I have a 2.0 type IV engine with 44idfs on it. I was going to sync the carbs today and noticed that even when not pumping the throttle the accelerator pump drips a stream of gas down into the throat of the carb enough that its pooling up a bit on the throttle plate. I'm getting popping back through the carbs. Timing is spot on and the valves are correctly adjusted. I take it this is a problem and they arent supposted to do this? It also smells like its still running to rich. I have 135 mains, 200 airs, 55 idles, 36mm vents, and no velocity stacks currently. Mixture screws are set 1.5 turns out. Its also hesitating from idle to around 3K rpm if I step on it hard like its flooding out. Time to put kits in the carbs? Does the jetting for the accelerator pump need to be changed or adjusted?

John

i had this with some 32 DCNF's...

there was a bit of preload on the accel pump arms even at idle, and every little vibration squirted out a bit more gas (making the vibration worse...).

i removed the accel pump actuator arms and ground in just a teeny bit of clearance, and it solved that problem. i had heard of it before, and sure enough, it happened to me. so check that you have a little clearance in the accel pump arm at idle.

also (first, actually...) make sure that the throttle linkage is not preloaded at idle - that'll cause the same thing. disconnect all the linkages, check for clearance, and if there still isn's any, look to the accel pump arms. if there is some, your linkage has some preload, and you're not seeing 'real' idle...

something to check ...

It is highly possible that the screw which holds the pump jet in place is loose. I had this happen before. The suction from opening the throttle causes excess fuel to be pulled into the carb.
It requires removing the top plate of the carb to tighten the screw.
If you are lucky no new top gasket will be required.

Does it drip while idling or with the engine off?
If it drips while the car is NOT running, then it could also be the neede/seats (float valves).
And while you're here, IMHO 36mm vents are a tad large for a stock 2.0.
Consider mixture velocity thru the carb- as the venturi gets larger (diam.) the air moves slower down thru the carb (for same amount of suction).
If you make the vent daim. smaller the mixture velocity will increase (at lower rpms) and can possibly take care of all of your hesitation.
You get better mileage too..it can possibly lose you a snippet of top end but you may gain power and smoothness all around.
And get some velocity stacks!!
-Bob O

I have the SAME F-ing problem on a customers car right now. Hesitation/stumble before 3k RPM. Stock 2.0 engine. 40IDFs. 115 mains/52 idle/200ac/28mm ventu.

It had: 145mains/52 idle/200 ac/36mm ventu.

What I have found so far:

Loose accel pump nozzles just like Chris said.

No matter what I do.. it stumbles. I have a hole slew of jets for testing..

The timing is set at 32 degrees running a 1.8 dizzy with twin lines hooked up to vac adv.

Starts fine.. idles fine.. new plug wires..


B

Thanks brad. Its always comforting to know I'm not the only one. I actually have quite a bit of experience jetting carbs having worked on motorcycles for a long time. I just really havent messed with webers much.

Well here's what happened since I posted earlier. I went out the garage to see if I could fix my problem with my right side tail light and front marker light not coming on. I noticed a new puddle under the car. The passanger side IDF throats were full of gas!!! I think the float stuck open. So I decided to go ahead and take that carb off as that was the one I was having most of the problems with anyway. I pulled it out and started tearing it down. I took the float out which had some trash in it. I was taking the fuel inlet barb off and broke one of the support parts(the split one) for the float pivot rod. Now I need a new carb top. I also had some trash in one of the idle jets.

On top of everything else while I was messing around with fixing the tail lights, the left side brake light quite working. While I had the key on trying to see what was going on with the brake light some wires decided to smoke themselves in the steering column. Now my blinkers and hazard lights dont work. My speedometer is hating me to at the moment. It will work sometimes but not others. I also have a nice vibrating wobble in the steering wheel at about 95. The trans is whinning in 3rd gear. The throttle pedal and pivot bushings need to be replaced. At least now I know I really love driving a 914 .

