TheSamba.com :: View topic

Fri Jul 15, 2005 5:23 pm

Let me start by saying I’m not a mechanic, I do like to tinker a bit but I’d much rather be out driving!

I purchased a used Fiberfab Speedster replica that was built by the seller. The car looks great and runs OK, I just can't seem to get it to run smoothly.

If I slowly increase the RPMs, it gets to about 4,000 and then starts to sputter and RPMs drop. If I then increase the throttle abruptly it jumps past 4,000 and seems OK.

The problem also shows up when at cruising speed. Runs well at idle and up to about ½ throttle or at full throttle.

Here’s what I have:

About 5,000 miles on a rebuilt (by previous owner) Type 1 1641 engine
rebuild was said to include: rebuilt crank, rods, new bearings, piston rings, cylinders, Engle 110 cam, rebuilt heads, new dual Weber ICT 34mm carbs with cross bar linkage and balance tube, 009 Dist., replaced generator with alternator. The carbs have stock setup with the exception of a 1.20 mm Main Jet instead of 1.30 mm and 1.80 mm Air Corrector Jet instead of 1.60 mm.

I added a Compufire DIS, new plugs, adjusted the valves, set the timing to 30 BTDC at 3,000 RPM, synchronized and adjusted the carbs and replaced the fuel filter. I also disassembled and cleaned the carbs.

I'm thinking it may be a fuel delivery problem.

This thing’s driving me crazy!

Any suggestions?

Fri Jul 15, 2005 5:45 pm

If it were a motorcycle I would tell you to its prolly a jetting problem. VW carbs arent my game though.

Fri Jul 15, 2005 6:14 pm

Sounds like you have a fuel delivery problem.Make sure the floats are set properly.Sounds like you're running out of fuel if it runs ok for a while at cruise then starts to sputter. you might want to check fuel pressure just for kicks. should be around 3-4 psi. Jetting may also be an issue. Can you get it to sputter while setting and revving?If so then when it starts to sputter, shoot come carb spray down the throats of the carbs.If it smooths out then it's too lean.

Fri Jul 15, 2005 6:59 pm

pdouthitt wrote: Let me start by saying I’m not a mechanic, I do like to tinker a bit but I’d much rather be out driving!

I purchased a used Fiberfab Speedster replica that was built by the seller. The car looks great and runs OK, I just can't seem to get it to run smoothly.

If I slowly increase the RPMs, it gets to about 4,000 and then starts to sputter and RPMs drop. If I then increase the throttle abruptly it jumps past 4,000 and seems OK.

The problem also shows up when at cruising speed. Runs well at idle and up to about ½ throttle or at full throttle.

Here’s what I have:

About 5,000 miles on a rebuilt (by previous owner) Type 1 1641 engine
rebuild was said to include: rebuilt crank, rods, new bearings, piston rings, cylinders, Engle 110 cam, rebuilt heads, new dual Weber ICT 34mm carbs with cross bar linkage and balance tube, 009 Dist., replaced generator with alternator. The carbs have stock setup with the exception of a 1.20 mm Main Jet instead of 1.30 mm and 1.80 mm Air Corrector Jet instead of 1.60 mm.

I added a Compufire DIS, new plugs, adjusted the valves, set the timing to 30 BTDC at 3,000 RPM, synchronized and adjusted the carbs and replaced the fuel filter. I also disassembled and cleaned the carbs.

I'm thinking it may be a fuel delivery problem.

This thing’s driving me crazy!

Any suggestions?
It sounds like you need to increase the
size of the main jets ,try and put the 130 in or get a drill reamer kit and ream what you have.
Johnny

Sat Jul 16, 2005 4:23 pm

Thanks for the suggestions.

I got a Fuel Pump Pressure gauge today and I'll try it tomorrow. I'll also give the carb cleaner trick a try.

Next will come checking the float positionin each carb.

I'll have to order the new jets or reaming kit.

Does anybody know of a good tuner in my area that could do the carb work?

I'm in WV, very close to Cumberland, MD.

