[urq] Fuel system diagnostics , failed on the very first test . :)

[Patrick Carlier]

Well , not quite the very first test , but close enough . 

The first test is to measure battery voltage . 
As I charged the battery overnight , it was at 12,80 V . 
Has to be 12,00 at least , according to the book . 
So that one passed . :) 

Then a remote control for the fuel pump is needed . 
That's easy . A length of 2,5mm² wire , to spades on one 
side , a switch on the other et voila ...VAG1348/3A replicated . 
Pull the fuelpump relay , plug the spades  in contacts 
87 and 30 and it should work . It does , sorta . 

Next test is to measure the voltage at the fuel pump terminals . 
I only have tension with the ign switched on . That's not supposed to be ! . 
Terminal 30 on the relay  comes straight from the battery . 
Certainly needs further investigation . 

Anyway , with the ign switched on , I measure 11,7 Volt and 12,65 Battery voltage . 
This already raised an eyebrow , as the meter represents no load . 
So where's the 0,9 volt gone to ? The acceptable limit is 0,5volt drop . 

With the pump wired in and running , voltage drops to 7,60V !  
The pump barely runs and makes a noise like a worn out bearing does .  

If I power the pump directly off the battery , the rpm increases significantly 
and voltage remains steady at 12,60 V . That's the way it should be . 
The sound is now a healthy buzzing like any normal fuel pump does . 

Finally measured the current draw , directly off the battery to the pump . 
That is close to 10Amp . Wich is a bit high , the limit being 8,50A . 
Possably an indication of a clogged filter . 



Conclusion 
I need to cure the electrical problem first , and check the filters . 

This is gonna be fun , the pre filter is most likely 28years old . 
And as usual , it's NLA .  So I'll have to machine something off a
std available filter .


To be continued .... 


Pat