TheSamba.com :: View topic - No power under load. I'm running out of ideas. *FIXED*

Sun Jul 13, 2008 12:19 pm

I decided to put smaller venturis in my dual Weber IDF 44's this weekend to try and get a little better low end power. I had 36 vents and changed to 34's. Before I changed vents, I had no problems, but now that I changed the vents, I have little to no power past 2000rpms under a load. It's also popping out of the exhaust. It seems like it's running to rich but I'm running out of places to look. Is it a jetting issue? I may just have to switch back to the 36 vents. Any ideas?

idle jets - 55
main jets - 140
air jets - 200
floats 11mm
fuel pressure 3.5psi

Sun Jul 13, 2008 12:23 pm

Switch back.

Sun Jul 13, 2008 2:58 pm

Apparently, that wasn't the problem. I switched back to the 36 vents just to test it, and it's the exact same problem with the 34's. Back to the drawing board...

Sun Jul 13, 2008 3:11 pm

You may have disturbed some crap and it is now plugging a main jet.....

Sun Jul 13, 2008 3:13 pm

vacuum? Hose not connected to distributor or carb?

Sun Jul 13, 2008 3:20 pm

I sprayed the carbs out while I was changing the vents. The jets don't look plugged. I checked for vacuum leaks but didn't find any. My spark plugs were pretty black. I'll try changing those out and see what happens.

Sun Jul 13, 2008 3:29 pm

along Karl's line of thinking, how is the fuel flow?
Could be filter or pump.

Mon Jul 14, 2008 8:42 am

isn't 'no power under load' a symptom to a bad condenser?
I may be remembering wrong, been a long time since i've had one bad.. but.

let the experts chime in on that.

Dan

Mon Jul 14, 2008 10:39 am

I know that you are working on a carb problem, but is there any chance that somehow a couple of spark plug wires got switched on the distributor cap? I recently discovered that this was the problem to my low-power problem. You definitely get the exhaust popping that you mentioned.

Thu Jul 24, 2008 5:43 pm

So, I finally gave up on trying to figure out what is wrong with my bus myself and took it to a mechanic. He said he thinks that my carbs are too big for my size motor and that the cam shaft is wore out. He said I need to rebuild my motor and put smaller carbs on it. He hasn't had the motor out yet, this is just his opinion. Keep in mind, that my car was fine before I took the carbs out to change venturis. Now...this doesn't sound right to me at all. I need some feedback here, please. :cry:

Thu Jul 24, 2008 6:06 pm

I think you ought to switch mechanics, or better yet be your own mechanic.

Thu Jul 24, 2008 6:09 pm

I agree, did he do a valve adjust and then warm it up for a compression test? What were the results?

Thu Jul 24, 2008 6:21 pm

He didn't really say what he did to come to his conclusion. Basically, he just said that my dual carb setup was too much for my engine, which resulted in my engine needing to be rebuilt now. I should have asked him what tests he did, but I was too busy thinking that I was being screwed over. I'll admit that I'm still learning with my car, but I can tell BS when I hear it.

Fri Jul 25, 2008 2:13 am

I agree 44's are too big for your motor (1915cc's) try getting your hands on some 40's or 36's.

Fri Jul 25, 2008 5:09 am

How do the plugs look for combustion. Are they black or dark brown. Might want to play a bit with the timing. Vacuum line might be off or cracked. Load works the advance. Just some ideas.

Fri Jul 25, 2008 10:58 am

IMO if it ran decently before with the 36 venturys then changing them back should have brought it back to how it ran before…

I did not see anyone mentioning to check the float on your carbs? it could be your dumping a lot of fuel in, making it run poorly… there is also the chance that you de synced your carbs and/or caused and ignition problem when you removed and replaced(RR) your carbs.

You may want to take the following approach to fixing your problem i.e. eliminate any ignition problems before trying to get your carbs dialed in...

