Hard bucking, 82 CA Van

[fiftybuckbunny]

It has been suggested that I have the wrong tank. The fuel outlet is only like a quarter inch in diameter. Perhaps this is it? The filter I got is about the same size as the stock one, just clear. Quarter inch in and out. It's pretty big. It surges with no filter at all on it.

[Amskeptic]

It has been suggested that I have the wrong tank. The fuel outlet is only like a quarter inch in diameter. Perhaps this is it? The filter I got is about the same size as the stock one, just clear. Quarter inch in and out. It's pretty big. It surges with no filter at all on it.

I am not in with this line of inquiry. A fuel pressure gauge that you can read underway will tell you. If it is able to maintain 36 psi through the bucking period, then starvation is unlikely to be your cause. An undersize fuel delivery system would let itself be known only under sustained demand, around 4,000 rpm under full load. This is usually a "softer" symptom with a more gradual loss of power preceding the "escape the parameters freak-out" bucking.
Colin?

[satchmo]

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.

I don't buy that there is a problem with fuel tank either.

So you say it runs pretty good but there is 'surging' during initial acceleration, right? Tell me if I am correct, but this sounds like you have a 'flat spot' off idle where the engine just bogs a bit, then really comes to life for a second, hitting you in your back side, and repeating with each gear change. Is that what you mean by surging?

The flat spot off idle is usually due to a lean condition, or possibly an over rich condition, but can also indicate a lack of advance at the distributor. You mentioned that the vacuum is only 5". That seems low. Check the vacuum advance on your distributor to make sure it isn't leaking, and check for leaks on any other connections along that hose (does your engine have an EEC valve?). Also make sure the distributor plate moves easily when vacuum is applied to the advance side of the distributor vacuum can.

Tim

[fiftybuckbunny]

Not sure what EEC valve is. Auxiliary air valve? When I say surge it's through the whole rev range mostly second and 3rd part throttle light load. Almost a bumping sensation not a flat spot. If you floor it it kinda goes away.

[Amskeptic]

Not sure what EEC valve is. Auxiliary air valve? When I say surge it's through the whole rev range mostly second and 3rd part throttle light load. Almost a bumping sensation not a flat spot. If you floor it it kinda goes away.

Ran into this just yesterday. Extremely persistent symptoms with Westyfrank's Vanagon. The ECU and AFM seem to conspire to make their wants unknowable by virtue of circuitry that is tied in to the O2 sensor input.

Join us in our experiment here:
MARK the black cog against any landmark inside of the AFM's black box so you can put it back.
Tighten black cog CW 3 teeth, test drive, do another 3 if necessary ... better? If no, return to initial location and thanks.
Colin

[SlowLane]

What is the frequency of the surge? Once per second? Faster? Slower?

I'm wondering if this isn't just some artifact of the ECU doing it's lean-rich-lean-rich cycling act to keep the cat happy? Colin, did you deploy your LM-1 on WestyFrank's engine?

[fiftybuckbunny]

An LM 1 would help a lot. I'm gonna see if one of the turbo VR owners I know will let me slap an a f meter on it to see what's going on. Also gonna try a gas can temporarily plumbed in to see if that changes anything. New afm is sealed so I want to eliminate other stuff before I crack that and mess around in it.

[fiftybuckbunny]

An LM 1 would help a lot. I'm gonna see if one of the turbo VR owners I know will let me slap an a f meter on it to see what's going on. Also gonna try a gas can temporarily plumbed in to see if that changes anything. New afm is sealed so I want to eliminate other stuff before I crack that and mess around in it.

[Amskeptic]

An LM 1 would help a lot. I'm gonna see if one of the turbo VR owners I know will let me slap an a f meter on it to see what's going on. Also gonna try a gas can temporarily plumbed in to see if that changes anything. New afm is sealed so I want to eliminate other stuff before I crack that and mess around in it.

Note:
new AFM + well-used engine = lean

When valve guides open up, you get more and more recirculated crankcase air in on the intake stroke instead of fully metered air from the AFM. Do not assume a new AFM is magic best mixture, nope sorry.
Colin

[fiftybuckbunny]

At this point I a assuming nothing, hence the desire to get an A/f measuring device so I can do it accurately. Haven't heard back from the aforementioned friend yet. The van endured 300 or so miles of travel last weekend and it's running ok, but just ok. We couldn't bear to miss a local Vanagon club camp out because of a not quite right van.

[Amskeptic]

At this point I a assuming nothing, hence the desire to get an A/f measuring device so I can do it accurately. Haven't heard back from the aforementioned friend yet. The van endured 300 or so miles of travel last weekend and it's running ok, but just ok. We couldn't bear to miss a local Vanagon club camp out because of a not quite right van.

I wince for your exhaust valves. Git er done.
Colin

[fiftybuckbunny]

A little update. Fiddled with the afm today and richened her up a bit as per the instructions on this site. Power has greatly improved. I will mess with it some more tomorrow when it's light out. Better is all I was shooting for this evening. Throttle response is still kinda sucky but I think I can tune that out. I also need a way to fix the throttle body as in add a stop or something so it doesn't stick closed. It is adjusted like Mr Bentley says but the engine tin flexes and it won't idle down or it idles too high when you don't snap the pedal. It's annoying as hell! Any suggestions there?

[Amskeptic]

I also need a way to fix the throttle body as in add a stop or something so it doesn't stick closed.

You mean the throttle plate? sticks when closed? Any stickiness beyond fully closed is the responsibility of the throttle cable and sheath, lubricate.
A sticking throttle plate is a little trickier, if your idle air screw is currently open a good deal where we get to reduce its bypass air, you can file the throttle plate edges a little more bevelled so they do not dig into the throttle passage. This may allow a little more air to pass, so you need an idle air screw that can be turned down. If it is already down because the engine is already passing too much air, then you best not file anything in there, try a little anti-seize or moly grease and work the throttle plate at the closed position a few hundred times to polish the edges so they will not stick. Lubricate the bushings with engine oil while you are there.
Colin

[fiftybuckbunny]

Ok. I'll pop her apart this weekend and try all that. It sticks too far closed so before I had the idle screw darn near all the way out and idle was too slow. Cable works pretty smooth but that can always be better.