Fuel pump, original or electronic?

Alty Ian · Post by **Alty Ian** » Wed Jun 24, 2015 9:35 pm

My fuel pump is dead and despite my attempts to refurbish it, I need to replace it. I was thinking of getting an electronic one, has anyone tried them, how do they compare with original ones with points?

chrisvine · Post by **chrisvine** » Wed Jun 24, 2015 9:44 pm

I converted mine to electronic and there's no difference in operation/performance. The main reason for doing so was to move away from the points set up, which I believe is the most common cause of problems for cars that are not used over the winter months.

paulsco · Post by **paulsco** » Thu Jun 25, 2015 7:07 am

I have had an electronic SU pump on my 340 for nearly 20 years of regular use and it has never let me down.

It is identical from the outside and ticks like the original.

Paul

Post by **mgcjag** » Thu Jun 25, 2015 7:50 am

Hi Ian...agree with all above have them on both my cars work great

Post by **Heuer** » Thu Jun 25, 2015 9:00 am

Alty Ian · Post by **Alty Ian** » Thu Jun 25, 2015 6:27 pm

New electronic pump AZX1308EN ordered ready for the big switch on this sunday

Alty Ian · Post by **Alty Ian** » Fri Jun 26, 2015 9:27 pm

Fitted the new pump and its great, system now filled and ready to go, lots of leaks at first but OK after lots of tightening up

Brinky · Post by **Brinky** » Sun Jul 19, 2015 12:27 pm

I was on the point of buying one but managed to get the original one working again a couple of hours ago. What got mine working was tapping it while it's connected to a power source. Tapping it while disconnected did nothing. I think the combination of power and tapping might solve some of these issues. The modern replacements include a pump that looks an awful lot like the one I just fitted to my XJ8, which I'm sure will work fine if everything's clean. I ran my XJ8 low on fuel, filled it up which stirred up the sludge, blocked the filter and burnt out the motor. I've subsequently read stories where the in-tank wires burn off their insulation while the fuse remains resolutely intact, so beware of that! I'm fairly sure my 3.8 pump is the original as it has '1 64' stamped on it - 3 months before the car was registered - and is now humming away again more than 50 years later!
Hope that helps someone.
Rob.

Post by **mgcjag** » Sun Jul 19, 2015 1:40 pm

Hi Rob....having to tap a points pump to get it going is very common...its a sure sign that it needs refurbing or replacing.....i can guarantee that you will be having to tap it again when the car packs up or doesntt stare......sort it now or regret it later...all the best Steve

Post by **Heuer** » Sun Jul 19, 2015 2:11 pm

The 3.8 uses the Lucas in tank pump and it does not tick like the SU pumps but has a continuously running motor. The modern in tank replacements are indeed based on a later Jaguar item. The Lucas pumps were problematic back in the day because the slightest bit of dirt can cause them to stop and it is imperative you have the filter fitted. You also need to remove the fuel tank sump every year to clean out any rust or debris. Even so the pumps do not respond well to lack of use so unless the car is a daily driver you may still want to consider the modern replacement.

trondvo · Post by **trondvo** » Sun Jul 19, 2015 5:25 pm

Cleaned out the sump in my 61 once in 18 years, maybe I should service it now. Its a good opportunity to rid old gas and deposits.

The only way I could get the sump out of my 62 FHC was to take out fuel pump, drain a gallon old gas and soak the area around sump flange with oil/wd-40 for a week. Still had to destroy it (plumber wrench) to get it out. Seems like it is in brass and it was "frozen".

MarekH · Post by **MarekH** » Sun Jul 19, 2015 8:31 pm

Dear Ian,

The difference in the two pumps is minimal.

With the old style pump, the high current (~4amps?) is switched by a metal cradle which completes the circuit and lifts the fuel out of the tank. This inevitably causes a bit of arcing and corrosion at "the points" as they open and close, switching the high current circuit on and off.

The electronic pump ultimately uses the same current, but this time the points close to feed a small current (~10mA) to a large transistor which is used to switch the larger current consumed by the pump as it turns on and off.

