Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

OK so POS LS-t EG is kicking my ass. Prob In boost fuel drops off and A/F's go into 15'sish before i can let off. So far ive replace, fuel filter, FPR,walbro pump, re-wired pump to alt voltage and double checked voltage at pump. Their has too be some kind of restriction in the fuel system but i cant figure it out any ideas?

Setup is a LS-t, 35e, Fatty delta cams, skunk 2 valve springs, walbro 255, deka 550's, 22psi+110 :8


Oh yeah and its snapped 2 timing belts and bent 4intake valves in the last week :X

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Put a toggle switch on all 4 ground wires going from injector to ECU.
Put vise grips on return line.

Go WOT and flip toggle switch. Guaranteed to rip. O0

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

ill try that hopefully this t-belt last more then 15mins :-X

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Bump for sweet ride. Im out of idea's.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

I think stock exhaust and exhaust manifold is going to fix this problem :-\

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

:3

Can you watch it on a gauge drop in boost or are you assuming its dropping?You try putting some air through the feed line to make sure it is not clogged?Check the strainer in the tank?

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Yeah fuel pressure gauge taped too the windsheild, drops around 20psi before i let off. When i replaced the Fuel pump/filter i blew the line out. The new walbro dosent have a strainer, but the first one did and was new. theirs plenty of gas 5 gallons or so :-\.

i need too take the head back off too replace the bent valves from the 2nd broken timming belt :3

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

walbros have been known to be dodgy. if your 550cc injectors are wide open, then the pump has to push 2.2l of fuel per minute at boost + base fuel pressure. thats quite a bit. what size are the stock lines fwd and back? what sort of fpr do you have? is it properly referenced to the manifold? hmmm

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

You aren't using one of those lame ass B&M style FPR's are you?

Those things are crap.


If you are, I'll post why later.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Also, is this a High Pressure walbro or the regular one?

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

just a regular walbro 255 and its a AEM FPR i also replaced it with a stock on that didnt make a diff.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

---- IT its fixed=NO Boost :-\

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

did you check the banjo fitting on the end of the fuel rail and make sure it has the right washer in it, or has a hole drilled in the rail... if not just drill a hold in it so the gas can flow.. i've had that happen 3 or 4 times.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Yep has correct washer/holes in the rail. The car just started doing this after i put 550's in, it was fine with 450's :l

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

walbro

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

eh i dont think so the first one was new, and the 2nd one worked fine in my buddys car

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

That is it you give up :3

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

did you try re-intsalling the 450's?

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

nope i sold them before i knew of this problem :-[ I dont see how injectors would make fuel pressure drop off in boost but who knows :-\

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

The current injectors might not be 550's.

Seen it before. If the injector scaling is way off, you can tell.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Thats true but odder stuff has happened ya know.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

their 550's with the part #on the injector. Even if they were stock injectors the fuel pressure souldnt drop

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

no, but as the revs climbed, at some stage they'd max out and you'd go lean. i think thats what hes getting at.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

You got it Fred.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

do you have some logs of duty cycle?

what ecu is this?

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

yeah it would go lean but the fuel pressure wouldnt drop. It was a P06 with 450's maxed out. :1

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Just a thought, some guys where having trouble with the sock on the pump. maybe yours has started?

1, fix the head.
2, put a flow meter on the pump or run the pump and measure what it puts out. This will eliminate the pump for flow problems. like the other guy said 2.2l+ min? search for it.
3, if the pump is good, he only other thing that can be the problem is the return system or fpr

If the injector was leaking it wouldnt go lean, so the only other place for fuel to go is back to the tank or out a line.

pump, return system, or maxing the fuel system enuff that it cant supply enuff flow to create preasure.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

it cant be the return line. if that was blocked you would get too much pressure.

it can be the pump, the reg, the feed line, or insufficient supply.

you did say that its not the HP version. you are trying to boost. boost + base + restrictions is what the pump sees. that could be like 90psi or so.

if you have an adjustable reg, pull the return hose off, feed it into a bucket, turn on the system, watch the flow, turn up the pressure, if you see it visibly decrease, then the pump sucks. otherwise its because as the flow through the reg drops off as the injectors open, it isnt restricting flow back to the tank enough.

fred.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

where are you measuring pressure? my friend had a problem with fuel pressure for quite a while, and he almost sold the car because of it. turned out it was the fuel dampener on the end of the fuel rail that was bad and was causeing his pressure to drop off at the rail in boost. it would drive just fine NA, but when you started to make boost, it would lean out. his also was fine when he had 450s and a stock pump, but started acting up when he dropped in his 680s and walbro. its super simple to change, and you can pick up 4 or 5 at the junkyard.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

i dunno about honda dampers, but the mazda ones are just a sprung mini accumulator with a path for the fuel to flow through. i assume the others would be similar. other than blockage, i cant see how they could mess up.

Re: Fuel pressure drops off in boost. :::::::::::::HELP::::::::::::
 

Honda's are basically the same design.
My bet's on the Walbro, mine did the same thing to me in my hatch (although I had an HP pump which made it even worse). A local guy had the same issue though with the standard walbro pump, and the only way I could get the fuel pressure to steady out was to raise base pressure up to around 50psi, then it would sit at 50 and bounce up just a hair in boost. What happens is there's too much pressure from the fuel pushing against the fpr spring, and it ends up pushing the spring open more and thus lowers the fuel pressure.