Temp and fuel gauge annoyance

[80s-new-man]

I’ve a new fuel gauge in 2020 that never seemed right on the gauge, reading far too high.
On a recent long journey to beaulieu I noticed the fuel needle went up then down then up again in constant straight traffic. Weird.

I’ve changed the temp sensor a few times now. I’m sick of it always reading so low it hardly gets off the bottom.
I measured voltage at loom and at sensor to block when hot. 4.6 volts at all locations.
I’ve swapped temp sensor again and yes I’ve tried white ringed and a new one from car parts in motion, which they say is a 2.8 version . I’m tired of keep changing them.

I’m just wondering - are these symptoms of fuel and temp behaviours the result of a possible faulty voltage regulator?
If so, can they still be bought?

Help most appreciated!
Cheers

[Mc Tool]

I would be lookin at the reg . I think they are supposed to regulate instrument voltage to a bit over 5v. Dunno if you can still get them new but a 5v dc reg is not that hard to come by .

[nemo]

You need to check the voltage on the lead when it`s disconnected from the sender (temp), If that`s showing about 5v the regulator`s probably OK, it may well be that the connections to the regulator on the PCB need cleaning? Making & breaking due to vibrations while moving?

[80s-new-man]

Ok thanks.. I have just dismantled the dash, soldered on a Capri club replacement voltage regulator and same. Took spade connectors off and on sender, seemed ok, but sometimes no reading at all. Put back in seems ok but just reads full but off the scale. It’s always done that.
I don’t think much of the clubs sender units, having had my mechanic repair the last one as it leaked at the connection points. But I think the readings got worse over the last 3 years. Especially the erratic ones.
The temp annoys me. I will buy yet another white collared version then and see what happens.
Gutted to have taken the dash apart and put it back together only to shear off one of the trims.
If anyone has a spare 2.8 lower dash trim right hand side that goes over the ignition and bonnet latch I would be grateful.
I really appreciate any other causes it could be!

Cheers!

[nemo]

Sorry that hasn`t solved your problem...

Put back in seems ok but just reads full but off the scale. It’s always done that.

That does sound to be almost certainly the sender unit shorting internally, maybe intermittently?
I wouldn`t buy another temp sender, it`s unlikely they`re all faulty. If you have a multimeter, check the resistance at room temperature, then put it in a pan of boiling water and check the resistance dropping as it heats up. (I got ≈32Ω at 84`c for a known working example)
Just to re-check, if you take the lead off the temp sender, what V do you get between the lead and the block? If that`s 5v, ± 5%, and the resistance of the sender with the engine hot is round 30Ω, then it really looks like the gauge itself?

[D366Y]

You mentioned your sheared off the dash trim - which bit do you mean? Just wondering if you had loosened the steering column slightly to let it drop when you are removing/refitting the dash? Gives some extra wiggle room

[Caprigear]

Ok thanks.. I have just dismantled the dash, soldered on a Capri club replacement voltage regulator and same. Took spade connectors off and on sender, seemed ok, but sometimes no reading at all. Put back in seems ok but just reads full but off the scale. It’s always done that.
I don’t think much of the clubs sender units, having had my mechanic repair the last one as it leaked at the connection points. But I think the readings got worse over the last 3 years. Especially the erratic ones.
The temp annoys me. I will buy yet another white collared version then and see what happens.
Gutted to have taken the dash apart and put it back together only to shear off one of the trims.
If anyone has a spare 2.8 lower dash trim right hand side that goes over the ignition and bonnet latch I would be grateful.
I really appreciate any other causes it could be!

Cheers!

I have a later 2.8i dash trim piece, the one with the extra hole for the speaker fader unit.. As for the fuel sender, try replacing the wiring and connectors to the unit itself, making sure that you connect it up properly, if not then the gauge will go right off the scale. I tend to trim off the last 2-3 feet of the wiring to the gauge and replace with new. The white ring temp sender is correct.

