Hard bucking, 82 CA Van

[Amskeptic]

Ok, so $230 worth of rebuilt afm, $150 worth of another shop diagnosing it and guess what? Still a bucking bronco! Only thing left is computer! I shoulda just got carbs.

Where are you located? I have yet to be stumped by L-Jet. The longest diagnosis on record, in 2007 I think it was, came in at 3 and a half hours.

I boast not to boast (I have a healthy humility at how many times my ass has been seriously kicked by recalcitrant machinery), but to inform you that there really are solutions just waiting to be discovered.

Bucking is annoying, but it is only an indication that something is exceeding the parameters of the program. Where are you?
Colin
(what is a fiftybuckbunny? I just went through Nevada where there was this "bunny ranch", see, are you the economy alternative?)

[fiftybuckbunny]

I'm actually in Maryland. MD's beautiful eastern shore

[fiftybuckbunny]

It's from a Gti I bought years ago for $50. Hence fiftybuckbunny

[fiftybuckbunny]

Bucking solved. Fuel filter doesn't flow enough. I'm now going to drink to forget about all the money spent.

[SlowLane]

Congratulations on finding the source of the problem. In your initial posting, though, you said:

fuel psi in spec, fuel volume 1 liter in 30 sec,

which would suggest that the filter wasn't impeding flow.

How did you get to the root of the problem: just a what-the-hell-let's-replace-the-filter-because-I-don't-know-when-it-was-last-changed? Do you have the big round metal filter post-pump, or the little square plastic filter pre-pump?

I'm now going to drink to forget about all the money spent.

Damn, why haven't I thought of that. 'course, I'd be a drooling alcoholic by now if I did, given how much my VW addiction has cost over the years...

[fiftybuckbunny]

Not so fast on it being "solved". Doesn't buck but it surges, has no power. We were all over this thing today and it's still not right! Apparently I am only pulling 5" of vacuum. Smoke tested it again and no leaks. Christ it barely idles! Idle screw almost all the way out and maybe only 700 rpm. What the hell is going on? Fuel filter was taken out of the mix because during high rpm, load we could see the pressure drop to 16 psi. Now it has good pressure but it's still not right. It feels like its just gonna stop running at any moment. New temp 2 sensor changed nothing. A friend was supposed to stop by with his van to swap ecu's but he never showed. We have places to go in a week and this thing has to run! What am I missing?

[SlowLane]

Not knowing anything about your cam, it's hard to say if 5" vacuum is normal. Sounds pretty damn low, though.

Brake booster leak might not get detected with a smoke test, since it's so far from the engine, and is isolated by the check valve.

Compression test? Leakdown test?

[fiftybuckbunny]

Gonna plug up brake booster hose, see if that changes anything. No compression check yet. Guess I'll buy one today. The cam is a scat c 20, one step above stock. This thing used to run really well. Not now. I just haven't found the smoking gun yet.

[fiftybuckbunny]

Update: reset the timing to 30 total advance and it seems to like it. Couldn't figure out why idle screw did nothing so I rechecked the old Bentley. The throttle plate can't be resting on the stop. I made a little brace on the firewall tin to keep it from flexing and kept messing with the cable adjustment and lo and behold the idle screw works like it should. Who'd a thought. Got idle so it's right around 1k. Gonna go get a new fuel filter and run it again. Now we should be ok for our upcoming trip north. Maybe I can get my money back for the incorrect diagnosis. $150 isn't a huge amount but it's nearly 2 days wages for me after taxes. I can't send back the new afm I didn't need. I'll at least get my core fee back or just sell it. Again, thanks for all the help and prompt replies.

[Amskeptic]

Not so fast on it being "solved". Doesn't buck but it surges, has no power. We were all over this thing today and it's still not right! Apparently I am only pulling 5" of vacuum. Smoke tested it again and no leaks. Christ it barely idles! Idle screw almost all the way out and maybe only 700 rpm. What the hell is going on? Fuel filter was taken out of the mix because during high rpm, load we could see the pressure drop to 16 psi. Now it has good pressure but it's still not right. It feels like its just gonna stop running at any moment. New temp 2 sensor changed nothing. A friend was supposed to stop by with his van to swap ecu's but he never showed. We have places to go in a week and this thing has to run! What am I missing?

