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TR2/3/3A Missfire and Backfire
- Thread starter Ken H
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This morning, I discovered an article helping to diagnose distributor problems. > Distributor wear diagnostics <. I hooked up the timing light to the coil wire (per the article) and watched the timing mark on the pulley. As I witnessed yesterday, the mark jumps around moving about an inch more in advance every few sparks. The article says the explanation for this is bearing wear causing the shaft to shift and point gap change.
I had difficulty starting the car and quickly learned that if I choked it at all, the engine stalled. (suggesting my 20 flats open was way too rich with the engine cold) I set the idle higher and without adjusting the carbs, started the engine and was able to get it to run for two minutes at 1200 rpm. Suddenly the engine stopped as if I cut off the ignition or fuel. After waiting 10 seconds I started it again and it continued to warm up.
I checked the timing light again and saw the timing mark jump back and forth as it had previously done. Because the article said this is a worn distributor, I decided to put the Portronics distributor back on. This is a new distributor which matches the old, but has a magnetic pickup inside to eliminate the points and condenser. I was sure this would eliminate the "wear" problem I initially witnessed.
I started the engine again which was still warm. I rotated the distributor to get the smoothest idle I could and was able to reduce the rpm to 700. (I didn't try to reduce it further) At that point, I looked at the advance again and saw the timing mark move as it had done with the old distributor. I took a video of the event, but the file size is too large to post (29meg) and I don't know how to compress the file.
I'm wondering if it could be caused by too much end play in the short shaft that drives the oil pump, tach, and distributor? It's a helical gear which could move axially if there were too much end play. This would affect timing, but I find it hard to believe it would jump back and fourth. Does anybody have experience with this? Or do you have another explanation for the timing to jump with a new distributor?
Online
How old is the distributor rotor arm I have old or bad repro ones arc off a rivet causing all sorts of misfires.
Get a good red one.
our guru in the uk is the distributor doctor.
www.distributordoctor.com
Get a good red one.
our guru in the uk is the distributor doctor.
Distributor Doctor
We rebuild Lucas distributors and sell related spare ignition parts including coils, leads, ignitors.
www.distributordoctor.com
There's a new cap on each distributor. The cap on the Pertonix distributor doesn't fit the original distributor.
Both distributors have new rotors.How old is the distributor rotor arm I have old or bad repro ones arc off a rivet causing all sorts of misfires.
Get a good red one.
our guru in the uk is the distributor doctor.
Distributor Doctor
We rebuild Lucas distributors and sell related spare ignition parts including coils, leads, ignitors.
I'll pull the distributor and check the end play in the shaft. It was ok last time I had it apart, but it's worth checking again.
This morning, I checked the strength of the spark by pulling number 1 plug wire and holding it close to ground. The spark traveled over 1/2 and inch! I was surprised how strong the spark is.
I also checked the float valves one more time. First, I pulled the vacuum chambers off the top of the carbs to see the level of fuel in each jet. The front carb level was lower than the rear. I could see the fuel in the jet, but it was about 1/8 of an inch or more below the top of the jet. The rear carb fuel level was flush with the top of the jet. I measured each float valve setting and they were 7/16 inch plus or minus .020. I replaced the front carb float valve with an old one I had laying around and reset it to 7/16. After putting everything back together, I turned the engine over without spark and got the same results. Front carb fuel level remained lower than the rear. The rear carb was still flush with the top of the jet. If anyone has some ideas how to fine tune the float levels, please share them with me. I'll continue to make adjustments until I get the same levels in each carb.
I also checked the float valves one more time. First, I pulled the vacuum chambers off the top of the carbs to see the level of fuel in each jet. The front carb level was lower than the rear. I could see the fuel in the jet, but it was about 1/8 of an inch or more below the top of the jet. The rear carb fuel level was flush with the top of the jet. I measured each float valve setting and they were 7/16 inch plus or minus .020. I replaced the front carb float valve with an old one I had laying around and reset it to 7/16. After putting everything back together, I turned the engine over without spark and got the same results. Front carb fuel level remained lower than the rear. The rear carb was still flush with the top of the jet. If anyone has some ideas how to fine tune the float levels, please share them with me. I'll continue to make adjustments until I get the same levels in each carb.
charleyf
Luke Skywalker
Offline
If anyone has some ideas how to fine tune the float levels, please share them with me. I'll continue to make adjustments until I get the same levels in each carb.
[/QUOTE]
When you pulled the suction chambers and looked at the fuel level in the jets, you were doing the first part of getting the float levels where you want them. Then you reverted back to the book and set the floats at the generic measurement. If the fuel level in the rear carb needed to be higher then change the float level the amount needed to change that fuel level. The book gives you a generic or average figure.
