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TR2/3/3A help needed! fuel problem

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Triguarin

Freshman Member
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Hello everyone,

I have rebuilt my TR3a engine and I haven't managed to get very far with tuning it. The engine uses 5 litres of fuel in around 10 minutes. I know this sounds impossible but its happened each time between 5 - 10 runs in the garage just trying to get everything warmed up and good to go so I can begin tuning. The engine is timed statically and the carbs jet screws turned down a few flats as per the book initially but its possible I have abandoned that and adjusted them up as much as possible to try and shut the fuel off. I have made a 5 minute film on youtube where you can listen and view the engine. Maybe you can spot something. I'm just about out of every single idea. You'll hear that it sounds like its missing and just running on two cylinders. I've done the whole pulling off leads from plugs thing to no positive result. The oil level is normal ( not increasing with petrol in the sump). The garage stinks like **** after the fuel runs out even with the doors wide open. It is as though the unburnt fuel is being pushed right out the exhaust. The carbs are as good as new. I had Burlen fuel refurb the throttle bodies and ream for new throttles. All stops and wear parts replaced. No air or fuel leaks. Compression check is constant on all cylinders. Float assemblies doing their job. No fuel escaping down the overflow pipes. Block has new pistons, rings, crank and bearings. Head gasket new. Tappet clearances all ok. Valves respond well with a light hammer tap and spring as they should. All new ignition parts.....

here is the link to youtube: https://youtu.be/EHQ-MRKqM9g

Would really welcome feedback! Don't worry about hurting my feelings. If I've done something stupid and screamingly obvious I'll be the first to laugh ( well after you've pointed it out, which makes me second..;)).

Many thanks.
 
Excellent video documentation and yes, something's not right.

Triguarin said:
...I've done the whole pulling off leads from plugs thing to no positive result...
Click to expand...

So when you pulled the plug wires one at a time the resulting change was consistent across all 4?

Triguarin said:
...The carbs are as good as new. I had Burlen fuel refurb the throttle bodies and ream for new throttles. All stops and wear parts replaced...
Click to expand...

Did this include jets and needles? Hard to tell with video sound but that is quite a loud sucking from the carbs. I would be tempted to verify that the needles and jets are correct.

I see some unusual things (distributor cap direction, fuel line routing, long overflow tubes, hole in forward carb piston) but nothing that accounts for the problem. This one is a puzzlement.
 
If the excess fuel is not on your garage floor, it is quite possibly in the oil pan. Stop running the engine until you get clear that this is not happening. Much gas in the oil is a cause of rapid engine failure. Drain the oil and check this issue. Cause of fuel overflow into the sump could be inlet needles failing to close due to mechanical obstruction or maladjustment of the floats. It could also be leakage from fuel pump into the sump from a bad diaphragm.
Bob
PS. I see you think no gas is going into the sump. Check this point anyway in that a mistake is expensive. Having seen and heard the video, the exhaust is not showing rich mixture but plugs 2 thru 4 look to be. 3 affected plugs is just weird. Have all the plugs been in the same holes throughout or was 2 maybe in hole 3 or 4 for a while? When you are sure you are not gassing the sump, check to see that the points open fully on all 4 lobes of the dist shaft. Try another dist cap. While it is running, pull one plug wire at a time to see which cylinders are not running. Then get back to the Forum.
Bob
 
Hi Triguarin, I think NutmegCT has the solution-- it looks to me as if the #2 and 3 plug leads are switched. The firing order is 1, 3, 4, 2 but is has been too long since I worked on a TR3 to know the rotation of the distributor etc.. Check which way the dist. turns and make sure you have firing order correct. I'd laugh but I did it on a friend's Volvo 245. Just be glad you aren't working on a V8, V10, V12 or V16 engine. LOL
As I'm a curious old man with no shame I want ask where you learned your English? It's perfect. In Swedish schools? Native English speaker living in Sweden (how's your Swedish coming along?)? Did you live in an English speaking country? JHB
 
I've had a chance to look (emphasis on LOOK) at some pictures in Piggott's book and it LOOKS like the distributor cap is 90 degrees out-of-whack. The book pictures show the wires coming out of the cap towards the inner fender well. In the video the wires are exiting towards the radiator. The dist. body in the video seems to be correct position but the cap...OY! Could it be the wrong cap? Are there notches in the cap to orientate the cap correctly? But then the retaining clips would be the wrong position! My vote: Wrong cap. JHB
 
Well, first you've got the wrong distributor cap. That's for an MG (B I think), not TR3. But best I can tell, the plug wires are right and the cap should work OK (but you'll get lots of comments about it being "wrong").

