Fuel Pump Failure - do I need a pre-filter or a flush?
Discussion
My fuel pump always used to make a reassuring whir for a few seconds before cranking. Not any more. After tracing the wiring I tried putting 12v directly on the pump (via a 10A fuse), got a spark but not much else. The old pump measures 1.3 Ohms, so I’m expecting it to draw about 9A.
So I drained the tank (the fuel looked clean) & fitted a new ‘Bosch type’ pump. This time the pump ran long enough to check for leaks but it did sound a bit feeble. Then, when I tried to start, it whimpered for a bit and went quiet. 12v on the new pump does nothing and it’s resistance is ~2500 ohms. So a dud, methinks.
The vendor says: ‘…resistance doesn't indicate anything, and it’s probably jammed with debris (I have found a couple of specs.) What type of pre-filter am I using?’ Well, hopefully there is a course mesh in the tank, but that’s it.
Apparently, our pumps can push 3 bar but don’t suck very well. So I’m thinking that fitting an extra filter on the pump inlet might restrict flow too much. Anyone have experience and a solution for this?
I’m not keen to remove, inspect and flush the tank, if I can help it, but maybe it’s time?
(Edit for typoids)
So I drained the tank (the fuel looked clean) & fitted a new ‘Bosch type’ pump. This time the pump ran long enough to check for leaks but it did sound a bit feeble. Then, when I tried to start, it whimpered for a bit and went quiet. 12v on the new pump does nothing and it’s resistance is ~2500 ohms. So a dud, methinks.
The vendor says: ‘…resistance doesn't indicate anything, and it’s probably jammed with debris (I have found a couple of specs.) What type of pre-filter am I using?’ Well, hopefully there is a course mesh in the tank, but that’s it.
Apparently, our pumps can push 3 bar but don’t suck very well. So I’m thinking that fitting an extra filter on the pump inlet might restrict flow too much. Anyone have experience and a solution for this?
I’m not keen to remove, inspect and flush the tank, if I can help it, but maybe it’s time?
(Edit for typoids)
Edited by Wicker Man on Tuesday 26th March 20:39
phillpot said:
Thanks, one of those is preferable to open tank surgery, but I think might need the 8mm version:https://www.carbuilder.com/uk/blue-8mm-fuel-filter...
Belle427 said:
No real need for one, id just work out why the pump wont run with a good 12 volts applied to it if your sure the 12 volts is actually good.
Yes, I connected my jump starter & voltmeter directly to the pump terminals, 12v present but dodo dead. I’ve ordered another pump from a third party. It’s suspiciously cheap, so almost nothing lost if it goes in the bin.Do the reputable suppliers actually use a different sources from the dis-reputable ones?
Wicker Man said:
My fuel pump always used to make a reassuring whir for a few seconds before cranking. Not any more. After tracing the wiring I tried putting 12v directly on the pump (via a 10A fuse), got a spark but not much else. The old pump measures 1.3 Ohms, so I’m expecting it to draw about 9A.
So I drained the tank (the fuel looked clean) & fitted a new ‘Bosch type’ pump. This time the pump ran long enough to check for leaks but it did sound a bit feeble. Then when I tried to start, it whimpered for a bit and then went quiet. 12v on the new pump does nothing and it’s resistance is ~2500 ohms. So a dud, methinks.
The vendor says resistance doesn't indicate anything, and it’s probably jammed with debris (I have found a couple of specs.) What type of pre-filter am I using? Well, hopefully there is a course mesh in the tank, but that’s it.
Apparently, our pumps can push 3 bar but don’t suck very well. So I’m thinking that fitting an extra filter on the pump inlet might restrict the flow too much. Anyone have experience and a solution for this?
I’m not keen to remove, inspect and flush the tank, if I can help it, but maybe it time?
So I drained the tank (the fuel looked clean) & fitted a new ‘Bosch type’ pump. This time the pump ran long enough to check for leaks but it did sound a bit feeble. Then when I tried to start, it whimpered for a bit and then went quiet. 12v on the new pump does nothing and it’s resistance is ~2500 ohms. So a dud, methinks.
