Riddle me this...falter on accelleration

[BDD]

For a 1972 GT
1.9 L engine.
Dwell, timing and valve train timing are correct.

With #4 plug sparking, the ball and pointer and timing marks on camshaft sprocket and camshaft rest block are aligned.

Car has a Weber 32/36 DGV carb.
The spark plugs were black but dry from burning too rich, I suppose. After the mixture screw was leaned out, the electrodes are starting to get tan (over the black) and one is getting slightly whitish and dry.

There were some vaccum leaks but I think I've corrected them.
Carb. had to be tightened down, brake boost hose replaced.
Could possibly still have an issue with the brake boost unit but I've probably fixed the vacuum leaks.

The car now starts right up.
It idles slow and the idle screw is all the way in to get that idle speed (after it warms up and slows down). After warming up it cannot be set to idle at 900 rpm.

Upon accelleration, the engine falters for a moment and may backfire out the carb. or out the tailpipe.

The mixture screw was formerly set too rich and I've been able to lean it out and reduce but not eliminate the backfiring.

How to correct the backfiring and faltering? Could it be a main idle jet issue?

Any suggestions? I have eliminated some of the possible other causes as you can see above.

[opelspyder]

Be 100% that the distributor is not 180degrees off. It is very easy to do when following timing instructions through the manual. Basically, you line up all the marks, then turn engine one revolution and then install distributor.
It can and may run 180 off, but will backfire, your carb adjustment might of been off. Also try to switch to electronic ignition so you can eliminate setting dwell.
Keith

[weatherman]

Yes I had that problem on one GT I worked on. I followed the manual and it sure enough was out 180. If I were you I would definetly check that.

[Jeff Pozorski]

Originally Posted by BDD For a 1972 GT 1.9 L engine. Dwell, timing and valve train timing are correct. Car has a Weber 32/36 DGV carb. The spark plugs were black but dry from burning too rich, I suppose. After the mixture screw was leaned out, the electrodes are starting to get tan (over the black) and one is getting slightly whitish and dry. The car now starts right up. It idles slow and the idle screw is all the way in to get that idle speed (after it warms up and slows down). After warming up it cannot be set to idle at 900 rpm. T

With your idle mixture all the way in you either have too large an idle jet or main jet. Engine should not run with the idle screw all the way in. Try reducing the idle jet down one size as the engine depends on the idle jet for most of the fuel it uses. Try searching for jet info on this site. It will help you alot and explain what you need to do the get the carb running right.

[BDD]

With the marks aligned as I've described, with #4 (back) cylinder firing, I believe that 180 deg. "mis-aligned" timing is not possible. Also, the distributor's vacuum advance unit faces backwards and with the engine running, the pointer and ball line up with the timing light on the #1 (front) cylinder (when I can get the idle up to 900).

Does anyone know what the jets Jeff described above should be for a stock engine?

One more thing: I do see that, when viewed from above, the top part of the carb. with the square air intakes is not an exact match to the carb. body below. On the front, drivers side of the carb, the bottom casting is a little bigger than the top. Is this normal for a 36/32 DGV (manual choke) carb? Is this a possible vacuum leak? I see exposed cast webbing in the part below which seems to be part of the inside of that carb casting. Does a gasket go here? Were they made this way so that tops and bottoms of these carbs. were interchangeable with other parts? This is at the top of the carb, visible with the air intake adapter off. At the top it would only affect intake air pressure....I think.

Maybe someone could check their 32/36 DGV carb. which is running right.

I think that the mixture screw setting and the idle screw settings are clues to a carburetor problem. Also, it is important to note that when I adjust the mixture screw....THERE IS PRACTICALLY NO CHANGE IN IDLE SPEED. It can start running rougher but not much faster or slower. That's why I adjusted it based on which setting reduced the backfiring/ power loss on acceleration. The other changes weren't very noticeable.

Thanks.

[BDD]

I don't think that I said that I have the mixture screw all the way in. The idle screw is all the way in just to get the engine to idle at 700 to 750 rpm after being warmed up and choke disengaged. From P.O. the mixture screw was turned pretty far out. I recently adjusted it after I had checked some other things first.

I moved it all the way in and then backed it out the recommended amount as a starting point for carb. tuning. Maybe backed out 1-1/2 or two turns or so. I forget. I moved it in till it ran rougher, then backed it out till it smoothed out and didn't backfire as much when accelerating. I'm not sure where it's at now but it is much leaner than from the P.O. and it's probably somewhere near the starting point for carb. adjustments.

[OrangPeEL]

I’m really thinking vacuum related timing*… but first I’d explore:
#1- poor idle… with car idling, crack loose the main idle jet holder-nut on primary side. If idle improves, I’d suspect the jet may be clogged/restricted.

Then to timing (static time and dwell already correct):
#2- distributor… cap off, points raised/open on lobe; push on side of rotor shaft towards the points & watch for point gap increase… this would indicate a worn distributor.

