1835 running issues

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knotsofast

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I can't quite get my engine to run properly. I hope you guys can help out.

What I have is an older HAPI 1835 engine that's been hiding in a barn since the mid 80's. Pusher configuration, 009 ignition, dual Weber 228's. Mechanical fuel pump putting out 3.5 lbs. pressure continuous using ethanol free pump gas, 87 octane. Advanced timing set at 15*, points set at .016, plugs at .025. Compression in all 4 cylinders is 105 lbs. cold, hand propped thru 4 compression strokes.

Issues I have are at idle (1000 rpm), #3 cylinder is sucking thru the exhaust a little. I can feel it sucking up to about 1500 then it quits. Pulled the head and the valve moves nice and smooth, no apparent sticking. I lapped the valves and swapped the #3 and #4 exhaust springs. No change whatsoever.

The engine starts easy and runs smooth up to WOT. Once the throttle is opened up all the way it will run smooth for about 10 seconds and then start loosing cylinders, seems like #1 and #2 just about quit altogether, along with some spitting and backfiring. Back off the throttle and it smooths back out almost instantly.

Thoughts?
 
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This is just an Internet guess - there is no substitute for hands on:

Based on what you have already checked my next area of investigation would be the carburetor that supplies #1 and #2 cylinders. Cylinder numbering of VW's can get confusing. The VW numbering system does not match aircraft convention and both get used for the VW. I'm basing my guess on the VW numbering with #1 and #2 being on the right side in a pusher (pulley end drive)- same as the car.

Are the carbs balanced properly?
 

TFF

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Im going to assume you have already put new cap and wires on, you have no intake leaks, carbs are right, and timing/ firing order is right. Have you swapped the carbs to the other sides and see how they act?
You might try longer exhaust pipes if you are getting a reverb.
 

knotsofast

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I did forget to mention it's pulley end drive. I"m using standard car numbering on the cylinders so you are correct. Sitting on the gyro #1 is front right, #2 is rear right, #3 is front left, and #4 is rear left. Firing order is 4123. Carbs are in sync.
 

TFF

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Floats in the carbs not sticking or dragging, flow through the seats ok? How is the fuel delivered to both carbs piping wise? what about hooking up a gravity fed tank to each carb independent of each other?
 
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After what TFF suggested, and a double check of the fuel filter on the right if you have two, my next test would be to hook up an oscilloscope to verify the ignition. If you don't have access to one even an old school timing light can often spot missing or erratic ignition pulses.

What kind of plug wires and ends are used?
 

bmcj

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Just a wild guess, but IIRC, the #1 & #2 intake manifolds merge together. Is it possible that you have a leaking/sticking intake valve on one of those two cylinders that might introduce backpressure in the intake manifold and interrupt proper fuel/air flow to both?
 

knotsofast

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Funny thing, I had considered switching the carbs earlier but never did. The sucking cylinder (probably just not firing regularly) that I was concerned with has gone from #3 to #1. The cutting out and miss has changed to a surge, hard to determine exactly what is cutting out now. Looks like it is a carb issue tho.

To answer previous questions, fuel goes from the seat tank, thru the filter, thru a primer pump, then the shut-off valve, to the fuel pump, then T'd off to each carb. Bypassed all that and hung a bottle to gravity feed the pump but ultimately, always maintained 3.5 psi fuel pressure with no air bubbles. Determined delivery to the carbs was not the issue.

New cap, plugs, and wires. Intakes carb cleaner tested and not leaking. Have to excuse my texting ignorance but I don't know what IIRC is. Since the sucking exhaust symptom followed the carb I'm guessing my valve concern was a wild goose chase.
 

Pops

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I did forget to mention it's pulley end drive. I"m using standard car numbering on the cylinders so you are correct. Sitting on the gyro #1 is front right, #2 is rear right, #3 is front left, and #4 is rear left. Firing order is 4123. Carbs are in sync.


