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Hi guys. It's been a while since I posted. Since then, I rebuilt and polished my A4's Carbureator, serviced the fuel pump, and installed a new fuel filter, new fuel hoses, new fuel fittings. I assembled everything, and tried to start the engine. No luck. Now, before you start getting ideas, I'll tell you what all has been tried, and the results.
So, according the the Moyer manual, there must be three things present for the A4 to start: Spark, Compression, and Air-Fuel mixture. When I assembled the carb, I took care to check gaps, etc, when rebuilding and installing.
I manually used the mechanical fuel pump to pull the fuel from the tank, through the new filter and hoses to the pump, so we know the fuel pump works.
When attempting to start the engine, we get good turn-over, and the sound seems to me that it is trying to fire. However, the enginge doesn't "catch". I adjusted choke and throttle, no luck.
First I suspected electrical. I pulled the plugs (have about 2 hours of use on them, perhaps less) and inspected. Two plugs had dry carbon , 2 had wet carbon -- makes sense since 2 cylinders would have been in either compression or intake mode. The carbon tells me that the fuel mixture is burning, were just not getting a clean burn. In fact, once when opening a plug, the mixture had burnt, but not been exhausted yet, and black smoke rose out of the spark plug hole.
I pulled a plug wire put it on a screwdriver, and turned the engine over with the screw driver about 1/4 inch from the block, the spark did jump the gap. I pulled a plug and grounded the plug and viewed the spark action. It was a good, white-blue spark.
So, then I suspected that we weren't getting proper fuel, I used di-ethyl ether with propane and butane starting fluid. It still did not start. This should eliminate carbeuration and/or fuel from being the cause of the problem, I would guess.
It was beginning to look like a compression issue. So, I returned the next day with a compression tester. I tested each cylinder 1-4: 115, 110, 115, 105. Which should be fine for a engine designed to be 95 or higher. One thing did happen though on one cylinder, it received a single reading of 150 eventhough the rest were 115. I think this means that the burn from one cylinder made it into the one being tested via intake or exhaust manifold. This may imply a stucky valve -- but the rest of the readings were good. But anyway, we do know that the engine has compression.
So I thought, maybe we have plug #1 identified wrong on the distributor(though the engine did work before the carb rebuild). I verified that the #1 plug was leading to the location on the distributor cap as previously identified by the Piston #1 TDC method. I double checked by rotating the plugs 90 degrees in each direction. Neither attempts did not even try to catch, so we can conclude that the #1 cable is in the right place. I then verified that the plugs were oriented 1-2-4-3 in a clockwise direction on the distributor. I then opened the distributor and looked at the rotor and disty cap. Both are in like-new condition (having less than 2 hours on them). There was no water or oil in or on the cap.
So, I thought that perhaps the timing was off, and the plugs were firing too late, and the pistor was already moving away from the flame before the gas burned. This could look like lack of compression, and cause carbon fouling. So, I advanced the timing a bit. Still would not start.
I did not try retarding the timing.
The fuel is old, but it didn't start with Ether, so it is unlikely that the fuel is the issue.
Did not check spark plug gap, points gap, etc. But since we were getting good spark and were jumping a quarter inch, then it doesn't seem like the electrical system is bad. Hmmm... Come to think of it, I only tested the spark on one wire, so it is possible that only one (or two) pistons are firing. However the carbon on each plug infers that all pistons are firing, without power.
I did not replace anything in the electrical system; it didn't seem necessary due to healthy spark.
So, I can't think of anything else to try other than the just start guessing and replacing things until I accidentally stumble on a working combination.
Thought. I had to manufacture a jet for the carbeurator. If the hole were too big, could it make too rich a mixture such that adding ether to the mix still wouldn't work? If so, then I should shut down the fuel pump (or disconnect it from the carb) and try starting it with just ether.
Any other ideas?
Oh yeah, I already tried drinking a beer, yelling at it, being nice to it, coaxing it, and threatening it. Nothing seems to work.
So, according the the Moyer manual, there must be three things present for the A4 to start: Spark, Compression, and Air-Fuel mixture. When I assembled the carb, I took care to check gaps, etc, when rebuilding and installing.
I manually used the mechanical fuel pump to pull the fuel from the tank, through the new filter and hoses to the pump, so we know the fuel pump works.
When attempting to start the engine, we get good turn-over, and the sound seems to me that it is trying to fire. However, the enginge doesn't "catch". I adjusted choke and throttle, no luck.
First I suspected electrical. I pulled the plugs (have about 2 hours of use on them, perhaps less) and inspected. Two plugs had dry carbon , 2 had wet carbon -- makes sense since 2 cylinders would have been in either compression or intake mode. The carbon tells me that the fuel mixture is burning, were just not getting a clean burn. In fact, once when opening a plug, the mixture had burnt, but not been exhausted yet, and black smoke rose out of the spark plug hole.
I pulled a plug wire put it on a screwdriver, and turned the engine over with the screw driver about 1/4 inch from the block, the spark did jump the gap. I pulled a plug and grounded the plug and viewed the spark action. It was a good, white-blue spark.
So, then I suspected that we weren't getting proper fuel, I used di-ethyl ether with propane and butane starting fluid. It still did not start. This should eliminate carbeuration and/or fuel from being the cause of the problem, I would guess.
It was beginning to look like a compression issue. So, I returned the next day with a compression tester. I tested each cylinder 1-4: 115, 110, 115, 105. Which should be fine for a engine designed to be 95 or higher. One thing did happen though on one cylinder, it received a single reading of 150 eventhough the rest were 115. I think this means that the burn from one cylinder made it into the one being tested via intake or exhaust manifold. This may imply a stucky valve -- but the rest of the readings were good. But anyway, we do know that the engine has compression.
So I thought, maybe we have plug #1 identified wrong on the distributor(though the engine did work before the carb rebuild). I verified that the #1 plug was leading to the location on the distributor cap as previously identified by the Piston #1 TDC method. I double checked by rotating the plugs 90 degrees in each direction. Neither attempts did not even try to catch, so we can conclude that the #1 cable is in the right place. I then verified that the plugs were oriented 1-2-4-3 in a clockwise direction on the distributor. I then opened the distributor and looked at the rotor and disty cap. Both are in like-new condition (having less than 2 hours on them). There was no water or oil in or on the cap.
So, I thought that perhaps the timing was off, and the plugs were firing too late, and the pistor was already moving away from the flame before the gas burned. This could look like lack of compression, and cause carbon fouling. So, I advanced the timing a bit. Still would not start.
I did not try retarding the timing.
The fuel is old, but it didn't start with Ether, so it is unlikely that the fuel is the issue.
Did not check spark plug gap, points gap, etc. But since we were getting good spark and were jumping a quarter inch, then it doesn't seem like the electrical system is bad. Hmmm... Come to think of it, I only tested the spark on one wire, so it is possible that only one (or two) pistons are firing. However the carbon on each plug infers that all pistons are firing, without power.
I did not replace anything in the electrical system; it didn't seem necessary due to healthy spark.
So, I can't think of anything else to try other than the just start guessing and replacing things until I accidentally stumble on a working combination.
Thought. I had to manufacture a jet for the carbeurator. If the hole were too big, could it make too rich a mixture such that adding ether to the mix still wouldn't work? If so, then I should shut down the fuel pump (or disconnect it from the carb) and try starting it with just ether.
Any other ideas?
Oh yeah, I already tried drinking a beer, yelling at it, being nice to it, coaxing it, and threatening it. Nothing seems to work.
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