'85 4.9 WITH ALL emissions equip vac routing RESOLVED (mostly)

[TheGeneral]

I guess I have to buy one tomorrow.  

Two more things I noticed were, it ran BETTER cold (1st thing after overnight), almost calm in fact-- but got progressively worse as it heated up.

  Also, my temperature gauge got higher than normal--ie, rather than gauge topping off at about 1/3 above flatline and then only going a bit over that no matter how long I drive it (never reaches 1/2way line--almost, but not quite--even on a multi hour trip).  It went all the way to the halfway line and then over, just while it warmed up, and did not go down until I started driving it...but even then it was a bit higher than normal.  That concerns me.

[Gary Lewis]

Ok, so you've found the right calibration code, as shown below.  Tomorrow I'll scan that page in and post it, along with a close-up of the vacuum routing.


CALIBRATION PARTS LIST NO. 392
(Calibration No. 4-51S-R02)-6 Cyl. 300 C.I.D. (4.9L)
1984/86 F150 - - 2/W/D-M/T-Calif

[mat in tn]

that too is a positive sign. it runs better cold. being cold is when it needs more fuel! the exact reason it has a choke. as it warms up the choke must relax, be pulled off to allow it to lean out and only draw the needed amount of fuel. at idle that amount is from a slight amount of air through the throttle plate combined with an amount of fuel rich air through the idle circuit below the throttle plate.

[Gary Lewis]

Well, memory would be a good thing to have.  

Turns out that I have the truck-related bits of the 1985 Emissions Fact Book on the site at Documentation/CALIBRATION INFO & PART #'S and then the 1985 Emissions Info tab.  So you can find all of the info there.  However, for the 4.9L engines I've put a link in the Index.  And I put a link specifically to your calibration code.  (I'll put in links to the other engines later, probably during the football game tonight.)

Also, since my scans at 600 dpi and 50% contrast aren't crisp, I scanned that particular page at 1200 dpi and 80% contrast, which gives a much crisper rendering.  (However, it is also much larger, file size, so I don't want to do that with every page.)

Then, realizing that it is hard to read the vacuum routing turned 90 degrees, I rotated and cropped that page to give the view below.  But, even cropped to just the vacuum routing that is a 2.1 meg file, and that won't post here.  So the one below is downgraded to .9 meg to get under the 1 meg limit.  However, if you want the high res file you can download it here.

Hope that helps.

[Machspeed]

Man, I feel for you. I had some issues sometime back with a bad reluctor pick up coil that gave me all kinds of grief. It would sit and idle nicely but if I gave it any kind of gas, it would bog and backfire. Incredibly frustrating! With patience, and much help on this forum from Jim, Gary and a couple of others, we figured it out. For me, the road block was a brand new faulty pick up coil. It's new, it can't be bad! Believe it or not, I went through two of those brand new faulty coils and then said screw it and went to another brand at a different auto store.

Regarding the hissing, my experience with hissing is a vacuum leak. When I was doing all that work to my engine sometime back, I left the brake booster hose off and had a huge hissing noise and a rough running engine. Be advised, I'm novice at best. Others on here know far more than me. Try and be patient and realize that you're learning. When YOU get it fixed, it will be a nice accomplishment and you will feel the satisfaction of it all.      

[Gary Lewis]

In my experience hisses are usually vacuum leaks.  However, Welder Scott's 2150 hisses, and I don't know why, although we are going to work on it soon and I may find out.  

One way to find out if it is a vacuum leak is to spray brake or carb cleaner around the area where the noise is coming from.  If it is a vacuum leak the engine will speed up.  We did that with Scott's truck and proved it isn't a vacuum leak.  So it must be the carb.

So you might try that.

[Machspeed]

That's good idea, Gary! Yes, spray around the base of that carb and even into the carb and see if it does not change anything.

[Gary Lewis]

Into the carb should speed it up, but won't prove there's a leak.

Another trick is to use a piece of hose as a stethoscope to listen for leaks.

[mat in tn]

it all depends on what the listener calls a hiss and where it comes from. I understood that it was coming through the venturi. if so its tunable. if from somewhere else then it's a breach. vacuum leak. often my engines have a bit of a louder exhaust note yet the carbs have a noticeable hiss type sound through even multiple venturis. as vacuum leaks get eliminated the vacuum "break" at the throttle plate gets increased. louder.

[Gary Lewis]

Yes, you are right, Matt.  We don't really "hear" the sound and are having to use someone else's ears and words to describe both the sound and the location.  Which is why we are guessing.  But with testing I'll bet we can get it right.  

[85lebaront2]

Gee, Gary, looks like the one I posted, just rotated 90°.

As to Carburettors hissing, try a group of SUs. You can however, synchronize them by the hiss using a length of vacuum hose held near your ear. Zenith-Stromberg CDs can also be set this way also Webers.

[1986F150Six]

Gary Lewis wrote

Into the carb should speed it up, but won't prove there's a leak.

Another trick is to use a piece of hose as a stethoscope to listen for leaks.

Or, one can purchase a cheap cigar:

https://www.garysgaragemahal.com/#nabble-td11511

[TheGeneral]

Have I mentioned that you all are SO GREAT for trying to help????

I am off to get a vacuum gauge, some hose, and a cigar ala Scotty Kilmer.  The hiss is definitely coming from right out the top of the carb.  I am probably going to replace the choke pull off too.  

