ignition timing, how to adjust? idle L Jetronic

[Pepite73]

HiHello
I am the proud owner of a 1976 Bay window 2 liters injection L-jetronic (
imported from san francisco).

I'm trying to find out how I should set the ignition advance because if I follow the official engine recommendations I should set to -7.5 degrees BTDC but if I trust the igniter in place (original VW Bosch) (number: 022 905 205 S / 0231 170 093), I have to wedge on +5 degrees ATDC.
I manage to ride on the 2 settings while respecting the dynamic feeds of 27 degrees if I set to -7.5 and between 20 and 24.5 degrees if I set to +5 degrees behind. The best hot idle speed of 900 rpm is possible over + 3 degrees; suddenly in dynamics I'm at -20.

it is true that I have more torque if I set to -7.5 but the hot idle becomes too high 1100 see 1200 rpm

What do you think ?
does the igniter take over the engine? or is it the other way around?

My idle speed would be too high, i.e. 1100 rpm, if I set to -7.5.

I find my idle a little too oscillating between 780 and 950 .. is this the alternator?

I changed:
-Sensor cylinder head temperature: OK
-Compressions: 8,8,8,9 OK
-Fuel pressures and regulator: OK (35 psi and 28 psi)
-New igniter head, new igniter finger, new spark plugs, new wires, new blue coil.
-I put the air system under pressure 0.3 bars by the auxiliary air valve: no leak detected but not sure ..
-I set the rockers this week to 0.15
-I have identified my high engine point mechanically with camera in cylinder 1, the notch on the pulley is good, I know that my advance adjustment must refer to the zeo of the reglette
-overall I have trouble adjusting the cold idle
the auxiliary air valve is new,
the Thermoswitch works well
I changed almost all the hoses, put on clamps,
There remains the throttle body that I want to find as well as the decel valve


Nobody in France knows the settings of the ignition advances in the event of injection. ;;

Thank you for your help!
I am an info collector, because I am just starting out
sincerely

[Wildthings]

Not sure of all you are saying, but the proper timing for any of these engines is 28° before top dead center, @ 3800+ rpm, with the hoses off and plugged.

Vacuum leaks are very common on these engines and can cause a high idle. You can remove one hose at a time from the plenum and plug the nipple where it was attached to see which one(s) brings the idle down

[telford dorr]

To expand a bit on Wildthings advice, if your distributor is a DVDA type (the vacuum can on the distributor has two vacuum connections), then the initial timing will be 5 degrees after TDC (this assumes that both vacuum diaphragms are good and don't leak vacuum). If the distributor is a SVDA type (only one vacuum connection), then the timing is 7.5 degrees before TDC. If someone has changed the distributor to some other type, or the vacuum can is bad, then you will have to set the timing at 28 degrees BTDC at 3800 rev/min with the vacuum hoses disconnected, and then adjust the idle as needed.

Regardless of how you set the timing, always check that the full advance is around 28 degrees with all vacuum hoses disconnected from the distributor.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[sjbartnik]

Also this negative/positive terminology on the ignition timing is unnecessary and confusing.

Ignition timing is expressed in degrees before or after top dead center (BTDC or ATDC).

An ATDC timing setting is only used on distributors that have a vacuum retard function. If your vacuum retard diaphragm is dead or if the distributor has been replaced then that specification is no longer relevant.
_________________
1965 Volkswagen 1500 Variant S
2000 Kawasaki W650

[airschooled]

Timing affects idle. That’s why you have an idle speed screw.

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[mikewire]

Robbie is correct, just adjust your idle and you should be good.

My thoughts after reading through your steps...you're on the right track but I think that you maybe missed adjusting your points (ignitor finger??) gap? Or maybe you just didn't list it. And, the erratic idle is not related to your alternator.

So we're on the same page...this is the order of setting your engine timing on a type 4 - the group can keep me honest here:

**Set the engine at TDC**

1. Adjust and set your valve clearance on all valves to .006in (0.15mm) - 1976 will be a flat tappet, non-hydro lifter
   
2. Set your points gap to .016 - .020
   
3. Adjust your timing to 7.5 BTDC, engine running, vac hose attached, turn the distributor until you get to 7.5 BTDC
   
4. Set your idle to 850 - 1000 RPM (use the big screw at the base of the throttle body)

It helps to have a nice timing light with the ability to read RPM, dwell, and timing. Innova makes a really nice one...not sure if you can get it in France.

