View Full Version : Officially at a loss......

Jim Lee
11-14-2006, 08:40 PM
I am officially at an almost complete loss on what is happening with my TR3A. Was running great before I put a ecored radiator in it. Now I cannot get it to quit backfiring under any but the lightest load/acceleration. New thermostat, new temp gauge, it barely registers over 155 degrees as compared to 180-185 before. Here are the things I have tried to absolutely no advantage or noticeable difference:

-Cleaned carbs up, changed Marvel Mystery Oil that has always worked fine in dampers for 20/50 motor oil. Adjusted
advance from about 3 degrees to probably 20 and many, many points in between. Replaced thermostat that tested fine. Watched carb piston/needles rise and fall smoothly and in unison to the best my eye can tell. Three, count 'em three, sets of spark plugs. All are looking black and sooty to the same degree but nothing worse than I have seen before. Slipped plug wire boots up to make sure that all wires were making good contact with plugs. Almost new rotor, cap and points...that had been working great before.

The only thing that is different that I am aware of is a newly recored radiator. Had a TR250 fan on there but went back to the original when I saw the temperature was so much lower. I am actually thinking of completely removing the fan to see if I can get the temperature up. I am going to check the points gap next but I am grasping at straws with that because they have not been in there very long at all. Also, if the timing was off wouldn't my changing it so drastically from 3 to 20+ degrees affect the backfiring? It is exactly the same at each end of that crazy spectrum and in between. It idles great at 800.

Here I stand. I cannot do otherwise.


Don Elliott
11-14-2006, 09:39 PM
You don't need to remove the fan to get the rad hotter. Just block off part of the ngrille with a piece of cardboard. Watch the temp. gauge and make the opening bigger or reduce it by shifting the cardboard till you get the temp you want. It'll work for the test till you get all the answers.

11-14-2006, 09:45 PM
Can you get rid of the backfiring by giving it a little choke? if so, adjust the mixture
if not
that is classic "bad condenser" symptoms.. Even if it's a relativly new one. Maybe check the points gap, and swap out the condenser. Also check the wires in the distributor and the mechanical advance (should be able to move the rotor a few degrees by hand) and make sure that the vacuume advance line is attached as it runs around the front of the motor, and may have been disturbed during the rad service

11-14-2006, 10:15 PM

As far as I can figure you must have a bad or very low temperature opening thermostat. What temp thermostat you put in and what temp is it opening at? Must be a 150. Try a higher temp opening thermostat. You also need to put the advance back to 4 degrees and lean out both carbs. Turn in (screw up toward carb body) your mixture adjusting nuts one turn of a flat side of the nut at a time to allow your jet assemblys to travel up further toward the carb body to lean out the carbs. You may have to remove the linkage and then re-adjust the linkage to allow this to happen. If you have a Bentley manual or a carb tune manual you probably should start from the beginning with the carb adjustment to get it right. It's amazing you get it to run and stay that cold when I have to run an extra fan in the summer. Anyway thats what I thinks.

11-14-2006, 10:23 PM
What color are the plugs? Personally, I would take the carbs back to where they were originally, if possible. The car ran well from there. I would find the cause of the change rather than adjust to the change.
What type of thermostat was in prior to your replacing it?

Jim Lee
11-14-2006, 10:36 PM
The plugs are covered in sooty black. Definitely rich but I have seen plugs as sooty that ran fine. I have not adjusted the carbs at all since it ran fine. I have cleaned it up as much as possible without removing them and checked the floats and the passage from the float bowl to the actual carb. I am not sure what temperature the previous thermo was but I tested it along with the new one before I replaced with the new one which is 190 degrees and they appeared to open correctly at about the same temperature. I am holding off on adjusting the carb mixture until I can check the points gap and condition though they are relatively new. Also will see if I can pick up a new condenser. Is that something I could find at a local auto store or will I have to mail order to TRF or Moss?

The only obvious change that I know of is the recored radiator and the temperature that is probably 30 degrees cooler (about 155) than it was before.

Jim Lee

11-14-2006, 10:57 PM
So your thermostat isn't even opening if it's a 190 and your only doing 150 on the gauge? Wow - thats strange! If your plugs are sooty black and they are fouling that fast it will definitely cause a loss of power and backfiring. but why they went rich if you didn't fool with it I'm not sure. It sounds like they need to be leaned out to me. Try Don's suggestion and see if the temp go's up. I think you will need to order the condensor from one of the two you mentioned unless you have a good part number then maybe NAPA. TR3 usually won't show up on their computer but the oil filter, spark plug, etc. will if you have a good part number.

11-15-2006, 08:18 AM
Did your car have the original style collared thermostat?

Simon TR4a
11-15-2006, 10:02 AM
Put the old radiator back in! (Sorry, I couldn't resist.)

Seriously, though, if the temp is that low it will affect mixture and timing, and you may want to check the thermostat is opening at the temp its supposed to.
Put it in a pot of water and heat on the stove. Using a thermometer check the temp when it opens.

11-15-2006, 10:38 AM
I can't imagine that a recored radiator will affect the temp that much. My 3A has a recored radiator, electric and manual fans and never goes below 185 after 5 minutes of running. Something else is wrong, these cars just don't run cold ever.

