Loss of Fuel Volume During Run

Hi,
At the Gatornationals this year, we took at a burst panel, and upon closer inspection....expensive engine damage.

We discovered (on the computer) that 2 seconds into the run we lost 3 gallons of flow at the flow meter, engine went very lean at the gear change.....and boom.

We think we know what caused it, but I would like to hear what some of you have experienced....I want to try and avoid a repeat.

What do you think??

Thanks!!
ML

 

what are to look at?

 

Fuel flow was following engine RPM, at 2 seconds the flow dropped 3 GPM. leveled out for the most part......

We think the fuel shut off vibrated, and closed part of the way.

We also flowed the pump, same numbers as last time we flowed it.

Just want to make sure there is nothing else going on.

 

You don't tape the shut off open? So that can't happen?

 

The shut-off and cable/lever is tight....has never been a problem....til now.
I now have an over center spring, and I will use tape too.
Are there any other things I should check?

 

check if your vent on the fueltank is big enough/open.

 

Also check your tank to fuel pump feed line with any hoses for possible collapse from a kink in the line, engine mounting shift from loading causing a kink, or an internal blader separation.

If there are any hoses in the connection and they are old, you may want to put a new one on or mount a large ss spring inside to keep it from collapsing. If it is old and collapsing, a leak may be in the near future.

Bob Szabo
bob@racecarbook.com
https://racecarbook.com
https://airdensityonline.com

 

Great....thanks for the ideas!

 

You don't really mention if this is a new car but is your tank vent big enough? A friend of mine had inadequate venting on his fuel car (we discovered) imploded the tank and blew the engine and tank sky high. When the engine quit it sucked the fire into the tank and boom.

Corey

 

I changed the idea on cars I have plumbed so the shut off arm is in the down position --- threw all the needless BS away --- I shake my head when I read this type of thread -- which is at least every 2 months somewhere -----

 

An after thought: we encountered a shut off valve that was scored on the inside. It leaked enough fuel that the engine would not shut off with the valve in the off position. We put air pressure on the fuel shutoff side with the valve in the off position. It was revealing. In your case, to see if it is going in the other direction, you could remove the return line with the engine running to see if there is any fuel leaking through that valve in the open position.

In the garage, you could connect a pressure poppet to the output of the shut off valve. Turn over the fuel pump with a drill motor or spin the engine with fuel in the tank, either way, with the valve in the open position and see if the valve leaks through into the bypass pathway.

Also check for any scoring in the barrel valve. There could be a bypass leak there as well such as through a pump saver or idle return pathway.

We often used a little bit of air pressure on a supply side with some type of pressure load on the output side to reveal if any unwanted leaks existed.

Years ago, I watched a top fuel car loose several motors due to an unwanted fuel pathway from a failed component before it was found.

Bob Szabo
bob@racecarbook.com