• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

TR2/3/3A Rough running / a lot of carbon on the plugs

GTP1960

Jedi Knight
Offline
I recently swapped out my mechanical fuel pump for a facet electric.
But I haven't adjusted the carbs. & I am starting to think that might be my problem.

previously she was running great, until I decided to "upgrade" several disciplines. (Note to self: don't make multiple changes, with out a test after each one)

So my question is : how do I lean out these. SU hs6 carbs? I think I might have more fuel flowing when I accelerate, than the current carb setting likes.

at idle she hums along fine, and I don't think I have a vac. Leak, as I tested with starter fluid & had no rpm effect.

also I disassembled & cleaned the carbs & refilled the dash pots, and switched back to champion y87
(I think) plugs


i will say the Macy's worm & peg steering rebuild & my rear suspension rebuild made a world of difference in handling and feel.

thanks for reading.
 

TR3driver

Great Pumpkin - R.I.P
Offline
To let the mixture go leaner when you first open the throttle, use lighter oil in the dashpots. Also make sure they aren't overfilled, they aren't supposed to be "full".

But changing the fuel pump should have no effect at all on mixture, unless the pump is overwhelming the float valves. In that case, you would have to fix the problem, rather than trying to adjust the mixture.
 
OP
GTP1960

GTP1960

Jedi Knight
Offline
Thanks Randall.

Must be something else then, I don't think the float valves are overwhelmed as no fuel is leaking out or pooling in the carbs. I used 5/30 in dash pots right after I cleaned up the carbs.
Could fuel starvation cause a rough run on acceleration?
( what would you make of the carbon deposit on the plugs? )

thx again
 

TomMull

Darth Vader
Silver
Country flag
Offline

sp53

Yoda
Country flag
Offline
The fuel pressure for a stock tr3 is like 2 to4 psi. I do not like the newer electric fuel pumps because they are set higher than that and often require a fuel pump regulator to reduce the pressure. Moss sells and old type fuel pump that runs low, so if you have that the carbon might be coming from somewhere else. If the distributor does not return after advancement or just lets the timing float around, that can cause carbon deposits also. The old saying “ what is wrong will your SU carbs is your Lucas ignition” is often true, but it sounds like you have done modifications, so I would not know. Sometimes what looks like carbon is actually oil deposits and some carbon mixed in. If that is the case, your oil rings are bad and you will get a lot of dieseling from the oil glowing red and running the engine with the key off.

I do not know much about the H6S so I am not sure how to lean them down, but from what you have said my guess would be high fuel pressure push fuel into the carbs and running way to rich
 

TomMull

Darth Vader
Silver
Country flag
Offline
The fuel pressure for a stock tr3 is like 2 to4 psi. I do not like the newer electric fuel pumps because they are set higher than that and often require a fuel pump regulator to reduce the pressure.

The Facet pump for the TR3 application shows 1.5 to 3 psi. I assume that's what Guy used. It should be fine but it would be good to put a gauge on it because a higher pressure would certainly cause the symptoms.

Tom
 
OP
GTP1960

GTP1960

Jedi Knight
Offline
Disassembled and cleaned carbs? Is enriching cable returning completely? Use the shop manual or internet resource (e.g. https://britishclassicmotors.com/3301.html ) to tune and set them up.
Tom

Tom, thanks for forwarding that link.
i have disassembled & cleaned the carbs.( but not the float bowels) They had a lot of carbon build up, but the jet needles looked fine.
though I can't claim success, with a smooth running 3A, I have learned a lot about the SU tuning process.

i did notice that the piston in the forward carb. had more resistance than the piston in the rear carb. ( when raising with your finger to check movement.). The rear piston slides up with no resistance, the first 1/2" or so. Not so with the forward piston, that has steady resistance from almost the start of its track.

