Potential electrical fault that blew feul pump

[Moffie]

Hello
I wonder if you might be able to clear up a matter for me?
my six month old electric fuel pump by Quinton Hazel gave up the ghost whilst on the moterway after only 2000 miles or so. There was three loud bangs and we stopped. (I tested it with the battery it's definately dead).
The fuses near the regulator seem o.k. and the contact breakers have minimal black on them but when pushed together there is still a good spark.
I have a replacement pump here, but before I do too many miles or even just a bit and the replacement also goes bang...... could there be another reason why it was 'taken out' so quickly?
Other possible elements are;
There was a disconected radio that came with the car. A machanic whom it turns out didn't seem to know what he was doing with the engine but did with his cash flow (details witheld!), has been at the electrics.

In march this guy re-wired the radio whilst replacing regulator etc.
The car has a negitive earth. I have heard that so does the radio so that can cause problem given time. The car has done just under a thousand miles since march.

Since the radio has no speakers anyway I hadn't taken much notice of it although on the 14th of may I did try a tape to see if it would turn it or chew! It worked all lit up and everything, but I probably then turned it off after awhile. Could this be the reason the car banged or is it a storm in a tea cup?!
Will it all be fine...if I fit this new pump?!.The aren't any speacialist garages nearby and that last mechanic caused untold woes... so I am a little afraid of garages right now!
Would you help a damsel in distress

[Kevin]

Well the Radio should not be wired in any way to affect the fuel pump and I must admit I have not heard of a pump going bang before. are you sure the fuel pump has gone (has it stopped ticking) because they normally last for many years or is the car not starting, can you give a bit more detail if possible. and do you know if the pump still has points in it or is it fully electronic as some makes have been known to cause problems.

[Moffie]

Hi Kevin!
Thankyou for your quick response
I think the pump is part electric also with points.
Also the banging could apparently be the electric failing and then rebooting whist in motion i.e. 50mph+ as the lights and and turnover are fine.
The thing about the radio is that I call a supplier today whom suggested that if the car has the original negitive polarity and radio's arial also have negative polarity, that this it can cause some sort of problems with things blowing etc, although it I think I got this right, it dosn't always happen straight away. I hope I'm quoting him rightly!

It just appears to be that when the pump is fully conected it dosn't tick, well it very occasionally manages one, then it goes to sleep again.
It was ticking away noisily when conected directly to the battery. When turning over there is no response and no chance of the engine firing up..
I've changed the fuses and wiggled the wires around the box, but no change to the situation.
I'm not yet so experienced with my engine so I'm probably not doing all the right things yet. If there is somthing daft that I've missed and could learn about to see if it helps I'm very open to suggestion right now!
Thanks Sam

P.S It's a 1968 saloon all mod cons. (now minus radio)

[bigginger]

It's very hard to see how the radio could have any bearing on this. I think that it's a red herring and you need to be fault finding the fuel pump and circuit, though it's hard to see how it could cause a bang by anything except detonation.

[rayofleamington]

My guess is that the QH pump is one of these useless German ones - they have a habit of being unreliable and will overheat and stop until they are cool or burn out completely.

The new SU pumps don't seem to be as good as old ones (heard a few reports of new SU pumps failing) therefore my preference would always be to go with a new-old-stock SU pump and if it is second hand, check/replace the points as appropriate. The original SU pump is not perfect but seems much less likely to fail completely as long as the points are ok.

The only genuine problem that is likely to come from a negative earth radio is draining the battery (eg when radio is faulty and draws current even when switched off)

If your pump works off the battery but not off the wiring then it could be a couple of things:
1) the pump is knackered and needs a LOT of current to run. This much current through the standard wiring is too much and the resulting voltage drop doesn't give enough juice to run the pump. (same result if you connected the starter motor off the pump wire - it wouldn't run but it runs when connected directly to the battery with thick wires.)
2) The wiring for the pump is faulty. This could just be due to age (eg a high resistance connection) or could be due to electrical overload (burnt out) due to supplying high current to a faulty pump.

[Moffie]

Thankyou Andrew and Ray.

I think I know what to do now.
Can you advise me, is an original s.u. pump still 'new' or actually 40 yrs old? I did keep the original, it was seriously sticking after lack of use in the drive for far too long. We did clean the points but it didn't help much!

