Injectors - What the heck - baffling myself here

I put in new injectors today (DW650 cc ones). I had the DW850s before, but I like a few others here, had some weird issues (that I think are fuel rail related). So I decided to go with DW650s, as that is all I need anyways.

Here is the drill, DW850s tuned fine at low flow, MAF scalar was normal, needed a touch of tweaking, nothing major.

I put in 650s, tune latency a bit, do low end of MAF scale (1.3-2.7 volts, within 2.5%) then I start to do high end. At 3.4 volts, to about 4 volts it is between 11-34% lean? I can't wrap my mind around it.

I logged fuel pump duty cycle, goes up to 100% quite fine.

When I replaced injectors I forgot to open up fuel filler cap. (don't know if that matters much) After pulling fuel pump fuse I started engine and used up all the remaining fuel (this time revving it at 3000+ rpm to try and get it all), then let car sit for a while. First injector I pulled still had a bit of fuel pressure behind it, but nothing major.

After injectors swap, car starts fine, drives fine.

There is no way my MAF scale is off an average of 22%. Could I have wrecked the FPR?

What about the vac hose that feeds the FPR? Check it for hidden cracks / tears.

I checked it, still there. I will check for cracks.

it's usually not a good idea to purposefully rev an engine you know doesn't have proper fueling.

You might have a bad injector. Did you buy new or used?

it's usually not a good idea to purposefully rev an engine you know doesn't have proper fueling.

Who said I did that? the only revving I talked about was before I installed the new injectors.

You might have a bad injector. Did you buy new or used?

New from DW (actually from Fred Beans)

Who said I did that? the only revving I talked about was before I installed the new injectors.

yeah, you pulled the Fuel Pump fuse and then revved the engine till it died. That's not good for it.

check your inlet tube and see if you knocked it off during the install. Check all the hoses and whatnot while you're at it

LBGT, you have an aftermarket fuel pump right? I'm guessing so with the 850cc you had before but just checking. I have red 650cc DW sidefeeds, when I used them with the stock FP around 3v on up it leaned way out. I installed a Walbro and it went the other way, way rich.

What is your latency at 14v? I think I'm at 92.

Aftermarket fuel pump, yes.

It is funny, cause I never ever had troubles with stock injectors, so far the biggest PITA has been bigger injectors.

I think it is the FPR, cause it was working good when I tuned the low end, very predictable, then after the car sat for a while it seemed like tip-in was way off (which it wasn't before), it was leaning out to 17:1 on throttle application, and then it was running very lean at even 2.8 volts, which was essentially tuned before.

It is not in intake boost leak.

The hose is still attached and well to the FPR. Just think, some areas are 30% off. Even 1 injector could quit and it would only be 25% off. I think something got in the system and is jamming the FPR or something like that, it is the only plausible scenario I can come up with.

It is interesting that tip-in was close before, than after an hour or so I went to do the upper region and it would go extremely lean on tip-in. Like something changed in that period of time.

What I know:

-Car did not hold fuel pressure over-night. (it has always done this, and started perfectly even after sitting for a month)

-regular crusiing is fine (so long as no tip-in)

-tip-in is waaay off, not normal tip-in like going from 10% throttle - 40%, but during normal shifting where the engine goes into vacuum then back to less vacuum or slight boost it goes extremely lean (17:1 and bucks a little)

-pressure tested intake, and all is well

All things lead me to believe something got into the system, and is jamming something, the only thing that something could (that I can think of is FPR), and other thoughts?

What are the little plastic things in between each pair of injectors?

Your symptoms are exactly like I used to have. Check my thread from the spring:

http://legacygt.com/forums/showthread.php?t=107219&highlight=maf

I don't know if I still have the problem. Replacing FPR and fuel pumps didn't really change anything. I quit investigating the problem since I had bigger problems (engine was buring oil like hell). Since I had the engine rebuilt I am still breaking in the replacement and haven't went WOT in high loads to see if I have the problem (in meantime I am still trying to figure out the pulsing at constant throttle problem - might be related - and I run stock injectors for now).

The car does not hold the pressure overnight. It starts perfectly but the fuel pressure goes down to 0 in few hours. I asked whether is normal in that thread and didn't get conclusive answer... all I got was:

People know, they just don't want to tell you

I'd suggest putting stock injectors back there to see if the problem goes away.

My problem is different. I pulled the fuel pump fuse, car wouldn't even fire once. No pressure (not talking about overnight either).

I pulled the FPR, and I could easily blow through it (yummy) I am pretty sure it is shot. How is it suppose to hold 43.5 psi if I can blow through it?

The funny thing is it did not do it when I put in the injectors, it did it after about 1 hour of driving, it was obvious something changed.

It won't even really drive right anymore.

 

I pulled the FPR, and I could easily blow through it (yummy) I am pretty sure it is shot. How is it suppose to hold 43.5 psi if I can blow through it?

Which end did you blow through?

Input or output should have little resistance to flow until it sees 43.5 psi on the output side.

The reference port should not be able to suck or blow through at all

Here is the FPR assembly:

http://i248.photobucket.com/albums/gg194/littlebluegt/FPR.jpg

I could blow easily through one side of the FPR (1 in pic) and fairly easily through the other. (not talking about the vacuum/pressure source)

What are the other two things for?

I removed all that from mine.

B and C should be easy to blow through.

A Shouldn't be able to blow through.

The two unlabeled ports should also be easy to blow through

The shaded object is the Fuel Bypass Valve.

These are dampers. Note the assembly consist of FPR and fuel bypass valve. It's quite a different arrangement than on 07+ cars.

That makes sense that they are dampers.

The ports that did not hold my breath power where not labeled in the diagram, they are part of the FPR which is #1 in the pic.

I'd try unhooking the return line at the FPR and routing it to a clear bottle. Prime the fuel system, then swap out for a fresh bottle. If the FPR is leaking, you will be able to see the leakage.

Failing that, get a fuel pressure gauge and an injector tester. All you need to do is prime the fuel system and go from injector to injector with the tester. The idea is that the tester opens each injector for a given amount of time (usually 10-20 mS). You observe the pressure drop after testing each injector. If one is really off, the drop will be less than the others.

These are dampers. Note the assembly consist of FPR and fuel bypass valve. It's quite a different arrangement than on 07+ cars.

Take a look at this pic:

http://i248.photobucket.com/albums/gg194/littlebluegt/FPR-1.jpg

The blue line is where I believe a bolt exists. When I tried to get the FPR off the assembly, it was attached to the fuel damper on the return line.

Is it as simple as unscrewing that bolt to get it off?

Why are they connected anyways?

IIRC there are two bolts that attach FPR to the rest of the assembly. That "4th" outlet (counting fuel in/out and pressure reference inlet) is the fuel bypass actually - i.e. the idea being excess fuel bypasses the fuel rails thus staying cooler (better for emissions) - if I understand it correctly. I may be wrong about this but it seems the bypass has been elimiated on 07+ cars, at least it's gone from the strut tower area.

The whole assembly mystified me quite a bit when I was replacing the FPR. Seems overly complicated.

IIRC there are two bolts that attach FPR to the rest of the assembly. That "4th" outlet (counting fuel in/out and pressure reference inlet) is the fuel bypass actually - i.e. the idea being excess fuel bypasses the fuel rails thus staying cooler (better for emissions) - if I understand it correctly. I may be wrong about this but it seems the bypass has been elimiated on 07+ cars, at least it's gone from the strut tower area.

 

The whole assembly mystified me quite a bit when I was replacing the FPR. Seems overly complicated.

I know those two bolts, but when I took them off it was still attached internally to the damper (circled in red).