[urq] Better fuel pump needed

[Cody Forbes]

I'd also like to point out that the pre-filter could be part of the problem. 
The supply to the pump is gravity. Our pumps are positive displacement, 
meaning they don't suck fuel in at all, they only pump fuel that has been 
delivered there by gravity. With no suction I would say a pre-filter could 
impede that gravity flow by a HUGE ammount when some real volume is 
demanded.

This would explain the failures. The pump starves for fuel when it's needed 
most, causing the pump to loose its cooling and it's lubrication. Ever taken 
one apart? It's got 4 tiny rollers inside. See this 
image:http://www.subscribermail.com/images/111/extcontent/266_689ccd9.jpg 
and exchange the 4 rectangles for rollers like in a needle bearing. If these 
loose the lubrication of the fuel even for an instant they will get very hot 
(high RPM's in the pump) and score the housing and themselves. This would 
compound with each successive instance, and reduce the pumps efficiency and 
throughput.


If a pre-filter is highly desired to protect the new pump I highly suggest a 
pre-pump before the filter, but now you've got 2 pumps so cost goes back up, 
not to mention twice the potential for failure. The pre-pump wouldn't have 
to be anything special, a low pressure (cabrurettor, read: availible 
anywhere and cheap) pump with decent volume specs would do fine.

-Cody Forbes
http://www.5000tq.com
'87 5ktq - Fast.
'86 5ktqCD
'86 5k
'86 5k