The vendor says resistance doesn't indicate anything, and it’s probably jammed with debris (I have found a couple of specs.) What type of pre-filter am I using? Well, hopefully there is a course mesh in the tank, but that’s it.
Apparently, our pumps can push 3 bar but don’t suck very well. So I’m thinking that fitting an extra filter on the pump inlet might restrict the flow too much. Anyone have experience and a solution for this?
I’m not keen to remove, inspect and flush the tank, if I can help it, but maybe it time?
My new-new pump arrived today: spot the difference.
Todays resistance measurements are:
Left, the original 26 year old Lucas - 1.4 ohms
Middle, Powermax ‘Bosch type’ - 188 ohms
Right, New-new dirt cheap ‘No brand’ - 18.6
I’m a bit puzzled by the variation in readings, but I guess the dc brushes account for that. I might give ‘em some volts tomorrow to see what happens. And maybe do a post mortem on the original. The outside of the aluminium case was very badly corroded under the clamp, so I suspect the internal clearance was compressed to nought. Or maybe it’s just knackered?
The cotton swabs show the debris I extracted from the inlets of the first two.
Todays resistance measurements are:
Left, the original 26 year old Lucas - 1.4 ohms
Middle, Powermax ‘Bosch type’ - 188 ohms
Right, New-new dirt cheap ‘No brand’ - 18.6
I’m a bit puzzled by the variation in readings, but I guess the dc brushes account for that. I might give ‘em some volts tomorrow to see what happens. And maybe do a post mortem on the original. The outside of the aluminium case was very badly corroded under the clamp, so I suspect the internal clearance was compressed to nought. Or maybe it’s just knackered?
The cotton swabs show the debris I extracted from the inlets of the first two.
Belle427 said:
I’d only buy a genuine Bosch pump too, they are readily available.
Yes, that was my first thought, as I don't want to venture beyond the end of my road with a cheap and nasty vital part. (Apparantly, the Lucas pump were Bosch copies, made under licences (or rebadged?)But the reputable dealers price is up to 7x the others, and they have the wrong terminals. So I thought I’d take a look on the dark side…
Pump no. 4 ordered today. One of these:
https://www.ebay.co.uk/itm/325831888628
The vendor assures me that it is a genuine Bosch pump with their logo etc engraved on the body. This sounds more promising! I wonder what its’ resistance will be?
https://www.ebay.co.uk/itm/325831888628
The vendor assures me that it is a genuine Bosch pump with their logo etc engraved on the body. This sounds more promising! I wonder what its’ resistance will be?
My new genuine Bosch pump arrived. It initially measured 3.3 ohms but after a quick buzz of 12V, this dropped to 1.7. That’s more like it! The length is the same as the original too. This is now fitted and whirs like the original, but for some reason, I still don’t have fuel pressure. 🧐
Whilst puzzling about what to do next, I took a peak inside the old original pump. The significant external corrosion appears not to have adversely affected the innards:
The brushes were fine but the commutator has significant wear and there was no sign of the missing copper. (In the filter down stream filter, I guess):
The brushes were fine but the commutator has significant wear and there was no sign of the missing copper. (In the filter down stream filter, I guess):
Sardonicus said:
Moisture in the fuel was the kiss of death for that pump,… I would say the car has spent long periods of no use or little use giving the moisture time to do its stuff
Sadly, you're spot on about ‘little or no use’; It’s been languishing in the garage for the last 10 years!But I now have some free time and some actual fuel pressure. Strangely, the note that came with the first replacement pump was exactly wrong. The large terminal is for the Positive supply:
Hurrah, my TVR now starts and idles and drives! That’s three things it didn’t do at all last year. It’s running rough, but at least it’s running 
The fuel pressure was a whopping 49 psi, so I’ve set that to 40psi, which is closer to the standard nominal 36psi. The AFR is all over the place, so lots more to do. Some fresh fuel might help. What’s the RON of ~ten year old petrol?
The fuel pressure was a whopping 49 psi, so I’ve set that to 40psi, which is closer to the standard nominal 36psi. The AFR is all over the place, so lots more to do. Some fresh fuel might help. What’s the RON of ~ten year old petrol?
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