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positive earth question.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4273
Location: South Cheshire

PostPosted: Sun Dec 14, 2025 8:34 am    Post subject: Reply with quote

Is the pump getting power or is there zero output from the timer?
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alastairq



Joined: 14 Oct 2016
Posts: 2135
Location: East Yorkshire

PostPosted: Sun Dec 14, 2025 2:23 pm    Post subject: Reply with quote

Ray White wrote:
alastairq wrote:
Is the pump insulated from the vehicle's ground? IE, is it completely insulated from the chassis, not touching any part of the vehicle with the pump body?


I'd be removing the pump itself, then seeing if it works away from the car, with those wires reversed?
In other words, it's possible the pump body and bracket are earthed to the pump, as it comes?


I have mounted the pump exactly as per the instructions. There are four securing screws holding rubber mounts to the chassis. Perhaps they could short the motor if it was not insulated ...but I would be surprised if it wasn't...and I expect Car Builder Solutions would have had complaints if the kit was no good.


But, don't the instructions [and maker's intentions?] presume negative earth?

Thus there may be no need, in their eyes, to insulate the entire pump [and additional manufacturing expenses?]...from the vehicle?

That was my thinking....
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Ray White



Joined: 02 Dec 2014
Posts: 7229
Location: Derby

PostPosted: Sun Dec 14, 2025 3:17 pm    Post subject: Reply with quote

I am utterly confused.

I have mounted the pump assuming it was insulated. There are two wires coming from it; a red and a black. As suggested, I have swapped these over on the relay. Now the red wire goes to 5 and the black goes to 2. The red is also connected to the new red ignition switched wire via a double connector after the 10amp fuse.

The switch body is earthed (black) via the chassis as per instructions and another black wire from the switch connector goes to 3 on the relay. No.1 goes to earth. (There is no No.4)

Switched on and the Ignition warning and oil pressure lights have gone out.

I just can't do this anymore.
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alastairq



Joined: 14 Oct 2016
Posts: 2135
Location: East Yorkshire

PostPosted: Sun Dec 14, 2025 6:14 pm    Post subject: Reply with quote

Like I said, there may be an assumption that applications will be negative earth.

Try lifting the actual body[of the pump] clear of its chassis connecting bolts....to remove the chance the pump is not insulated from its base. Therefore not in contact with the car's structure, which will be positive [earth]!
Then just make some temporary connections to the pump leads, as ukdave has suggested?
Just to see if the pump runs?

If it does, without creating other issues, then the solution would be, to mount the pump fully insulated from the car's structure, wiring as above???
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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