78 SuperBeetle FI Phantom

[got_the_bug]

I have 17" of vacuum at 3000 RPM.

Your diagram of the hoses is fairly different than my setup. I don't have a brake booster and no line to the air cleaner for one thing. The EGR/manifold/advance lines are different as well. So I guess that didn't help much.

I consulted a "bone stock" 78 Super to ensure I have the lines straight which assumes his weren't messed up but all I have to go on.

[Amskeptic]

I have 17" of vacuum at 3000 RPM.

Your diagram of the hoses is fairly different than my setup. I don't have a brake booster and no line to the air cleaner for one thing. The EGR/manifold/advance lines are different as well. So I guess that didn't help much.

I consulted a "bone stock" 78 Super to ensure I have the lines straight which assumes his weren't messed up but all I have to go on.

So advancing the timing a total of 12 degrees towards it's correct "static " position just barely helped? Well, at least it is out of the way. . .

OK, so a warm engine is idling barely at 400 rpm. Fine. Let's go to the next step, now that the timing at least in the ball park.

Where is your idle speed screw? It is a big brass deal and you need to turn it counter-clockwise to get the idle up to 850-950 rpm. With a non-functional retard, your problem should be that you cannot get the idle to go down to the correct rpm.

Can you run the engine with the black cover off the AFM so you can play with the wiper while the engine is running, or is it crammed in too tight and you can't access it?
Colin
Colin

[got_the_bug]

So advancing the timing a total of 12 degrees towards it's correct "static " position just barely helped? Well, at least it is out of the way. . .

OK, so a warm engine is idling barely at 400 rpm. Fine. Let's go to the next step, now that the timing at least in the ball park.

Where is your idle speed screw? It is a big brass deal and you need to turn it counter-clockwise to get the idle up to 850-950 rpm. With a non-functional retard, your problem should be that you cannot get the idle to go down to the correct rpm.

Can you run the engine with the black cover off the AFM so you can play with the wiper while the engine is running, or is it crammed in too tight and you can't access it?
Colin
Colin

I flipped the AFM around on the S-Boot so I could watch the AFM wiper. I had to remove the air cleaner to do that but I have nice visibility to it now.

The big screw on the throttle body is turned out far enough to be flush with the outside of the throttle body, much further and it will fall out. I can't turn it out (CCW) much further and it doesn't raise the rpm's when I do. Turning it in about 2 turns does slow the idle further which kills the engine at this low RPM.

[Gypsie]

Your mix screw is all the way out, indicating that someone was trying to lean out the idle mix and reached the max. (CCW =Leaner).

To get to a start point (I think it was mentioned) Turn the mix screw all the way CW to seat it and then about 4 full turns CCW (this will set you in the middle ground. This screw is for idle circuit only and has very little impact on running speeds.

Then you need to get it to idle using the speed screw though it may not be possible at this point if it is so rich that it will not hold a decent idle.

I think you would benefit by reading up on Colin's wiper adjustment method. Use that to ascertain where the afm is putting your mix.

in essence:
get it to run. The following tests are with the engine running. (you may want to connect a remote starter or have an assistant restart if it keeps dying). slightly push the wiper in the ccw direction (so the tip of the fuel pump activator boom moves 1/8-1/4 of an inch. Revs up or down? I would presume down as you will be telling it to give more fuel in the CCW direction and it sounds like it is too rich as it is.
Then push it in the CW direction the same amount. Revs up or down? I will again presume it will go up as the engine sounds like it wants less fuel.

If this is the case (ie needs less fuel) then you can adjust the over all mix (the little partial arc held with a screw that holds the wiper down to the base).
First determine where the wiper sits at rest to have a starting point to come back to if needed.
Secnond make notes of all adjustments for reference as you make them.

Now adjust the wiper 1 notch CW (notice I said notch and not click. The big cog will adjust with 'clicks' and is intended to adjust the 'dynamic' mix (ie more or less fuel at high and low rpms) that will come later.). The notches on the partial arc under the tiny screw are very tiny so my practice has been to use the tip of the FP boom as a reference point as it is easier to note how much you are adjusting. adjust so the tip of the boom moves about 1/8" CW. You will now have told the AFM to give less fuel across the board and you may be better positioned to fine tune. I only loosen the screw enough to allow the wiper to move when 'pushed' rather that freely loose. I find that it makes the movement more controllable during the adjustment. and then use a small standard screwdriver wedged between the notches and the base metal and twist for this very fine adjustment.

Gypsie 2 cents.

[got_the_bug]

Your mix screw is all the way out, indicating that someone was trying to lean out the idle mix and reached the max. (CCW =Leaner).

My thoughts exactly

To get to a start point (I think it was mentioned) Turn the mix screw all the way CW to seat it and then about 4 full turns CCW (this will set you in the middle ground. This screw is for idle circuit only and has very little impact on running speeds.

