Minor L-Jet woes

cshogen · 07-03-2002, 05:11 AM

Hi Everyone,

Hope someone can lend a hand here. I have a '75 with L-Jet FI. Never dealt with L-Jet before, but I have what seems to be a minor problem, but before I mess with it I thought I better ask you guys.

The deal is that it seems to idle low most, but not all of the time (80% I would say). Starting off it is tough to keep from stalling but once you hit 2-3K it's fine and runs smoothly to redline. Also, sometimes at steady speed with revs low it seems to run a bit unevenly. My first thought is to adjust the idle a bit, but I have heard that once you start messing with stuff you sometimes make it worse.

One off-the-wall thought I had was that it might be running differently due to the climate. It was a California car all its life in a very dry climate, now it's in a very humid one. Does that make a difference?

Thanks a lot for the help,

JWest · 07-03-2002, 05:38 AM

Here is an online manual of the VW L-jet.

http://www.conservatory.com/vw/manuals_nyx/L-Jetronic.html

I would say that adjusting the idle in not the way to go. The first thing I would check if the ignition system. Maybe the centrifugal advance is hanging.

From there make sure the idle switch is working and check the resistance across the air flow meter as you manually open it. You want a smooth change - you could worn or gummed up wipers inside it. The airdoor could also be mechanically sticking - make sure it moves smoothly.

James

ejm914 · 07-03-2002, 05:59 AM

I would check the boot between the throttle body and air flow meter, it could be loose or torn. A vacuum leak here could cause the problems you describe, if the boot is OK check the other hoses carefully.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Make sure that the basic operation of the engine is in good shape. Check the valve adjustment, do a compression test if you have a tester. While the plugs are out for that, check their condition and gap--and see if they are showing rich (black soot) or lean (white/grey deposits) or OK (tan/brown). Check the ignition thoroughly--dwell, point gap, timing, etc. Make sure the points/cap/rotor/wires/plugs are all in good shape. Make sure the timing is consistent and doesn't move around on its own.

Check for air leaks, as Ed M said. The 1.8s hate air leaks.

Then start chasing FI problems. You can find some L-jet articles on http://www.type2.com , as the later Buses used L-jet.

--DD

cshogen · 07-03-2002, 09:37 AM

Thank you everyone very much (and keep it coming please!).

I should have mentioned that the engine was recently rebuilt 5K ago and valves done VERY recently, but you're right Dave I should check the basics such as timing, dwell, etc.

Personally, I think it's a teeny air leak myself, but once I download that monster online manual I will be able to better troubleshoot. It's really not that bad, and I was going to leave it alone, but noooooooo I have to mess with it as usual.

This is just another great example of the help and support Pelican and this board supplies. Do you have any idea how much this would have cost me at a garage or (gag) a Porsche dealership!?

Buy it at Pelican if you can folks.

Thanks Again,

anthony · 07-03-2002, 09:45 AM

My car behaved exactly the same way. The culprit was the timing/dwell. My distributor is a little worn and the dwell angle would move. I'd set it to 48 and then it would be 55 the next day. The timing was also difficult to set with the mark moving around so much

I got a Pertronix and the car is running extremely well now. It's still kind of band aid since I'll need new bearings pressed into my dizzy one of these days.

dave blackburn · 07-03-2002, 02:54 PM

My 75 1.8 was the same problems. I replaced all the vacume lines and put clamps on all the hose connections. Thats all it needed. Runs great now. Also check the air bypass valve, as this could create a big leak.

jamcleod · jamcleod's Garage

i'm trying to restore a 74 1.8 Ljet and after installing a new fuel pump (thanks Pelican Parts!!!), i finally got it running but it runs poorly, like it is only running on 3 cylinders and doesn't seem to rev freely. i did a top end rebuild with in-spec stock pistons and cylinders, new rings, valve job with flycut, cylinder head temp sensor, new plug wires. when i got it started the first time, i ran it at 2k for 20 min per Tom Wilson book. i have been checking hoses and putting clamps on and changing hoses. i adjusted the valves when putting the engine together and have rechecked the clearance on monday. monday i checked fuel injector output squirting into beakers.. output seemed equal and this test implies that FI system is ok. today i rechecked dwell (in-spec) and timing (mark aligned) and checked fuel pressure (32 connected, 35 unconnected; Lash says 28 unconnected?) changed AFC with another unit i have on hand... no difference. changed condensor, rotor,cap.. no change, i did the "pull the spark plug wire" while it was running and it seemed to indicate #3 cylinder. i changed the spark plug.. no change (has new wires). i put the inductive connector of the timing light on each plug wire and light flashed. when i put the engine together, i cleaned the connectors (dremel wire brushed). i turned the CO screw and seemed to run better when turned almost all the way in. what would you suggest next? i have been over alot of this engine and have only a few checks left (compression, FI resistors).

Ron Meier · 07-03-2002, 06:11 PM

What color was the sparkplug out of #3 cylinder?

Did you look at the plug to see if the gap was closed up? You flycut the heads, but didn't state what pistons you have.

Take a can of Ether (KwickStart) and with the engine running, spray the mating surfaces of the intake runners and head (do remember that Ether is FLAMMABLE). If engine speeds up you have an airleak in the manifold gasket or injector sealing rings.

WD40 works also, but is messy. Carb Cleaner, Brake Cleaner will also work and have the little hose so you can hit the interface easily.

Just thoughts -

cshogen · 07-04-2002, 06:56 AM

Hey again,

It's probably just me looking at it wrong, but in the hose diagram section of the PP site it seems that the vacuum hose sizes identified in the diagram itself are different than the summary of lengths needed at the bottom. Anyone know about how much I need of each length right offhand for the '75 1.8L stock L-Jet, or which part is correct?

TIA,

cshogen · 07-04-2002, 02:35 PM

OK sorry everyone let me clarify. My brain obviously needs a jump start today or something. I need to know the widths of the vacuum hoses for the 1.8L L-Jet, not lengths. For example, in the diagram it might say 13mm for a given hose, and at the bottom in the summary it says 12mm. Just need the sizes of the hoses, I'll guess the lengths myself.

Any help would be appreciated.