• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)
Tips
Tips

Runs Rough Under Load

N233TX

Freshman Member
Offline
Midget 1500/Weber Carb Runs great at all RPM in shop. Intermittent rough running under load, especially uphill. Stumbles big-time under quick acceleration. Timing, points, rotor, valves, plugs, FP A-OK. Electric choke carb adjusted per manual including accelerator pump. This engine will sometimes completely fail to start when it gets hot enough. The coil has less than 500 miles and ten years on it. No vacuum leaks apparent.

Most of this seems like a fuel/carb issue of some kind but it has been suggested that bad plug wires and other ancillary parts could be the culprit.

Since this is a problem under load, what does this suggest? I know aircraft plugs can misfire under high pressures but can voltage be momentarily lost elsewhere in the ignition circuit when you punch it going up a hill?

I have absolutely no problem getting new wires and maybe an electronic distributor but before I start throwing parts at this, can somebody tell me if there is further carb trouble-shooting to be done.

This problem has gotten progressively worse since carb installation a few years ago. Tailpipe looks rich but plugs are perfect.

TIA, Jim
 
G

Guest

Guest
Guest
Offline
make sure the intake is tight, the bottom rear (the one that's hard to get to) sometimes comes loose.

Yes, bad plug wires can/will do that. Could be fuel delivery/vapor lock too (hot start). Make sure your tank is being vented properly as well. No, leaving the return line open you are no longer using with the Weber isn't good enough. Make sure you have the right gas cap and it's working properly. You already have an electronic distributor if it still has the stock one (albeit not the best one). It wouldn't make sense to buy a new distributor and still use old unknown condition wires.

If it were me, I'd put new wires (Accel V8 solid core universal kit, you can make two sets and they should be around $20) and an electric fuel pump. You may be having some vapor lock issues. When I had the DGV on mine I had trouble after letting it sit after running. It would crank and run but kill a short time later. I was able to "cure" the problem by just letting the fuel pump run and push the vapor out. Put the pump in the back by the tank.

What is your timing set at?
 
OP
N

N233TX

Freshman Member
Offline
Thanks for suggestions. Will try all...one at a time. Starting with the coil. Will post solution when and if one is determined. Timing set to US spec.

I have heard a different jet in the Weber cures similar symptoms. Any specificity on this? Elevation hereabouts is around 1,000' MSL.

Jim
 

nomad

Yoda
Offline
Never heard of anyone having good luck with the Weber downdraft on a 1275. Probably the same on a 1500. As mentioned you may need to change some things on your carb. I had one on a 1275 engine in a car I acquired that the PO had been modifying. Car ran great but barely beat 20MPG.

Kurt
 
OP
N

N233TX

Freshman Member
Offline
It was the coil. Popped on a spare (removed from car in last century) and the problem went away. Astounding. My only experiences with coil failure were normal ops followed by completely nothing when hot, then miraculous regeneration after cooling off. Never experienced loss of spark under acceleration/load. It just seemed so fuel-related!

Hope the Weber lasts longer than that 1,000 mile coil...

Again, thanks to all who responded. Jim
 

drooartz

Moderator
Staff member
Gold
Country flag
Offline
:banana: Woohoo!

These cars present many ways to learn new things. Some good, some frustrating.
 
G

Guest

Guest
Guest
Offline
It was the coil. Popped on a spare (removed from car in last century) and the problem went away. Astounding. My only experiences with coil failure were normal ops followed by completely nothing when hot, then miraculous regeneration after cooling off. Never experienced loss of spark under acceleration/load. It just seemed so fuel-related!

Hope the Weber lasts longer than that 1,000 mile coil...

Again, thanks to all who responded. Jim


What you are describing is the symptom of another problem, not the coil itself. Excessive resistance (i.e bad wire) will cause a coil to find another path to ground. Once it does, it will usually take that path even after the initial problem is fixed. There is no doubt your old one was bad, but it just didn't go bad overnight. You have a problem somewhere else that caused it to go bad. (defective crap being sold as new parts not withstanding). There is a chance this will happen again. Seeing you say everything else is good (I'm assuming new) but the wires, you owe it to the car to change them. Piece mealing ignition, electrica, brake or fuel systems on a 30+ year old car is asking for headaches. Do it all at the same time and you're done with it for several years. Screwing around with it here and there only assures you will be doing so again in the future and a lot more than you'd like to.
 
Offline
Watch the wires while the car is idling outside in a dark location. You will probably note some arcing.
 
OP
N

N233TX

Freshman Member
Offline
New wires on the way. Appreciate the explanation. Will temporarily install bad coil after wire installation to see if this was, indeed, the cause.

Still learning about this car after 32 years ownership... Jim
 

Pythias

Jedi Knight
Country flag
Offline
Never heard of anyone having good luck with the Weber downdraft on a 1275. Probably the same on a 1500. As mentioned you may need to change some things on your carb. I had one on a 1275 engine in a car I acquired that the PO had been modifying. Car ran great but barely beat 20MPG.