Already did this. It now runs so rich anything behind the tail pipe gets instantly black.[/quote]

Then you need to get it to idle using the speed screw though it may not be possible at this point if it is so rich that it will not hold a decent idle.

I can't get an improved idle. My idle screw (the big nickel sized screw on the throttlebody) is turned all the way out.

I think you would benefit by reading up on Colin's wiper adjustment method. Use that to ascertain where the afm is putting your mix.

in essence:
get it to run. The following tests are with the engine running. (you may want to connect a remote starter or have an assistant restart if it keeps dying). slightly push the wiper in the ccw direction (so the tip of the fuel pump activator boom moves 1/8-1/4 of an inch. Revs up or down? I would presume down as you will be telling it to give more fuel in the CCW direction and it sounds like it is too rich as it is.
Then push it in the CW direction the same amount. Revs up or down? I will again presume it will go up as the engine sounds like it wants less fuel.

Ok I did this test with someone holding my RPMS at 800. Moving that wiper up to 1/4" either way makes no change to the RPM's that I can notice by ear. I can't really move it 1/4 " to the lean (CW) side. The big mainspring that auto rotates the wiper clockwise when the engine is at idle or off puts a lot of pressure on the copper grounding tab if I move it any further clockwise.

The wiper is already cocked over to the lean side so far that the big mainspring forces the wiper to contact the copper metal tab and shove it up against the side of the AFM wall. If I move it even 1 tooth it shoves that tab way over. If you look at the picture of my AFM above you can see the screw inside the oval is way to left. So I have plenty of room to rotate the small cog but the pressure of the mainspring then forces that tab over well beyond what appears safe.



Notice how much bend there is in that copper tab on the right with the engine off. (The mixture screw in this picture no longer applies, as I've turned in to the mid point for now)

[got_the_bug]

Here's another tidbit of info I just discovered that I don't know what to make of.

I pulled off the oil filler cover and could feel air pushing out of the oil filler. It was very noticeable.

[Amskeptic]

Here's another tidbit of info I just discovered that I don't know what to make of.

I pulled off the oil filler cover and could feel air pushing out of the oil filler. It was very noticeable.

Consider that normal for now. Normally, any issue with crankcase breathing would cause lean condition. Since you are Rich City, you can forget about wasting time tracking down crankcase blow-by or vacuum leaks. I was surprised to hear that moving the wiper CW did not help you find a nice clean idle.

Something is goofy, and it sounds similar to our problem with jtauxe in Los Alamos where his engine could not draw enough air to idle. Somebody had even drilled out the AAR disk to give his engine more air.
He has an engine with low compression in one cylinder and high altitude (which makes an airflow-measuring injection engine run rich).

If you are uncontrollably rich, and the sensors are at 2,500 ohms at 68* (with wiring that is not chafed and shorting), and the fuel pressure is correct, then I think your last check may have to be compatability of AFM, ECU, AAR and even throttle body. We are almost at "subsitute with known good unit" stage of diagnosis.
Colin

[got_the_bug]

If you are uncontrollably rich, and the sensors are at 2,500 ohms at 68* (with wiring that is not chafed and shorting), and the fuel pressure is correct, then I think your last check may have to be compatability of AFM, ECU, AAR and even throttle body. We are almost at "subsitute with known good unit" stage of diagnosis.
Colin

Sorry, you lost me here. Sensors at 2,500 ohms at 68*???

Also not sure what you mean by "compatibility" of ...

I do have a local guy who may be willing to let me swap out sensors from his good running 78. Incidentally, I have 2 ECU's and tried both with no change.

[Gypsie]

Ok I did this test with someone holding my RPMS at 800. Moving that wiper up to 1/4" either way makes no change to the RPM's that I can notice by ear. I can't really move it 1/4 " to the lean (CW) side. The big mainspring that auto rotates the wiper clockwise when the engine is at idle or off puts a lot of pressure on the copper grounding tab if I move it any further clockwise.

The wiper is already cocked over to the lean side so far that the big mainspring forces the wiper to contact the copper metal tab and shove it up against the side of the AFM wall. If I move it even 1 tooth it shoves that tab way over. If you look at the picture of my AFM above you can see the screw inside the oval is way to left. So I have plenty of room to rotate the small cog but the pressure of the mainspring then forces that tab over well beyond what appears safe.



Notice how much bend there is in that copper tab on the right with the engine off. (The mixture screw in this picture no longer applies, as I've turned in to the mid point for now)

Ok, I'm a tad confused.

You had the engine running and an assistant held the accelorator to keep it at about 800 rpms and then when you manually pushed on the wiper to make it rich (ccw) or lean (cw) you had no change in rpms?

Can you manually lean or rich it to the point the engine dies? You should be able to.