If you are still having erratic timing after all that, I may suggest you verify the advance plate inside the distributor rotates freely, and verify the vacuum advance cylinder is working properly.

Hopefully that helps and I'm not just telling you things you already know
_________________
-Mike

@countdowngarage
@bigskyeuro

1972 VW Kombi 9 Passenger Deluxe w/ 2.0L F.I. VWAC swap
1965 VW Beetle Deluxe Bahama Blue

[Pepite73]

thank you my friends I am happy to have new friends
I have only one suction pipe on my igniter
the ignition is electronic Accufire
I will try so dynamically by putting a lead of 27-28 max to see in dynamic at 3400 tpm, the idle on the other hand will be quite high

Mikewire, "If you are still having erratic timing after all that, I may suggest you verify the advance plate inside the distributor rotates freely, and verify the vacuum advance cylinder is working properly.
",
Can you explain me ? because i have ignition electronic..

Thank you very much
Pepite73

[AshC]

As mentioned, if using the "hoses connected at idle" method of setting idle then if you do have a DVDA distributor (the part number you gave suggests you dont) it would be 5 degrees ATDC.

The reason I'm repeating that is this comment in the first post:
Quote: " it is true that I have more torque if I set to -7.5 but the hot idle becomes too high 1100 see 1200 rpm "

I do have a DVDA distributor on my 79 and someone had set the timing to 7.5 BTDC at idle. The idle was 600RPM at cold and 1000+ RPM at hot. The cause for that can be the fact that the Decel valve and the distributor are paired parts. The Decel designed for the retarded DVDA timing at idle might not shut properly with 7.5 BTDC once opened by the deceleration pulse. This is because it has a lower threshold and the idle vacuum is higher with 7.5 BTDC idle timing. In my case could get the idle at hot to drop by slipping the clutch or restarting the engine when this was happening. I did a lot of searching and measuring vacuums before solving that.

Depending on which half of 76 your bus came from you may now have an SVDA (7.5 BTDC) distributor (ignitor) paired with a Decel valve designed to work with the DVDA idle timing. That may need a compromise on the idle timing to get right. Can you read the Decel valve part number? (there are several resources including ratwell.com which list what parts go together)

Equally, high idle problems can be caused by vacuum leaks or a stuck open AAV - in my case I had several leaks to solve before I hit this exact problem and was able to finally curse the specialist who set my engine up too advanced.

Note also that the advance mechanisms (mechanical and vacuum) are independent of the electronic ignition here.
_________________
- 79 CA FI Bay Window Bus
- 92 Mk1 Golf Cabriolet

[Wildthings]

I want to add something here, you can not set your timing accurately at idle if the rpm isn't correct while you are setting it. If the idle is already so high that the distributor is giving centrifugal advance then that advance will make it so you can not set you timing accurately. It is much better to set you timing at full mechanical advance, 28° BTDC at 3800 rpm, with the hose(s) off and plugged. Also note that the exact rpm is not important when doing this and there is zero reason to use a tachometer, just rev the engine until the timing quits advancing to determine if the timing is correctly set at 28° BTDC or not.

The original timing specs for these engines when they were used in the Type 4 cars, was 27° BTDC @ 3800 rpms, with the hoses off, why VW later specified than the timing be set at idle and thus much harder to set accurately is beyond me. Maybe it was just for safety reasons as working on an engine that is revved to sh*t adds a certain level of danger.

[Pepite73]

the number of my decel valve is: 0280160303
you think my advance timing should be to -7,5 before tdc?
i can send photos of the ignition system to your mail ?

it's clear that the idle change when it's cold start and after running when it's hot

[AshC]

That appears to be the correct decel valve for the SVDA (single-can) distributor so you can remove my theory from your list!

See "vacuum limiter" here: http://www.type2.com/library/fuel/fuelibo.htm

I would suggest following the expert advice (not me!) already given to set timing the other way and chase the idle problems from there (check for vacuum leaks, pinch AAV hose etc).

But, yes, from the parts you have described it seems that you should arrive at around 7.5 BTDC after setting timing and idle speed as others (e.g. Wildthings) have directed. If you dont then you might have a problem with the mechanical advance sticking.

You can post pictures here in the forum (or in the gallery and then here) of your setup - someone may spot something from that.
_________________
- 79 CA FI Bay Window Bus
- 92 Mk1 Golf Cabriolet

[Pepite73]

Thanks a lot
but on this site the timing advance with the number of igniter with bosch number give 5 degrés after tdc....

so I don't understand 🙁

see the link:

https://aircooledoutfitters.com/distributor-application/B1974AF

If i do it like this the max advance is 17 degrees before tdc....