I would start with figuring out why the carb pistons do not move in unison when you open the throttle. Possibilities include the rear throttle plate is not moving as it should (eg slipping linkage), or something is blocking the motion of the rear piston (like maybe damage or dirt in the dome, wrong springs, wrong oil, jet not centered, bent needle, bent damper, etc). A valve problem or bad cylinder could do it too, but you seem to have eliminated those possibilities. Note that piston movement should depend only on the air moving through the engine, not mixture or timing. "Normally", they move exactly in unison. But the motion has to be absolutely free (except for the action of the damper). One good test is to raise the piston to the top with your finger, then drop it and listen for the click.

That screw being visible in the front carb worries me as well; the pistons have a definite front and back (the bottom is not symmetrical) and there is supposed to be a key that keeps them from turning. It would appear that you either have the wrong parts, or the key is damaged/missing.

Once all that is right, I would either clean the plugs or (better yet) replace them. Plugs that are badly fouled will often develop an invisible "glaze" that will cause them to keep misfiring even once the mixture is correct and the visible fouling burned off. In a pinch, one way to clean them is to soak the end with carb cleaner, then hold the plug with a pair of pliers and heat the end with a propane torch. Keep heating until there is no trace of yellow in the flame. (Then let cool before trying to reinstall them.)

As a last comment, don't assume the carbs were rebuilt correctly. I've seen a lot of mistakes made by people who should know better (like Burlen). Just for one example, jets are available in both .090" bore and .100" bore, along with needles to match. I've seen a professionally rebuilt carb where someone picked up the wrong needle (for a .090 jet), which of course resulted in extremely rich mixture.

I've also seen them come back with the pistons swapped between domes. The two components are matched and not necessarily interchangeable. Here's an old video, showing how to do a "drop test" to check for them being swapped
https://www.youtube.com/watch?v=IfU47Oqq9wA
 
It is obvious it is running on only the front cylinder. You get no black smoke because there is no heat in the back 3 cylinders and the fuel usage is high because you have the throttle up so far to get 1000rpm on just one lung. I see the following:

1) As Randall pointed out, the front carburetor slide is backwards. I didn't think it would install that way...so something is askew there. The vacuum ports to raise the slides are dependent on the slide being oriented correctly.

2) The fact there is no back firing at all with plenty of fuel going in indicates ignition to me. If you were dumping that much fuel into the back 3 cylinders AND getting good spark, then tailpipe backfires are inevitable. No backfire leads me to suspect no ignition. Perhaps flat lobes on the distributor cam? Cap not centered on the rotor? Plug wires not set fully or with broken wires?

3) To start a motor on one cylinder with no choke means the carbs are set WAY rich!! If the jet and needle are new and not worn out, and you are certain the choke has the jets fully up...then float level is all that is left to be off. Since the front cylinder is higher, most gas will run to the rear of the manifold...there is a good chance the rear plugs are fouled after the first pop, but the front is just barely able to keep the fire going.

4) I am not sure if you mentioned it in the video, but a compression check would be a good idea, just to make sure the valve train timing is correct. Once you are sure about the mechanical, you can limit it to spark or carbs. I would start with carbs, personally, to figure out the slide problem...then move to spark.

My first check for spark would be to remove each plug in turn, then hold it against the block with the wire attached. Crank the motor and look for a strong spark. I suspect no spark or weak spark on 2,3 and 4. That check takes the entire ignition system into account at one time.
 
Oh, forgot to mention : Check that the jet heads are firmly against the adjusting nuts. Sometimes they stick down, especially if the glands are new. IMO it's a good idea to polish the surface of the jets until they shine as well (to reduce friction both lowering and returning the choke).
 
Hi, yes new jets and needles, 0.90, I checked them with a drill bit to that measurement. I thought maybe 0.90 needle in a 0.100 jet, but all is ok. I called Burlen to check the parts order too and their records match. Hole in forward carb, yes well spotted going to look into that....
 
"It could also be leakage from fuel pump into the sump from a bad diaphragm."

I replaced the diaphram with an old stock new part. That is an interesting point and I will double check the condition and fit of that.
 
