I am trying to adjust the air fuel ratio on me 2056 Ljet. I read the article that was posted a while back. I adjusted the wiper arm and set the idle at 1100 rpm (Raby 9550 cam) with the idle AFR at 13.2. When I check the high rpm the AFR is at 12.1. If I adjust the high rpm AFR to 13.2, (moving the large wheel 7 teeth CW) the the idle AFR is 16.9 with the mix screw all the way down. If I readjust the wiper arm to 13.2, then the high rpm AFR goes back to 12.2. Can't seem to find a happy medium. I know when you adjust the wiper arm it changes the mixture linear from idle to high rpm. How much more can I adjust the large wheel CW?

Is any of this under load?

No. The idle is going to be the idle. The only thing I see changing is the high rpm AFR reading. According to the article you are making the adjustments with the car sitting in your garage.

Oh, so this is just setting the idle afr? What is the l jet supposed to be at idle? I would just go with whatever smells good.

Load AFR with iron jugs should be just under 13:1, I like 12.7:1-ish.
Idle doesn't really matter (within reason) as it's not under load.

Sounds like were on a parallel path. Following
Im still chasing a acceptable idle so I can perform the adjustments
Edit: BTW this is also a 2056 but cam is either a 9530 or 9580 cant quite make it out.

Geezer, seems to me you were fine with the values you started at. Hopefully, you marked so you can set it back. Because for a performance build, those AFRs should keep you in a good spot. And I also agree that testing under engine load is far more valuable that revving the engine unloaded.

Hopefully the Geez is making better progress than I.
Im still at square one trying to get this thing to idle.
I did find a an AAR that was closing fully but still had a leak ... solved.
Now instead of dealing with fast idle, I cannot get it idle at all.
TB air bleed screw results in 0 change which leads me to believe its running VERY lean or so rich that it has no effect.
I did hook an LM-1, & while holding it at about 1500 I get a 13-1 AFR !

Hmmm… AFM screw is 3-4 turns out, correct?

What’s it like when you are starting it? My gut is telling me timing may be incorrect… but I would like to hear more before I indulge that hunch.

If your idle is high and no change when you adjust the air bypass screw on the throttle body, then you have a vacuum leak. Do a smoke test. My injector seals were leaking.

I ended up with 13.1 at 3000 rpm and 16.9 at idle. Just like Mark said, the idle is lean but not under load.

No. that was prior to testing & locating a AAR that would close but still allow air past.
Then started back at square 1.
Valve adjust. Static timed. Checked or reset all sources for vacuum leaks. Set AFM bypass screw to baseline (4.5 turns from closed). TB plate is seating full closed & cracked the idle screw .5 turn. Full charge on battery. Will take a few trys to start but will ..roughly. Fuel pressure is 36-38lbs & reacts to opening the throttle.
Now I have to manually feed throttle to keep it running
EDIT: Timed to the 27BTDC (mark) at 3400, cannot get a reliable idle (800-1k) to time at the 7.5 degree mark seems to run well on throttle but as revs drop stumbles & will not stay lit.

This was a carbureted 2056 originally D-jet so the impeller has marking for both D-Jet & L-Jet (0=TDC, 7.5 & 27 degrees BTDC)

There is no 27 degree mark for the L-Jet. I wonder if you have a fan from a D-Jet on that car? You should only have one red paint mark that is 7.5 degrees BTC.

Having timing off like that would make your AFRs off as well.

Something is amiss down wind of the AFM? Vac leak with DJet results in an uncontrollable high idle. Opposite with Ljet.

New phenolic spacers and inj seals? New intake runner to plenum tubing?

L-Jet needs 28-32 PSI. The regulator on L-Jet is not adjustable. Put the proper L-Jet fuel pressure regulator on it and recheck the pressure.

The timing should NOT be set at 27 degrees at 3400 RPM. That is only for D-Jet. L-Jet uses7.5 degrees at 900 RPM. Different distributor so setting it at 3400 RPM will end up with the timing way off.


I have been working on L-Jet for over 35 years. This sounds like a major vacuum leak or false air that someone tried to compensate for by increasing the fuel pressure.

Did you check the oil cap seals? Do the heads have vent tubes? L-Jet didin't use the vent tubes, so they have to be plugged. That will cause false air issues.