The mechanical side of the pump is identical. It is a good time to put a fuse into the circuit. If you so wished, you could probably convert your own pump for about ?5 or less.

kind regards
Marek

Post by **mgcjag** » Sun Jul 19, 2015 9:01 pm

The difference isnt minimal.....one has points the other dosent, the pointless electronic version should be more reliable....however from above Ian is now sorted.... Steve

JagWaugh · Post by **JagWaugh** » Mon Jul 20, 2015 2:46 am

Steve,
Both have points, in the electronic ones those point carry the full load of the coil.

The electronic ones will still need the points adjusted periodically, the mechanism does wear.

Andrew

Post by **mgcjag** » Mon Jul 20, 2015 8:17 am

Hi Guys....please see the link to Burlan re SU fuel pumps and the section re pointless electronic switching http://sucarb.co.uk/technical-su-fuel-pump-polarity

abowie · Post by **abowie** » Mon Jul 20, 2015 9:31 am

Alty Ian wrote:My fuel pump is dead and despite my attempts to refurbish it, I need to replace it. I was thinking of getting an electronic one, has anyone tried them, how do they compare with original ones with points?

Electronic. No brainer.

christopher storey · Post by **christopher storey** » Mon Jul 20, 2015 11:22 am

I have 4 original type SUs, all between 46 and 51 years old , and ( famous last words ) none have ever given me any trouble. Having seen 2 of the electronic type which have gone on fire - fortunately without destroying the cars to which they were fitted - I know which I prefer

What is it about modern aftermarket electronics which makes them so unreliable ?

MarekH · Post by **MarekH** » Mon Jul 20, 2015 1:14 pm

No one who sells "upgrades" ever mentions how fitting them will change the characteristics of the system as a whole.

For example, in this case the power transistor doing the switching may now be capable of switching 15amps, 150volts in a fraction of a second that the old pump did all day and all night at any temperature below a continuous 125'C, but this is still connected unfused, via 50 year old wiring, straight though the ignition switch. The likely "failure mode" of the new system will be different and potentially far more serious than it was before.

The transistor switches very quickly and the electrical "shock" of pulsing on and off may be far more severe than before, as at switch on, the rate of change of current through the transistor is infinite and decreasing exponentially, whereas with crusty points offering some resistance (with attendant moderate and safe heating) the rate of change of current would be ameliorated. Eventually, the old pump dies and draws no current and causes no fire whereas the upgrade will draw more and more current until one of its attendant (lesser rated and hence cheaper) components spectacularly goes bang.

The nice thing about the old school technology like points is that a bit of emery paper and a hammer will probably get you home, whereas the average Joe is probably clueless about pointless even when you put a circuit diagram in front of them and explain that a transistor is like a switch.

I'll say it again - you might want to think about fitting a fuse.....

kind regards
Marek

JagWaugh · Post by **JagWaugh** » Mon Jul 20, 2015 6:28 pm

mgcjag wrote:Hi Guys....please see the link to Burlan re SU fuel pumps and the section re pointless electronic switching http://sucarb.co.uk/technical-su-fuel-pump-polarity

Steve,

I wonder if Burlen have a new pointless system then. I did fit a few of their electronic upgrades a few years ago, but that was the same mechanical points arrangement but with some electronics to carry the load of the coil.

If the electronic upgrade is still available I would go with that, rather than some fully electronic system which senses the stroke. At least with an old fashioned set of points you have a chance of removing the electronics, and connecting the points as tradionally, to get home (and drive another 20 years or so).

And Marek is right... a fuse wouldn't be amis, regardless of which type of pump.

Andrew

Andrew

MarekH · Post by **MarekH** » Mon Jul 20, 2015 7:03 pm

There will be more than one type and they work much the same way. You'll either see a mechanical connection for a small current which feeds a larger transistor or you'll see the diaphragm movement operate something ferrous against a hall effect proximity (magnetic) switch which generates the same 12v square wave signal to the power transistor. Both start with a mechanical movement and use a small signal to switch the big signal.

kind regards
Marek

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