Regarding the copper tab to the far right of the afm box. It doesn't look too awful far as it sits, and appears to have room to move over some. Keep in mind that, if needed, you can bend the 'boom' (the silverish rod) a bit. the booms only function is to hold the copper contacts apart while at rest to open the fuel pump circuit and turn off the pump when the key is on and the engine is not running. once you start moving air through the af portion of the m the boom moves ccw andallows the copper strips to complete the circuit so the pump will continue to operate after you are done cranking the engine. While cranking another circuit powers the pump. But for right now that issue is a red herring.

I might suggest doing some afm testing. Bentley will tell you what pins to connect an ohm meter to and what you should find.

I do not understand why you cannot move the wiper 1/4" CW when the engine is running. That wiper boom (that at rest, as shown in your photo, is sitting at about 2oclock) should be between 12 and 1 oclock while at idle. That should give more than an inch of room to move the wiper cw.

I think that the compatability thing Colin refers to is whether the parts are all made to play together nicely. different resistance etc. Many pieces and parts get put where they oughtn't to over the years. Possibly, but not likely if this bus ran with the current pieces at some point.

I say try to adjust the all over mix (tiny screw with tiny cogs) so that the boom tip is 1/4" CW. Then give it a try. If you are worried about the copper tab being pushed too far, first bend the boom (near the base where it has a little bend already) so the tip is 1/8"-1/4" ccw. The boom just needs to open the circuit when at rest.

Just curious, does the wiper jump ccw when you are cranking? Where does it sit when it is at 800 rpms?

Don't give up, believe it or not, we are making headway.

[Randy in Maine]

If it all goes bad a rebuilt AFM is about $100.....

http://www.fuelinjectioncorp.com/store/ ... cts_id=240

[bretski]

Sorry, you lost me here. Sensors at 2,500 ohms at 68*???

This is in reference to Temp Sensors I and II. Those are the spec resistance readings at 68*F.

Also not sure what you mean by "compatibility" of ...

There are model year changes in the AFM and ECU. It's possible that parts were "mixed and matched" by the PO(s).

[got_the_bug]

Regarding the copper tab to the far right of the afm box. It doesn't look too awful far as it sits, and appears to have room to move over some. Keep in mind that, if needed, you can bend the 'boom' (the silverish rod) a bit. the booms only function is to hold the copper contacts apart while at rest to open the fuel pump circuit and turn off the pump when the key is on and the engine is not running. once you start moving air through the af portion of the m the boom moves ccw andallows the copper strips to complete the circuit so the pump will continue to operate after you are done cranking the engine. While cranking another circuit powers the pump. But for right now that issue is a red herring.

I might suggest doing some afm testing. Bentley will tell you what pins to connect an ohm meter to and what you should find.

I do not understand why you cannot move the wiper 1/4" CW when the engine is running. That wiper boom (that at rest, as shown in your photo, is sitting at about 2oclock) should be between 12 and 1 oclock while at idle. That should give more than an inch of room to move the wiper cw.

I think that the compatability thing Colin refers to is whether the parts are all made to play together nicely. different resistance etc. Many pieces and parts get put where they oughtn't to over the years. Possibly, but not likely if this bus ran with the current pieces at some point.

I say try to adjust the all over mix (tiny screw with tiny cogs) so that the boom tip is 1/4" CW. Then give it a try. If you are worried about the copper tab being pushed too far, first bend the boom (near the base where it has a little bend already) so the tip is 1/8"-1/4" ccw. The boom just needs to open the circuit when at rest.

Just curious, does the wiper jump ccw when you are cranking? Where does it sit when it is at 800 rpms?

Don't give up, believe it or not, we are making headway.

At 800 RPM the boom/wiper is sitting at about the 1:00 position so yes while running I can move it 1/4" CW. My issue was that with the key then off, it shoves the copper tab way over. Bending the boom would give it more so that's an option.

However, moving the boom CW or CCW is having no effect on the RPM's so I don't see how changing at the postion of the small cog will make any difference. Somehow I need to figure out why it isn't responding to the changes of the wiper.

[got_the_bug]

Ok, this week my plan is to:

-Install new fuel segments on all remaining spots I skipped before.
-Install a permanent fuel pressure gauge between cylinder bank 3/4 and the fuel tank inside the engine compartment.
-Install a new fuel filter and cut open the old one.
-Put new gaskets on the valve covers and re-check the valve adjustements while I'm under there.

-Retest my Temp Sensor 2 per Bentley.
-Retest the AFM per Bentley.

If nothing new turns up, I'll ask a club member if I can try his AFM.

[Gypsie]

good plan. Looking forward to hearing the results.

[got_the_bug]

good plan. Looking forward to hearing the results.

A local mechanic told me I should be able to just pull the head temp sensor plug off and the ECU will "reset" to a default designed to let the engine run at an "average" temperature.

I'll try it, but curious if anyone else has found that to be accurate.