Fuel starvation

Coming up a steep hill this weekend my BJ8 started to falter and backfire. Returning to level ground everything returned to normal. I'm guessing the fuel level must have got so low it ran to the back of the tank whilst coming up the hill. I hadn't realised the tank was so low as the gauge is very erratic/unreliable. First time for this to happen so maybe the sender is broken.

I have an after market aluminium fuel tank and the take off is on the side of the tank at the front and at the top rather than the bottom so there must be a pipe inside that runs from top to the bottom of the tank. Also, I don't think that there can be any/many baffles in the tank because when the tank is less that half full you can here the fuel splashing around when you go around sharp corners.

The gauge is relatively new so I'll start with testing the sender. I can't think how I could test the sender in situ so I guess I'm going to have to take it out and replace it if necessary. Then I think I'm going to try Dan Hardies fix of fitting a 1 farad capacitor across the sender terminals so I'd be grateful to know if anyone has any experience of how effective this fix is and if it gives a more reliable indication of how much fuel is in the tank.

Thanks
AJ

Hey AJ
Yep, there is a pipe inside but it is all at the 'front' of the tank so on a really steep hill and really low on fuel it would seem to be empty.

I had a home made Ali tank and there was at least one baffle in there but you could still hear the fuel splashing about on occasions.

Some one has posted a test on the sender some time ago - it was in a glass tank if I recall and wired up to a battery and a fuel gauge, you may be able to search for it.

Alternatively you could try using a stick, marking the position of the bottom of the tank and also the top of the tank and all points then in between and relate that to the sender. You could also remove the sender and check that the float is not leaking. Funnily enough my old float rocked about a bit, according to the gauge, and it is to be expected, when the juice was splashing about in the tank but it was quite reliable, further more the arm had been cobbled up for some reason. I am in the middle of replacing the boot floor and have a new tank and sender in the garage waiting to be installed so I will be have some fun and games then myself.



Bob

It could also be that fuel flow is restricted by debris in the tank and/or a partial clogging of the little filter built into your SU fuel pump--or perhaps there is an aftermarket inline filter somewhere in your supply line that needs cleaning.

AJ - also make sure your sender arm points forward. If toward the back, it'll stop reading at 1/4 tank and you may run out of gas while still showing 1/4 tank on the gauge.

Pull the sender out of the tank, leave the wire on it, and using another wire with alligator clips
ground the body of the sender. Turn on the key and move the sending unit lever slowly up and
down. Have a friend watch the gauge. It should go from empty to full as the lever is moved.

In any case stick for fuel level, many times float on sender arm will go bad leak removal is the the only fix. Steep hills are only a problem when long and fuel pump can not keep up with more gas peddle. If the the hill is not near run in lower gear at high RPM and see if RPM goes flat it should only take a mile. My TR 6 went flat RPM at about 95 MPH long straight road carb adj. was needed. Madflyer

Thanks guys, I'm going to take it out to test it with an ohm meter but made the stupid mistake of filling the tank up so I need to wait a while for the level to go down.
I have Petronix fitted and am a bit paranoid about leaving the ignition on for too long but thinking about it perhaps I could protect the Petronix by taking the dizzy cap of first, not sure about that.
I ordered a capacitor to fit across the terminals. I'll let you know what I find out and whether the capacitor makes any difference to the gauge fluctuation.

AJ

Pertronix switches primary current 'upstream' of the coil, whereas points switch 'downstream.' When I need to have my cars' ignition in the 'run' position for some reason, I disconnect either of the primary wires to the coil. Current can't flow through the Pertronix, even if it's in the forward-biased (current passing) state if the circuit is open. Taking the distributor cap off won't work, since current would still flow through the coil.