You are correct, the facet fuel pump is suppose to be low output. I have it mounted parallel to the frame( because I mounted it inside the frame "I" beam, under the driver side rear shock housing for more protection) however facet recommends mounting it in a upward tilt angle. So I do need to ck my fuel line pressure, for that reason, also.

i'm going to take a step back and follow the "DIY engine check up" list you sent me.


thanks again
 
OP
GTP1960

GTP1960

Jedi Knight
Offline
Thx SP53,
If the distributor does not return after advancement or just lets the timing float around, that can cause carbon deposits also. The old saying “ what is wrong will your SU carbs is your Lucas ignition” is often true, but it sounds like you have done modifications, so I would not know. Sometimes what looks like carbon is actually oil deposits and some carbon mixed in. If that is the case, your oil rings are bad and you will get a lot of dieseling from the oil glowing red and running the engine with the key off.

my issues may very well be ignition timing (new flamethrower distributor & coil), But on the good side, I have no dieseling problems & she starts better than ever , hums along at idle with hardly a hiccup. ( though she's always had a bit of a throaty galloping idle @ 900rpm, I assume, is common for these TR3 engines.)

my next step is to start over & go by the #'s:
a compression test.
valve clearance check
fuel pressure & flow ck.
ignition timing
vac leaks
then back to the carbs.


Thx again.
 

TR3driver

Great Pumpkin - R.I.P
Offline
i did notice that the piston in the forward carb. had more resistance than the piston in the rear carb. ( when raising with your finger to check movement.). The rear piston slides up with no resistance, the first 1/2" or so.
Usually, that would indicate not enough oil in the damper. But it's also worth checking the plunger for obvious damage, misassembly, etc. Although the pistons are matched to the domes, the plungers are not matched, so it's OK to swap plungers (to see if the problem follows it).

If memory serves, some of the original HS6 floats were not ethanol-resistant and would sometimes sink when used with E10.
https://sucarb.co.uk/hs-stayup-float-kit-hs6-hs8-large-bore-needle-valve.html

Just as a side note, the little rectangular Facet pumps come in a wide range of pressure ratings; but look identical. You pretty much have to either check the stamped part number (and assume Facet didn't make a mistake), or check the pressure yourself.

With a stock cam, it should idle evenly (not necessarily smoothly but without the rpm varying) all the way down to 500 rpm or so. A "gallop" says to me that something is wrong. Of course, I've usually had something wrong, so my idle is currently set to about 800 rpm indicated. (Another common problem is that the old mechanical tachs read high at the bottom end.)
 

DougME

Senior Member
Country flag
Offline
(Quote) "Sometimes what looks like carbon is actually oil deposits and some carbon mixed in. If that is the case, your oil rings are bad and you will get a lot of dieseling from the oil glowing red and running the engine with the key off."


Until the underlying cause is found I have used this trick successfully. As you're turning off the key, give the throttle a quick burst and hold the pedal down until the engine stops turning, this will draw in large amounts of cool air, preventing the run on. Hope this helps.
 

TR3driver

Great Pumpkin - R.I.P
Offline

Until the underlying cause is found I have used this trick successfully. As you're turning off the key, give the throttle a quick burst and hold the pedal down until the engine stops turning, this will draw in large amounts of cool air, preventing the run on.
Oddly enough, I used to do just that on an old tractor, because of the impressive backfire that would usually follow. Holding the throttle open with no ignition and the engine spinning ensures that the exhaust manifold gets filled with combustible fuel/air mixture. If the engine was good and hot, sometimes it would light off after a few seconds. (Obviously not my tractor :smile: ) Better yet was the rare occasion when a cylinder would fire before TDC and start it spinning backwards. Then it would suck in the fuel/air from the exhaust and actually run backwards for a second or two, blowing big clouds of blue exhaust out the intake.

Easier and more certain IMO to leave it in gear and let the clutch out, with your foot firmly on the brake, just after turning off the key.

Having the idle set too high seems to increase the tendency to run-on, and I used to run a "3/4 race" cam in a TR3A that didn't like to idle below about 1500 rpm, so I just got in the habit of killing it with the clutch every time.
 
OP
GTP1960

GTP1960

Jedi Knight
Offline
Follow up:
Just as a side note, the little rectangular Facet pumps come in a wide range of pressure ratings; but look identical. You pretty much have to either check the stamped part number (and assume Facet didn't make a mistake), or check the pressure yourself.

the facet fuel pump failed after only a couple months. Just stopped working, no obvious reason why.(could be because I had it mounted parallel rather than angled up).
i replaced it with an airtex low output (2.5-4psi) that actually fits the same location, works well & is quieter.

