-pinched and twisted fuel hoses

And since I still have this cold start issue, I know there are more problems to discover.

I’m just tired of striking out. I can’t really say I’ve enjoyed my 914 ownership so far… especially when I have this beast of a 996 sitting next to it that is always ready to party!

joy of a vintage car van.
its half a century old, and you have sorted out a ton of dickskull mechanical work done by others and general decline reversed.

i've got a little renault RS clio i can take out anytime and its always up for a party.
as per your 996. mines a wolf in sheep clothing. cops don't even look twice at it.

but the steering feel will never equal the 914.
esp since i stuck the 165s on the 14.

i'll put up with the warm up in mine if i can't solve it.
sounds like i might hit the same brick wall as you.



PS - the other way to look at it is that L jet is such a heroic bit of wartime style engineering that it can keep the engine going even though some component is letting it down. like a machine gun full of dirt that just keeps on firing.
rather than seeing it as a fault its like something that just won't give up even in old age.

i'll use emery's handy figures on what to look for roughly on a f r by sticking a probe up its tail pipe on a cold start and see what happens. i figure if the a f r is ok when its all warm and operating normally then its not suffering any damage during normal use.

its important not to be tempted to put too much boot into it when its cold via the accelerator as you can get a backfire and that will do the AFM no good at all.
its a balancing act to get it up to temp and oil circulating but also avoid the back fire.
mid 70s 911s used to be famous for blowing up their airbox and doing all sorts of damage on a cold backfire even down here in emission free (relatively speaking) australia in the easy going "she'll be right" era long past. i think they ran K jet. but i don't really know. 911s have always been outside my budget. and now they are so outside it they are in another universe. but a mate of mine has one. a 75. had it since new. he never sells any of his cars. he has some technique or mod to his airbox so it blows the hose off before it blows anything else up. i think its as dumb as not having a hose clamp done up too tight. only he is allowed to do up the hose clamp.

this is of interest van.

in 5 parts.
guy with an l-jet opel manta tuning the afm.


https://www.youtube.com/watch?v=PqEBgS6hSGQ

Yeah, I’ve seen those videos. Would love to have those tools!

yeah i want his a f r machine.
have to keep my eye out on ebay.
was especially into the way it had CO arrayed at bottom as well.
it had it all in a nice little box.

we have got a much bigger version and just as analogue down the workshop.
it looks like it dates from the 1970s.
but there is something wrong with it that needs fixing.

A weird thing happened last night. I went out to start the car, mostly out of boredom and frustration... and after cranking a few times it fired up and jumped to 1400 RPM! As I sat there in existential confusion, it slowly climbed to 2000 RPM. At that point I got a little concerned and blipped the throttle and the car cut out and died.
So, like a good little monkey, I started the car again. Same result. That's when I realized I never plugged in the 6-pin on the AFM after testing it the day before. So, I plugged it back in and started the car once more. This time it started and went to a normal idle. No doubt the resulting normal third start was due to the fact that it was warm out and the car had already warmed up sufficiently.

What I'm struggling with now is that this happy little accident has seemingly ruled out a mechanical fault. I mean other than taking more cranks than what most people report as the norm, when it started with the AFM unplugged, it behaved just like my 996 for the first few seconds... a smooth high idle.

@wonkipop @StarBear would either or both of you be willing to replicate this experiment for me on a cold start to act as a control? In other words, would you unplug your AFM and attempt a cold start and let me know what happens? I would like to know whether this behavior is atypical or if it's standard.

Van

Very interesting!

To put it mildly.
I plan to mess with the points settings tonight and see if that changes anything. From reading the manual, .4mm is the start setting, and .3mm is the minimum. I don't have a fancy dwell machine, but I think I'll move the points gap in and out and see what changes... if anything.

They aren’t that fancy. Don’t guess at the setting. You should be able to find a dwell meter for ~$20.

I have an ancient dwell meter from back in the 80s when I had an opel. Critical equipment. My opel wasn't that sensitive to point misadjustment but the 914 was super sensitive. So sensitive that the 123dizzy was a god send...

