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That's a good idea. It's complicated, even for me. I'll put together a document to share.
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TR2/3/3A Missfire and Backfire
- Thread starter Ken H
- Start date
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You're transmission looks different than mine. Is that an overdrive unit?
Today's update. Sorry for the delay in new information. I ordered a fuel pump kit and installed it yesterday. The old diaphragm, although it was intact, it was stiff compared to the new one. The checkvalves looked ok, but I suspect they may have leaked a little. After installing the rebuilt fuel pump, I started the engine without the use of ethanol. This was the first time it started without ethanol in a month or more. After ten seconds of choke, I released the choke and the engine continued to run.
After warmup, I reduced the idle to 600 rpm and attempted to check the carb adjustments which resulted in leaning one carb by one flat. (I forget the number of flats open at this point, but I know it's more than 16)
I adjusted idle to 900 and tightened the throttle shaft clamps to see how the engine would do on a drive around the block. The engine would run fine when holding steady rpm, but upon light acceleration, it would misfire badly and whenever I accelerated slightly harder it would backfire through the carbs. I never took the engine over 2000 rpm.
For quite a while I've had a tapping sound from one of the valves. It sounds like that valve is adjusted too loose, but all valves are adjusted to spec. The tapping is constant, and slightly louder than the other valves. I'm pretty sure it's just one valve because it's rhythmic. If this valve is sticking open, that would account for a backfire through the carbs. I'm wondering if this valve is somehow hanging up during acceleration and why it doesn't hang up at constant rpm. Any thoughts?
After warmup, I reduced the idle to 600 rpm and attempted to check the carb adjustments which resulted in leaning one carb by one flat. (I forget the number of flats open at this point, but I know it's more than 16)
I adjusted idle to 900 and tightened the throttle shaft clamps to see how the engine would do on a drive around the block. The engine would run fine when holding steady rpm, but upon light acceleration, it would misfire badly and whenever I accelerated slightly harder it would backfire through the carbs. I never took the engine over 2000 rpm.
For quite a while I've had a tapping sound from one of the valves. It sounds like that valve is adjusted too loose, but all valves are adjusted to spec. The tapping is constant, and slightly louder than the other valves. I'm pretty sure it's just one valve because it's rhythmic. If this valve is sticking open, that would account for a backfire through the carbs. I'm wondering if this valve is somehow hanging up during acceleration and why it doesn't hang up at constant rpm. Any thoughts?
Hi, An erratic spark can also be caused by the mechanical advance in the distributer. Pop the cap off and twist the rotor in one direction, let it go and it should snap right back. If it does not, the springs might be broken, or it needs a good cleaning. My TR-3 had that problem (broken springs and toggles). The timing light would jump for 2 degrees BTC to 10 degrees ATDC at idle. It dropped about 400 rpm doing it. Once the revs were above about 2500 RPM, it was fine. Below that, the RPM was random.
Good Luck, Roy G.
Good Luck, Roy G.
Everyone has been so supportive and given me many ideas to check out. I was asked to summarize the list of things that have been tried, so I wrote a book which is attached. I'm running out of ideas and hope some of you have the time to look this attachment over and offer suggestions. Thanks!
charleyf
Luke Skywalker
Offline
IMHO when you try to accelerate what is very possible is that the piston&needle are rising to fast and trying to flood the engine. This produces both a stall and often a backfire through the carbs due to the excess fuel.
Take a look at the system that retards the rise of the piston in the suction chamber. A good seal at the damper and the spring inside the chamber. You say your oil level is good.
Additional item is that the HAYNES SU manual lists the float level adjustment to be .44" which is about 7/16" not 5/16".
I do not think either of these items would cause the poor running or power loss at higher rpms. Only the acceleration issue and backfire issue.
Have you tried disconnecting the chokes to be sure there is not any interference with the operation of the jets?
Charley
Graham H
Jedi Warrior
Offline
As Charley said you need to set the float level to 7/16", if your plugs are sooty it is running too rich. With the tapping noise have you used a listening device, large screwdriver, wooden stick, or stethoscope to locate the noise? It is possible it could be the woodruff key on the distributor/oil pump drive shaft is worn and loose in the keyway. You may need to bruise it with a center punch which helps keep it from falling out when you reinstall it or replace the shaft and the key.
Graham
Graham
I must have made a typo. I've been using 7/16 all along. I like you're thoughts and think I should try to slow the piston rise. Every time I run the engine I end up smelling of fuel which supports your theory. The plugs soot quickly.
The springs are original and have never been rusty. Stress levels in the springs are very low due to the number of coils and size of the wire, so I doubt they have weakened over time. It seems like everyone goes for light oil or ATF, but I think heavy oil is the way to go. I have some 30W I can try.
The engine runs very rich on very low octane fuel. Timing is somewhere around 15 to 20 deg btdc. Low octane burns quickly. Can you explain how this combination can result in backfire through the carbs? Slowing the pistons down will help me lean the mixture. Does a rich mixture burn slowly?
