Thomas Erb wrote about problems with the fuel pump of his TR5 during hot
weather...
Thomas,
As one who has owned a TR5 PI since new, I can claim wide experience with
the Lucas 110 psi fuel pump, which is a common topic of conversation with
these cars.
Firstly, listen for the sound of the pump with the ignition turned on.
It should be a steady, high pitched whine from the rear mudguard. If the
note is low, or varies in pitch, the pump is not running at full speed.
If the pump speed is OK, you need to check your pressure relief valve
(PRV), located under the car on the rear chassis. It is adjustable (with
care) - should deliver 106 - 110 psi. I have installed a T-piece in the
fuel line, with a pressure gauge on the console. If you have a problem
here, come back to me and I will provide more detail. However, the PI
fuel pump is more likely to be the problem.
If your pump is not running at full speed:
1. Service the motor. Disconnect the battery and clamp the fuel line
from the tank. Undo the two screws retaining the pump motor magnet
housing and CAREFULLY withdraw the housing. Take care not to damage the
brush assembly with the armature. Clean out all the soot - there will be
a lot if the pump has been neglected.
** If the brushes are badly worn, replace the brush assembly - some
windscreen wiper units will fit if you remove the third, "parking" brush.
Check for fuel leaks from the pump into the motor - leaking petrol dries
out the motor bearings, causing overheating. Clean the armature and
magnet housing, especially tidy up the commutator and its segment
grooves. Lubricate the armature bearings with light grease and CAREFULLY
reassemble.
** You MUST line up the indicator arrows on the base and the magnet
housing, or the pump will run backwards!
2. If the pump is still not running at full speed, your motor stator
magnets may have lost strength. Check the current drawn under load - it
should be about 9 amps. Weak magnets are not repairable.
3. MOST PI pumps overheat in hot weather. I have fitted a large copper
heatsink, made from plumber's copper pipe (75mm dia), slit into a "C" and
clamped with large radiator hose clamps around the motor body. The ends
of the pipe are split into strips and flared out like a large transistor
heatsink. You can also fit a 12V computer fan to blow on to the motor.
It is a good idea to rewire the motor supply line with much heavier wire,
the fit a relay.
4. Finally, if none of these work, fit a Bosch pump - they work well,
but are expensive. Make sure you can attain 110 psi - Bosch K-Jetronic
systems work at only 70 psi.
Please tell me how you succeed - I may be able to help further.
Good luck!
Max Blyton
1968 TR5 PI (original owner)
1980 TR7
1978 TR7 (Mazda rotary powered)
AUSTRALIA
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