A.) Make sure your distributor and timing are setup correctly-

1.) Figure out witch distributor you have and if it is appropriate for your vehicle (bus advance curve is different than that of bug advance curve)
2.) Have an DVAD or SVDA distributor that is working correctly check the vacuum can by sucking on the hose and see if the distributor plate moves in the right direction (Do not Use a 009 distributor unless this is an industrial engine running at a constant speed 99% of time) if you must use a mechanical only distributor get Mr. 010 to setup an 010 or 019 distributor for your bus or a Mallory Unilite from ACN; setup however they recommends based on your engine setup…
3.) Is there a spring under your distributor drive to keep it from moving up and down? There should be, maybe the previous owner/builder forgot it, check for it.
4.) Check to see that you do not have excessive endplay in your crank (it can make your timing vary +-+-…)Push and pull on the front pulley, you should not be able to feel it move back and forth, if you think you have excess endplay get a dial indicator and check that it is within speck…
5.) Use a Top Dead center finding tool to find true Top dead center for your motor; the pulley on the motor may not be the one that came with your engine from the factory, mark the pulley at TDC after finding it with the TDC tool.
6.) Install magnetic points; your timing will become more stable & engine easer to time, (if it does not stabilize your timing, timing mark bounces around as you are trying to time it using a timing light, and RPM are steady, your distributor or motor may need rebuilding)
7.) Adjust your valves to spec, 6 thousands of an inch…
8.) Check to make sure you have the correct Bosch pugs and that they are gaped correctly
9.) Make sure you have good quality Bosch plug wires and that the resistance is within speck and that the firing order and plug wires is correct.
10.) Make sure you check your distributor cap’s condition do not use non Bosch distributor caps on Bosch distributors,(clear caps etc) it should not have corroded connectors in wire receptacles in top of cap, check them, also check that the inside of the cap dos not have any crusty carbon deposits on the connectors, make sure you have the correct Bosch rotor and that it does not have carbon crust on the end, clean any carbon dust out of the inside of the distributor cap.
11.) Before timing your distributor(If you have a vacuum + mechanical distributor) make sure you have the correct size vacuumed line and that they are tightly on where they are supped to be. Make sure you do not have any vacuum leaks in your intake system, (it will cause wrong signal to distributor). If your distributor timing adjustment require you to keep the vacuum hoses connected check to make sure someone did not adjusted the idle using the chock came screw so your carburetor throttle can’t come to a fully closed position; because if that is the case your vacuum distributor is not working correctly (distributor vacuum hole is just above throttle plate and if the throttle plate is open any it will start advancing the vacuum distributor) to check, take the air cleaner off (engine off), and use your fingers to open up the chock plate in the carburetor all the way open, now adjust the chock came screw on the top of throttle lever so that it just touches the fast idle cam. Then turn it in 1/4 turn.
12.) Use a timing light and make sure that you have the distributor timed correctly to the distributors specks, at the same time check to make sure that your timing is advancing evenly as your RPM’s increase and that your total advance is what it should be at 3500+ RPM
13.) Now that that is done you should be able to fine tune your carburetor(s) knowing that your timing is correct and that it is not the cause of you flat spot or rpm sluggishness above xxxx-rpm…

B.) Remove your carbs and clean thoroughly with compressed air, make sure all the seals, o-rings and gaskets are in good shape, adjust the floats to speck (Very important), see URL below on how to :0)
http://www.piercemanifolds.com/Float_Level_1.htm

Follow instruction on Rebuild and Setup information from Mark Harney (mharney)
http://www.carburetorclinic.com/weber_tech.htm
(notice the picture of the proper Weber carb sync tool that is on top let of most of his pages, with out one it would be very hard to get your carbs syncked up properly…

Also, check to make sure your are getting full throttle when you pres all the way down on the gas pedal.

Maybe also invest in an AF Meter, it will one of the best investments you have ever made for your tuning and drivability issues…. Ideally one for every cylinder but that can get complicated and expensive, so one to start with ;0)

http://www.cbperformance.com/catalog.asp?ProductID=1673

Hopefully the above should eliminate your problem if it is not something like a big vacuum leak or flat cam(unlikely if it ran well before) and the worst thing that could happen is that you will have a well timed engine & A1 ignition setup + some nice carbs to sell or trade for some 40 IDF’s :0)

Fri Aug 01, 2008 5:15 pm

Well, I told that guy a big NO on rebuilding my motor. I had someone else I know take a look, and he said it's definately something to do with the carbs. He said that they're flooding the engine, which makes way more sense, seeing as this all started after I took the carbs off. I set the floats to 11mm when I had them out though. Maybe my needle and seat are messed up? Anyway, I'm going to try cleaning both carbs extra well and double checking the floats and needle and seat. Hopefully, that will fix it! :?

Fri Aug 01, 2008 11:06 pm

with that motor 44'sare right on the edge of being to big... any time you change vents,, you will also need to change emulsion tubes and jets .. no where in his did you say any thing about changing the E tubes,,

Sat Aug 02, 2008 4:51 pm

BellePlaine wrote: I know that you are working on a carb problem, but is there any chance that somehow a couple of spark plug wires got switched on the distributor cap? I recently discovered that this was the problem to my low-power problem. You definitely get the exhaust popping that you mentioned.

Oompa, I had the same "problem under load" and found it to be my plug wires were switched. I think it was 3 and 4 that i had switched. I could rev all i wanted in neutral but then driving in first and accelerating resulted in popping and i wasn't going anywhere. A quick and easy check.

Sun Aug 03, 2008 12:03 pm

Finally!!! I took the carbs apart to let everything soak over night in cleaner. The only major thing I found wrong in the carbs, other than a plugged jet, was that the accelerator pump wasn't working on one of the carbs. I opened it up and the spring inside the accelerator pump was missing. I replaced it and it runs great. I guess I may have forgotten to put it back in when I had them apart the first time :oops: Anyway, I was even able the put the 34 vents in, and it runs even better than with the 36 vents. I'm SO happy I get to drive the bus again! Thanks everyone for your help! WOO!