Clay

Thanks for chiming in Clay. @ClayPerrine
Ive never had the need to deep dive into L-Jet so Im still feeling my way.
Heads are plugged. Stock "non-adjustable" pressure regulator, the pressure referenced may not be as high as I noted as the gauge Im using isn't that granular. The gauge does respond as expected to throttle inputs.
Pretty confident I've eliminated all the air leaks, as I stated, I'm now at a point where Im feeding fuel via throttle to keep it running vs chasing a high idle.
New ...everything. Hoses seals, injectors you name it.
Still cant get it down to anywhere near the 800-1K idle necessary ... stumbles & dies.

On last time: Does your fan have the single red paint mark or is it the D-Jet fan?

it might be that its a bus fan or something.
but your point is right @Van B .
should have only that one mark at 7.5 and thats the one you want.

there may assist @914werke getting that timing mark.

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question for @914werke .
do you have a decel valve hooked up to this engine?
if you do have one it could be a source for an air leak/extra air that fits the bill on the initial high idle issue.
i'd take it out of the equation and plug its hose to the air boot from aircleaner to throttle body. you can come back to the decel valve later and test it.
@Van B has all the tips for that.
just a thought - in relation to that first high idle problem you had.

as @rhodyguy notes, usually an air leak downstream means it just won't idle.
but that would be restricted to an air leak that is letting air in that is not influencing the AFM. hence my pointing to decel if its there. that will pull extra air and influence the afm and give you a high idle you can't bring down.

check your oil cap. make sure its not leaking and the gaskets are good.
and what kind of pcv valve is set up on this engine.
is it the L jet oil cap and pcv valve?

check the throttle body to plenum gasket.
i had this problem once. it was caused by a gasket that had gone hard.
and it only came up when the engine got fully warmed.
drove me nuts until i tracked it down.
car would just start to idle erratically, then stumble then die unless i gave it some boot to keep it going. really surprised me as in the end it was quite a small leak somehow around the circumference of the the t/b.

from factory manual on timing marks.

(interesting note i had never bothered to read before about new/replacement fans only being supplied with TDC mark - and is from manual dated XI 1974 (nov 1974) well after the 1.8s were introduced.)

esoteric point but looks like the way factory did it was to mark up a universal fan part two different ways depending on which car it was going in after 1974 MY. if a dealer had to install a new replacement looks like they had to notch it up themselves before installing more useless historical information.

anyway. Van & mr perrine are right. ignore all other marks other than TDC and 7.5

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the way the pressure regulator works in an L jet is it drops the fuel pressure when you close the throttle from higher revs. thats when you get a high enough vac in the intake plenum to operate the pressure regulator. don't quote me on this but i think momentarily it will cause fuel pressure to drop to around 20-24 psi or something like that.
it lowers it. once the vac subsides the pressure goes back up to normal. at idle and all other times it just stays at around that 28-30 mark that mr. perrine indicates.

thats the only response you should see in relation to throttle.

there is always the question of flow as well as pressure. but i don't think you got any kind of fuel pressure problem by the sounds of it.

So thanks to all who chimed in.
Sometime you get too close to something & start 2nd guessing yourself.
I just had to step away & think less about it so I could come back ..with fresh eyes.
As I had commented I solved my only vacuum leak. Timing was an effect not a cause.
I had to solve that ...One of the couple thing different on this install was the TB, on which is mounted the TPS.
That (is a) switch on L-jet only affects idle & WOT ... Bingo.
I had to make a plate which to mount the TPS & it needed a bit of tweaking
Reinstalled & walla ..idle & adjustment
Got it timed
Now trying to tune it in, was wildly lean getting closer.
I need a beer~

good stuff.



good looking throttle body.
whats that from?

Ah yeah that’ll do it. When you said TB was good, I just assumed it was OE.
I wish those were dual vac, I’d have one then.

@wonkipop he’s customized a gowesty throttle
https://gowesty.com/products/gowesty-throttle-valve-housing

UGH. Im back.
Well I thought I have this dicked by now but it seems to have me running in circles.
Once rich'end up I was able to road test & it ran pretty good cept it would hit a hard stumble when feeding partial throttle around 3K in any gear.
Looking at the LM-1 of course it was going lean, so I ve been going back & forth
Back to square one

i'm probably not much help - i have an entirely stock set up thats reasonably low miles and hasn't given me too much trouble - apart from cold start issues to do with AAV same as @Van B .

all i can offer is that at idle and at WOT the throttle valve switch lets the ECU know what the mixture should be (and at idle the screw adjustment on the AFM). in between its down to the AFM flapper and the signal it sends to the ECU.

that is assuming everything else is set up right. valve adjustment, timing etc.
and there is no reason to doubt you don't have all that set up right.

so i would probably try and get it right for mixture at mid range - and i guess the only way to do that is fiddle with the flapper and AFM.
someone like @Van B or @clayperrine would know exactly how to counsel advice on that. i've never had either the nerve or the need to go into the AFM. but it is all discussed in that article Van B linked to.

if the idle gives you a problem after that you take care of it with the screw adjustment on the flapper and the idle screw on the t/b. entirely separate matter.
thats how i have always understood the L jet.

good luck and hopefully the other guys chime in to assist.