I am also going to check the alternator.   It is either original, or OLD.  My cab light randomly dimmed yesterday and that has never happened before!  Wouldn't it be something if voltage fluctuation was wreaking havoc on the feedback electronics!  Why did I not think of this sooner.  

Will report back later today/tonight.  


PS what is a group of SUs??

[mat in tn]

"Skinners union".  that's the proper name of the company that made the carburetors for many British cars

[Gary Lewis]

Glad you are getting help.  That's what we are all about.  

As for "a group of SU's", they seemed to come in flocks, and looked like hungry birds.  

[85lebaront2]

SU carburetters are a British unit with two moving parts, the throttle valve and the piston to which is attached a metering needle that goes into the jet. The series is an H, and there are H HD and HS versions, size is expressed as the number of 1/4" parts to the diameter of the bore (H4 = 1". H6 = 1 1/2", H8 = 2") The second letter is used for the design variants, H being the original design with an internal fuel passage to the jet which slid in a gland assembly, HS for the style with an external plastic line enclosed in a spring for protection, HD the jet is molded to a rubber diaphragm that seals the fuel from leaking.

Starting enrichment is done by pulling the jet down into the bottom of the body so the tapered needle has a smaller cross section and admits more fuel. Float chambers on the H and HD models are rigidly mounted to the main body on the HS they are mounted with rubber inserts. There was one last version called the thermal type SU which has the float chamber integral with the main body and uses a short bimetal tab to adjust the jet height allowing the jet to move up to a leaner setting as the under bonnet temperature rises.

Since Gary has weighed in. SUs are generally found in pairs, sometimes alone and occasionally in trios. I have not seen them in a quartet, but have seen their cousin, the Zenith-Stromberg CD in a quartet on early V12 Jaguars (which are a nightmare all their own).

[mat in tn]

not unlike the mikuni four pack i had on a suzuki 844 gs cafe racer I had a lifetime ago. anyway, I took my meds and I'm feeling much better now.

[TheGeneral]

Well...

Battery is 12.6 before start, Alternator is 14.0 at start, choke plate was just a bit open when cold, then after 1 gas pedal depression it was fully closed--

I double checked that everything was tight, including shaft and base of carb, manifold bolts, EGR, TPS (a tad loose), top of carb (was actually a bit loose on a few of the star bolts, I was always so fixated on making sure the base nuts were secure that I never checked these!)....found one hose at the manifold vacuum port that was hiding a small crack at the end, so I snipped the cracked part off...sprayed everything after I started and nothing jumped out at me...

there seemed to be a fair amount of play in all three of the wire links between choke and 'dashpot'?(pics is just a screenshot, not mine) , NOT SURE IF THAT IS NORMAL?



After using one of the vacuum ports off the manifold I was just about 16" Hg,  So I played with the set screws until I got it to pull almost 20" Hg....but when I hit the gas it only drops to about 5", never to zero, and it shoots up high (25") afterwards, then drops down to ~15, before settling back around 19-20.  

That's the best I can do, and I am NOT going to touch it anymore for now unless specifically advised to!

*****I did, however, think that the alternator should be pushing at least 14.5?  or maybe even 16?  My head is a jumble lol.   I think that the next logical steps are to replace motor mounts to reduce vibration and loosening, and then upgrade to a 3g alternator.  

Seems like one of those, "10 minor things = a big problem" situations.  (that and I didn't know, or still only barely know, how to set my carb w vacuum gauge!)

And now for a test drive and well deserved sunset walk.

[Gary Lewis]

When you say you "played with the set screws until I got it to pull almost 20" Hg", what "set screws?  If you are adjusting the idle air/fuel mix, then ok.  But if you are adjusting other screws then you shouldn't be.

However, it is normal for the vacuum to go towards 0 when you push the throttle, and then shoot back up high.  So that sounds normal.

As for the alternator, I wouldn't go changing that right at the moment.  The battery appears to be getting charged, and 14.0 volts isn't bad.  You sure don't want more than 14.5 volts.  So I'd get the other things sorted out first before tackling the alternator.

So, what problems are you having now other than engine mounts?  I've lost track.

[mat in tn]

well done! the description and the effort. vacuum sounds really good. the slight looseness of the choke pull-off links is perfectly normal as it's not as precise as other things and that is a manufacturing way of keeping things from binding etc.
   alt numbers sound fine unless you are running added accessories like lights, winches, kicking stereos etc. when it comes to vacuum caps for ports unused. take the extra step to buy a pkg of vinyl caps. usually, a multi pack with three to five different sizes and colors. these will probably be the last you buy. rubber caps degrade very quickly, and vac leaks come back to be dealt with later. not so with the proper size vinyl caps.
  I'm guessing the engine sat there running quite smoothly. throttle response sounds about correct as if it dropped more than that it would be way lean and then it would have no power. however, the engine draws from the idle circuit at idle but when opening the throttle, it transitions to drawing through the venturi and the larger main jet due to that being the path of least resistance. carburetors do NOT make an engine run or run faster! they only allow them to.
  as to loose screws on the carb. i know we dont want anything loose but many have overtightened them also. dont use a torque wrench. i dont even like to use any type of leverage wrench. screwdrivers and nut drivers are best to snug them without over tightening. even the throttle plate screws which you must remove the carb to get to are phillips and just tighten as good as possible with a good fitting driver