• 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

MGB Running out of gas symptoms

Rut

Obi Wan
Silver
Country flag
Offline
Good morning all. I have a somewhat minor problem that I’ve been unable to solve on the MGB. When running along at 65+, in 4th or 4th OD for 10 minutes or so, the engine sounds like it’s being starved for fuel. It’s a performance build using a later block after I blew up my original 1970 engine...9.5:1, VP12 cam, Abarth exhaust system, big valves, etc. I’ve removed the vented gas cap, checked the fuel filters and verified that the fuel pump is working well. I have a new gas tank and rubber lines, but the original hard fuel lines. The carbs have been rebuilt and adjusted and it runs just a touch rich, but not bad and drivability is excellent. If I let off the gas for about 5-10 seconds it cures itself until I run another 10 minutes at speed. This has been going on for a couple of years, but hasn't bothered me enough to seek help...I thought I could figure it out. Now I need your expert trouble shooting to guide me!
Thanks, Rut
 

NutmegCT

Great Pumpkin
Offline
Just a thought, but you say the fuel pump is working well. Is it the right fuel pump (providing sufficient pressure) for the engine/carb setup you have?
Tom M.
 

Grantura_MKI

Luke Skywalker
Silver
Country flag
Offline
Had this symptom with a car years ago....turned out to be a small rub on the hard line. It wouldn’t leak petrol when stopped, so was a joy to find.
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
I’ll check both the hard line and fuel pump for leaks, pressure and flow. Iirc, the fuel pump is a generic 2-4# variety that replaced the pump that was on the car when I bought it. Thanks for the thoughts and it could be either one of those issues, but never any smell of gas.
Rut
 

Stewart

Darth Vader
Country flag
Offline
If you're still using the metal braided lines to the fuel pump inspect them for cracks and if they are hard. I kept loosing power randomly as they had cracked and would randomly suck air starving the engine of fuel. I cut the banjo fittings off and replaced the hoses with the gates barricade hose. Also it could be electrical. I had something similar in my gt and in the end it was a bit of corrosion at the big wire junction on the right side of the engine bay. Look for the white wires and give them a good cleaning.
 

DrEntropy

Great Pumpkin
Gold
Country flag
Offline
Insufficient volume from the pump? Pump gets too warm after running at higher speeds and starts to fail intermittently? Full tank vs. less than half full?

My WAG would be to replace the pump with a Jag/Rolls "double-side" S.U. Not cheap but correct pressure and good volume through the whole range. That pump supplies V-12 Jag (four Zed-S carbs) and V-8 Rolls (two HUGE SU's) engines. It would keep up with what you describe as the engine build.
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
Thanks again and once I get my back up and running I’ll check all this out. I’ve got a few other things I need to check out that I’ve neglected over the last year, so I’ll add these to the growing list.
Thanks, Rut
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
Update...new fuel pump, filter and she runs well, but symptoms persist if I run at a steady high speed. I can let off the gas and it will catch up and run fine. The engine runs just a touch cooler than normal on the gauge and nothing to indicate anything is amiss, but I now have a little run on when I turn it off...same gas as always, timing unchanged, plugs look good, etc. I’ve got a friends MGA taking up the MGBs space in the shop and I’ll dig into it some more once the A is gone. Just for grins I’ll post some spark plug pictures.
Rut
 

Attachments

  • B647E9AD-7130-4BDB-8641-F97E7514239D.jpg
    B647E9AD-7130-4BDB-8641-F97E7514239D.jpg
    77.1 KB · Views: 20

Mickey Richaud

Moderator
Staff member
Platinum
Country flag
Offline
Off-the-wall idea here: Gas cap? Try running without one and see what happens.
 

DrEntropy

Great Pumpkin
Gold
Country flag
Offline
Assuming good methodology (And I know ya Rut, so confident the plugs are in order!), odd the two middle ones appear to be running richer than the outer ones, and considering the firing order, could you be seeing a distributor/cap/rotor issue as a combination with coil/wiring contacts?

"If you've got carburettor problems, it's probably electrical!"