I don't ever recommend changing the settings on the internals of the AFM. It is setup at the factory with a certain spring tension and requires a special Bosch tool and manual to reset it correctly. Changing it can change the fuel curve dramatically and cause crappy running.

If your AFM has been opened, I suggest you get one that has not been touched and try it. You may find the majority of your problems go away after that.

Clay

Well, perhaps that is useful advice if you are working with a stock (1.8L) motor & the stock induction for which it was tuned in the 1970's
not to mention the differences in gas formulation from then to now
or the likelihood of finding an unmolested AFM for a system that hasent been installed new in a car for over 30 years.
But if you've spent a chunk of change on a motor and dont want to run the risk of frying that investment due to less than optimal air fuel ratio (IE overly LEAN) the only way I know to do that is with the use of a wide band 02 meter and judicious adjustments of those elements, fuel pressure, adjusted timing, ect.
With a system that is as sensitive to vacuum as L-Jet is, the addition of a non stock camshaft can add to the challenges. In my case Its ALL of that.

Look up Internet Air Cooled Air Flow Meter. There is a complete article on how to adjust the AFM.

Love ya Brother! Which is why I don’t mind telling you that every time you give this warning, I smile and immediately ignore it

That said, your words are wise.

Just an FYI.. I had factory training on L-Jet back in the 80s. I understand the system. And I found out the hard way that the engineers at Bosch who designed this know way more about it than I do.

The air flow meter is designed to make the mixture richer with more airflow. When you change the spring settings in it, it changes the mixture curve. Rather than f**k with the insides of it, you can do things like increase injector size, or increase the fuel pressure to compensate for more displacement. And the difference between the 1.8 and a 2056 is not enough to cause an overly lean condition.

I have been running L-Jet on various 914 engines for 36 years. Never have I had an "overly lean" condition cause damage to the engine. And I have multiple air flow meters that have never been opened.

You can change things on your car at a your pleasure. And you can deal with the drivability issues that come with the reduction in spring pressure. I have already been down that road, and I was hoping to save you the trip.

Good luck.

Clay

Well great Clay, I appreciate any insight and advice you can provide. But admonishing me & suggesting I start from Zero isnt that helpful.
Clearly the reason for the post is to solve my EXISTING problems using a mixture of stock elements that may or may not have been messed with, & parts that would effectively mimic those installed on a 912E. The biggest departure from from stock is the cam installed, that while not over the top, apparently has enough overlap to impact the vacuum & simple start idle run.
As to overly lean, using the LM-1 it was easy to identity a VERY lean condition that was causing driveability (throttle load bucking) & could not be left as is.
So given that, where do you suggest I start, or questions youd ask?
Based on your stated "resume" this should be a slam dunk & benefit others who may find themselves down this path, but if you'd rather not troubleshoot in an open forum PM or call me
Thanks again

what clay says makes sense to me re airflow.
i myself would be very reluctant to mess with the AFM.
if i ever had to do anything with it there is a guy here in aus who rebuilds and tunes them and is trained to do it. we recently sent off an AFM for a 964 to have it rebuilt.
those kind of guys know exactly what they are doing setting one up.

re - the 912E did run slightly different injectors than the 914 1.8s.
they had slightly more flow. it is a 2 L engine so maybe porsche-vw had to do that.

you can google around and you will find some old shop talk forums that go into this.
i just did a quick google and turned one up.
had some of the blokes who are still active on thesamba discussing it.
L jet going on to bigger capacity 2L + engines with hotter cams.

what injectors do you have on it?

Rich,
I apologize if I came across as admonishing you. My suggestion is not to start from Zero, but to eliminate a variable in your troubleshooting. Using a known good AFM would eliminate that from the items you need to check.

Do you have someone close to you with a running L-Jet car you could borrow the AFM from for troubleshooting purposes?

Clay

No worries. I have several but all have been opened.
As it happens our old friend Troy @Messix dropped by out the blue the other day & while he's been spending all of his free automotive time on his Jeep, he still has his 914 that may be pressed into this effort. Not sure when the last time he ran it, but assures me it does
But hold on ... it just so happens I have a complete 912E motor I got from Ralph Meaney's shop after he passed. & it has a AFM on it that looks like its never been touched.
More to come..