I'll try the heavy oil and let you know what happens.
Thanks for sticking with me.
Ken
I must have said 5/16 by mistake. I've always used 7/16. I've tried the listening device which led me towards the rear of the engine, so I assumed it's valve related on number 4 cylinder. The key word is assumed. I'll listen down near the distributor drive and see if I hear anything.
Thanks for your continued support. I can use all the help I can get.
Ken are you sure you are not a tooth off on installing the distributor and that you have compensated for the tooth off by advancing the timing so the car will start, but the timing falls off the scale when you give it gas to advance .
If you pull the plugs out, and spin the engine over with your thumb over the spark plug hole to feel the air push out on number one piston (this insure both valves are closed.) Then look at the timing marks on the cover and pulley, and bring them both in line because they probably past each other by an inch or so before the engine stopped.
Now pull the distributor cap and see where the rotor is pointing. It should be pointing straight at the number one push rod tube. If not, you are a tooth off at the distributor.
Can you take a picture of the distributor with the cap on to see the orientation of the distributor relative to the block? Sometimes you can see the distributor is too far advanced by looking at the cap placement.
steve
If you pull the plugs out, and spin the engine over with your thumb over the spark plug hole to feel the air push out on number one piston (this insure both valves are closed.) Then look at the timing marks on the cover and pulley, and bring them both in line because they probably past each other by an inch or so before the engine stopped.
Now pull the distributor cap and see where the rotor is pointing. It should be pointing straight at the number one push rod tube. If not, you are a tooth off at the distributor.
Can you take a picture of the distributor with the cap on to see the orientation of the distributor relative to the block? Sometimes you can see the distributor is too far advanced by looking at the cap placement.
steve
charleyf
Luke Skywalker
Offline
I will not claim to any expertise regarding the difference of fuel burning by octane. On a more simple side. The piston/needle is part of what is referred to as the damper. That is to dampen or slow the amount of fuel and air allowed into the intake. To much fuel and air moving into a low rpm engine floods the system leaving unburned fuel .
Back to the damper system. This is a metered system for air intake. So things like a loose knob on top or a poorly matched piston and suction chamber allow air to enter to fast.
One of my TR4's had a loose fitting knob on top of the suction chamber.
The symptoms were the same with the stalling and backfiring including through the carbs. That car also seemed to lose oil from the carb with the bad damper knob seal. I could never determine where the oil went, but it was low a lot.
Charley
I'm pretty sure the shaft is in the right tooth although it's easy to get it off a tooth. Here's a pic of the current distributor at TDC on compression stroke.
Attachments
charleyf
Luke Skywalker
Offline
Although I realize that there is a procedure for setting up the timing gears if they are not marked. But I have successfully with 3 rebuilds now been able to use the old marked gears to determine where the marks should have been. To me it says a lot for don't throw old parts away. I have seen that there is very slight change in the alternate positions for the timing gears.
Charley
Hey Charlie, I'm excited for the first time in months! I put 30W oil in the damper and did a quick drive around the block leaving the carbs and distributor alone. (one variable at a time). The engine started easily but ran very rough with the choke out for 30 seconds. After a few minutes warmup I drove around the block. The engine ran rough, but it was difficult to get a backfire through the carbs.
Back at the house I threw the timing light on and discovered the timing was around 30 deg. BTDC at 900 rpm. (that's where the engine ran best at idle last time it was started. I turned the timing back to 13 deg. btdc and took another trip around the block. This time, I could not get a backfire! Hurrah! Acceleration was pretty good although not great. The engine misses a little, but not too much. I drew a distributor advance curve. (more on this later)
Back at the house I adjusted timing to 10 deg. btdc at 800 rpm. ( I choose 800 because the engine runs rough below that) At the same time, I leaned up the each carb one flat. Again, I drove around the block. Acceleration and misfire was about the same. I drew another advance curve.
Both spark timing checks began at 800 rpm because below that, the engine misfired and I could not hold a steady rpm. Later, when tuned better, I hope to be able to start a distributor curve around 500 rpm. As I increased rpm to 1400, the timing seemed to be erratic. (I had observed this once before on the old distributor) I would adjust the timing light to so the mark at TDC on the pulley lined up with the pointer on the block. I would see most sparks line up with the timing pointer, but occasional sparks fell half and inch to one inch before the pointer (early). Increasing the rpm to 1600 made the timing more erratic. The engine was a little rough, but not too bad.
During the second attempt to do a timing curve, the same anomaly occurred at 1400 rpm and above.
Note: I mentioned a few days ago, I left the distributor where the idle rpm was the highest. That is, I would rotate the distributor a little and the rpm would increase. I would then reset the idle screw to bring the rpm back down to 800. I repeated this process and found the place where the engine ran best at 800 rpm. At that time I did not have a timing light on the engine, but I knew it was well advanced by the position of the distributor. Today, my first drive was with the distributor in that position. It turns out it was 30 deg. btdc as mentioned above.
This morning as I retarded the distributor each time, I had to keep raising the idle by adjusting the idle screws to keep the engine running.
