Will fuel pump change improve performance

[russellbaldwin]

Hi

 

There's nothing wrong with the original Lucas fuel pump (dangerous last words!) fitted but it's been on the car for 41 years.

 

There are a couple of reasons tempting me to change to a 'Bosch type' system

1) Performance/drivability - the car can feel a little sluggish at low revs - some have suggested it is missing although it still sounds smooth enough - which disappears higher up the Rev range

2) reliability - I'm doing first long European trip this year so looking to build in some protection

 

Some say to stick with the original Lucas pump and chucking a spare cheapie Chinese replacement in the boot if I need it is a lot cheaper than an upgrade and unless there's a good performance/drivability benefit I'm tempted to leave alone.

 

Any views on performance/drivability/reliability and which is the best route to go? And do you need the PRV change as well?

 

Thanks

[Andy Moltu]

If the problem is at low revs it probably isn't the fuel pump itself. If anything if the pump is failing it will cavitate at tickover when warm - suddenly scream and the car stall, or run out of go at the top end if it can't pump enough to supply full load at maximum demand.

 

Missing low down could be one of many things but worth checking out the voltage being delivered to the pump.

 

Whilst I'm not a an of the Lucas pump I wouldn't blame it for this.

 

Just be aware that if you are planning to carry a Bosch or other non-standard pump with you as a spare, make sure you have the right adaptors as the outlet on the high pressure side will be a metric thread and you will need to get the correct threaded adaptor or carry a high pressure pipe with metric unions at one end and imperial at the other. The threaded adaptor is easier to use and change pumps in a hurry as you don't have to clear your luggage to get access to the PRV. The inlet may differ too but as that's just tank pressure it's easy to link with simple unequal adaptors.

[TriumphV8]

As you may know the Pump is a modified windscreen wiper motor.

Its up to you to judge if that is a perfect solution especially under

the info that LUCAS itself did not use it that way.

 

Originally this race injection was feed by a mechanical pump and

only for starting the electrical pump was involved.

 

So if you believe that fuel pump technologie made some improvement over

the last 50 years a swap might be invisaged.

 

Under all circumstances the new pump must be fitted in a way the constructor

had in view and not what is found in the trunk, otherwise the benefit might not

be as large as expected.

 

If there is a benefit at all it depends on the setup of MU and the state of wear

of the pump itself and the way of driving.

 

Besides the performance of the engine I would like to give a hint I did not read here:

Planing to go to Germany means driving longer and maybe come into traffic jam.

The pump has the problem when worn that it still might give enough pressure but

not enough to open the PRV and let fuel pass back to the tank. This means that fuel

is kept and heated in the pump and will get bubbles when pressure drops.

The problems rise after a jam or a short stop because the heat caused bubbles than

in the whole fuel line.

I avoid that with the help of a fuel cooler, today used in many modern cars because

its simply necessary. Mine is from BMW but also VW has some.

 

So clear vote for a complete tuning of the trunk from a specialist who knows what he

is doing. The aim is that you forget that you have a PI and simply drive without

stumbling, not hot starting and refuelling that half full tank.

[Peter Cobbold]

I ran the same Lucas pump for ca. 200k miles over about 20 years. It only had to be replaced because the lower seal started to weep petrol onto the road. I'd take a Lucas spare as belt and braces, as it is far easier to fit at roadside.

Uneveness at low rpm might be butterflies needing synchronising, or spark timing. I very much doubt it would be the pump.

Timing the MU might help.

Peter

[k_raven_smith]

Pm sent