TheSamba.com :: View topic - Hesitation when I accelerate

Sat Aug 02, 2014 3:23 pm

Hey all . . thanks for all your help in the past. I have a problem that has got me nuts ! I have duel Kadron carbs 40/44's on my 1700 engine (stock case with slip in 88mm thick wall pistons) I got machined heads and a Phat boy Bugpack exhaust. All was fine and well with my engine until my transmission went on me and I got a "Freeway Flyer" put in by a shop that was suspect to their Vintage VW knowledge. They did lots of NEWER German cars . . but not Vintage (as they had told me). So here is my problem, I got a great idle and my timing is spot on (.009 Bosch mechanical advance dist.) I have the timing set at 28 degrees BTDC. I have both carbs synched spot on and my idle is at 900 RPM's. When I take it out on the road . . It hesitates and chokes at the higher RPM's before I shift to the next gear. It only happens when it's under a load. If I rev the engine in neutral (got it up as high as 4000 rpms no hesitation) but when I have it on the road and I get it up to 3000 - 3200 rpm's in gear it starts to hesitate and choke almost as if it's out of gas. I have a fuel pressure gauge on it and I'm dead on at 1.5 PSI coming out of the regulator. I set my valves to .006 yesterday and put new plugs in it (old plugs had A LOT of soot - was running rich) so I took out the rich carbs and put my stock 130 jets with 28mm Venturis back in. No difference . . just as bad on the hesitation at higher rpms.

So - I'm F'n loosing my mind . . do I have a valve issue ? should I set them back to .004 as they used to be when I lived in upstate New York (moved to FLA recently and I decided to give them a little more breathing room with the heat) both heads have only 10 K on them at best. The engine fires right up and idles like a champ . . BUT I DO NOTICE that one Maifold (#1 & 2) runs colder and sweats a lot more then #4 & 3 . . I was wondering if this is a clue to the issue ?!

Please advise . . I have changed wires / Coil / Plugs / distributors & dropped down to a less rich set of carbs . . and I still can not figure this out.

Thanks !

Sat Aug 02, 2014 3:56 pm

Try increasing fuel pressure to 2.5 to 3 psi. Cads can handle the higher pressure as long as the needles and seats are good. It sounds like it's starving for fuel.

Sat Aug 02, 2014 5:40 pm

Really . . ? I thought they were not happy above 2 PSI ? ! I will try it
(I will try anything at this point - I'm so frustrated) I swapped out the higher jets (145's) for stock 130's and lower Venturis (was 30mm - dropped to 28mm) and after seeing my plugs (lots of soot and a good coating of it in the exhaust pipe) I thought I should go leaner / less rich. But it did not seem to make a difference.

I screwed in the accelerator pump nuts - thinking it was not getting enough gas. Did not seem to make a difference, I checked both sets of carbs (richer and leaner) to make sure the accelerator pumps were working and they were. I recently rebuilt both sets . . and they are clean as a whistle. The richer ones were working for months (3 months) like a charm. As I mentioned . . I broke down on my way to Florida (transmission issue) and I had to order a new transmission from Wright Gear Box and have shop in DC put it in. They had NO experience in Vintage VW's (only NEW German cars) so I had to undo a number of stupid things they did. Ever since I drove out of there . . the hesitation in the higher RMP's has been an issue. Just to recap here is what I have done over the last week:

Replaced Coil - Ignition wires - Plugs - New Ignitor 1 Ignition kit. I have 40/44 Kadrons running 130 main jets (5.5 idle jets) 28mm Venturis. Set valves to .006 (they were at .004) had a tight # 3 exhaust and intake. The engine was rebuilt 10K miles ago and has running great up until transmission failed.

Any & all suggestions are welcome . . . I'm thinking this is a valve issue - both heads are relatively new. If the idle was not so good and solid I would think this is worn valve or keeper issue. I'm thinking of resetting them back to .004 or less (I read new engines can handle tighter settings ?) any thoughts ? !

Thanks all . . !

Sat Aug 02, 2014 5:49 pm

Maybe they dented the gas line when they replaced the trans. Maybe your tank and or fuel filter is clogged and unrelated to trans.

