Fuel sender unit and reserve tap o-ring

T

typonaut

Member
My fuel gauge is not working. I have jacked the car up and checked the wires/connections to the tank, and they all seem ok. Checked the power-in cable with a voltmeter and this shows up to about 11v (seems to float up and down for some reason). Plugged the power-in connector on to the power-out connection on the sender, and the gauge went up well above the "full" level.

Surmise from this that (a) the power out connector/wire is redundant, because it must earth to the sender/tank/body directly, and (b) the sender unit, rather than the fuel gauge, is faulty.

I see that Wadhams has fuel sender units, but the reviews indicate that these are not exactly OEM, and you may need to do a bit of work to get to fit.

Is the fuel sender unit repairable, and is it at all likely that the problem is just the float? I saw someone post that there was some info here relating to repair, but could not find it.

Gauge not working after car had a 25 year lay-up, was working previously.

Also, fuel reserve tap is leaking – which I take to be the often reported o-ring. Again I see that Wadhams has this part, but I would like to get it a bit sooner than a week's time (not so bothered about the sender). Does anyone know the original part number, or whether some standard size, fuel resistant o-ring would fit (that I can perhaps get locally)?

Thanks.
 

Petrol tap O ring size?

Just noticed at bed time a strong smell of petrol coming from the garage (internal access) a quick look underneath and I could see a steady stream of drips from the bell housing drivers side onto the garage floor :( . so pulled the reserve tap knob which has reduced the stream a little. But...
classicroverforum.net
 
The Wadhams senders look practically identical to OE and fit as they should, but they are neither durable nor accurate. The one in my car has failed after four years, and even when working it read empty when there was still a third of a tank left. The reason is that the float doesn't drop down far enough and the sender operates over too narrow a range. I have raised this with Wadhams (seemingly the sole supplier of new senders) but they refuse to acknowledge that there's a problem. The new one they sent me had the same problem of inaccuracy as the one in the car had when it worked, so I returned it. I managed to get a good used one from Pierre Janusz of Rover Parts Service.

Wadhams' blind spot over this is puzzling and frustrating. 'We've sold dozens of these and no-one has complained', they said. Maybe buyers' expectations are too low. It wouldn't take much re-engineering to make the sender read accurately.

John
 
johnsimister said:
The Wadhams senders look practically identical to OE and fit as they should, but they are neither durable nor accurate. The one in my car has failed after four years, and even when working it read empty when there was still a third of a tank left. The reason is that the float doesn't drop down far enough and the sender operates over too narrow a range. I have raised this with Wadhams (seemingly the sole supplier of new senders) but they refuse to acknowledge that there's a problem. The new one they sent me had the same problem of inaccuracy as the one in the car had when it worked, so I returned it. I managed to get a good used one from Pierre Janusz of Rover Parts Service.

Wadhams' blind spot over this is puzzling and frustrating. 'We've sold dozens of these and no-one has complained', they said. Maybe buyers' expectations are too low. It wouldn't take much re-engineering to make the sender read accurately.

John
Click to expand...
I had the same accuracy issue with the JRW sender. WINS had one available for a while and I purchased one. It has good accuracy but has problems with the connection points being too close together to fit the compression fittings. The fuel reserve outlet tube is also too high off the bottom of the tank because of the way they have designed the fuel reserve outlet filter. This leaves quite a bit of unusable fuel at the bottom of the tank and turns removing the sender into a fuel shower. Geoff has stopped selling the units due to the problems with them.
I was able to modify the one from WINS and install it. I now have an accurate fuel reading, but the installation is far from elegant. It would be great if one of the suppliers could make one that works.
 
I ended-up going down to WINS to get the o-ring. Asked them about the sender, and they said Wadhams was the only supplier.

How likely is it that the problem is just a faulty float? Perhaps I'll buy a Wadhams unit, then see if I can repair the original - so at least I'll have a spare in the future.

Thanks for the feedback.
 
typonaut said:
I ended-up going down to WINS to get the o-ring. Asked them about the sender, and they said Wadhams was the only supplier.

How likely is it that the problem is just a faulty float? Perhaps I'll buy a Wadhams unit, then see if I can repair the original - so at least I'll have a spare in the future.

Thanks for the feedback.
Click to expand...
I had 2 units from Wadhams. Both had the same issue with accuracy. I also had a failed float but that was easy to detect as the level gauge went to empty and would not move off even when the tank was filled. Jon indicated to me that there has been no change in the units he is selling since he started offering them.
 
Well, perhaps it is the float - gauge doesn't move at all. Not sure I’ve filled it up, but there certainly has been at least the reserve plus 5-6 gallons. As above, when I short the sender power to earth the gauge goes up as far as it can.

