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DB18 Petrol Tank Sender

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Hedgie
Posts: 31
Joined: Tue Aug 16, 2016 8:33 pm
Location: Streatley, Berkshire, UK

DB18 Petrol Tank Sender

Post by Hedgie » Tue Mar 12, 2019 4:43 pm

I have a 1950 DB18 DHC very near the end of its restoration (see photo). Chassis Number: 56049. Engine Number: 42200

We are onto the "snagging" and have found that the Petrol Tank Sender (top mounted) is caput (see 2nd photo).

Can anyone tell me the make and model of the Petrol Tank Senders fitted to the later DB18's and where (if anywhere) it is possible to get a replacement?
My fuel Gauge is made by AC.

Many thanks

Hedgie
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Salmons
Posts: 357
Joined: Thu Feb 11, 2016 7:56 am

Re: DB18 Petrol Tank Sender

Post by Salmons » Tue Mar 12, 2019 5:33 pm

I think David Beales can supply new or rebuilt Units
Salmons

terryfrombury
Posts: 152
Joined: Fri Feb 12, 2016 10:25 pm
Location: Cheshire, UK

Re: DB18 Petrol Tank Sender

Post by terryfrombury » Wed Mar 13, 2019 11:16 am

He can indeed supply rebuilt units.

Sydsmith
Posts: 746
Joined: Sun Feb 14, 2016 11:15 pm
Location: Aberystwyth Wales

Re: DB18 Petrol Tank Sender

Post by Sydsmith » Wed Mar 13, 2019 12:06 pm

Hedgie, before you rush off and buy a new sender are you certain it is duff.

Fuel gauges are a strange animal,they work back to front to what we logically would think.

12 volts is applied to the fuel gauge on the panel and wire from the gauge runs to the sender. That wire carries 12 volts and you should be able to measure that at the red wire on your sender, if you earth that 12 volt feed at the tank end the gauge should read full, if it does not your fault is in the connection from the gauge to the tank sender and not the sender. Which also suggests that if the tank sender on the other wire is not properly earthed the sender cannot work.

So the test is check for 12 volts at the sender red wire, if it is there earth it and check the gauge reads full or near enough, if it does check the sender is earthed correctly, if all that checks out, you are quite right the sender is probably duff.

I should say, don't rely on the black wire in your picture for an earth, find a good earth (not the tank) to measure and check from, the black wire may be your problem as it may have become unearthed at the other end.

Sorry if I am teaching granny to suck eggs but I have come across this so many times and invariably the sender if fine. Syd

Johnsson
Posts: 54
Joined: Fri Feb 12, 2016 11:23 pm
Location: Brisbane, Australia

Re: DB18 Petrol Tank Sender

Post by Johnsson » Wed Mar 20, 2019 12:42 am

If you do the above electrical checks and they show the gauge is working then the float arm is probably seized due to rust.

Trevor

qantasqf1
Posts: 109
Joined: Mon Mar 07, 2016 10:13 pm

Re: DB18 Petrol Tank Sender

Post by qantasqf1 » Wed Mar 20, 2019 3:18 am

Hedgie wrote:
Tue Mar 12, 2019 4:43 pm
FWIW I completely agree with these comments. Since the sender will probably be removed in any event (brass screws, so they won’t shear off) why not connect the active wire to it after removal and, ensuring a good connection, connect the housing to earth using a jumper wire and operate the float arm. (Good advice about a possibly seized float gear, by the way, and it’s simple to free up if it is.) If the petrol gauge follows the movement of the float then all is OK.
These units can actually be stripped. The upper and lower halves are held together by 3 hollow brass rivets equally spaced at the location of 3 of the brass retaining screws and they can be removed - carefully! The top of the unit will come away from the lower half exposing the resistance coil in the upper half and the and wiper arm in the lower, so it’s easy to clean. I admit that’s desperation tactics, but I can (modestly) claim to have done it. Mind you, althought mine passed resistance tests on the bench I haven’t actually tried it out yet!
Steve

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Hedgie
Posts: 31
Joined: Tue Aug 16, 2016 8:33 pm
Location: Streatley, Berkshire, UK

Re: DB18 Petrol Tank Sender

Post by Hedgie » Wed Mar 27, 2019 8:58 am

Just returned from holiday.

Thanks everyone for your replies and suggestions.

We knew it was the Petrol Tank Sender which was at fault because we had previously tested the Fuel Gauge.

Having replaced the Sender that sub-system is now working correctly, and with other de-snagging having been completed, the car will take its first trip on Her Majesty's Highways for 40 years next week (hopefully !!).

Best regards
Tony

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