fuel pump

sibbat2 · 10th November 2006, 10:00 AM

I have CAV gt40 (number 51). A few days ago I noticed that no fuel was being drawn from the right fuel tank. On both "ON" positions of the fuel tank toggle switch on the dash, I can only hear the left fuel pump working. I have put in a new toggle switch resulting in the same symptoms.
Can anyone help?. Is it a faulty right fuel pump or an electrical problem?. It is odd that the left fuel pump should work on both "ON" switch positions.

Pat · 10th November 2006, 11:16 AM

Something may be wired incorrectly. The pump switch has three positions for off-left-right pumps. One pump should only be on in one switch position.

You may want to pull the leads on the right pump and see if any of the positions send power to it. Compare the color of the lead to the schmatic in the handbook and see if the right pump is wired to the switch. If they don't match my money would be that you don't have the right pump wired to the switch and have the left pump wired to either a two position switch or both hot leads to the left pump.

Hope that helps.

Jim Cowden · 12th November 2006, 02:21 AM

The 3 term switch should have power to the centre term.
Power will go to other term when you move the switch to L or R/H pump.

Use a test lamp at the switch first and see if it is doing that.
If it is go to each pump with the test lamp , it will light if switched to that side.
If it lights check the earth by putting the test lamp earth clip to the pump earth it should light when you probe its power again.
If it doesnt it is the earth.

If you have power and earth its the pump.
If you dont have power start looking.

jim

CliffBeer · 12th November 2006, 06:33 AM

sibbat2, there's a good wiring diagram in your CAV owner's manual - it's a pretty simple layout.

You should only have one pump running at a time obviously. So, there's definitely some wiring issue(s) at work here.

I belive on the CAV fuel pump switch the hot lead is at the top with position 1 (left tank) next down (center) and then position 2 (right tank) at the bottom. Make sure you don't have a hot lead going to both pumps at the same time at the switch end then go to the pump end and see what leads are hot (note the color and xref to the wiring diagram).

I think you'll be able to track this one down w/o too much trouble. Good luck!

sibbat2 · 12th November 2006, 06:18 PM

Thanks for your very useful input. Will look into it tommorow and let you know of the outcome.

Ian Clark · 13th November 2006, 11:42 PM

Hi Pal,

That's a mystery if the problem just developed. Check to see if the pumps get power as the switch would indicate and resolve that one first if a problem. If the pump has power and makes no sound it's most likely the pump.

If it gets going and still nothing comes out, try filling the tank on that side of the car. Sometimes the pumps have a hard time priming from a low fuel level. There's also the possibility the fuel pickup has gone up the side of the tank so it won't pickup from the bottom.

That's the basics, you could also swap the pumps side to side to be sure it's a pump problem. Give me a call if you're still stuck from overseas 905 637 9362.

Cheers

sibbat2 · 27th November 2006, 08:23 PM

After carrying out the suggested investigations, it seems that the fuel pump
is faulty. I am thinking of replacing both facet pumps. What other pumps are the CAV's in the USA using which would be suitable with a holley 750?.

Ian Clark · 11th December 2006, 02:46 PM

Hi Sibbat,

Off the top of my head I can't advise on specific fuel pumps for a Holley 750 however any high volume low pressure 5>6lbs pump should work fine.

Something else just came to mind about your problem, bit of a long shot but worth looking at... Have you checked the one way valves on the firewall to be sure ones not backwards? Happened to us once and caused cross feeding on one side and no fuel flow on the other, took a while to find that one

PS: We have new original Faucet Pumps in stock. It will bolt right up.

Cheers