TR2/3/3A Missfire and Backfire

[Ken H]

I could probably "fill a coffee can" with Grose jets I've removed from TR6 carbs

Thanks. I'll steer away from them.

 

[Ken H]

The plugs are black with carbon very quickly after cleaning.

I'm pretty sure I checked those passages when I did a major cleaning of the carbs months ago, but I can't be positive.

 

[Ken H]

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

My clear filter also doesn't completely fill with fuel except on rare occasions. When the filter was dry and I first cranked the engine, I saw the first spurt of fuel enter the filter. I expected it to fill quickly after that, but it took longer than expected to fill. (2/3 full) That made me wonder if something is wrong with the fuel pump. Check valves not sealing well or worn cam lobe. At this point I'm really reaching for a solution.

 

[LarryK]

If they blacken that fast you are way over rich. That might be a choke adjustment.

 

[sp53]

Yes the chokes are tricky and often do not shut off completely or if the spring for jet return are not hooked up correctly or if the spring is wrong the carburetor will flood and sputter because the spring does not return the jet for a warm engine to run smooth. Do the crabs drip? Can you push the jet back up any be hand

The whole spark deal with the timing moving around is puzzling. I cannot image a way for the timing gears to cause that effect. Could the woodruff key on the distributor shaft driven by the oil pump be sheared and slipping?

Could the distributor be off a tooth?

can you post a picture of the carbs just sitting and maybe a picture with #1 TDC compression stroke and the position of the rotor with the distributor cap off

steve

 

[Sarastro]

The erratic spark timing could be caused by the distributor drive-gear end float being too great. That's worth checking, as it could affect oil pressure, too. There is a procedure for checking this in the shop manual (p. 1-130)

If the distributor drive gear is a tooth off from the factory-specified position, it won't affect timing unless you can't rotate the distributor enough to get the right timing.

In my experience, the fuel filter will almost always have a bubble in it. It is of no consequence unless it is so bad that fuel can't get through, and it has to be really bad for that to happen. Fuel these days bubbles like ginger ale in the lines, and unless it is really severe, it won't hurt anything.

 

[Ken H]

If they blacken that fast you are way over rich. That might be a choke adjustment.

Thanks Larry, Choke is not engaged. My cable does not lock in the out position and once started and choke released, the jets move into their "up" position. The carbs with SM needles are adjusted to 17 flats open (way too rich) and if I close them another flat the engine dies at idle. The engine will not idle below 700 rpm.

 

[Ken H]

Yes the chokes are tricky and often do not shut off completely or if the spring for jet return are not hooked up correctly or if the spring is wrong the carburetor will flood and sputter because the spring does not return the jet for a warm engine to run smooth. Do the crabs drip? Can you push the jet back up any be hand

The whole spark deal with the timing moving around is puzzling. I cannot image a way for the timing gears to cause that effect. Could the woodruff key on the distributor shaft driven by the oil pump be sheared and slipping?

Could the distributor be off a tooth?

can you post a picture of the carbs just sitting and maybe a picture with #1 TDC compression stroke and the position of the rotor with the distributor cap off

steve

Hi Steve,
The jets and gaskets are new and very low friction. Every time I run the engine (which is daily) I check the choke to ensure the jets are up. Everything is fine with the choke.
Yesterday, when I put a timing light on, the spark was not fluttering as it had before. I don't have an explanation for that. The engine was running a tad smoother, but still would not adjust to less than 700 rpm. If it went lower than that, it would die. I played with the needle adjustment and ended up around 17 flats open. If I closed them more than that, the engine would die.

The distributor is aligned correctly, but if it were off a tooth, rotating the distributor would correct that. The pin on the shaft driving the distributor is good.

 

[Ken H]

My clear filter also doesn't completely fill with fuel except on rare occasions. When the filter was dry and I first cranked the engine, I saw the first spurt of fuel enter the filter. I expected it to fill quickly after that, but it took longer than expected to fill. (2/3 full) That made me wonder if something is wrong with the fuel pump. Check valves not sealing well or worn cam lobe. At this point I'm really reaching for a solution.

I forgot about the screen at the top of the fuel bowl. It's been years since I've looked at it. I'll check it next. Thanks for pointing that out.

 

[sp53]

I run mine with no fuel filter. I had a glass filter once and inside the filter a small ball of crud which turned out to be body putty from the shop it was in for like 6 months. The body putty dust collected into this small ball and would fall over the hole in the filter and seal it plugging the fuel line and then would roll back when the fuel pressure was off. I just remembered that story. Take the fuel filters off until this is sorted out. Perhaps blow your fuel back to the tank and move stuff and crud around in the tank and line to see if that helps

Idling at 700 with fuel today is difficult they usually like running at 900 to 1000 to 1100 unless you are very good at tuning

the carbon is weak spark or rich mixture or both

steve

 

[Ken H]

My clear filter also doesn't completely fill with fuel except on rare occasions. When the filter was dry and I first cranked the engine, I saw the first spurt of fuel enter the filter. I expected it to fill quickly after that, but it took longer than expected to fill. (2/3 full) That made me wonder if something is wrong with the fuel pump. Check valves not sealing well or worn cam lobe. At this point I'm really reaching for a solution.

