TheSamba.com :: View topic - I Need Help with L-Jet / AFC Fuel Injection Topic

Thu Jul 05, 2012 1:08 pm

I was thinking they are all the same size.

Thu Jul 05, 2012 11:02 pm

Randy in Maine wrote: I was thinking they are all the same size.

they are never the same size was, at least, thats what she said.

sorry couldnt resist.

back to being a quiet little person... :P

Tue Jul 10, 2012 6:34 am

phoneguy wrote: Anybody have a source for the cable clamp that goes on the throttle body, German Supply is out of stock and I can't seem to locate it anywhere else.

the fuel injected barrel nut is unavailable new.

http://germansupply.com/home/customer/product.php?productid=17619

the one in randy's link works but lacks the little shoulder at the top. the diameter and length of the 311 129 777 heater cable barrel nut is the same as the one for the fuel injected bus, except the shoulder. so it works, just not as elegantly because it can fall through the throttle arm until the cable is attached.

Tue Jul 10, 2012 10:53 am

Would low fuel pressure cause backfiring and misfiring?

Tue Jul 10, 2012 10:54 am

It could.

How are you measuring yours?

Tue Jul 10, 2012 1:22 pm

Randy in Maine wrote: It could.

How are you measuring yours?

I haven't yet. I've checked all ignition (replaced cap/rotor/plugs/wires), timing, and vacuum lines and it is still backfiring and missing. Maybe a bad coil?

I have a fuel pressure tester that I will use tonight so hopefully that will give me some info.

Tue Jul 10, 2012 1:37 pm

Humor me and tell me....

The complete number on the distributor, what the dwell angle is, and how you have it timed.

I will give you a hint though....you want to see 47º +/- 3º for the dwell angle.

You will be timing it to 28º BTDC with the vacuum hose(s) off and when the distributor has absolutley no more centrifical advance to be had no matter how fast the engine goes. That should happen at about 3500-3800 RPMs, but the exact number of RPMs doesn't matter, it just has to have all of the centrifical advance "in" and the engine will be wound up pretty good.

If you have "platinum plugs", throw them in the trash and buy the correct NGK plugs.

Also tell me that you have made 100% sure that you have no exhaust leaks. Easy to backfire when you have exhaust leaks.

Before I spent any money taking this to a shop, I would have Amskeptic visit me and have him show me how to maintain the bus. Money well spent.

Tue Jul 10, 2012 3:36 pm

Randy in Maine wrote: Humor me and tell me....

The complete number on the distributor, what the dwell angle is, and how you have it timed.

I will give you a hint though....you want to see 47º +/- 3º for the dwell angle.

You will be timing it to 28º BTDC with the vacuum hose(s) off and when the distributor has absolutley no more centrifical advance to be had no matter how fast the engine goes. That should happen at about 3500-3800 RPMs, but the exact number of RPMs doesn't matter, it just has to have all of the centrifical advance "in" and the engine will be wound up pretty good.

If you have "platinum plugs", throw them in the trash and buy the correct NGK plugs.

Also tell me that you have made 100% sure that you have no exhaust leaks. Easy to backfire when you have exhaust leaks.

Before I spent any money taking this to a shop, I would have Amskeptic visit me and have him show me how to maintain the bus. Money well spent.

I'll have to checked the dizzy number tonight. It has pertronix, so no dwell. Should I disconnect only the vacuum hoses that are at the dizzy? Or more of them? I can time it to 28 BTDC, but it is running well enough at 8.5 BTDC.

Thanks for your help Randy!

Tue Jul 10, 2012 4:32 pm

What happens if you remove the Pertronix and go traditional? Lots of folks are happy with the Perts. and many are not. And 8.5 is at idle, 28 is at WOT so to speak. You need to rev the engine to 3500 rpm. It will sound like cruising speed on the highway. the timing needs to be 28-30. NO MORE THAN 30!!

Tue Jul 10, 2012 5:43 pm

Just the hose going to the distributor can. I think you only have one.

Petronics is fine and we won't need to dink with it.

We don't really care where the timing lands at idle since you don't drive at idle. We shall note it, but not change it.

Do that timing a couple of times and note if the timing really does retard back to about the same idle position.

All engines are of course a little different. If you are above 5000 feet, I usually set them closer to 30º BTDC and if the engine runs rich for some reason, they will tolerate a couple of degrees more.

Time it that way to 28º and see how it runs.

You can also shove a wet rag or a potato in the tailpipe while you are under there looking at the exhaust system connects to see if anything is leaking. All of the connections are suspect.

Tue Jul 10, 2012 10:27 pm

Big thanks to Stuart!!

He came over tonight and figured out the majority of the problem. My mechanical and vacuum advance on my dizzy was not working at all. Also had two spark plug wires (new from auto zone...) that were not sending consistent spark.

Stuart pulled the dizzy, took it apart, lubed everything up, and it runs much better now!

It still has a backfire when I let off the accelerator so I need to figure that out, but it is in a much better place now than before. I think I will check the decal valve and go from there.

Thanks again, Stuart! And thanks Samba!

Wed Jul 11, 2012 10:36 pm

where is the decel valve, and how do i test it? anyone have a picture?

Thu Jul 12, 2012 6:48 am

The decel valve should be mounted up by the firewall.....

Fri Jul 13, 2012 11:10 am

Thank you....i thought thats what it was...but wanted to make sure.

Mon Jul 16, 2012 10:21 pm

I've got a 78 super vert with a 1600 FI. I'm about to reinstall the engine I had rebuilt to OEM specs but don't have anything that shows all the vacuum and fuel line connections. Some I have figured out from pictures and posts here on TheSamba but some elude my best efforts. Something that shows the start and end points on the hoses for the air (Vacuum - breather - air cleaner) is what I need.

I'm a noob and this is my first VW project. Not a mechanic but out of necessity have learned to read the wiring diagrams now (so can look and learn) but can't find a 'complete' diagram of the hoses.

Thanks in advance for any help.

Tue Jul 17, 2012 6:21 am

Buzz64 wrote: I've got a 78 super vert with a 1600 FI. I'm about to reinstall the engine I had rebuilt to OEM specs but don't have anything that shows all the vacuum and fuel line connections. Some I have figured out from pictures and posts here on TheSamba but some elude my best efforts. Something that shows the start and end points on the hoses for the air (Vacuum - breather - air cleaner) is what I need.

I'm a noob and this is my first VW project. Not a mechanic but out of necessity have learned to read the wiring diagrams now (so can look and learn) but can't find a 'complete' diagram of the hoses.

Thanks in advance for any help.
Have a look through this and see if it helps: http://www.thesamba.com/vw/archives/manuals/afc_fi_11_1974.php

Tue Jul 17, 2012 8:46 am

Thanks Busdaddy - have downloaded this already but the quality of the pics leaves a lot to be desired. Some help so not a waste, not to mention the trouble shooting steps. Have the AFC guide also -- will just keep plugging away.

Thanks again!

Tue Jul 17, 2012 9:07 am

Well there's really not many lines on L-jet, post some pics and we'll tell you what they do.

Tue Jul 24, 2012 5:20 pm

Thanks Busdaddy - I'm out of town for a few days and will set the engine when I get back - I hope. If I can't figure them out with all the air cleaner stuff in place I'll take you up on the offer.

Tue Jul 24, 2012 6:16 pm

As I sit here at Table Rock Lake, thinking of my 78 SB vert I just remembered a plug that is on the back side of the engine plugging into the top of the clutch housing.

Since I'm about 400 miles from the engine I can't post a pic. But it is the only electrical plug behind the engine so thought someone might know what it is. Engine is 1600cc FI.

Thanks