The first QH pump is definatly dead as we checked it with the battery. The replacment o.k.
I managed to get the new pump clicking like crazy after fiddling with the connections around the fuse box.
The car still won't start!
If I replace the 'fuse box',change the wires to the pump, Should I also change other wires since the coil had been on the blink for a long time unsuspected by my ex machanic (and me)
Also the car's other problem since I've had it is a split in the radiator pipe. This went undetected for a while too, so antifreezed water had also been spraying on new elecrical work, i.e. Dynamo and Voltage regulator.
Although after changing pipe, drying + WD40 -ing I think it's called the distributor- (black plastic, with a clip on/off lid) and then in a little while I got a new coil, all seemed to be well for about 320miles till my current problem!

I'm certainly learning to take better care. I appologise profusely for my ignorance because it's a nice car and I'm very proud... I'll order a new fuse box and wires and take it from there.

Thanks a lot lads!
Sam*

[rayofleamington]

I'm certainly learning to take better care. I appologise profusely for my ignorance because it's a nice car and I'm very proud... I'll order a new fuse box and wires and take it from there.

Don't worry - we all had to start from somewhere.

New fusebox - all that may be needed is to clean the terminals / connections on the old one.

Can you advise me, is an original s.u. pump still 'new' or actually 40 yrs old?

an original one is 40 years old. Hoever some people had spare ones sitting in their garage for 20 or 30 years and if they weren't used then they are called 'new old stock' (sometimes reffered to as NOS). You can get brand new SU pumps (still being made) but as mentioned, I'd prefer an older one with new points if required.
If your old pump was stopping but would go again if you tapped it (eg with screwdriver handle) then that would indicate a problem with the points and the points can be replaced.

I managed to get the new pump clicking like crazy after fiddling with the connections around the fuse box.
The car still won't start!

Maybe I'm reading too much into that, but if the fuel pump is ticking rapidly then it isn't filling the carburettor! It will stop ticking when the carb is full (unless there's a leak but you'll see petrol everywhere )
There are a few possible reasons why a pump will keep ticking:
1) petrol tank empty
2) air getting sucked into the feed pipe (often at the pump connector)
3) the pump is faulty internally
4) [not likely in this case] that the fuel pipe gets very hot (eg in a traffic jam where there isn't enough fresh cooler air blown into the engine bay) the petrol turns to vapour when it is sucked up the pipe to the pump.

However if you didn't mean it quite that way (ie the pump stops ticking when the carb is full, then you need to check that you've got a spark.
If you remove a plug and rest it on the engine somewhere it can ground itself like at the side f the thermostat housing (still connected) you should be able to see a spark when turning the engine over. (it is hard to see in sunlight so during our few weeks of summer this is better done in the shade or in a garage.
Problems with the timing/coil etc.. are more likel;y to cause a banging when conking out. Fuel pump problems tend to just run you out of fuel (running out of fuel symptoms: 10 to 20 seconds of stop/start/stop/start jerking from the engine before it stops completely)

[Willie]

I will remind you that the fuel pump is NOT fed through a fuse for safety
reasons.

[Moffie]

Thank you, Ray!
Your reply was very clear . Yes the clicking stops eventually, but it did click a lot. I'll see how I get on cleaning and checking points and tighten the petrol inlet.
I' m sorry I havn't been in contact, but my computor has stopped booting up so I'm relagated to my local library!
Don't know what I'm doing wrong this week, I might have a 'negative' earth myself! .
Thanks for not telling me off for being a usless machanic!

Thanks again Sam*

[bigginger]

Why would we? S'why the board's here

[ColinP]

Yup, as BigG hints - we all start somewhere.

The only really stupid question is the one that starts "Why didn't I ask that months ago?..."


Colin

[bmcecosse]

Take the fuel delivery pipe to carb off - stick it in a jam jar, and try the pump briefly. Does petrol come out ? If so - the problem is ignition - or terrible mechanical malady. Check for spark as Ray says - but worth checking and cleaning rotor arm/inside of dizzy cap - look for the little carbon brush in the middle - is it springy ? And check for obvious loose connections at dizzy and coil.