I did a compression test and found all cylinders held 160-165psi, dry.
wet they ran 175-180psi.
however I must have used to much oil, & have fouled my plugs.
i sprayed sea foam in the plug holes to breakdown the oil, cleaned & left the plugs out for a couple days. And will try to restart it tomorrow.

took the engine down opportunity to reset the valves to .010 ( For me, that dance took a little practice).

Randall, also thanks for pointing out about the mech. Tach not running true.
i found a inexpensive digital tester on Amazon.

Best regards

guy
 
Similar threads
Thread starter Title Forum Replies Date
C Rough-Running 3000 Austin Healey 29
tr6web TR6 TR6 rough running - what can it be? Triumph 17
BierRunner TR6 TR6 Running Rough Triumph 5
T TR2/3/3A rough running after 20 min shutdown Triumph 9
J Spitfire 1979 Spitfire Running rough [sputtering, exhaust poping] at start up Triumph 2
N Stuck Needle Valve - Rough Running Austin Healey 15
glemon TR5/TR250 Stumped TR250 Running Rough--Follow Up Triumph 3
glemon TR5/TR250 Stumped TR250 Running Rough Triumph 8
D Rough running BT7 3 carb HELP Austin Healey 13
B Thoughts...rough running at cruise. Austin Healey 3
K TR2/3/3A Dead Petronix and rough running..... Triumph 10
I BJ8 is running a bit rough. . . Austin Healey 7
B Pics of my ’63 BJ7 and Questions on Hard Starting and Rough Running Austin Healey 11
bigbadbluetr6 TR6 TR6 carb question and running rough Triumph 13
M Rough Running 99 XJ8 after Overheating Jaguar 42
T TR2/3/3A TR3 Running Rough - Cause[s]? Triumph 8
K TR2/3/3A TR3 Running Rough Again? Triumph 7
bighealeysource BN6 runs rough on restart after running great Austin Healey 7
M 87 Series III XJ6 Rough Running Jaguar 16
G Rough running and backfiring MG 30
M TR2/3/3A Another rough running TR3 Triumph 1
T TR2/3/3A TR3 running rough Triumph 6
vping Running rough MG 9
bighealeysource Up-date on engine running rough on my BN6 Austin Healey 1
A rough running after long idle or long low rpm driv Triumph 1
R TR2/3/3A TR3 Missing [running rough not stolen!] Triumph 4
tahoe healey surging and rough running Austin Healey 20
K TR2/3/3A TR3 Running rough..Cam or Carbs?How to diagnose? Triumph 10
H MGB-GT Help with my 1967 MGB GT running very rough MG 5
R TR6 Rough running TR6 = Pertronix? Triumph 27
Woodie rough running Spridgets 7
S TR2/3/3A Rough Running TR3A - help with diagnosis Triumph 11
A TR4/4A TR4A running rough question[s] Triumph 11
Woodie missing, running rough etc etc Spridgets 25
J running rough / missing Spridgets 7
77MidgetMkIV Rough running at weird intervals-any thoughts? Spridgets 22
77MidgetMkIV Now running really rough-help?!?! Spridgets 15
beebopbogo Engine running really rough - 2 cyls? MG 8
D TR6 Gp 2 cam, head shaved ,shorter pushrods, with a rough idle Triumph 10
P Spitfire 1979 Triumph Spitfire starts then runs rough Triumph 2
K TR2/3/3A Mystery clunking and banging from rear of car when driving over rough road or bumps? Triumph 14
H TR4/4A 67 tr4a runs rough and losses power when hot but not over normal temp Triumph 14
skystryd remind me it's fun. good idle. rough when accelerating Spridgets 6
RAC68 Loose Metal Knocking/Banging Sound during Rough Idle Austin Healey 32
C Rough Idle - What to check? Austin Healey 12
55modified Wanted Wanted rough BN1/2 hood for cutting up Austin Healey Classifieds 0
M TR2/3/3A Engine rough on acceleration Triumph 19
N Runs Rough Under Load Spridgets 15
Gliderman8 General TR Rough looking '67 Vitesse Triumph 7
JPSmit Rough Bugeye hood Spridgets 0

Similar threads

Top