[80s-new-man]

cheers for sharing the advice gents.
I replaced the wire , last 2’ of it , 4.6v from loom wire to earth. I’ll try and do the other tests.
Martin, please can you reserve that dash piece, thank you.
If you can let me know how much you want I can PayPal you.
Cheers!

[Caprigear]

OK
I've just sent you a pm.

[80s-new-man]

Hi Martin, excellent thank you! All sorted D

[80s-new-man]

Quick question- the pipe from rad to expansion tank always spews out water at the rad outlet connection. No matter what I do, replace clips, new pipe… could it be the tank is somehow pressured because the expansion tank’s outlet itself is blocked? I can see the expansion tank outlet hose runs into what I presume is a thermostat fitting? It seems to have the temp sensor into it and the coolant sensor below it.
If this is gunged up or stuck/broken? Would that affect both the spewing water and the temp sensor?
Help most appreciated!

[Caprigear]

Quick question- the pipe from rad to expansion tank always spews out water at the rad outlet connection. No matter what I do, replace clips, new pipe… could it be the tank is somehow pressured because the expansion tank’s outlet itself is blocked? I can see the expansion tank outlet hose runs into what I presume is a thermostat fitting? It seems to have the temp sensor into it and the coolant sensor below it.
If this is gunged up or stuck/broken? Would that affect both the spewing water and the temp sensor?
Help most appreciated!

Check the two outlets from the expansion tank, they both have metal liners inside the pipe and are sods for getting blocked, I usually just run a small drill bit by hand to clean them out. Also, the casting on the plenum chamber where the small hose from the expansion tank goes is also a prime candidate for blocking. On the same casting , at the bottom is a larger outlet, this goes to the heater matrix and again, is prone to blocking. Lastly, the casting with the temp sender and the thermotime switch has a vertical pipe coming out of it, take off the rubber hose and make sure that the metal pipe isn't blocked.

[80s-new-man]

Okay.. fuel gauge- new from CC in 2020. (Repaired by my mechanic as it leaked at a Seam). Cleaned contacts. Stripped off old spade connectors and stripped the wires and put on new ones. Same. It’s reading higher than it should.

Martin - (and others!) as ever extremely helpful, before I did those checks I took off the hose from expansion tank end (the one that goes to the engine. ) I fired her up - coolant gushed from it.
So I guess no blockage on that hose…? so coolant pumps round the engine from there and into the expansion tank higher inlet?
The slightly lower opening on the tank has the hose that leads to the rad cap end on mine.
Have I got these the right way around? (She has the BOB engine)

I’ll double check again for blockages but - I’m even more uncertain about why I’m getting coolant wanting to spurt out of the hose end to the rad. I’m guessing the rad is full anyway. If the rad fills up, does it go out of the rad end down the hose into the expansion tank? However I cannot see hardly any coolant left in the expansion tank.

The 2 pics (with engine now off) are both ends of the hose that goes from expansion tank to engine) then another one that shows the effect of the joint there on the rad ( pressurised water wants to spurt out of the pipe) when hot.
I guess though that this isn’t anything to do with the temp sensor not registering hardly anything.

[Caprigear]

Can't really tell in you picture but make sure that the rad cap is just a plain cap, not a pressure cap. The pressure cap needs to be on the expansion tank.

[80s-new-man]

Ok cheers!

[80s-new-man]

I took apart the wiring. (I’d already replaced the regulator with a club one) Cleaned it up. Installed a new sensor (white collar). Re checked voltage. 5.01…ran up to temp and luckily was all fine. Touch wood, after dismantling the hoses and cleaning in and outlets with a bottle brush, she didn’t bubble out of the rad pipe orifice.
Fuel gauge I’ll see how it goes.
All in all, that’s 3 temp gauges in 3 years. One from the club. The re made parts are crap IMHO, and temp gauge isn’t easy to get in and out without rounding the head.