Just thinkin' out loud.
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
Dr,
They are in order and I thought the same thing. I had the distributor rebuilt by Advance and he set it up to match the engine mods and I’m using points. I’ve also removed the vented cap just in case, but the symptoms still exist...it’s a minor problem, but one that puzzles me. I’m going to install a dual AFR meter so I can get an idea of what’s happening and different loads and RPM...I’ve got one on the bugeyes 1275 and it really helps.
Thanks, Rut
 

PAUL161

Great Pumpkin
Silver
Country flag
Offline
Have you checked the hose from the tank to the pump for cracks or vacuum leaks? Had this same thing happen on our 72 and the flexible line from the tank to the pump had a crack in it and it was sucking a very small amount of air in. It ran fine until more demand was put on the pump and the carbs would slowly drop in fuel level, letting off the throttle the carbs would fill up with enough fuel to resume running. Just a suggestion. PJ
 

JPSmit

Moderator
Staff member
Silver
Country flag
Offline
Assuming good methodology (And I know ya Rut, so confident the plugs are in order!), odd the two middle ones appear to be running richer than the outer ones, and considering the firing order, could you be seeing a distributor/cap/rotor issue as a combination with coil/wiring contacts?

"If you've got carburettor problems, it's probably electrical!"

Just thinkin' out loud.

I had a similar issue with Ms Triss - turned out to be the coil. I replaced it with a proper Bosch coil and the difference is like night and day. There is much interweb conversation about what makes a proper Bosch coil

this is the one you want https://www.busdepot.com/catalogsearch/result/?q=blue+coil&dir=desc&order=default_sort_order

here is the article

https://www.ratwell.com/technical/BlueCoil.html

Jeff used to sell them but it seemed like he couldn't get stock
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
Have you checked the hose from the tank to the pump for cracks or vacuum leaks? Had this same thing happen on our 72 and the flexible line from the tank to the pump had a crack in it and it was sucking a very small amount of air in. It ran fine until more demand was put on the pump and the carbs would slowly drop in fuel level, letting off the throttle the carbs would fill up with enough fuel to resume running. Just a suggestion. PJ

Paul,
Original steel fuel lines, but all new rubber hoses, pump, gas tank, etc. I’ll go thru to entire fuel system to see if I missed anything and the clear fuel filter that’s never full always freaks me out...I may change to a different style.
Thanks, Rut
 
OP
Rut

Rut

Obi Wan
Silver
Country flag
Offline
I had a similar issue with Ms Triss - turned out to be the coil. I replaced it with a proper Bosch coil and the difference is like night and day. There is much interweb conversation about what makes a proper Bosch coil

this is the one you want https://www.busdepot.com/catalogsearch/result/?q=blue+coil&dir=desc&order=default_sort_order

here is the article

https://www.ratwell.com/technical/BlueCoil.html

Jeff used to sell them but it seemed like he couldn't get stock

JP,
It won’t hurt to check since I have a couple in the shop and it’s easy to swap.
Thanks, Rut
 

JPSmit

Moderator
Staff member
Silver
Country flag
Offline
Paul,
Original steel fuel lines, but all new rubber hoses, pump, gas tank, etc. I’ll go thru to entire fuel system to see if I missed anything and the clear fuel filter that’s never full always freaks me out...I may change to a different style.
Thanks, Rut

Fuel filter won't be full - at 2-4 pounds pressure it doesn't.
 

LarryK

Obi Wan
Gold
Country flag
Offline
Like JP I had an XJ6 that would cut out while driving to work. Pull over start and go to work. Same thing on the way home. Started watching exhaust and right before cut out, black smoke (rich?). Opened bonnet and coil extremely hot. Tightened electrical connections cured. Just a could be.
 

SpeedieJag

Freshman Member
Country flag
Offline
I had the same problem on my E-Type at higher rpms. It turned out the SU carbs were leaning out at higher rpms resulting in fuel starvation. The solution was to replace the carb fuel metering needles with a set that was richer at higher rpms. I went from the standard UM needles to UO needles which resulted in a 23% increase of richness at full rpm. Some use UB 11%, UI 16%, UE 23% (what I used) or UO 37%. All these needles have the same fuel mixture ratio at idle. I was told that today's gasoline is not as "powerful" and thus the carbs require more fuel at higher rpms. I am not sure which needles are standard in your carbs but a change to a more rich needle may solve your problem. It certainly solved my problem. Good luck, James.
 