A new day, a new direction. This morning I removed the glass fuel bowl from the pump and cleaned the sediment out of the bottom of the bowl. It was very fine "mud" with no chunks that could have clogged lines, etc. While I was doing that, I also replaced the 1/4 inch rubber fuel line running from the steel line from the fuel tank to the fuel pump. (about 2.5 feet) The old line looked fine, but was seven or eight years old, so I replaced it.

At this point the pump was dry with no fuel in the new line. I tried pumping the fuel up to the glass bowl using the lever on the bottom of the pump. The pump would not pull the fuel up the line. I'm thinking the air lock is preventing the fuel from coming or perhaps the check valves (although wetted with fuel) don't seal well enough to pump air.

I then tried turning the engine over with the starter to see if the pump would fill the bowl with gas and it didn't after thirty seconds of turning over. Either the pump is not working, or it just needs priming. Thoughts? If I need to replace the pump, should I rebuild or replace. I've read some horror stories about replacement pumps on the forum. Do you recommend a source for a kit or pump?

 

[Mickey Richaud]

Rebuild is the way to go, IMHO. In the meantime, you may want to get a cheap inline electric pump (be careful of its pressure rating - don't want more than ~3 psi) to see if you can get the juices flowing. Nice to have as a backup as well.

 

[Ken H]

A new day, a new direction. This morning I removed the glass fuel bowl from the pump and cleaned the sediment out of the bottom of the bowl. It was very fine "mud" with no chunks that could have clogged lines, etc. While I was doing that, I also replaced the 1/4 inch rubber fuel line running from the steel line from the fuel tank to the fuel pump. (about 2.5 feet) The old line looked fine, but was seven or eight years old, so I replaced it.

At this point the pump was dry with no fuel in the new line. I tried pumping the fuel up to the glass bowl using the lever on the bottom of the pump. The pump would not pull the fuel up the line. I'm thinking the air lock is preventing the fuel from coming or perhaps the check valves (although wetted with fuel) don't seal well enough to pump air.

I then tried turning the engine over with the starter to see if the pump would fill the bowl with gas and it didn't after thirty seconds of turning over. Either the pump is not working, or it just needs priming. Thoughts? If I need to replace the pump, should I rebuild or replace. I've read some horror stories about replacement pumps on the forum. Do you recommend a source for a kit or pump?

I just had another thought. For a while, I was using ethanol fuel before I learned about it's corrosive issues. I wonder if that fuel could cause the rubber in the fuel pump check valves to warp making them less effective?

 

[poolboy]

Been using 10% ethanol for more than a decade in my TR6....no negative effect, but I don't let it get old
I drive that car year round... fuel up every 2 weeks
You are about to run out of things to check..
Maybe you could make a current list of everything.

 

[charleyf]

First you did not mention the fine screen located in the top of the fuel bowl on the fuel pump. It is not visible but it is up there. You can use a mirror to see it. It simple pulls down to be cleaned.
Second the line going from the tank to the fuel pump is 5/16" not 1/4". The line from the pump to the carbs is 1/4".
Third a stock setup for our cars does not have 2.5feet of rubber fuel line. Though rubber lines are good, if it were me I would get some steel or copper-nickel line 5/16" to replace it. There is a very short 4-6" piece in two locations.
Charley

 

[DavidApp]

When you had the 1/4" rubber line disconnected at the fuel pump did fuel come out of it? There could be a blockage at the tank.

David

 

[Graham H]

You can see part of the fuel lines I made out of copper tubing in these photos

Graham

 

[Ken H]

When you had the 1/4" rubber line disconnected at the fuel pump did fuel come out of it? There could be a blockage at the tank.

David

There was a strong flow from the tank that unfortunately ran up my arm before I got the hose connected.

 

[Ken H]

You can see part of the fuel lines I made out of copper tubing in these photos

GrahamView attachment 78581View attachment 78582View attachment 78583

Wow. Beautiful work.

 

[Ken H]

First you did not mention the fine screen located in the top of the fuel bowl on the fuel pump. It is not visible but it is up there. You can use a mirror to see it. It simple pulls down to be cleaned.
Second the line going from the tank to the fuel pump is 5/16" not 1/4". The line from the pump to the carbs is 1/4".
Third a stock setup for our cars does not have 2.5feet of rubber fuel line. Though rubber lines are good, if it were me I would get some steel or copper-nickel line 5/16" to replace it. There is a very short 4-6" piece in two locations.
Charley

Sorry, I forgot to mention the screen. I didn't have one! I'm going to order a replacement. I became aware of the steel tube when I looked at the Moss illustration, but for the interest of expediency decided to just replace the old rubber. The 5/16 diameter makes sense since it's on the suction side of the pump. That explains why I had to push so hard to get the 1/4 in inch hose to fit. I like to keep it original, so I'll get the steel tube.