*Then to vacuum related timing:
#3- vacuum… verify carb and intake is properly secure & gaskets sealing. Get/use a mighty-vac type hand vac.pump/gauge (usually sold in a “one-man brake bleeding” kit).
->Engine off, use vac pump to apply vac at retard tit of distributor vac can; watch that it DOES mechanically actuate timing and DOESN'T leak off. Repeat on advance tit.
->Engine off, test integrity of vac lines by plugging one end and applying vac to other. Also bush-up a fitting to apply pump vac to brake booster line. After confirming booster line is good, check that valve holds vac when pump is released, and also that booster can doesn’t leak.

#4- Last resort, compensation... If vac system components test good, then engine may be internally sick- unable to control/create vac or align valve/ignition timing. If so, you might regain some runability by: Hook vac meter to top intake mnfld tit (right before head) & cap the disconnected end to carb. At idle, note vac reading. Slightly rotate/adjust timing @ distributor to achieve peak vac @ idle. If/as idle increases, back off the “idle stop-set” screw (close throttle plate) to obtain higher manifold vac. Rotate distributor & back-off idle screw as needed to achieve optimum manifold vac and acceptable low idle. Not positive, but I think you’re shooting for about -15psi manifold optimum… I believe near -8psi required to fully engage vac advance @ distributor.

HTH
-Dan

[baz]

just a thought but what are you fueling with , stock pump or electric as it sounds almost like over fueling because the needle valve is getting beat
,is the float ok in the carb not leaking and level set right , does the needle valve shut off ok ,not sticking open a little
is the accelerator pump ok ,if the diaphragm leaks a little you can get an over rich situation when you floor the peddle

[BDD]

It's a stock fuel pump and I looked at the carburetor accelerator pump diaphram last week. Couldn't see any damage.

This is something that specifically affects the acceleration from idle...plus the carb. is goofy in othre respects too, the idle setting, unresponsive mixture adjustments, etc.

I thought I was reading that backfiring and faltering from idle was commonly a problem with Weber carbs.

[Jeff Pozorski]

Originally Posted by BDD It's a stock fuel pump and I looked at the carburetor accelerator pump diaphram last week. Couldn't see any damage. This is something that specifically affects the acceleration from idle...plus the carb. is goofy in othre respects too, the idle setting, unresponsive mixture adjustments, etc. I thought I was reading that backfiring and faltering from idle was commonly a problem with Weber carbs.

The SOLEX carb is the one with the above problems, not the Weber. My Weber was having some of the similar problems yours has: running way to rich, no power what so ever, poor gas mileage, back-firing, etc. I bought the carb supposedly all setup and ready to to, just not for my engine! (basic 1.9) Turns out the carb was jetted way to large on all jets and was dumping gas like crazy into the engine and most was blowing out the rear tailpipe as black smoke and unburnt gas. After reducing jet sizes per most of the problems disappeared except that the idle screw must be in all the way in order to get the engine to idle decent. Bob L. posted that this was a sign that either the main jet or idle jet was still a size to big. Weber carbs run off the idle jet for most of the time and the main jet kicks in as more power is needed. You said adjusting the screws doesn't do a whole lot anymore so that would seem to indicate that the jets are still to big to be properly adjusted by the screws. In the past 3 weeks or so there were quite a few postings by Charles and Bob about proper jet sizes for different types of 1.9 engines. Do that search and you should find the answer to your problems!

[BDD]

Jeff:
Thanks for the replies.
I have been looking at those other posts trying to sort out what jets, etc, are recommended for a STOCK 1.9L. engine and 32/36 carb. Many of the posts seem speculative and often the successful results don't get posted.

I was just out looking at my carb.
The main idle jet is a 55 (must really be 5.5 mm) and the secondary idle jet is MISSING! I've cannabalized a secondary jet (size 70, 7.0mm) from another Weber that was on a 73 GT that I owned but never drove (I drove it once on a test drive when another owner had it. by the time I found it again the next owner had really screwed things up) . It's the wrong carb. though (28/36?) and that jet doesn't really fit in this opening. The threads are too long and it bottoms out. So it's just in finger tight for now.
Of course I'll replace that but I need to know which jets, emulsion tubes, main jets, etc. to order.

I also see that my idle jet is NOT located hidden under the acceleration diaphram which is the indicated position on a 32/36 DGV exploded diagram that I downloaded...possibly from webber.com.

I also see that there are two angled hose attachment points on the front of the carb. One of these has a line running to it and the other is completely open. I assume that has to be plugged. If I remember right...it could POSSIBLY be an attachment point for a line from the original charcoal canister.

There is also a small hole in the carb on the drivers side, way down low, probably aft of where the secondary idle jet is supposed to be.

Any thoughts?

[Jeff Pozorski]

I will check my jet sizes tonight when I get home and post them for you. It should be a good starting point for you, especially knowing that the idle jet should be a size smaller.
The hole on the drivers side of the carb, is that on the outside or inside of the carb? Is it possible that you are missing more jets? With the one jet for sure missing that will really screw things up for you.
I will do some more digging and get back to you later this evening.

[BDD]

Jeff:
Thanks. Note, I added to this at 3:47 p.m, Central Time.

