Fuel starvation issues!!

[kayarubin]

fuel pumps??

hey im just wondering if this is a fuel delivery problem:

my car starts cutting in and out when i plant my foot....it has a surge tank and one of those clicky fuel pumps that feeds the fuel into the surge tank and a bosch VL turbo fuel pump sucking it out of the surge tank....

the bosch pump is in front of the surge tank and about 5-8 cm above its feed line so im thinking that the clicky fuel pump isnt delivering enough to keep the tank full and when on boost its actually pushing the fuel to the back of the tank and not feeding into the bosch pump.....which is making the system lose pressure and it cuts out!

should i get a different pump for the pick up do you think? or should i run the clicky pump off the accessories power instead of the ECU power thats running both right now??

i have a pic of the setup here:

 

[tharaka]

no
with a surge tank, you're meant to be able to run even a stock lifter pump

 

[kayarubin]

so what do you think it is??

i have the timing set at 10 degrees BTDC and im using 98 octane with octane booster....but heres the thing.....im not running the knock sensor...but theres no noticable knock....

it only happens at mid revs but not under about 3-4 grand...

cheers guys!

 

[tharaka]

could be the complete opposite - running rich

 

[kayarubin]

it is exactly the same thing that happens when a car has very very little fuel in the tank and you go around a corner while accellerating.....it sorta cuts out until the pick up tube gets back into the fuel supply... :?

 

[rob323]

That clicky type of pump you refer to, if that is a high flow, low pressure facet type that they use on carbied cars, then most of them need to be mounted below the level of the fuel pick up, they don't like to suck fuel up against gravity and if they get a little sip of air instead of fuel, most of them will not self prime.

Where have you mounted your lift pump?

 

[kayarubin]

its a facet type one used on carbie cars and its mounted next to the efi pump....you can just see the corner of it behind the surge tank....

do you think its cutting/leaning out because of the efi pump isnt gettin enuff fuel??

cheers!

 

[rob323]

either the efi pump is using more fuel than the facet pump can keep up with or if its only happening when the fuel level is getting low, then maybe the pickup in the tank is sucking air (is the tank baffled?) and it takes a while for the facet pump to prime itself.

If you remove the fuel line from the tank to the facet pump, does fuel flow out due to gravity?

 

[kayarubin]

no fuel doesnt flow out of the line when i take it off...but the fuel filter holds a bit in it....see pic....

could i run 2 pumps in series on the same line?? would that boot up the pressure and flow at all?

cheers!

 

[rob323]

Was the car originally fuel injected or carburetted?

One thing you can try is just bypass the facet pump and the catch can and see if it still does it, or, do you have a fuel pump suitable for efi that you can put in place of the facet pump?

 

[kayarubin]

the car was Carbied to begin with...

i do have another facet pump handy herewould it be wise to put that closer to the bottom of the tank and put it on the "on" position of the ignition....in other words...let that pump prime the other pump and in turn have more pressure and more fuel??

it will be kinda hard to bypass the facet and surge tank coz the line going to the efi pump is quite a big deal larger than the one going to the facet pump....

the car doesnt have a knock sensor either...do u think it could be cutting it out coz it hasnt got one?? (brand spanker is coming very soon from the states)

but yeah....does this do any damage to my engine when it cuts out?? is it the same as it leaning out or what?

 

[kayarubin]

oh and the spark plugs are sorta light oxidisation coloured :S

both the electrode and the ceramic lip are that colour??

white means running lean eh?

cheers!

 

[rob323]

What ecu are you using? Does it look to the knock sensor for info? If so and you do not have one fitted, it could be cracking the ***** because of this.

Yes, running out of fuel when on boost is dangerous as it run lean.

I do not like facet pumps at the moment as they have been causing me and a mate some grief of late on his rally car. He has had one in there for 3 years with no problems and has gone through 3 of them in the last month.

I guess, if you add another facet pump and it fixes the problem, at least you at least know where the problem is.

I know its a silly question, but is the facet pump actually working? Is there fuel going out from the return line back into the tank?

 

[kayarubin]

yeah the facet pump is working....u can see the fuel being sucked thru the filter so yeah its all good there!

my previous question still stands....what does it mean when ur plugs are a brown colour??

cheers!

 

[kayarubin]

the ECU is a jap spec VR4 RS one by the way!

cheers!

 

[Entaran]

It means replace them, they should be silver or black (rich) or white (lean).

Anything else is very very bad.

 

[kayarubin]

i only replaced them not even 100 km's ago!

what does it mean when theyre brown?? :?

 

[kayarubin]

well! i read up about plugs and it says that my plugs colour is fine...light brown in colour this means that the engine is running perfectly (not rich and not lean)

heres the link:

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Mine looks most like 14 and 16!

so yer! sounds about right to me!

cheers!

 

[kayarubin]

hey!

my fuelling issues are resolved!!

it turned out that i had to run the return hose to the surge tank and not back to the fuel tank!

it runs real smooth now and revs above 3 grand without spluttering!

YAY!!!

thanks for your help guys!

cheers! kaya rubin.

 

[rob323]

that would seem to point to the facet pump not being able to keep up then.