[DML] Fuel tank baffle

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

Hi All,

With all this talk about pumps and fuel tank stuff, I just wanted to 
share my experiences of the fuel tank baffle. In my opinion, a properly 
working original baffle and pickup setup is vastly superior to John's 
setup (sorry, John)

The original setup is awkward to assemble and prone to the pickup hose 
collapsing due to particles clogging the pickup filter, and the original 
soft rubber the pickup hose was made from.  I believe the particles 
mostly come from a rusty filler neck and/or from a tank that has been 
left to sit. Many DeLoreans have been left to stand with fuel in their 
tanks for some years. Tar-like deposits build up, and when they break 
down again, having been soaked in fresh fuel, the pickup filter can clog 
- sometimes months after the car has been put back on the road.

The fuel pump makes a groaning noise when the fuel is cavitating in the 
suction side of the pump - in other words, boiling. It condenses back to 
a liquid very quickly after being compressed by the pump, but it's not 
good for the pump and suggests either a kinked hose, a collapsing hose 
(if original) or a blocked pickup filter. These problems get worse when 
the fuel is hot, but it's not the pump that's at fault.

DMC Texas has inexpensively remanufactured the pickup hose in a stiffer 
rubber for some time now and as long as the tank is CLEAN, and the 
baffle assembled correctly with a clean filter, and the return line 
correctly returning to the baffle, this will work better than any other 
baffle setup. It is designed to live in the middle of the tank for very 
good reason, and this is principally why it's a bit of a sod to assemble.

The baffle is essentially a "cup" that sits in the centre of the tank, 
and has a few small holes to let fuel in SLOWLY.  The engine uses fuel 
at a fraction of the rate that the pump moves it. What it doesn't use, 
gets sent back to the tank, and should drop straight back into the 
baffle. So the flow into the baffle from the rest of the tank should be 
restricted to a small amount. Simply mounting a ring shape to the bottom 
of the tank isn't good enough, as DMC themselves discovered and issued a 
service update to add a base to the original baffle. This means that 
under cornering, braking and accelleration, the baffle acts as a 
"buffer" and allows the fuel to get much lower before causing a problem. 
It should be obvious that this ideally wants to be in the centre of the 
tank.

I had a customer on the phone once swearing that his automatic 
transmission was causing his car to cut out. He could reverse it out of 
his garage, but as soon as he put it in drive, the car would stall.

I scratched my head for a bit and then it occurred to me to ask if he 
had one of John's baffle kits... I then told him to go and put more fuel 
in his car, and consider reverting back to the original setup which 
allows the tank to get lower before you need to fill up.

My advice: Stick to the original design, and the improved parts 
available for it. I'm sure the 909 Bosch pump is available in the US - 
try BMW or Mercedes dealers to start with as it's used as standard on 
most of them.

Martin
www.delorean.co.uk






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