Sat Aug 02, 2014 5:52 pm

Might be time for another compression check. Last time I did this (3 months ago) I got 115 across the board on all cylinders. I can't imagine it would be any different 3 months later (2,500 miles since) with a recent oil change only 1k ago. Really making me nuts . . I have to say I do nothing but baby this engine and it seems to need constant attention. What happen to these engines being work horses ? ! Mine seems to be a thoroughbred that needs the doctors attention on a regular basis.

Thanks !

Sat Aug 02, 2014 6:05 pm

You might be on to something . . I did change the gas filter (brand new) but it's possible the fuel line from tank (it's a '59 panel bus) could be clogged. Let me ask you . . I have two fuel filters on it, one is on the line from the tank to the pump and the other is on the line after the fuel pump (mechanical) between the fuel pump and pressure regulator. All filters are filling up with fuel . . and the bowls on the carbs were full of fuel when I pulled them (and I pulled them a few times - and each time they were filled with gas) but that does not mean it's getting enough when I step on it.

I discussed this with Rick at Wright Gear Box . . and he said "You don't have a transmission problem . . you have a gas delivery issue, when it's in gear . . it's in gear and it would not hesitate or choke due to the transmission . . unless you had a slipping clutch (I had a new clutch put in when put in the "Freeway Flyer")
and that would exhibit issues like higher rpm's and jerking when putting in gear.

So . . I don't know . . maybe I have to blow out the fuel line . . from the tank . . or flush the tank . . but I don't see a whole lot of Sh@t in the filter . .of even at the bottom of the carb bowls when I pulled them a few days ago.

FRUSTRATED ! ! ! !

Sat Aug 02, 2014 6:45 pm

Just curious, but where in FL are you now?

As for the symptoms, it MIGHT be the vent for the tank. It's possible it's restricted and not allowing good fuel flow when under load, when the most fuel volume is needed. If a pump ducks fuel out, the vent has to allow air in, otherwise the tank tries to implode.

Try driving with the gas cap loose and see what happens.

Sat Aug 02, 2014 6:51 pm

That's another good point ! I will try that ! I'm in Orlando area.

Sat Aug 02, 2014 6:56 pm

One of the 2 best VW shops in Florida is there. Look for R&S Performance just off Orange Ave, south of downtown. Scooter is the man to fix you up if you can't solve the problem.

Also, the local VW crowd meets at the Sonic drive in on 436/Semoran one Saturday evening a month. Scooter would know what weekend that falls on.

Sat Aug 02, 2014 7:11 pm

This "scooter guy" has come up in a few conversations these past two weeks. I have his number (given to me from the Guys at Triangle parts on Fairbanks).

I will give him a call .. Thanks !

Sat Aug 02, 2014 7:14 pm

just my personal opinion.... 28 degrees of advance sounds a bit excessive. try toning it down to say 12 degrees and see what happens. It might not be the answer, but it certainly can't hurt. hope you get it resolved.

Sat Aug 02, 2014 7:44 pm

As I said . . I will try anything. Only issue is Kad bible (and a number of other books) state the .009 mechanical Distributor wants to be advanced to its max (between 28 - 32 BTDC) when timing. So that's were I set it. I will pull it back and see if it changes anything . . thanks !

Sat Aug 02, 2014 8:35 pm

Er, I would keep the 28-32 degrees advance at high rpm. A total of 12 would be a disaster.

Sat Aug 02, 2014 8:58 pm

Agreed.

Sat Aug 02, 2014 9:01 pm

bugguy076 wrote: Try increasing fuel pressure to 2.5 to 3 psi. Cads can handle the higher pressure as long as the needles and seats are good. It sounds like it's starving for fuel.

X2 on fuel pressure.
1.5 psi is too low. Official specification from Brosol for ALL carbs made in Brazil for Ford, Fiat, GM and Volkswagen for adjusting the bowl level is 0.2 kg/cm2 = 2.8 psi

I prefer using 3.5 psi , this way I have some margin of error. If the needle valve can't handle this pressure, probably it is worn-out.

Sun Aug 03, 2014 5:54 am

3.5 PSI . . WOW . . OK I will try it. Jeff at Kaddie Shack (experts on Kads) rants up and down about keeping it under 2 PSI or expect issues. I know me seat and needles are good (I rebuilt these myself 5 months ago) and they ran great. ALL of a sudden I have issues. Could it be the change of climate (from upstate NY to Florida) could the humidity and heat make that big of a difference ?! The sea level change from the Hudson valley to central Florida is about the same. So it's not that.

