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

Mon Jun 25, 2012 1:03 pm

tootype2crazy wrote: Just a quick question: what should the normal vacuum be? I have a mighty vac with a gauge on it and would like to see if I'm pulling the correct vacuum. Also I would read this on the plenum, right?

yes at plenum - vacuum can vary with camshaft and valve gap but typically between 17 and 20 inches at idle.

Mon Jun 25, 2012 3:27 pm

Hi guys,

Bit of an update from my problem a few pages ago.

I finally managed to get a second hand fuel pump so installed it this weekend. Connected it all up, got a mate to turn the ignition and it whirred into life and I could see the petrol sloshing around in the filter so I was happy that it was now working and the original one was definitely dead.

However, the engine turned gave a few pops but didn't catch. It's now back to pretty much the same problem, it turns but doesn't seem to catch.

So, I went back to my trusty VW FI troubleshooting guide and followed the steps again.

Ignition system - ok
Hoses - ok
Pressure on starting - yes thanks to the new pump
Voltage at connectors - yes
Temp sensor has resistance
Cold start ok and not leaking

Which leaves the intake air sensor or air flow monitor, (whatever you prefer to call it), checking resistance between terminals 6 and 9 gave the correct reading but I got absolutely nothing between 7 and 8.

The troubleshooter then had this pearl of advice 'replace sensor'.

Does anyone have any advice for a work around or way of tricking the sensor to prove it is that. Also, I've done a little check and it seems these are not very cheap. I'm now in two minds as to what to do...

Do I dare utter the word carbs, for the time and effort chasing my tail with my FI and adding up the wasted money on tax and insurance with a static bus I don't want to be but I am seriously thinking carbs may be the way to go so I can get out and enjoy the bus. Especially as I can pay for a new sensor only to find that something else is also wrong with the FI.

Ho hum

Mon Jun 25, 2012 3:44 pm

the double relay in the 76 2000cc f\i bus is that year specific? or is it the same bosh part on all the f\i

Mon Jun 25, 2012 3:59 pm

The 11 pin double relay is the same for all but the 13 pin 79CA model.

Other uses of this relay includes FI beetles and non-CA aircooled vanagons (and perhaps others).

Mon Jun 25, 2012 4:00 pm

SGKent wrote: yes at plenum - vacuum can vary with camshaft and valve gap but typically between 17 and 20 inches at idle.

Ok I tested the vacuum and I am pulling steady 12-14 inches @ 800 RPM. I suppose there is a leak somewhere that I can't find. I guess I'll get some starting fluid and start spraying.

Mon Jun 25, 2012 4:46 pm

I just found that when I disconnect the vacuum lines coming off the plenum and going to the pressure regulator and the decel valve and plug it, it cures the problem. That being said the vacuum with those being disconnected is only 12-14 inches. I sprayed all over with soapy water and didn't see any evidence of leaks.

Mon Jun 25, 2012 4:58 pm

tootype2crazy wrote: I just found that when I disconnect the vacuum lines coming off the plenum and going to the pressure regulator and the decel valve and plug it, it cures the problem. That being said the vacuum with those being disconnected is only 12-14 inches. I sprayed all over with soapy water and didn't see any evidence of leaks.

not all cams are created equal. Use a vacuum pump to see which is leaking vacuum.

Mon Jun 25, 2012 5:15 pm

It is a hydraulic cam so it may not be too robust. I will go out and pump up the items now, hopefully I'm reaching a cure here soon!

Mon Jun 25, 2012 5:43 pm

Well I think I narrowed it down. The decel valve and the fuel pressure regulator both hold vacuum fine. The valve in the air cleaner for the fuel tank gases does not. When I took off the line and plugged it, it runs just great. It's amazing that such a small thing could make such a difference. I'm off to fix it now. Thanks for helping me think!

Mon Jun 25, 2012 7:22 pm

I got the EEC valve apart and the diaphragm has a huge crack in it around the edge. I tried Colin's fix, we will see if it holds. If it doesn't then i will delete the valve and run the gas vapor hose directly into the air cleaner. I understand its purpose was to reduce hydro carbons upon start up, and since I don't have to worry about emissions here in Missouri it is not a necessary item.

Mon Jun 25, 2012 7:31 pm

tootype2crazy wrote: I don't have to worry about emissions here in Missouri it is not a necessary item.
Just don't go plugging it up, the fuel tank needs that hose to breathe and vent, if the diapragm fix fails remove the diaphragm and spring, cap the small nipple and reconnect the big hose, run the advance directly to the distributor omitting the Tee.

Mon Jun 25, 2012 8:00 pm

Actually I will probably remove the entire eec assembly and run the vapor hose directly through the left over hole. It's about the right size to just shove the hose right in. I would never just plug up the gas tank venting system, that would be silly!

Mon Jun 25, 2012 8:55 pm

anyone have a base setting solution for the AFM on a 78 FI? looking to get a base setting to go off before i get it tuned properly at the local VW shop.

Thu Jun 28, 2012 8:28 pm

Stuartzickefoose wrote: anyone have a base setting solution for the AFM on a 78 FI? looking to get a base setting to go off before i get it tuned properly at the local VW shop.

just mark where it is right now. put a tiny bit of white paint or a dot of red nail polish on the silver slider and the black cog. you could later rotate them back to their current position if the re-tune doesn't work out.

Sun Jul 01, 2012 6:47 pm

I posted this in the forums for lack of help here.

Mon Jul 02, 2012 8:35 am

Update on my problems, it was the fuel pump and after a bit of tickling on the AFM that is now also fine.

So, at the moment we are working.

Thanks for all your helps, support and advice. I'll keep returning to the thread and see if I can pay it forward!

Thu Jul 05, 2012 11:00 am

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.

Thu Jul 05, 2012 11:21 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.

Borrow a heater cable clamp in the meantime. Who needs heat today?
Colin99*InVegas

Thu Jul 05, 2012 11:58 am

Amskeptic wrote: 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.

Borrow a heater cable clamp in the meantime. Who needs heat today?
Colin99*InVegas

Been here?

http://www.busdepot.com/311129777

Thu Jul 05, 2012 1:02 pm

Yeah , that's the small one for a type 1 engine or heater box cable.