Oh, I did have a question about the reserve tap. When I'd fitted the o-ring and tightened-up the grub screw the tap would not move, so I backed it off about a quarter turn and it was ok. I am pretty sure that the valve is fitted correctly, because the tap stops work correctly (ie the valve is retained by the grub screw fitting into the slot in the valve body). Is this the normal behaviour?
 
typonaut said:
Oh, I did have a question about the reserve tap. When I'd fitted the o-ring and tightened-up the grub screw the tap would not move, so I backed it off about a quarter turn and it was ok. I am pretty sure that the valve is fitted correctly, because the tap stops work correctly (ie the valve is retained by the grub screw fitting into the slot in the valve body). Is this the normal behaviour?
Click to expand...
That hasn't been my experience. Do you have the correct lock washer under the grub screw? If not, the screw can thread in too far and interfere with the valve stem. It should be an "internal star" lock washer.
 
Last edited:
There was a little black washer - I didn't really notice what type it was – I think it did not detatch from the screw, so I put it back in with the screw.
 
I can't think of any other reason for the valve to bind if the grub screw is fully tightened. The fact that there is a lock washer strongly indicates that the screw should be tight. It would be a bad day if the grub screw were to back out and the selector valve fall apart.
 
Yes, indeed. I'll have another look at it. Perhaps the washer did come off the screw, and I've put it back the wrong way around (if that's possible).
 
It is possible to put it in the wrong way round, but the lever would then be obviously in the wrong place.
So I’d bet on the washer being missing.

Yours
Vern
 
Vern Klukas said:
It is possible to put it in the wrong way round, but the lever would then be obviously in the wrong place.
So I’d bet on the washer being missing.
Click to expand...
Sorry, I meant that I'd put the washer in the wrong way round, ie upside down (or something). Pretty sure I have put the tap back together correctly (apart from this issue with the washer), otherwise the grub screw wouldn't go in and the tap wouldn't "stop" in the correct places.
 
I have now fitted the used-but-good, original-equipment sender from Pierre Janusz, and it works perfectly with credible fuel gauge readings. The 2019-vintage Wadhams pattern part, always hopelessly inaccurate, ultimately failed because the float filled up with fuel. How does that happen? What could have punctured it?

Having replaced the rubber seal in the reserve changeover tap, it's a good idea to open the tap fairly regularly to keep the seal exercised and to make sure fuel flows through the reserve line from time to time. In preparation for fitting my new-old sender I was running the tank right down so there would be less fuel to drain. Sure enough, the engine started to misfire signalling the end of the 'main' tank's contents, so I pulled out the reserve knob expecting the misfire to clear and the journey to continue. It did not. The reserve line was full of sediment, which then found itself in the fuel pump and both carb float chambers. This is despite the filter gauze on the reserve pipe within the tank, and another in the fuel pump.

It's all cleared out now and everything is working normally again, but I shall be exercising the reserve system regularly from now on. With luck it will continue to work on the way to the Brooklands New Year's Day event tomorrow, and back home again. Fingers crossed.
 
John S Wrote "The reserve line was full of sediment, which then found itself in the fuel pump and both carb float chambers. " - no post pump filter which should catch such sediment?
 
Indeed. I should probably fit one, but how to do it neatly with the nylon pipes? The trip to and from Brooklands went perfectly, so all is currently good. Five other P6s were there, Series 1 TC and 3500, Series 2 3500 x2 (one Australian-built) and 3500S.

Happy new year to all

John
 
The neatest installation (I think) is the metal & glass cleanable type of filter spliced into the plastic line that runs from the pump to carbs, placing the filter just to the right of where the fuel line is clipped to the hoisting bracket. The filter nipples are (assuming the same part) sized so that a rubber hose that fits the nipple also fits the nylon fuel pipe so it looked quite neat.

I’m not sure if I have an example in the cars I have now, but I’ll have a look.

Yours
Vern

Screenshot 2024-01-01 at 1.33.43 PM.png
 
On the other hand, now that the sediment is gone & you have a plan to avoid future build up, why bother?

That’s basically why I’m not sure I have a example to show you, lol.

Yours
Vern
 
My experience with replacing the reserve O ring was disappointing. With the gearbox out I could get to the little bolt trapping the wire to the lever - it promptly broke off, leaving the wire trapped. I had to cut something off to get the lever and barrel out so I could change the Oring. I then had to replace the wire from the knob - bicycle brake wire does the job nicely. Having taken the knob and wire right out, on refitting it I found the adjustment of how far to thread knob on to the rod the goes into the cable casing critical - if threaded too far you dont get full travel of the valve - the lever needs to move 90 degrees, so its easy to check the travel. I also had trouble getting the retaining screw to engage in the groove in the barrel, but managed in the end.
Separately I have just fitted a diposable fuel filter (cos I had one) to the inlet to the electric pump on the inner guard.
 
You must log in or register to reply here.
Back
Top