If you are using standard numbering as when the engine is in the car, the firing order is 1432. Easy to get a intake leak in a VW and cylinder on one side going to lean and quit firing. Also the total ignition advance timing for a 1835 VW engine is 28 degs, for a 2180 and up its 25 degs. You are running a lot of carb for a 1835 engine at low prop rpm's. Your engine is not in an auto turning 4 or 5+ thousand rpms. When using a 009 distributor with certain carbs you can get a large flat spot at about 1500-2000 rpm's. VW single port head stock carb is OK, but not the VW dual port stock carb with the 009 dist.
 

knotsofast

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the firing order is 1432. Also the total ignition advance timing for a 1835 VW engine is 28 degs,

This is what I get for writing from memory, in the morning, while still on my first cup of coffee. Firing order is, of course, 1432.

I'm not sure where I read 15* for timing but that is also incorrect. I broke out the protractor to check the timing marks on the prop hub and indeed the 2 marks I have are TDC and 28* BTDC. So timing should be correct.

The problem is following the carb. Nothing blocking or obstructing the float, needle, or seat. Fattened the mains from 125 all the way up to 175...no change.
 

delta

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It sure sounds like you're running out of fuel supply to the cylinders but a weak coil could act that way as well. It should jump a nice blue spark at least an inch with the engine running. Make sure there is a ballast resistor either in the coil or before the coil to keep your points from burning. Check for slop in the cam lobe. A dwell meter would be nice to adjust your points correctly. A loose condenser would keep you barking up a lot of different trees.
 

knotsofast

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I had considered the coil. Tested the resistance while it was still hot and over a short period of time watched it drop from 9 ohms, to 8, to 7... About a week later my shinny new Blue Bosch shows up in the mail. Put it on and no change. Turns out one of the leads on my multimeter went bad. More spare parts.

I also considered the condenser but never saw one only act up only at high rpm like this. Dwell meter would be nice but honestly, even if I had one I've never used one before. Been quite lucky with simply static timing (on bikes at least) in the past.

Looks like I may have to break down and replace my leaky old Brazilian made Weber 228's. Long obsolete, I can't get parts, or even gaskets for them. Any suggestions on replacements? Maybe more important, what should I stay away from?
 

fly2kads

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I am not familiar with those old Webers. On some carbs, wear around the throttle shafts can allow air leakage, leading to lean/erratic running.

A similar, single-barrel setup would be to upgrade to dual Weber 34 ICTs:
Dual Weber 34 ICT Carb Kit, Type 1 (Upright), Type 3, and Type 4 Engines, CB Performance - Aircooled.Net VW Parts

This is a pretty common setup in the VW car scene, and seems to work well. With the restricted RPMs of an aviation application, I wouldn't see any need to step up to two barrel carbs.
 

N8053H

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I am not familiar with those old Webers. On some carbs, wear around the throttle shafts can allow air leakage, leading to lean/erratic running.

A similar, single-barrel setup would be to upgrade to dual Weber 34 ICTs:
Dual Weber 34 ICT Carb Kit, Type 1 (Upright), Type 3, and Type 4 Engines, CB Performance - Aircooled.Net VW Parts

This is a pretty common setup in the VW car scene, and seems to work well. With the restricted RPMs of an aviation application, I wouldn't see any need to step up to two barrel carbs.

I myself like the carb mounted under the engine. there are a couple reasons for this. 1. You can use a gravity feed system. 2. I also like a single carb setup for then one can use carb heat. I guess you could setup carb heat for two carbs, but that seems like a lot of extra weight for how little the airplane is that has something as small as a vw engine to pull it around. Keep it simple and keep it lite. Two carbs and everything it takes to make them work without icing up, seems like a lot of extra weight. IMHO

Tony
 

knotsofast

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The dual 34's would keep the theme of the mid 80's gyro that I'm restoring. What about the EMPI copy of the Weber? What's the word on those?

On the other hand a single carb is easier to set up and likely be lighter. But I was under the impression that downdraft was better for the Armstrong starting method, my only electrics is a small battery powering the ignition. What size single carb would I be looking at to replace the dual 34's?
 

N8053H

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My setup does not draw intake air from outside the cowl. The airfilter is in the cowl. With this setup I have never experienced carb ice. The air inside the cowl is warmer then Outside air temp. I installed a OAT gauge or probe in the cowl. It gets about 30 degree's warmer in the cowl then it is outside.

As to starting. Apply choke. Turn prop over three to four times she will start on the third or forth pull of the prop. Once running remove or shut off choke. Its that easy to start one of these.
 
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