The hole on the drivers side is drilled through the outside of the carb. It's on the side of the carb. body and right on the centerline of the carb. It's also down low and right between the bolts that go through the carb. base. I don't know if a jet or a threaded plug goes there.

There is no place for a diaphram jet under the diaphram. I expected to see one but there's just metal under the diaphram spring.

If you could, also look down at the carb. from above. As I noted earlier, the front left corner of the bottom of the carb. I have projects out a bit from the top casting of the carb, (the part that has the square barrels cast into it). This is looking down with "front" meaning towards the front of the car. This is right above the place that's cast to receive a secondary acceleration pump (which does not exist. on this carb.).

There is also an opening in the back of the carb. low, between the base bolts that has nothing in it.

I also have the angled hose inlet on the right side (front) with nothing going to it right now.

There is also a Y type hose connection at the front/ top of the carb. when viewed from above. A hose connects to the pass. side one but not to the drivers side. I can't tell yet if this is blocked on the inside but a small screwdriver fits in a 1/2" or so.

I suppose that all of the jets have to work together and the Main fuel and air jets feed the idle jets, etc. So all sizes are important. Any help is appreciated.

[Jeff Pozorski]

One quick thought on the "holes" in the carb: can you feel any vacuum pressure when the car is running if you put your finger over them? This would let you know if you have multiple vacuum leaks that could be part of the problem.

[BDD]

Jeff:
I'll check this when I can, maybe later tonight. I think I did this earlier to some of these openings but will double check. I have ignored the carburetor till now because I was checking through the other possible problems and think I have mostly eliminated them. As it is, the carb. does have some real issues.

[Jeff Pozorski]

OK, back as promised!

First thing, I took a look down the throttle of my Weber but everything looked fine, nothing like what you described. Could it be that your carb is possibly 2 different carbs put together. That may explain why yours looks so different. Can you maybe take a picture to post?

Secondly, I dug up what my Weber is currently setup with. Jets are as follows: Primary: main 150, air 185, idle 55. Secondary: main 150, air 160, idle 55. As I mentioned earlier I still need to either drop down on my main jets or idle jets. I did some more digging and found a posting from Otto where he recommended to someone else with a stock 1.9 engine & Pertronix ignition the following: Primary: main 140, air 160, idle 50. Secondary: main 150, air 170, idle 60. He also strongly recommended a cold air setup to further boost performance.

My jetting was setup from Racetep after I told them what my engine setup was. I failed emissions badly and the car ran like crap before I made the switch. It runs much better now but you can still feel that something is holding it back. I am probably going to try Otto's setup and see what I gain from it.

I hope this helps you with your carb. Let me know how things turn out. I forget, where in Wisconsin are you again? Maybe we can get together and do some trouble shooting if this doesn't work for you.

[73 gt man]

Guys I hope this helps, my car is a stock 1.9 low compression 73, I failed emmisions terribly here in Phoenix. After talking to Gil at OGTS I did the following to my carb, I will give the before and after.

Primary fuel 140/125
Primary air 160/160
primary idle 60/55
secondary air 170/170
secondary fuel 140/140
secondary idle 55/55

I also made sure there were not any vacuum leaks, now with just a bit more in timing it will run even better, but those jets made a world of difference.

Hope this helps.

Sean

[BDD]

I notice that one of the suggestions on response 6 of page 2 of the thread "so many jets" or something like that indicates the opposite of how my carb. is jetted. Mine is jetted just like how the 32/36 carb's. are set per the factory....the larger jets were on the primary side and the suggestion had the same jet sizes but reversed them with the larger jet sizes being on the secondary barrel. That was for a 2.0 L. Opel engine, may have been high compression. See that part of that thread for those jet numbers.

Thanks for the jetting suggestions for stock engines. They seem to make a big difference for people.

I'll look around on the site when I have some time to see how to post photo's.

[BDD]

Does anyone have a spare #50 size idle jet for a Weber 32/36 DGA carburetor
that they could sell me? That's what's missing on my carb. I'm going to start with that setup, then I'll probably try some other jets to see what happens.
I want to be able to get this right away so I can try it out.

Thanks

[BDD]

Here are some pice of my Weber 32/36 DGV 5A carb. I have the choke mechanism temporarily detached to get inside. Does everything seem to be hooked up right? No missing hoses, etc?

I guess the open spot on the front left corner of the carb body, when viewed from above, is normal for this carb?

Is the angled tube at the front right of the carb supposed to be "empty" and open with nothing attached? It is not blocked off inside and continues into the carburetor.

Photo's didn't load....how do I reduce file size of digital photo's?

Thanks for the photo advice.

[kwilford]

Originally Posted by BDD Photo's didn't load....how do I reduce file size of digital photo's?

Use pretty much any Photo-Editing software (the Irfanview free download is on the front page here, but ACDSee, MS PhotoEditor, or any of the Camera-based viewers) can be used. Find the "Edit Image" choice, and change the resolution so that it is bigger than 640 pixels in any one dimension (usually 640x480 works fine) and save it (use a different file name if you want to keep the original at HiRes). HTH

[BDD]

I've posted pictures of my carburetor. Does it look like it's hooked up right?
See the question I've posted above with the pictures.