John

When it rains it pours, lol.
Sorry to hear it is all coming down at once. That never helps.
I might be able to weld the split support on the carb. I used to do things like that for a cycle shop nearby.
Find out how much a replacement is first.
Burned wires sometimes start with a bad ground - or a short in an odd place.
I had the connectors on a license plate light reversed once during reassembly and had the worst time figuring out why I kept blowing fuses. It turns out they can only go one way because the housing is grounded and one connector is attached to the housing. The power has to go through the lamp first.


That sounds like an accelerator pump problem. If the pump diaghram is ok then the adjustment of the pump is wrong. Could be either not enough or too much fuel. If the linkage is working right then try a different size pump jet.

Welding the carb top will not be fun. Those castings look really ugly. I built a custom oil pan off a cut up GSXR 600 flange and it was ugly welding my nice plate to casting and it was a pretty clean casting.

Brad as far as the stumble goes, get a bigger idle jet. at least a 55 or maybe even a 60. Yes it will be a little rich but hell I could run a 65 in the winter on my car. got rid of the stumble. I would toss a bigger main in there also, but fix one problem at a time. Are your idle jets clean? Pull the jets out and spray some compressed air in the idle circuit and check the idles for obstructions.

John, since you have the carb apart go ahead and pick up the smaller vents that we were talking about last week. If you want I can try welding that carb piece if you don't want to ship it to Chris. His job will probably be much better but I can stick them back together and grind it clean so it looks good. I should be over at school this weekend so give me a shout and we can hook up sometime saturday.

"I have the SAME F-ing problem on a customers car right now. Hesitation/stumble before 3k RPM. Stock 2.0 engine. 40IDFs. 115 mains/52 idle/200ac/28mm ventu."



Hey Brad,

Sounds like you are having as good a time with my car as I did. Nice to know even the pros get stumped sometimes!
Those carbs had better be clean as a whistle since I rebuilt them....

Carrie

Brad,

What does the exhaust gas analyzer show below 3K? With that gear, seems like it would be obvious if the car was running lean do to small idle jets. You don't have a dyno at the shop for your disposal though, eh? It's always nice to be able to chase down fuel/air delivery gremlins with an EGA and a dyno. Could be that her car needs smaller air correctors too. What size does Carrie's car have now?

Good luck,

This is a tough issue with her car. I found two GREEN wire terminals leading into the cap and a coil wire hanging on by the dust cover. Of course when I pulled two wires off to check them, I didnt pull the two that where green with algae until MUCH later. The chances that I would pick the two good ones is pretty slim, but I managed to do it.

Anyway. She said that it ran fine. This leads me to beleive that it was tuned fine at some point.. so the question remains: what changed between now and then ? I have tested a new coil. It currently has a different dizzy in it. I have hot wired the new and old coil to eliminate any voltage issues to the coil. I have checked all grounds. I found the floats to be WAY off. Somebody measured them with the ball collasped.

We will see. The dyno I need to do this only exists in a few shops. The 4 gas analyzer wont tell you anything that is load sensitive like this. I can make the car very crisp off idle, but it will still stumble on acceleration. I need to check the fuel pressure while driving.


B

*cough*
That would have been me... hmmm.. Someone will have to explain the "ball collapsed" concept cause I have done this more than once under supervision and the last time around used the same methods...

Measure once with it open, once with it closed... I set it to 11.5mm closed and 33-32 open...

Cornfusedly yours,
Carrie

Welcome to the BBS, Carrie.

Don't mind Brad. He's... Brad.

-Rusty

She knows who I am... I have her car right now.


B

well hellooo, good to see you finally made it over here

haven't seen you in quite a while!
Andy

Hey Andy!

Yeah, I've been MIA for a while, pissed at my car. Hopefully these guys can figure out what the deal is so I can go road-tripping this summer!

Carrie

I was just playing with my carbs for my 2056. They were rebuilt not too long ago but the car melted #1 piston at Willows so I was trying to check things out. (thats why I got a deal on the car )

The jettings (40IDFs) are 130Main/160Air/50 idle/32 Venturi/F11 emulsion - does the Air sound a little small?