Kurt

I am having fantastic "luck" with a downdraft Weber on my 1275. The thing is, it's not LUCK. the biggest difference i think is that I took mine to a dyno shop where they know their business. They had all the knowledge and the jets to get it right. I have no off idle stumble, the idle is perfect after the car warms up and unlike SUs is the same no matter the ambient or running temperature its the same. I'm getting a touch over 30 mpg. While this is not as high as SUs, it's still perfectly acceptable (to me) especially since I don't have to fiddle the carbs anymore.
 

nomad

Yoda
Offline
Well, yes, Bill but that is probably what is needed to make the Weber downdraft run right on a spridget. I have one on a Datsun pickup that runs far better than the original carb and gets better gas mileage. Carb was right out of the box. Some guys with MGB's seem to get by OK but for Spridgets I would think they need a little massage. Nothing wrong with the Weber just the tune.

Kurt.
 
G

Guest

Guest
Guest
Offline
Never heard of anyone having good luck with the Weber downdraft on a 1275. Probably the same on a 1500. As mentioned you may need to change some things on your carb. I had one on a 1275 engine in a car I acquired that the PO had been modifying. Car ran great but barely beat 20MPG.

Kurt


I've had almost every induction setup for the 1500 known to man and I couldn't get higher than 25 mpg if I pushed it off a cliff with the ignition off.
 

JPSmit

Moderator
Staff member
Silver
Country flag
Offline
I've had almost every induction setup for the 1500 known to man and I couldn't get higher than 25 mpg if I pushed it off a cliff with the ignition off.

Yeah, but that's not the carb, it's your right foot. :smile:
 
Similar threads
Thread starter Title Forum Replies Date
H TR4/4A 67 tr4a runs rough and losses power when hot but not over normal temp Triumph 14
bighealeysource BN6 runs rough on restart after running great Austin Healey 7
RickB MGB 70 MGB runs rough - sputters & backfires esp. cold MG 44
EastBoundJoe Engine runs rough then die's while at stop sign Spridgets 7
M Midget runs inconsistently Spridgets 7
S TR2/3/3A TR3 has me stumped, it runs then dies over and over and the exhaust system was pulled Triumph 9
F TR6 1975 TR6 runs lean Triumph 11
FlyingCat Spitfire Runs, but not well Triumph 26
B Fuel pipe runs BJ8 Austin Healey 2
D TR2/3/3A Alternator dial runs high Triumph 5
D Its Runs! Spridgets 6
Drone Dog Lilly test runs Austin Healey 4
2billydavies TR2/3/3A runs excellent but starts hard after use Triumph 8
C runs better without air cleaners?? Austin Healey 19
KVH General Tech TR4A Runs Terrific Triumph 2
Tinkerman TR2/3/3A It runs! Triumph 8
B T-Series 51 td runs rich MG 17
Gundy Runs a bit...then quits Spridgets 18
HealeyRick Runs a Bit - Then Quits Spridgets 23
K Hard Start, runs poorly when cold Spridgets 10
gbtr6 TR6 Help! Starter runs with ignition in on position Triumph 18
drooartz MGB-GT It runs! MG 6
C Ship deliberately runs aground carrying Jaguars and Land Rovers, but why? Jaguar 0
M TR6 TR-250 CC engine runs great, then nada, wait > 2 days, then runs great again, repeat Triumph 7
B Everything runs better with this mod - all models!!! Spridgets 7
DanLewis Runs on 3 cylinders at idle, but all 4 at higher rpms??? Spridgets 25
D TR6 Blower runs off and on Triumph 4
Sarastro T-Series It runs! MG 8
R engine runs cool Austin Healey 16
B MGB 1972 MGB, Head Gasket replaced...runs very poorly. MG 30
martin_burtt TR6 TR6 - runs but no power under load? Triumph 11
af3683 TR2/3/3A Set Static Timing on TR3B - Car Runs Poorly Triumph 27
T She runs! She won't stop running! Triumph 2
C '72 Midget Runs On 2 Cylinders at Highway Speeds Spridgets 73
N After 30 years, it runs! Austin Healey 7
S TR2/3/3A TR-3 hard to start, but runs well once started Triumph 5
G Well, it runs and drives Triumph 5
V Fuel pump runs continuously! Spridgets 18
livinginthepast After a long winter's nap - BE runs around town... Spridgets 7
Wizardd MGB '77 MGB runs for a bit, then shuts down MG 28
C My car runs unevenly...... Triumph 4
DART IT RUNS!!!!!!!! Other British Cars 3
jlaird New. She runs but. Spridgets 7
Westfield_XI MegaJolted 1380 starts and runs Spridgets 6
livinginthepast Runs good...starts missing...and then.. Spridgets 10
mikecyc72usa Finally, it runs! Triumph 8
S Jag barely runs in cold weather Jaguar 7
Cottontop ALERT ! Healeys Return to Bonneville Speed Runs Austin Healey 23
abarth69 My Sprite Runs Spridgets 5
Stick Car runs better with vacuum leak? Spridgets 4

Similar threads

Top