I'm very excited about the progress and feel like I have a baseline to work from and hope I can get some incremental improvements in performance.
If I had to summarize the issues which affected performance so far, I'd say.
1) initially the choke was sticking due to excessive friction and possibly a bad cork gasket on the carb jet. This was fixed by getting new jets and replacing the jet seals. No more sticking of the choke.
2) The old distributor caused the timing to "drift" due to excessive wear. Also, the vacuum advance did not work on the old distributor.
3) Finally, the carb pistons were rising much too fast with 10W30 oil making the mixture much too rich during acceleration. Thanks to Charlie, I now have 30W oil which is working much better. I may try even heavier oil just to see what happens. Possibly 40W.
I feel like I owe you guys a lot of thanks for helping me so far. I need to ask for a little more advise before we call it a day. (or month)
The engine starts and runs reasonably well, but still needs some tuning. I've always followed the manual's tuning instructions which begins with getting the engine to idle around 500 rpm which isn't likely going to happen. I have a few questions for you to help guide me through this.
- What fuel should I use. 88 Octane without alcohol or high octane with alcohol?
- What process do you use to adjust the carb jets if you cannot get a low idle?
- does anyone have comments about the jumping around of the spark at 1400 rpm and above? There is no arching between plug wires. I'm wondering if it's a problem with the timing light. I don't see arching inside the distributor cap.
thanks, Ken
charleyf
Luke Skywalker
Offline
Ken,
Regarding the idle setting. Although some owners attest to getting their car to idle in the 500-700 range. Mine do not and that does not bother me in the slightest. For initial tuning 800 to 1000 rpm is good.
Most of the sources I see recommend starting the timing at 4 degrees btdc. My friend, mechanic and long term TR4 owner sets the timing at about 30-32 degrees at 2500-3000 rpm with the vacuum advance disconnected. This has worked well for me over the years.
I use 87 octane fuel most of the time. I find little difference in the fuel octane.
I have 2 TR4s both cars are set up the same as far as I know. But one car definitely has more pep than the other. I have no idea why. It makes driving them interesting. I am just finishing a TR3A and will have it on the road next month. It is also set up the same as the TR4s. It will be interesting to see how it compares with the TR4s.
I have never experienced an erratic timing , so am no help there.
Glad you are working through what sounds like several variables.
Charley
Regarding the idle setting. Although some owners attest to getting their car to idle in the 500-700 range. Mine do not and that does not bother me in the slightest. For initial tuning 800 to 1000 rpm is good.
Most of the sources I see recommend starting the timing at 4 degrees btdc. My friend, mechanic and long term TR4 owner sets the timing at about 30-32 degrees at 2500-3000 rpm with the vacuum advance disconnected. This has worked well for me over the years.
I use 87 octane fuel most of the time. I find little difference in the fuel octane.
I have 2 TR4s both cars are set up the same as far as I know. But one car definitely has more pep than the other. I have no idea why. It makes driving them interesting. I am just finishing a TR3A and will have it on the road next month. It is also set up the same as the TR4s. It will be interesting to see how it compares with the TR4s.
I have never experienced an erratic timing , so am no help there.
Glad you are working through what sounds like several variables.
Charley
Looks like a tooth off to me. The distributor vacuum advancement line should sit about parallel to the engine and I believe the rotor should come back counterclockwise the thickness of a tooth on the distributor drive shaft for the rotor to point better at the push rod tube, but heck I could be wrong. I will set mine up at TDC tomorrow and take picture.
steve
steve
Many years ago, I always tuned my TRs (I had this 3B and I had a 66 TR4) at idle, 450 rpm. After tuning I'd set them at 600 for driving. I think I read that in a manual, but am not sure of the source. It's been a long time since I've been able to idle at 450. Someone suggested it's today's fuel. Who knows. I have two manuals and after sending my last note I went to them and one says 600 rpm and the other 1000. It's the first I remember seeing you could adjust at 1000. I learn new tricks every day. Thanks for confirming the method works at 800 to 1000.
I read on the forum that non ethanol gas is intended for small engines and doesn't have some of the additives that larger engines require. That person was recommending high test ethanol gas. Any thoughts? If that works, it's a lot easier for me. I have to drive half an hour to get non ethanol.
As far as the pistons go, I think I'll order new springs to see if they are stronger. They're inexpensive and may help. I'll also experiment with 40W oil. Our Autozone carries it.
The sparking still confuses me. I'll call Pertronix and see if they have any ideas. I took a video of the timing light to show everyone what the jumping around looks like and then I learned that I can't attach because of the file type.
Thanks again for your help. I'm encouraged. Maybe I'll even get around to sprucing up the rest of the car. My 7 year old grandson says he wants it.
Thanks Steve. If I remember right, I could never get perfect alignment with the push rod tube. One tooth over put me on the other side of the tube. The vacuum advance is out of position because I was timed at 30 deg. btdc when the photo was taken. I'm now at ten degrees and the vacuum advance is more parallel with the engine.