Fuel pump /alternator problems (groan)

[piersmcg]

Typical! With this georgeous weather we're having (in Kent at least! ) I brought my car into work and made an excuse to drive into town at lunchtime. Lo and behold, after driving around for about ½hour, and stopping a few times, that dreaded sound came from the pump, and my engine coughed and died.

This has happened before, and I know to wait till it cools down and carry on, so I did, but as I was stop-starting my way sheepishly back to work, I have realised that something is going on ....

I reckon that the pump is not getting enough power from the alternator. Now this can't be the only cause, but certainly sitting at traffic lights at idle with the indicator going you can hear the change as the lights go on and off.

My immediate reaction is to say "get a bigger alternator", but I have a number of questions:

1. This was design - was it this marginal?

2. Does one have to have a period alternator, or can I fit a modern one (please no comments on originality! )?

3. It could (gulp) be the fuel pump itself. It's original as far as I can tell, and not converted for unleaded. Is it time for a change? ???

 

Incidentally, I've got a minor wiring problem which is causing the dip and main beams to be on. The switch is shorting I think - I need to investigate this first.  :0

[scotty]

I cant give you any technical advice but the Lucas pump on my 6 was playing about like yours , a meter showed it to be using 3.5amp when should be 5 and only 9 volts.

It could have been something simple like worn bushes but I decided to just change it for a bosch ( practicalities above originality ~ I use it frequently ) . this works fine with  no alteration to the wiring .

I did try to run my old Lucas off a spare battery directly  just to see if the wiring was tired and causing voltage drop or whatever . I didnt make the slightest bit of difference .

On a side note the misses took the 6 out for the first time the other day and had a complete change of heart about it .

What do I do now , change the locks or hide the keys?   ???

[grmills]

My 6 has a Bosch pump which runs fine in all weathers, touch wood.  When I put a new alternator in (part-exed at Unipart) one of the chaps at Enginuity subsequently commented that if running a Kenwood fan they usually fit an uprated alternator.  So I guess the answer to your question is 'yes, it can be done'.

[jean]

The wiring on these cars was from the beginning under-rated

and with age the whole wiring loom is deteriorating,as a matter of fact the cables burn out slowly.You will notice when stripping a cable the wires are all black and sticking to the isolation. The first alternator uprate would be a Lucas LRA100

rated at 34A. They look almost the same as the original and were used on Land Rovers/Fords etc. As they have internal control units you will have to bypass the original external unit as on the early TR6. To understand  alternator conversion or repair have a look - at

http://www.vtr.org/maintain/maintain.html

under Electricals

The design was marginal, at the time like now costs had to be kept as low as possible.

The best advise is to uprate the whole pump system to Bosch

and to add a larger gauge cable for the pump and work with a relay in the boot.You can use the original wire for the switching current. Pay attention that if not mounted correctly the Bosch pump could also be subject to vapor lock under hot weather conditions.

By the way the original Lucas pump should work with unleaded in the same way as with leaded petrol no problem on that side. Keep in mind that to prevent overheating a certain amount of fuel has to be recirculated into the tank via the PRV.

Jean

[piersmcg]

Jean - thanks for that.

I'm in the process of redesigning the pump/coil wiring anyway. I can't quite believe that most the current for the electrical stuff goes through the ignition switch! This evening I've just fixed my main/dip beam problem, and I've noticed that the plug where the brown/white charge wire joins the brown/blue light switch wire is showing signs of overheating and melting around the plug. V. worrying. Last time I had a problem with the pump, I replaced this join (it was rusted through - hence heat), but it looks like it's still doing it.

I'm proposing to isolate the pump/coil circuits so that they are switched with relays and wired directly from the charging wire (brown/white) which should help.

 

Incidentally, my car seems to have very odd wiring. I've got a horn relay (I thought this was USA market only), and lots of oddities. I think someone's had a go at it in the past, probably compounding the problems I'm experiencing. Since I put on the return fuel cooling around the pump it's rarely played up, but I think a lack of power is causing this, due to the wiring!!

Additionally, the alternator control unit is already bypassed, so I think it was probably already upgraded, but I want to fit a modern one rather than a period one anyway. Any suggestions?

[jean]

Piers,there is nothing wrong with the old fashioned alternators, period ones are no better. These light weight alternators offered by some suppliers come from japenese cars are are in no way better than the NOS Lucas. I have a 65A alternator on my 6 from Revington don't remember the make no indication on it except a large W ,but It has to feed the EFI with 6 electronic injectors and an electric fan. I had to bypass the A meter, because at start the needle is made 2 full rotations before coming to rest.I also have to keep my battery in good condition to prevent melting the brown wire

what should be a larger guage in fact.

The next step will be a second brown lead direct to the battery,this will overcome the extra load on the A meter when battery is low.

Jean

[Andy Moltu]

If you haven't done so already check the inertia cut out switch - dodgy connections to it and within the switch can be a trouble spot - effectively reducing the voltage to the pump.

[piersmcg]

Haven't got a cut-out! 1968 car! I've got a second-hand one coming though.

 

Is the 65A alternator from Revington a period piece? Is it any more expensive than a modern one?

 

What I really want is an alternator that will provide good charge at idle, which is when the problems occur. There's no point in fitting a 30 year old piece of kit when there's cheaper, more reliable options available now.

 

I suppose the other thing is to look at the state of the battery. As said before, if this is in good condition, then it should provide back-up current when required.