[ImAddicted]

From the advice you are getting here (and it has worked for many, many people and the sources are fantastic), forget what you are getting from other sources.

1) Remove vacuum lines from distributor, plug them (the hose side, not the distributor side)
2) Loosen distributor clamp so you can rotate it smoothly with a little force.
3) Hook up timing light
4) Rev engine until timing advance stops moving
a) is it about 28 BTDC? If yes, go to #5
b) is it not about 28 BTDC? If no, adjust until it is. Go to #5
5) Now that timing is accurate, adjust idle using the big screw on the TB until hot idle speed is ~900 RPM
_________________
1979 Transporter (sold)
KC1MUR

[AshC]

That link isnt for your year although does list your distributor

This: http://www.type2.com/~keen/ignition.html#B7679

For 76 also lists your distributor and says 7.5 BTDC. Wiser people than me can say if this came with and without the retard vacuum can over time or if one of the sources is wrong. But it is worth knowing that they didnt change once to the 5 ATDC - they went back and forth a bit.

But, for now I would do what ImAddicted and Wildthings said first and see where that gets you.

EDIT: still do the above, but just for interest is the engine a GD engine code and is there still a sticker with the timing recommendation on the engine lid still? (doesnt mean you have the parts it came with anymore)
_________________
- 79 CA FI Bay Window Bus
- 92 Mk1 Golf Cabriolet

[Wildthings]

It does not matter if you have a Hall igniter ignition, have old fashion standard points and condenser, or some aftermarket ignition system, when you have the pedal dead to the floor and revved up going up a hill, your engine wants about 28° of advance. In fact it hardly matters what make of engine it is, all my VW, aircooled and watercooled, my Dodge Truck, and old Land Cruiser all time pretty much the same. The physics of the gasoline engine just requires this.

Unless you have ALL new factory parts to your ignition system it is better to time at full mechanical advance than at other conditions, because full mechanical advance mimics the full load, high rpm conditions when you are asking the most from your engine. You don't drive at idle so having the book timing at idle doesn't benefit you much.

[Pepite73]

Thanks AshC

it's written on your link:
Bus & Pickup Late 1976-1978 All States, 1979 Federal * 2000

Distributor: VW 021-905-205P, Bosch 0231 168 005 > 022-905-205S, 0231 170 093
Note: 0231 170 093 dist primarily used on California Late 1976-1978 and all Federal 1979 Models
Can Use:
Points: 01 011
Condensor: 02 074
Rotor: 04 033
Note: 0231 168 005 dist originally equipped with Speed Limiting Rotor 04 016 (5400rpm)
Cap: 03 010
Coil: 00 012
Vacuum Can: 07 060
Ignition Wires: 09 171
Spark Plug: W8CC
Timing Set At:: 7.5deg BTDC @ 850-950 rpm (Man Trans), 900-1000 rpm (Auto Trans) w/strobe, vacumm hose connected
Advance/Retard Range: Vacuum: 8.5-11deg Adv @ 7.9 In. Hg; Centrifugal: 8-13deg @ 1600 rpm, 20.5-24.5 @ 3400 rpm"

so it's max 20,5-24,5 ?

i will try 28

My engine is GD and its 7,5 BTDC on the little sticker

[mikewire]

[Wildthings]

[Pepite73]

Hi everybody
I have just done 200 kms stalling dynamically on 24 degrees BTDC and the result is very good under full load, I have done 110 km / h under load and on hills and things are going well.
the sound is mostly good;

So I think the value is dynamic seems to be between 20 and 24.5 in dynamic. this is what I did while hot, then by letting the engine return to idle I obtained 3 degrees BTDC in static.
Before driving I went from 24 to 22 degrees after 200 kms. I am happy with the result! this therefore corresponds to the link: http://www.type2.com/~keen/ignition.html#B7679. Thank you for your advice. I played a little on the richness screw on the top of the air flow meter to play on the idle ... is this recommended?

the idle returns well to 900 rpm but I have to wait a while and play with the idle screws, the one on the box and the one on the flowmeter ...
I know you have to measure CO optimally. it will remain to check that the igniter by opening it is well "oiled", to possibly change the vacuum capsule, to test correctly if there is an air leak ...?

[mikewire]