British-Cars.org

Welcome to the DMR Site for British Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Start up problems

Just got her started and having the following probelms: -

1 Oil pressure when cold at 85-90 psi. Haven't got her warmed up yet so I have no further info but it seems a bit high. I've had a new rocker shaft and a few other bits and pieces such as bearings etc but I've read somewhere that the new rocker might have something to do with the problem and that the banjo bolts in the copper pipe from block to head have different orifice sizes. Does anyone have any info on this please.

2 Idles at 2000 rpm. Overhauled the carbs, new jets, needles, seals etc I but didn't touch the butterfly valves and it worked fine before I fiddled with it!

Any suggestions as to where to go next would be appreciated.

AJ
A R Jones

High idle could be caused by timing that's way advanced or possibly a vacuum leak.
JE Carroll

AJ,
TD or TF or ?
Mort 1950 TD Möbius

AJ Check that the throttle plates are in the shafts correctly. The edges of the plates are beveled to make a tighter fit to the bore of the carb. This will cause a high idle speed if they are not in correctly.
Cheers,
Bob
Bob Jeffers

Mort,

TF.

Bob, thanks, I'll check the throttle plates but I didn't do anything to them.


AJ
A R Jones

Binding shafts can cause a sticky throttle. Make sure the carburetors are 'settled' before tightening the carbs to the intake manifold.
Dave Braun

AJ, You've probably already done this, but check that the fast idle adjusting screw is clear of the rocking lever when the choke is pushed right home. Also, make sure that when you retightened the clamping bolt on the coupling of the throttle interconnecting spindle, that the throttle position was not disturbed. Let us know how you make out. Cheers Phil
Phil Atrill

AJ, With regard to the orifice sizes of the head to block banjo bolts, I examined both the round head version found on earlier TD's and the hex head bolts found on later TD's, as well as the banjo bolts with fex line adapters, and did not notice any difference in the size of the orifices, contrary to such mention in the archives. You will get slightly higher pressure readings if the take off is taken from the bottom banjo fitting rather than the top, however. Just make sure that your new rocker gear was installed correctly and that the oil feed hole is not blocked, which could cause a significant increase in oil pressure. Look under rocker cover with motor running to make sure oil is present. Cheers Phil
Phil Atrill

AJ,
Too thick oil viscosity, cold, fast idle, overcast skies... there is no reason the pressure should be up to 90 psi. There's a spring loaded relief to limit pressure.

Could your gauge show a metric value, like millilightyearPascalKelvinNewtonmeters, and not PSI?

Fast idle- too much air usyually. Disconnect throttle linkage and see if it drops down. As said before, binding shafts... throttle stops, whether fast idle with enrichener or warm... maybe loosen the linkage between the carb shafts as it may hold one carb open... loosen butterfly screws and readadjust to see if they settle down farther... You may hunt for a vacuum leak with some flammable spray, like propane or starter fluid, shooting it around carb flanges and head/intake flanges, looking for a jump in revs... check timing............

Do keep us in the loop!

JIM
Jim Northrup

To follow up on Jim's comments, with the throttle shaft connection loose (and the throttle pedal linkage removed), make sure each throttle snaps smartly shut. If the end springs are not adjusted correctly the plates may not close. Oil pressure: try another gauge to make sure the reading is correct. I think 90 is too high. The relief valve in the oil pump cap may have a problem. It was common for people to shim the spring in an attempt to raise pressue to make up for worn bearings and parts. You can access this from the big brass plug on the bottom of the pump. There should not be any shims under the spring. George PS- you can also pull plug wires one at a time and see how much RPM drop you get- if there is no change at 1 and 2, then you know the rear carb is at fault, etc.
George Butz

Sorted the fast running. One of the butterfly valves was open. I undid the small bolts on the throttle shaft which allowed me to close it.

AJ
A R Jones

George
Your comments remind me of the first "B" that I restored....Carbs were so out of whack, when I got the car, that it would run as well on one cylinder, as on 4....I didn't think that was possible, but pulling 3 plug wires, and watching the lump continue to run, proved me wrong.
Edward
E.B. Wesson

This thread was discussed between 11/12/2011 and 14/12/2011

MG TD TF 1500 index

This thread is from the archives. Join this live forum now