Spark or Gas? Jr. Tech at work

Good job "scoping" it out!

The backfire almost always means there is a tiny leak in the exhaust system. Hold your paw over the exhaust outlet(s). If it is leak-free, you'll be able to stall the engine (or burn your hand).

Speedy Jim

recheck torque on all exhuast flanges(and donuts)....this is "classic" exhuast leak behavior...(not related to your ignition woes...)

------------------- Chris Perdue

"Sometimes you're the windshield, sometimes you're the bug!"

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Thanks Speedy and Chris. In about 100 miles it's time for the new engine to get another oil change and valve adjust. I'll re-torque all the exhaust bits at the same time -- I have noticed that those guys like to loosen up pretty fast. What's that all about -- thermal cycling?

But one more thing to add: AFTER going downhill and noticing backfires, when I come to a stop, clutch in, engine dies. Re-starts easily.

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

Just don't enlist the STRENGTH OF KONG (tm) to tighten them down or you'll stip them, sure as shit.

then you need to also check for leaks on the intake side....*under* the carb..meaning endcasting to head seal and end casting to intake boots....use carb spray or similar to spray downt these joints and listen for a change in engine speed...if you find a spot that does affect the engine you have located your leak...good luck

------------------- Chris Perdue

"Sometimes you're the windshield, sometimes you're the bug!"

Remove "PANTS" to e-mail

Lemme think about this -- I'll probably get it wrong but here goes: I'm going down a long hill. I'm using the engine to limit my speed by keeping it in gear with with no pressure on the pedal. Engine is revving at 2500 rpm or so. Okay, the engine is sucking hard on the output side of the carb, but it's closed, so we have a long period of time with vacuum in the intake manifold. If there is a leak, the manifold brings in outside air, so there is insufficient fuel in the mixture to keep the engine turning over when I push in the clutch. Am I warm?

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

Roger that. No strippee the exhaust port studs.

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

not only warm but starting to sweat....the extra air over powers the fuel that is pulled in through the idle circuit while the butterfly is closed....this

*could* also account for a lean condition that *could* cause an afterfire(out the exhaust commonly(and wrongly) labeled a "backfire")...BUT i still suggest you recheck your exhaust fittings for leaks also, as discussed in earlier posts....

------------------- Chris Perdue

"Sometimes you're the windshield, sometimes you're the bug!"

Remove "PANTS" to e-mail

I have been chasing some similiar problems with my new setup. Erratic idle and stalling. I solved mined. Here's some things to check;

Does the throttle plate close in the same spot? Can you see and feel that the screw is contacting the choke cam? Mine wasn't due to the fuel pump stroke being too long. Makes it a bitch to tune and idle consistently.

Remove the idle jet and blow it out with some carb cleaner or Brake Kleen. Stick the little red hose inside the opening and blow out the circuit. Yes, your motor is new but you've also disturbed many items during assembly. A little speck with give you the kind of grief you describe. If you can't easily peak the idle mixture by ear, there's something partially plugging it.

RT

Afterfire. I stand corrected.

Muffler has about 1200 miles on it, heater boxes about 2,000 miles. Though everything was tight when I installed the new engine about 400 miles ago, I was careful not to break an exhaust port stud, so nothing is super tight (yeah, there is a torque spec for those nuts, but I can only a get an end wrench on some the nuts, so I was cautious).

In a couple days it'll be time to change the oil and adjust valve lash. I was planning to touch up all the exhaust bits at that time anyway. I'm curious to see how much everything has loosened.

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

Idle jet clogged with dirt maybe.

Jan

Ah - ha! Spritzed carb cleaner at the flange where the carb mounts to the intake manifold and rpms dropped -- pok, pokita, pokita . . . and the engine died. Those nuts were pretty tight, but there was a little more room for tightening, maybe 1/2 turn, which is a pretty hefty distance considering the thread pitch. Carb cleaner no longer caused any difficulty. Mebbe I got it. Will know later today when I drive that downhill.

And, whoo-hoo, the Wonderbus is getting 18mpg with its new engine, even including yesterday's 15 mile gimp-along with the bad condenser. The old

1776 never saw 18mpg at the best of times. More like 14mpg.

And, even better, here in Southern California we are experiencing one of the two reliable seasons (wildfire season) that we get each year. The other is mudslide season. Once in a while we have earthquake season but that's rare. The harbinger of wildfire season are the infamous Santa Ana winds (AKA "Santana winds" AKA "Devil wind") that raise the temperature

20 or more degrees F in some areas. The new engine is showing no signs of getting too hot, even with 65 mph driving on the freeway.

I am, as the astute reader might tell, very happy that I finally have a Working Wonderbus!

Tomorrow the 84 Vanagon Westy comes home and I got work to do on it. Change AT fluid and filter, install aux battery for camping . . . but that's watercooled stuff and I'll take it outside.

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

excellent....you have come a LONG way squirrelman....congrats....

------------------- Chris Perdue

"Sometimes you're the windshield, sometimes you're the bug!"

Remove "PANTS" to e-mail

Perhaps so, but alas, sealing that leak did not solve the stall-on-downhill issue. Back I go, carb cleaner gun in hand!

--

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

Well, here's what I got: today I spritzed everything even remotely associated with the intake manifold with carb cleaner: all over the carb, the advance hose, the carb/manifold mating area (which did have a leak yesterday), BOTH boots where the manifold joins to the two DP intake manifold vertical pieces, and BOTH intake manifold/intake port mating areas. NOTHING caused the slightest change in engine behavior. But a little puff into the air cleaner intake caused rpms to drop a moment afterward. So, unless I am totally missing something, I do not have a significant intake leak. Or I need a more sensitive test.

Yet, I still get a stall on downhill: 1/2 mile, throttle closed, grade steep enough to keep rpms to 2500 while in third. Push in clutch and apply brake (good brake booster action) at bottom where the light is ALWAYS red, and engine stalls. It only takes a moment of starter to get it running again. Typical idle rpm is in the range of 850 - 950 (depending on what meter I use:Sears cheap-o or dash VDO cheap-o) and while the engine does sometimes drop down to maybe 600 rpm on the flats when I push in the clutch, it recovers quickly and never stalls. The squirrel is puzzled but not giving up.

The after-fires during downhills also persist. Looking for exhaust leaks I re-torqued all the head exhaust port nuts . . . there is no sign of leakage at any of the four exhaust ports -- they were assembled with copper gasket compound and those pressed tin exhaust port gaskets. Mongo did not break any studs but Mongo did make them tighter. And those dopey little double-C clamps between the heater boxes and muffler are as tight as they can go. I've got a bug muffler on the Wonderbus, and I plugged both peashooters with my hands -- the engine did not die though it began to labor. Initial inspection is that there is a leak at a peashooter-muffler clamp joint. Muffler too hot to remove peashooters and repeat test, so results are inconclusive. Will do better test tomorrow. In the meantime, I have these black circles on the palms of my hands. VW owner's stigmata?

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

Are you sure your mixture is okay? After I put in a new carb some years ago I had the same symptoms and it turned out that I had mis-adjusted the mixture and it was running too lean.