Have you checked the timing at 3,200 rpm? Make it so.
Then check idle timing. If you have dual advance/retard can, idle timing should fall around 5* atdc.
If you have a retard that is functional, vacuum reading will be low 10s. If you have normal single advance, anywhere between 7.5* BTDC and 0* is fine as long as you do not exceed 28* at high rpm.

If you have a "performance" camshaft, the marketers who dangle "performance" in front of you are not smarter than the factory engineers. It looks like you are suffering from too much "performance". The L-Jet HAS TO HAVE IDLE AIR FLOW. Drill a 1/8" hole in the throttle plate and wing that AAR up to max opening and pray. Understand that this issue is not the fault of the car.
Colin

[fiftybuckbunny]

When I first built his three years ago. It idled fine and did everything it was supposed to do. Now it does not. I suppose I could split the case and return it to stock but the cam isn't the problem. Current issue is now a valve cover that won't seal. Two weeks, 2 sets of caskets and it just drips. I'm so ready to just push this heap into the Bay or burn it to the ground. In 20 years of VW ownership I've never had this many problems. Shoulda kept all my Splits.

[fiftybuckbunny]

Total advance is at 28-30, goes to about zero at idle. It's a advance/retard distributor. Put a clear fuel filter on it to keep tabs on things. Noticed when it's running I can see bubbling inside the filter. Filter is before the pump. I did blow compressed air into tank outlet thinking something may be clogged up inside. Do these things have a screen or sock in them? No way to get at it if there is. I'm sorry for the anger, it's just so frustrating to have pissed away so many weekends in a row, cancel plans etc because I'm afraid to drive this once good running vehicle. Labor rate here is $95 an hour for a mechanic to guess what's going on in a vehicle they don't want to work on so I'm a bit stuck

[satchmo]

When I first built his three years ago. It idled fine and did everything it was supposed to do. Now it does not. I suppose I could split the case and return it to stock but the cam isn't the problem. Current issue is now a valve cover that won't seal. Two weeks, 2 sets of caskets and it just drips. I'm so ready to just push this heap into the Bay or burn it to the ground. In 20 years of VW ownership I've never had this many problems. Shoulda kept all my Splits.

Wow, two sets of caskets. I can certainly feel your sense of hopelessness.

After reading the thread, I'm not sure how things are right now, except for the leaking valve cover gaskets. Are you using the cork gaskets or the rubber ones? I never had much success with anything but the cork gaskets, using Hylomar on the cover side and just dry on the head side.

Please reiterate how your engine is running currently and we will get to the bottom of it. No need to throw in the towel just yet. And for heaven's sake, send those 'caskets' back.

Tim

[fiftybuckbunny]

Damn auto correct. Gaskets. They are cork. Ordered some new bails to fix that problem. Runs pretty good but it's surging part throttle light load. You can just feel it in your backside. The notion that the fuel pump is cavitating is what I'm going with. Not sure what I can do about that. Really need to run a filter before the pump to keep the crud out. It just feels like its not getting enough fuel.

[SlowLane]

Total advance is at 28-30, goes to about zero at idle. It's a advance/retard distributor. Put a clear fuel filter on it to keep tabs on things. Noticed when it's running I can see bubbling inside the filter. Filter is before the pump.

One of those aftermarket glass cylinder thingys with the screw-together caps? I'm not sure that those are suitable for the high flow rate the recirculating L-Jet fuel circuit requires. They're meant for carburated applications, which typically don't have anywhere close to the same flow rate.

I'd recommend putting the stock square plastic filter ahead of the fuel pump (stock for everything except CA-spec cars, it seems). NAPA carries them as well. Can't remember the part number off-hand.