My plugs are sooty and black too but car runs fine; if I lean it out one more flat, it sputters on acceleration. Timing is static.

Check/reset your points and make sure the lead in the distributor is not shorting to ground. Also check coil with a new or borrowed one.

And check to see that the vacuum advance is not full of gas (mine was).

Jim Lee
11-15-2006, 11:19 AM
"Put the old radiator back in! (Sorry, I couldn't resist.)"

I wish I could unring that bell but that old core is probably melted down and in a Caterpillar tractor by now.
I did test the previous thermo and the new 190 degree one that I put in there after noticing how cold it was running and did the kitchen pot test and they both tested perfectly.
Adrio who has experienced a similiar problem with a very low temperature on his tr4 had a crescent shaped gap in his thermostat which after correcting got it back up to temperature. I was crestfallen when I removed the original (though relatively new) thermostat to find that it was intact and in place. Unless replacing the condenser or I find something wrong with the point gap or the wire going from the coil to the distributor I am going to check the new thermostat again to make sure it is seated correctly. It is still hard for me to believe though that a droopy thermostat would lower my temperature by about 35 degrees so I do not have any high hopes for that.
I suppose the silver lining here is that I am getting much more familiar with my TR. Though I have heard that familiarity can breed contempt.

Thanks to all for the cards and letters. Keep them coming.

Jim Lee

11-15-2006, 12:32 PM
I would agree with Peter that keeping a tr3 running cool actually requires extra effort and having them idle nice requires a well turned engine. I guess I can not figure out how the spark plugs are extra sooty and the engine idles nice. Anyways if I had the problem I would: Check the fuel pressure, Try a different coil, If that did not work, I would try a completely different distributor and wires. I do not feel that the problem is engine temp. Perhaps, if you had an oil cooler, custom radiator, custom fan, no thermostat, and lived in Alaska, then maybe.

11-15-2006, 01:30 PM
Though I have heard that familiarity can breed contempt.

Jim Lee

[/ QUOTE ]


Or it could make you more of a TR addict especially after it's sorted out.

I agree and believe you have two seperate issues going on here. Even if the engine temp is 155 the plugs should not be turning sooty black. I would go with the suggestions you have so far and eliminate one by one. Always start with the easy. I still can't get over the 190 thermostat and the car still running that cold. It's an engine temp issue and not too much to do with radiator if the thermostat isn't hot enough to open and allow the pump to circulate water from the radiator. Had to ask, is the temp gauge reading right? I would be cleaning coolant off the floor with-in the first ten minutes with a 190.

Jim Lee
11-16-2006, 10:55 AM
Checked the point gap. A little bit of a drag at .016" so I
made that a little wider. Replaced condenser. Checked all wires to and fro the distributor. Same deal. I don't even think it is varying when I advance or retard the timing.
Will try another coil I have hanging around and one more set of 4 new plugs.

In the possible realm of grasping for straws I did notice that my battery is weak. Measures just under 12 volts at rest and starting the car barely gets it above 12 whereas I would think it should be charging (on revving) up to about 14 volts. Also, all the test driving that I have been doing has been at night. Thus the lights are on. Ammeter is showing the battery as discharging. The only time it shows as charging is when all the lights are off and it is above idle. I am thinking either my regulator/control box is not doing its thing. Which is discouraging because I have had that generator rebuilt twice and am on my third regulator.

One thing that I know is not working is the vacuum advance. Everything I have read though is that the lack of a vacuum advance would not product these symptoms. I am beginning to wonder about that but can only wonder until I get either a new distributor or find one with a good vacuum advance mechanism to cannibalize.

So my main question now, before I go about replacing all the secondary ignition parts (new condenser and rotor today and I will be switching out the coil with a known good coil, is anyone running a TR3 or TR4 without the vacuum advance working. If so are you getting a serious bog and backfiring under load?

Thanks very much,
Jim Lee

11-16-2006, 11:35 AM
I had similar backfiring when my vacuum advace was full of gas. But I swapped out the distributor and that took care of it so hard to tell if will work for you.

11-16-2006, 12:05 PM
Battery at rest should be 13.5 to 14 volts.

With the car not running - Unlatch the wire holding the control box cover on and take the cover off the control box. You will see two seperate contact type points with-in. Take a very thin strip of cardboard and insert between the two contacts and rub back and forth to clean off any junk between them. Be careful not to bend anything or change the gap. It's very similar to cleaning the points in the distributor. Then start the car and observre the contacts to see if they are closing and opening at all up to 1500 rpms, if neither is opening or closing you will need to adjust the control box settings. If it needs adjustment I would have to refer to the manual. If cleaning the contacts helped and they are opening and closing with increasing and decreasing the rpms the voltmeter attached to the battery should show a fluctuation of current being sent to the battery high as 15.5 to 16 volts at 1500 rpms. If current is traveling to the battery but the battery is not holding the charge the battery is cooked. You should check each cell with a hydrometer or test with a battery load tester to confirm the condition of battery. Also Confirm the choke isn't sticking on and the jet assemby linkage attachment point is bottoming up against the mixture adjusting nut at the base of the carb when the choke is off.