‘74 tii fuel delivery issues: last mile? Or rabbit hole?

[0257]

Hi all.  Well, since last post on this subject I have had mixed results with Zouave’s fuel mix.  Verboten screw good, and warm idles were in the 11-12.2:1 range with excursions into the high 10s for no apparent reason.  Midrange was fine except under light to medium throttle in 3-5th, when it got so lean I was glad there’s not a taller hill around here than a freeway overpass.  And cold idle was below 9, or right at it.  Not so the engine smelled flooded, but scary low.

 

I thought some of the mischief must be coming from the WUR, which leaked warm or cold.  I attributed lean readings at medium throttle to that, and resolved to find a working WUR.  After a couple of tries Harry Malkasian came through, and the new WUR is in.  But as I replace linkage bits and go to adjust the d-cam, I have an issue I have had from time to time: when the linkages are at rest and the d-cam loose in the collar, I cannot quite “easily” fit my 5mm rod into the first hole on the KF enrichment lever.  I can kind of angle it in, but this moves the linkage visibly.  I wonder if this is contributing to my rich (and incredibly rich cold) idle.  Seems this conditon would really starve the system of oxygen at idle, no?

 

Both my terminal fuel linkages are bang on 85mm.  I am pretty sure the KF pump has been manhandled in the past (eg, the verboten screw pivot has been twisted so that the vs hits the stop at a bit of an angle), but it acts right enough that I don’t suspect it of being the cause.  What to do about this?  Leave it, as it’s close enough, and just tune the idle mixture screw (I had done this before, but the results were mixed - see above)?  Or what?  My reptile brain tells me to shorten the KF to intermediate shaft linkage a twist or two til the first hole on the enrichment lever sits level with the hole in the body of the pump.  But my math-deficient pre-frontal cortex says there has to be a problem with that.

 

Ideas?  Cars n Coffee is in 15 hours!

[dlacey]

2 hours ago, 0257 said:

when the linkages are at rest and the d-cam loose in the collar, I cannot quite “easily” fit my 5mm rod into the first hole on the KF enrichment lever.

What is acting on the KF lever? is it pressure from the throttle linkage back to the bulkhead? If Yes, i would adjust  rod 14:

[0257]

39 minutes ago, dlacey said:

What is acting on the KF lever? is it pressure from the throttle linkage back to the bulkhead? If Yes, i would adjust  rod 14:

Would you do that even if it shortens it beyond the 249mm (I think) specified?

[0257]

Just now, 0257 said:

Would you do that even if it shortens it beyond the 249mm (I think) specified?

I should clarify: there’s some slack in that long rod portion of the linkage:

 

 

[bergie33]

4 minutes ago, 0257 said:

I should clarify: there’s some slack in that long rod portion of the linkage:

MG_0373.MOV 9.47 MB · 0 downloads  

 

 

Do you have the little plastic ball cup in the warmup regulator that the intermediate shaft ball sits in?  The slack that you have may be due to that cup missing.

[dlacey]

8 minutes ago, 0257 said:

48 minutes ago, dlacey said:

Would you do that even if it shortens it beyond the 249mm (I think) specified?

Yes, or at least pop that rod off its pivot at one end and check if your KF lever is now free to insert the 5mm idle stop...if that proves that tension in this linkage is the culprit then lengthen that rod to relieve the tension.

Make sure you still get full throttle movement from idle to WOT. (I think that's the only reason the specify this long rod length - to make sure throttle pedal has full function)

[ray_]

(There are some smart people here. Not me)

 

[0257]

1 hour ago, bergie33 said:

 

Do you have the little plastic ball cup in the warmup regulator that the intermediate shaft ball sits in?  The slack that you have may be due to that cup missing.

You can imagine my horror when I was trying to connect the intermediate shaft to the WUR and it popped out and disappeared into the darkness!  Happily landing on the floor below, and promptly popped back into place.

[0257]

1 hour ago, dlacey said:

Yes, or at least pop that rod off its pivot at one end and check if your KF lever is now free to insert the 5mm idle stop...if that proves that tension in this linkage is the culprit then lengthen that rod to relieve the tension.

Make sure you still get full throttle movement from idle to WOT. (I think that's the only reason the specify this long rod length - to make sure throttle pedal has full function)

Will pursue this tomorrow.  Though not sure — lengthen or shorten?  Lengthening would just push the linkage further forward, no?  When we’re trying to pull the enrichment level backward….

[0257]

45 minutes ago, ray_ said:

(There are some smart people here. Not me)

 

But Ray!  I was counting on you.

[ray_]

22 minutes ago, 0257 said:

But Ray!  I was counting on you.

Patience... patience!

 

[dlacey]

1 hour ago, 0257 said:

lengthen or shorten

Whichever works ...with the KF pinned at the idle position, you should be able to pop rod 14 onto its pivot ball without moving the linkage.

[0257]

Adjusted the long linkage rod down to about 285mm.  This seems to hold the KF enrichment lever at about the right place; it ‘suspends’ it, if you will, keeping the enrichment lever from rocking all the way forward past the hole. Best I can tell it allows me to get full throttle.  Agreed that the only reason to specify the length of that rod must be to ensure “hole 1 pinnability” at the enrichment lever and pegging full throttle stop at the rear of same.  

 

That adjustment accomplished both things, so I readjusted the d-cam a little further over the hole than previously and tuned idle.  Cold start (and it is pretty cool here now) was brilliant with the new WUR, idle starting around 1250 and dropping to about 1000 as the cone rises.  

 

Problem?  To get to 1000 rpm idle, I have to back the idle speed screw out till it just contacts the d-cam. In fact, I could remove the idle speed screw altogether and put tape over the hole without affecting idle speed.  As for AFR, idle continues to be between 11 and 12:1, with excursions into the 10s and even as low as 9.8.   I have experienced this “off the cam” condition previously when attempting to tune the KF. Seems to be wrong, but don’t see how to affect it

 

As for running AFRs, in 3d-5th, middle acceleration still gets verrry lean (up to 18:1), but returns to the safe zone quicker.  Cruise AFR in those gears around 3000 rpm is between 14.7 and 15.5.  Next pass I’m going to dial the d-cam a little richer, which ought to help settle down both mid-acceleration and cruise AFRs.  No idea what to do about idle.

 

 

[0257]

I’ll add one thing to the above: Zouave sounded and felt happier running lean as s##t than it does now.  As currently tuned, it is throatier, rougher, somehow…

[ray_]

There's unmetered air at the WUR right? Can that me meddled with to lean the idle (I forget)?