There were two different air flow meters. 74s used a 6 pin meter, and 75 used a 7pin. I think the 912E used a 7 pin but I am not sure. So make sure the pin count is the same.

Clay

here's what Im working with:
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thats a 75 1.8 AFM.

i believe it pairs with a 75 1.8 ECU.
porsche vw part # 474 906 301 bosch part # 0 280 000 111

interesting the way it has a blank space below the bosch part # where the VW-Audi part # is usually stamped.

part #s / details for the L Jet components on a 912E engine.

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link to a 912E L jet EFI manual if you are interested.

https://www.912bbs.org/forum/downloads/912E...ical_Manual.pdf

clay is right. the 912 has a 7 pin plug like 75 1.8s.

This does bring up a good point. The ECU And the AFM are matched. Check your ECU and make sure it is for a 75 and not a 74.

Clay

@914werke

some one who might be able to help with this is @nihil44
he lives up in brisbane in australia and he dropped in to see me a couple of months ago when he visited melbourne. we stood around in the freezing cold and took a good look over my car and he was telling me all about his second 914 that was nearing completion.

i believe he used a 73 two litre engine (which would have been originally D-Jet) and he has installed L Jet on it. i don't know all the details but he has put it together out of bits and pieces he has been able to locate around the place. I think he has got it working.
he has just been battling away quietly with it along with his mechanic up there in brisbane.

i'm surprised he hasn't come on here but maybe he hasn't been visiting the site lately.
if he gets this notification he might come on with some suggestions.

IIRC, yes, the 912E used a 7-pin AFM. In 912E LJet guide on Jeff B’s site.

I have been outed by @wonkipop . I have been loitering in the shadows observing but I've had very little to offer in the foregoing discussions.
The specs on my project car are as follows
’73 2.0 DJet converted to LJet. 3 stud intake runners cut and welded to line up with L Jet plenum
’75 AFM – rebuilt by someone in California. Looks pristine inside
’75 7 pin ECU
No decel valve
FJ6 Standard Motor Products injectors
123 Distributor
Rebuilt throttle body by Phil Eslin
Current ailments – long crank to start and stumbles to stalling under load. Strong of petrol which seems to emanate from engine bay.
Booked into mechanic who has dyno and exhaust gas analyser. I am getting nowhere with my fiddling

Just some observations following which may be of use or interest
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I made a tab to hold down cover on AFM for ease of observation only - @ClayPerrine . Hate the idea of silicone sealing

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Inside ’75 7 pin AFM. Note counterweight on wiper and dob of silicone on top of black plastic cog indicating absence of tampering - @ClayPerrine . Looks factory quality. 2 white wires coming from temp sensor 1

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Inside Kombi 7 pin. Small or no counterweight

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Inside 6 pin ’74. Swapped out because of poor function. Note presence of counterweight and no silicone on adjustment screw and evidence of galling on adjustment screw from prior monkeying. No white wires coming from position of temp sensor 1

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Note comparative size of intakes. ’74 has plastic tit in intake which is embossed with ‘1’ but no wires leading from it. Same position on Kombi intake is temp sensor ‘1’ – see wire connections

I have fitted the Kombi AFM to the car and it starts and runs but have not driven it.

I don't understand why you would have to "cut and weld" the intake runners. A little tweaking side to side and the 2.0 Runners fit the 1.8 intake plenum fine. Yes, they are a little short, but that can be compensated for.

I wouldn't mess with using a Kombi AFM on a 914. Unlike current fuel injection, the parts on the early systems like the 914 L-Jet are matched and don't really work well when mismatched.

Good luck.

Clay

Clay,

I was just having a play with the Kombi AFM just for interest. I am not intending to deviate from the '75 AFM ECU combination.

thanks for the images @nihil44

great to be able to see inside without having to tear mine open.
which i don't want to do since it ain't broke.
interesting too to see the differences and evolution of the equipment.

That ‘74 6 pin doesn’t look like either of mine.

Apologies to the group for posting photos of what I believed to be the AFM from a 74. @Van B alerted me to the possibility that the photos were incorrect. I believed it to be a genuine 74 AFM as that was the AFM that came on the car when I got it.
I popped the top of the AFM which is on the car and indeed it is quite different inside. I don't know where the other AFM came from as the black plastic cap bearing the part number has been lost. Updated photos below. There are 2 black wires coming from the position of temp sensor ‘1’
I looked up PET and the change over point for the different AFM and ECU is the same – engine # ECO 037 551. 6 to 7 pin change over. No surprise there. Part # on this AFM is correct for '74

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