If your rear carb shows the fuel 1/8" low then adjust your rear float by 1/8". I.e. 7/16." --1/8"=5/16". Continue adjusting until you are satisfied.
Charley
[/QUOTE]
When you pulled the suction chambers and looked at the fuel level in the jets, you were doing the first part of getting the float levels where you want them. Then you reverted back to the book and set the floats at the generic measurement. If the fuel level in the rear carb needed to be higher then change the float level the amount needed to change that fuel level. The book gives you a generic or average figure.
If your rear carb shows the fuel 1/8" low then adjust your rear float by 1/8". I.e. 7/16." --1/8"=5/16". Continue adjusting until you are satisfied.
Charley
There are 2 small passage ways in each carb where you put a wire through. There is one in the float chamber and one in the carburetor body between the float hook up bolt hole and the jet and where the fuel enters the jet. When you pulled the plugs, where they all black with carbon?
steve
steve
When you pulled the suction chambers and looked at the fuel level in the jets, you were doing the first part of getting the float levels where you want them. Then you reverted back to the book and set the floats at the generic measurement. If the fuel level in the rear carb needed to be higher than change the float level the amount needed to change that fuel level. The book gives you a generic or average figure.
If your rear carb shows the fuel 1/8" low then adjust your rear float by 1/8". I.e. 7/16." --1/8"=5/16". Continue adjusting until you are satisfied.
Charley
[/QUOTE]
Charlie, That's what I expected to hear, but wanted confirmation. This morning, I played with the adjustments and couldn't home in on the same levels in each jet. I eventually gave up and started the car and let it run at 1000 rpm for a few minutes to begin warming up. Without touching a thing the engine would suddenly drop to 600 rpm and stay there for about three seconds and slowly increase rpm back to 1000. It would then run for a minute or so before repeating the process. I threw the timing light on it to see if a change in timing was causing the drop in rpm and saw the timing remained steady with a slight shift due to centrifugal advance. That leads to me think the erratic drop in rpm was caused by a sticking float valve or something else in the fuel system. The float valves are clean and nothing seems to be sticking, but I'm inclined to order new ones anyway.
I've seen this sudden drop in rpm before, but attributed it to having the old distributor on the car and perhaps something had shifted (weights, sticking plate, worn bearings, etc.) I didn't think of float valves at the time.
Moss offers a Viton tipped valve or a Gross Jet which they claim to be superior to the original. Do you have a preference?
While I was in the carbs, I measured the SM needles at 1/8-inch increments, and they matched the specs perfectly. Although this morning's trial, never got the engine fully warm, I started the run with the jets opened 16 flats. Perhaps after replacing the float valves I'll be able to adjust the jets down to twelve.
charleyf
Luke Skywalker
Offline
When I first learned about Gross jets some 10 + years ago I tried them and they worked well. Until one day one of them stuck shut. I then learned that the original company had sold out and somebody else was making them . They were putting out a poor product and had lots o complaints. I got rid of mine and never looked back. I do not know what the current product is like. I had heard that some of the more recent problem was caused by packing grease or some such nonsense.
I have continued to use the original style valves . Be aware that a debris particle can get into the line prior to the valve and cause a lot of heartache.
Charley
I have continued to use the original style valves . Be aware that a debris particle can get into the line prior to the valve and cause a lot of heartache.
Charley
I tried one other go today. I had a box of old float valves and put together a pair that looked good under a magnifying glass. I put them in the carbs and adjusted with the 7/16 drill bit. While I was at it, I replaced the fuel filter (in-line clear plastic) and put in five gallons of fresh gas. The only ethanol free gas in town is 89 octane. I started the engine with either and after 20 seconds or so it ran on it's own with idle set at 1000 rpm. After ten minutes I was able to lower the rpm to 750 without stalling, but the engine ran rough. I turned the distributor more advanced and the rpm increased slightly, but I was not able to reduce the idle speed less than 750. The engine did not drop in rpm like it had this morning, so I think the new float valves may have resolved that issue.
One thing I observed was the clear filter canister which is mounted near the carbs. took longer than I thought to fill. It seems like the fuel pump wasn't putting out enough flow. A few weeks ago I checked the fuel pressure and it was putting out around 2 psi if I remember correctly. I also pumped some unrestricted flow into a can. The flow was pretty good. I'm wondering if the fuel pump won't put out flow with a back pressure. It's the original mechanical pump which has been rebuilt within the last ten years. What are your thoughts about the fuel pump?
charleyf
Luke Skywalker
Offline
I have a clear filter near the carbs and find that the filter never fills with fuel. But the car runs fine. If you were able to pump fuel out of an open line , I would guess you are good. I am assuming the filter screen at the top of the fuel pump bowl is clean.
Charley
The plugs are black with carbon very quickly after cleaning.