Thanks

Paul

Sat Jul 16, 2005 4:30 pm

There is a guy in Reading, PA. I will try to find out the name of the shop. There is also a shop in St. Johns, PA. Think about 3.5 hours from you that is very good. It's called Valley VW. They do good work, and are excellent engine builders

Sun Jul 17, 2005 10:32 am

Got a chance to try the fuel pressure gauge...about 4.25 psi

When it started to sputter if I sprayed carb cleaner in either carb it smoothed out.

Have not check the float levels yet.

One other thing, checked the spart plugs and they are very black, not oil, just black.

I haven't had the car out on the road much lately. Mostly just running at idle in the garage trying to figure this problem out.

Paul

Sun Jul 17, 2005 10:50 am

Sounds like the fuel pressure is ok.It's tough to get an accurate reading from the plugs if you don't know how old they are.And a lean condition will cause a missfire so the plugs can get fairly black anyway.I would check both Intake gaskest for leaks then get into float level and jetting. if it does smooth out like you said when spraying into the carbs then it is definately running lean.

Sun Jul 17, 2005 4:46 pm

I checked the fload levels and they are dead on, 6.5 mm.

I did a quick search and found that CBperformance recommends:

1.35 mm main jet
1.60 mm air corrector
F78 emulsion tube
.60 mm idle jet
.50 mm pump jet

Seems like a good place to start.

-Paul

Mon Jul 18, 2005 9:32 am

I had a similar problem when my accelerator pump was not adjusted correctly. It would accelerate slowly but if I punched it the engine would sputter or die. The Main Jet control mixture at 3/4 throttle and above. With the engine off look down the throat of the carb and push down the linkage slowly you should see fuel squirting if not your accelerator pumps need either adjustment or the diaphragms replaced.

Mon Jul 18, 2005 3:35 pm

Check the gas tank,it may not let all the gas through!!!!!!!! Thats the same problem i had and now its fixed!

Mon Jul 18, 2005 8:30 pm

If the tank was plugged the fuel pressure would be off.

Mon Jul 18, 2005 10:05 pm

make sure your muffler bearing are torqued to the factory specs..... i think its 18 ft.lbs.

Tue Jul 19, 2005 5:40 am

Not sure where the muffler bearing is located, is it somewhere close to the radiator cap?

I'll ask my wife, she's sure to know!

Tue Jul 19, 2005 8:57 am

baja5 wrote: If the tank was plugged the fuel pressure would be off.

Wrong!! I had perfect fuel pressure,after driving for a mile or so a rust flap of crap would then slow down the gas! :roll:

Tue Jul 19, 2005 9:28 am

So what exactly did your guage say after the rust stopped the fuel flow?And did your engine run normally?

Tue Jul 19, 2005 6:04 pm

It was strange the problem i had,at idle or slower speeds it ran perfect,then at faster speeds the fuel would be gone. all because of a flap of rust in the tank right at the bottom covering the gas outlet,i bought this bug off of a vw mech shop,he had it for months and couldnt figure it out,he did everything,when i bought this nice bug off of him cheap he still told me that it was an elctrical problem but still couldnt pin point it,then after a week of me going crazy and it making no sense i said well the only thing left would be to check the gas tank which i thought it would be a waste of time,came out to be my problem,one i have never ran across.

...................Same thing i had at half pedal mine would do that also,but again that was just my problem,who knows its a good last resort to check if all the other fail.

Thu Jul 21, 2005 5:16 am

I checked the fuel tank, looks OK.

Did so while installing a rotary fuel pump that I had previously ordered.

I sent an email to John at Aircooled.net and he was kind enough to recommend:

57.5 Idle Jet
135 Main Jet
160 Air Correction

Hopefully they will be here by this weekend.

I'll let you know the outcome.

Thanks for all your advice; yes, even the muffler bearing bit! :?

-Paul

Mon Jul 25, 2005 7:07 am

Got the new Jets and rebuild kits on Saturday, and rebuilt the carbs.

Not very difficult and what an improvement.

I still need to do some fine tuning, but the sputtering is gone!!! :D

Thanks to all for the help.

Paul