Hey I was reading that you can have same issues I'm having if your heat riser is clogged ? ! But I don't see a heat rise tube in my manifolds . . is that only for single carb setups ?

I know my pump is putting out fuel . . I know my bowls are filling (pulled carbs and saw bowls full) I know I have good spark (got all new wires and coil and plugs) I have a great solid idle and she fires right up when I turn the key. I do have one Manifold (#1 & #2 cylinder) that is colder and sweats much more than the other. That is the same Manifold that I have my inline fuel pressure gauge on. My filters are clean and I pulled the jets (Main and idles) and blew them out - inside carbs are so clean you could eat off them (but why would you ? !) don't know . . I'm going to try some of the suggestion people have suggested as far as fuel pressure and checking the line for obstruction.

FRUSSTRATED . . ! ! !

Sun Aug 03, 2014 7:49 am

Heat riser is only for single carb manifolds. What bothers me about your problem, is figuring out what changed.

Sun Aug 03, 2014 9:21 am

I had a similar issue in my '63 Beetle. Engine ran perfect for thousands of miles, then started sputtering at higher rpm on the freeway. I replaced everything you did to figure it out. I pulled the gas tank. Clean. Filter, clean.
It was the hard line in the tunnel. I sprayed carb cleaner in it, let it soak and then hit it with compressed air. It looked like coffee coming out the other end! I did this a few times until it came out clean. No more issues.

Sun Aug 03, 2014 10:30 am

dma1260 wrote: 3.5 PSI . . WOW . . OK I will try it. Jeff at Kaddie Shack (experts on Kads) rants up and down about keeping it under 2 PSI or expect issues. I know me seat and needles are good (I rebuilt these myself 5 months ago) and they ran great. ALL of a sudden I have issues.

I think this recommendation is based on the bad quality of the replacement parts of today.. Even the genuine Brosol parts are not the same as before, but overall better than the its counterparts. The original disc needle valve has a built in ball bearing at the tip. Undoubtedly, materials and machining tolerances were far better...

So, setting the fuel pressure to 1.5 psi seems to be a compromise. Probably works well with the right pressure regulator. Note the original setup didn't include a pressure regulator. It was meant to work right from the original Brosol pump.

Quote: I know my pump is putting out fuel . . I know my bowls are filling (pulled carbs and saw bowls full) I know I have good spark (got all new wires and coil and plugs) I have a great solid idle and she fires right up when I turn the key.

You know your pump is putting fuel when the car is parked. As soon as your car start moving a lot of variables will be introduced.

Quote: I do have one Manifold (#1 & #2 cylinder) that is colder and sweats much more than the other. That is the same Manifold that I have my inline fuel pressure gauge on.

This is not expected.

Quote: My filters are clean and I pulled the jets (Main and idles) and blew them out - inside carbs are so clean you could eat off them (but why would you ? !) don't know . . I'm going to try some of the suggestion people have suggested as far as fuel pressure and checking the line for obstruction. !

The most sensitive part of the dual Solex/Brosol/Kadron carbs is the idle circuit. If you achieve a great idle at 900 rpms this does not means that your idle circuit is working properly. And if it's not working properly all the rpm range will be messed. I had problems before with "invisible" dirt partially clogging the circuit.

I think that brand new fuel filter and hoses may have small loosen particles inside, and it is enough to clog the small fuel passages of the carbs and drives someone crazy. Running some fuel inside the new hoses and filter, before connecting, seems to be a good preventive measure. Since everything is clean it will be good in the long run.

Tip: To check if your fuel pressure is good, try to drive uphill. If the car will getting worse and worse it's a clear symptom of fuel starvation. If it loses power, but at a constant rate (don't wants to stop) probably it's a clogged passage.

Sun Aug 03, 2014 12:30 pm

I found bits of rubber from the insides of the fuel hoses when I changed mine.

One major change you have is that you now have a freeway flyer transmisson.

This means your car acellerates more gently in fourth gear. It uses up the squirt of fuel from the accelerator pump and sits there lean for longer without building RPM so fast. More like a bus..

So you might need the boost of ignition advance from a vacuum advance distributor if you can find the signal from the carburettor to compensate.