DrEntropy

Great Pumpkin
Gold
Country flag
Offline
Any progress on this, Rut?
 
Similar threads
Thread starter Title Forum Replies Date
D Running out of gas Austin Healey 19
T Gas running from carburator tube?? MG 1
tr6web TR6 Quit running after a few minutes - need advice Triumph 4
B For Sale 57TR3 Small Mouth with OD Project. 12 yeqrs running. I'm not going to finish Triumph Classifieds 0
sparkydave Trouble running hot Spridgets 7
T TR2/3/3A rough running after 20 min shutdown Triumph 9
S TR2/3/3A Running rich SUs. Triumph 25
Y Wanted Looking for running 3.5L MK V engine Jaguar Classifieds 0
J Spitfire 1979 Spitfire Running rough [sputtering, exhaust poping] at start up Triumph 2
Gliderman8 Starter keeps running TVR 20
K TR2/3/3A Anyone running NGK spark plugs? Triumph 26
T TR2/3/3A Anyone running tubeless radials on TR3 steel radials? Triumph 2
N Running Cold Austin Healey 12
bugedd Car running poorly Spridgets 7
Bob_Spidell Running hot/Overheating Austin Healey 44
Martinld123 SU carbs lose fuel prime when not running Austin Healey 3
mailbox For Sale 76 TR 7 project car [non running] Triumph Classifieds 0
N Stuck Needle Valve - Rough Running Austin Healey 15
J For Sale 1976 Sptifire with 1.8L Miata engine/5-speed [running like a boss!] Triumph Classifieds 0
BN6 Breaking In Running In a newly built Healey Engine Austin Healey 15
R TR2/3/3A TR 3A running hot at high rpm Triumph 12
M Proper running temp for 1275 Spridgets 28
HighAltitudeTR3 TR2/3/3A Running a little hot... Triumph 14
Drone Dog Lilly running #3 / since last we talked.... Austin Healey 7
Drone Dog Lilly second time running... or trying Austin Healey 8
Drone Dog Lilly first time running in 15 years.... Austin Healey 19
sd80mac7204 TR6 Interesting TR6 running issue Triumph 19
glemon TR5/TR250 Stumped TR250 Running Rough--Follow Up Triumph 3
glemon TR5/TR250 Stumped TR250 Running Rough Triumph 8
F TR2/3/3A SUs Running Rich Triumph 25
S TR2/3/3A Struggling to stay running during warmup? Triumph 0
vette Constant Engine Running RPM. Austin Healey 20
S TR2/3/3A Oil Leak Dripping from Front and Rear of Left Side Oil Pan---Only While Running Triumph 14
C T-Series MGTC Running Boards MG 1
gbtr6 TR6 TR6 no start after running amazingly well til now. Triumph 16
K TR4/4A Running the motor witout the gearbox installed? Triumph 3
D Rough running BT7 3 carb HELP Austin Healey 13
M TR5/TR250 problem getting engine running Triumph 15
H Nice to hear the old girl running again. Austin Healey 2
R MGB-GT Just purchased Tuned for sea level, but I live at 7500', running rich MG 7
cpbol Sharing story - Solving issue of starving for fuel after running for 10 minutes Austin Healey 67
B Thoughts...rough running at cruise. Austin Healey 3
Sopwith_Camel MGB-GT running when parked MG 11
H bleeding the clutch and not running Austin Healey 17
F Running out of fuel - gauge problem? Austin Healey 5
trrdster2000 GT6 Barn find is up and running. Triumph 3
KVH TR4/4A Running Badly Triumph 8
nicko Running like a pig Austin Healey 19
doc50 TR2/3/3A Running rich Triumph 9
RickB MGB 1980 Starter Relay & running problems MG 14

Similar threads

Top