The distributor runs anti clockwise and I'm trusting my memory when I say that. Four pots suit me fine, defientely leave the V's to others!
I grew up in Liverpool! I have lived 10 years in London and 20 in Sweden. My Swedish children speak better English than I do, but thank you very much. 30 years ago I sounded like a Beatle but time and other geography takes its toll...
 
"I've had a chance to look (emphasis on LOOK) at some pictures in Piggott's book and it LOOKS like the distributor cap is 90 degrees out-of-whack."

Its a lucas cap. The moulding is different. Its the same as Austin and MG. They all fit, look different.
 
"Well, first you've got the wrong distributor cap. That's for an MG (B I think), not TR3. But best I can tell, the plug wires are right and the cap should work OK (but you'll get lots of comments about it being "wrong")."

Yes, its an MG one, but its wired correctly for the sequence.

These are new plugs but I'll get some new ones.

The dampers in the carbs click on the bridge, so nothing bent or sticking.




"That screw being visible in the front carb worries me as well; the pistons have a definite front and back (the bottom is not symmetrical) and there is supposed to be a key that keeps them from turning. It would appear that you either have the wrong parts, or the key is damaged/missing."

Thanks for spotting that, will investigate. Jets and needles all match.



 
"It is obvious it is running on only the front cylinder. You get no black smoke because there is no heat in the back 3 cylinders and the fuel usage is high because you have the throttle up so far to get 1000rpm on just one lung. "

I like this theory, this could be true...


I see the following:

"1) As Randall pointed out, the front carburetor slide is backwards. I didn't think it would install that way...so something is askew there. The vacuum ports to raise the slides are dependent on the slide being oriented correctly."

That is my first fix then.

"2) The fact there is no back firing at all with plenty of fuel going in indicates ignition to me. If you were dumping that much fuel into the back 3 cylinders AND getting good spark, then tailpipe backfires are inevitable. No backfire leads me to suspect no ignition. "

Right, I'm going to go with that.



Perhaps flat lobes on the distributor cam?

Distributor cam looked as good as new.
Cap not centered on the rotor?

Cap centred.

Plug wires not set fully or with broken wires?
Plug wires brand new. Good push on fit but I will look closer.

"3) To start a motor on one cylinder with no choke means the carbs are set WAY rich!!"

Couldn't agree more.

"If the jet and needle are new and not worn out, "

Brand new.


"and you are certain the choke has the jets fully up"

not possible to get them any higher...

then float level is all that is left to be off.

I have adjusted the stirrups in the float assemblies to the clearance in the book. But worth another look. Although I've checked them a few times already.

"Since the front cylinder is higher, most gas will run to the rear of the manifold...there is a good chance the rear plugs are fouled after the first pop, but the front is just barely able to keep the fire going."

Yes, not a lot of power if I actually engage the gears and reverse,

"4) I am not sure if you mentioned it in the video, but a compression check would be a good idea,"

Compression check all consistent.

"just to make sure the valve train timing is correct. Once you are sure about the mechanical, you can limit it to spark or carbs. I would start with carbs, personally, to figure out the slide problem...then move to spark."

"My first check for spark would be to remove each plug in turn, then hold it against the block with the wire attached. Crank the motor and look for a strong spark. I suspect no spark or weak spark on 2,3 and 4. That check takes the entire ignition system into account at one time."

I have a new coil and brand new loom. Could still be a week spark though.

Thanks so much for all of this. Its a solid line of enquiry and I have much to think about.
 
Triguarin said:
Hi, yes new jets and needles, 0.90, I checked them with a drill bit to that measurement. I thought maybe 0.90 needle in a 0.100 jet, but all is ok. I called Burlen to check the parts order too and their records match. Hole in forward carb, yes well spotted going to look into that....
Click to expand...

A TR3A should have jets that are .100 and needles that are .100. On the bottom of the jet it should be marked .100 .It sounds like there may be the possibility of getting needles with the same number, but the needle chart that I have does not show any SM (standard), RH ( rich) or SL ( weak) needles in the .900 series.
I run SM needles which is the standard. This lettering is found on the shaft of the needle that is inserted into the piston. So you have to remove the needle to be able to see the lettering.
Regarding what a company tells you TRUST BUT VERIFY!!!!!

It sure sounds like your problem is deeper than just the wrong jets and needles , but while you are looking this is easy to check.
 
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