Anyhow, I dismantled the top end and it was pretty clean and everything looked good. I tipped it upside down to remove a little dirt at the bottom of the float bowls and out floated a 2mm X 1.5mm sliver of metal from the emulsion tube hole of #1 (I'm pretty sure thats where it came from)! So, would a large piece of foreign matter blocking the main jets cause an instant leaning out and hence a melted piston? Or wouldn't that explain the problem?

Hoping that its the smoking gun I'm looking for...

Richard

Anything over Idle on that hole would be lean if anything was blocking the main jet.

Brett,

I tried 55's in it and it would foul the plugs in no time flat. I'm down to 50's right now and it idles fine and starts perfect. Revs crisp with NO load and still stumbles on accel.

I checked compression yesterday: 120-125 on every hole. Not great.. but not bad enough to cause any real issues.

Next step is to check the valves. It sounds fine, but I realized it would not run correctly if they where tight. I'm getting a lot of reversion out of the velo stacks when I blip to wide open.

Help.


B

I realize that this is a bit of apples and oranges, but.....my 2.7L has a smaller hole (450 cc) than the 2.0L. I run 60 idles, 135 mains,145 air corr., and 34mm venturi. Is this rich?....or whut?
I also like NGK plugs. For a low compression motor, something on the order of BP5ES.

Welcome to MSD "burn thru". I didn't go to that stuff cause it's pretty. Guys say the MSD ain't worth spit cause you don't get any hp from it.....true, no hp, but it makes them run smooth down low....when your a *tad* rich. I got tired of fouling plugs.

The point is: carbs is carbs....tho the engine characteristics are a tad different. I know diddly bout T-4s, but you seem lean on the mains.

Odd to get fuel reversion from a motor/cam with minimal overlap....or so it seems to me.

I'm running 55 idles in 40IDFs with 28 vents on a nearly stock 1.7, with no plug fouling problems. 50s were too lean (bucking at light throttle). I'm a still rich now (idle mixture screws down to 1 turn out, and plugs are still black), and will probably drop to 52s, but it runs cleanly with the 55s, and I'm getting gas mileage in the low 20s, so it has to be close.

I just went through the same thing on a T4 conversion in my bug. Here's what I found.

Either too small idle jet or too small a main jet will cause the hesitation you describe. The hesistation will occur slightly sooner with idle jet too small, but the difference is subtle. I found if I could drive around the hesitation by slipping the clutch off the line, it was the idle jet . The hesitation from the main jet came just a bit later so you'd have to slide the clutch like mad to drive around it.

Keep in mind the "idle jets" only control the fuel flow to the transition ports. The idle of the engine is really controlled solely by the screws. The taper on the idle screws of IDF's makes them really sensitive. Even with 45 idles the difference between light and dark plugs at idle was 1/2 turn. One thing worth checking here is that no one previous has filed the edge fo the plate causing the transition ports to always be uncovered at idle. That will foul plugs for sure. Use the procedure in the Pat Braden weber book to size the idles. Works everytime.

125's made my engine hesitate like crazy. 130's still had a small hesitation, and 135's were just right. 45 idles were too small and 55 idles did not fix the hesitation without the 135 main jet. Here's my engine specs and what I ended up with.

Motor
1911
Stock 1.7 heads
mild cam something like .430x290 forget exact
8.8:1 cr
twin 40 IDF's
135 main
200 air
F11 emulsion tube
50 idle

This setup runs like champ and gets about 27 mpg on the highway in a bug with a .82 4th, 4:12 rear, 205-60-15 rear tire. I drive 80 (that's a clocked 80, not by the speedo) all the time.

There is an alternate setup in the back of the Pat Braden book that uses an F16 emulsion that changes the point that the air correction is functional. I think it uses a 125 main and a 180 air. I'm going to try that next.

I'd be interested to hear about what you find on this engine.

Kelly