@Van will do and let you know.
Yes, get a dwell meter. I find mine is very sensitive.
EDIT: Spec is 44-50 degrees; I get mine right on 48 though takes several attempts even starting with gap tool.

My math runs like this:
Pertronix > points+dwell meter

I placed an order for the Pertronix Ignitor III with built in rev limiter. In this way I can remove points from the equation entirely.

I don't see enough info on the L-Jet out there for me to pull the trigger on the 123ignition just yet.

As long as the points go, you should be better off.

Funny thing on these engines is the rev limiter is kinda useless. It's the overrun that will blow your motor.

you mean the ole full throttle 4th to 3rd? That should be near impossible on a bolt action shifter like the 914 lol!!

A lot of us 1.8s have had trouble getting Petronix to work; others no problem.

@Van B didn’t get hone till late and snow/ice tonight and tomorrow so might not get to it until Saturday or Sunday. If I recall in the past, when I did the same it just cranked and never turned over (informing me I had not reconnected it).

wow, yours started with the 6 pin out.
i already know what happened with mine once.
i changed my air filter out and forgot to plug it in.
no start.

i can try again later when i have a moment and see what happens to double check that.

right on.
that rev limiter rotor was/is a waste of time.

fyck up a gear shift and bye bye engine despite the stoopid rotor.

@Van B

those you tube videos with AFM - you can see the little track i was talking about.
with the sweeper.

people sometimes go in and make sure the track is super clean and also adjust the sweeper very slightly so it runs in a different spot.
it can wear a groove as years go by.

however i don't think this would be affecting warm up idle.
but maybe if the first section of track is a little worn its possible.
be right at the start of the track.
that is one of the connections between the flap and the ECU that is important to the ECU knowing where the flapper really is and how much air is coming in.

------

Like I said earlier, I pulled the top off and everything looks new in there… brand new. It’s a rebuilt unit from Fuel Injection Corp.

And yeah it started but any touch of throttle would kill it. So, clearly fuel injectors are commanded to send fuel even without the AFM. But there was no way for the computer to adjust fuel.
What was really bizarre was the high idle and that it jumped right to it from a first start.

If y’all can at least try it, it would be much appreciated.

i'll give it a shot later.
have to get the renault out of the way.

will report back when i have done it.

ok

i just did it.

it started.
straight away like it does connected.
one crank and bang it went.

i touched nothing like i usually do.

did not go to high revs.
was at about 850 rpms.
then stopped on its own after about 10 seconds.
never got higher than 850.

i reckon it ran off the cold start injector.
reminded me of the time when we recommissioned it and the same thing happened.
fired straight up, ran for 10 seconds then stopped.

so i don't believe i was getting an injector signal when i just did that.

i remember now when i last did the disconnect thing accidently.
it fired up and then stopped.

i reconnected it.
did a normal (ie abnormal) start.
ie it went weak for that first 2 minutes and then came on.
but it needed that plug in for the regular injectors to be signalled to fire.


so--------this is gettng real interesting now.

So mine ran for several minutes without the AFM plugged in. It definitely was not the cold start injector that kept it going. That thing can’t put out enough fuel to support 2k RPM.
But it is interesting you didn’t get a fast idle… I’ll see what results Steve gets. I don’t yet know if this is a thread I can pull on or not. But I can’t get past the fact this is the first time the car did not struggle on cold start.

Wow, I think you guys are on to something! No idea what but this definitely looks like a worthy lead.

after reading one of your posts a few back where you mentioned the 912E manual you were looking at, i searched that up.

came across something i thought was interesting.
they really changed the characteristics of the cold start injector and thermo switch on the L jet 912 2L.



Click to view attachment


its currently 19.8C right now in melbourne.
maybe its a little cooler in the garage.
but its definitely not 13C out there.
and it definitely ran off the cold start injector for sure when i fired it just then and nothing else. but who is to say that info there is strictly correct from that manual.

point is i found it interesting that they really beefed up the cold start for the 912E.