Air fuel ratio Ljet Options

[Geezer914]

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?

[emerygt350]

Is any of this under load?

[Geezer914]

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.

[emerygt350]

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.

[Mark Henry]

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.

[914werke]

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.

[Van B]

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.

[914werke]

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 !

[Van B]

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.

[Geezer914]

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.

[Geezer914]

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.

[914werke]

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.

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)

[Van B]

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.

[rhodyguy]

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?

[ClayPerrine]

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.

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)

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

[914werke]

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.

[Van B]

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

[wonkipop]

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.



-------

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.

[wonkipop]

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 (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) more useless historical information.

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

[wonkipop]

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.

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.