pcmhacking.net

Pinched or blocked return line?

UCMatt wrote:Pinched or blocked return line?

Thank you for the suggestion. I don't think that is the case here based on results I am seeing.

Update:
I had the charcoal canister out the other day while awaiting a new canister. While there I blew air through the lines and all seemed clear. Even to the point that I blew the pumps vent valve of inside the tank and ended up having to drop the tank to rectify the error it created.
I have now since replaced the canister and that has only resolved the issue of fume smells when the engine is off. It has also improved the filling of the tank issue where it would cut off when filling the tank. ( i think now it just needs to be calibrated as to the correct fuel levels. But I will do that after I resolve the rich issue).

While waiting for a spare MAF sensor to arrive. Today I had a little time to check some more items as further confirmation that they are actually working.
EGR valve: Seemed to function fine. As it didn't seem to make any difference (other than a codes set) to the engines idle or rev increases. Not sure yet how else I can actually test it further on the car.
Purge Valve: Disconnecting the canister hose at the valve, thereafter noticeable pulsing in the valve which meant there was vac from the manifold. As it was pulsing, it also meant the valve was being operated by the ECU as it is meant to. I then refitted the hose and removed the valve to manifold hose. This hose made the engine revs change as expected, effectively making it run slightly leaner, however the fuel trims still didn't change. Which to me means the valve is working fine. While we also then don't have any significant vac leak elsewhere.
TPS: Registers fine and smoothly, confirmed with the software also.
IAC Valve: I disconnected the connector to the unit and nothing altered (just a code set). This also means to me that as I don't have issues starting the car, nor idling as per say. That the valve is functioning as should be otherwise I would experience other issues that are more directly related to the IAC vale.

I disconnected the IAT Sensor, code set, no noticeable change to fuel trims.
I also disconnected the MAF sensor, and again, no noticeable difference to the engine. However it still didn't change the G/s on the software. Which again leads me to feel the MAF sensor (or wiring) has an issue.

I received my second-hand MAF sensor this evening. I will try to clean and fit it to the car tomorrow. I will keep you all posted on the results.

PS: If the MAF sensor makes no difference at all. Then as I have had the new spark plugs in for about a week now (only low driving distance). I will pull them out and see if there is a specific cylinder (injector) that is possibly at fault.

Thanks Guys, I am almost at my wits end with this issue.

In all of this I dont see where you have measured the fuel pressure. It's basic diagnosis. I am sure they do have a return line system and what UCmatt mentioned is possible. The return line is only small inside the tank and yes it can get blocked. I remember years ago a workshop called me to look at a VL and the car was pig rich and it turned out the return was blocked inside the tank. Picked up a simple pressure test.

Charlescrown wrote:In all of this I dont see where you have measured the fuel pressure. It's basic diagnosis. I am sure they do have a return line system and what UCmatt mentioned is possible. The return line is only small inside the tank and yes it can get blocked. I remember years ago a workshop called me to look at a VL and the car was pig rich and it turned out the return was blocked inside the tank. Picked up a simple pressure test.

Thanks for your time and suggestion Charlescrown, all feedback is appreciated.

Sorry, I thought I mentioned it with relation to the fuel pressure. I have also replaced the pressure regulator (which made no difference). But yes I have done a fuel pressure test. Came back around 40psi and maintained that while at varied revs.

I have replaced the MAF sensor with a working second hand one today. The issue of rich is still there. In fact worsening with time it seems. Readings of STFT were around the -ve 48's while the LTFT were around the -ve 30's after about 5-10 min and at Closed loop. Almost choked on the fumes coming out the car while testing.

I feel i am narrowing it down to a fuel issue, or at worse a bad earth somewhere in the car (though <25% likely). I plan to retest the fuel line pressure today or tomorrow. I will also do a fuel pressure drop test on all injectors while in the vehicle to see if any or all are failing in some way. I am also going to pull out and check the new spark plugs and see it there is a significant colour to just one or two or if it is even across all. That should also give me direction to tell if it is just an injector or a full fuel rail pressure issue, I think?

I will be relieved, while also annoyed should there be a couple or more faulty injector. As they are new, genuine, weren't cheap and have done less than 15,000km and less than 12months old.

Bad earths can cause all sorts of issues.

Another user recently hid all wiring on his car and put all the earths together and the car would not run, timing was off, fuelling was doing weird shit. Separated the earths as per OEM loom and hey presto it all worked good again.

There are 2 critical earth points on the engine for PCM and sensors etc, one at the front of the engine on one of the studs that holds the tensioner bracket and coolant lines and another on the back of the passenger side head as well as the main earth down on the engine mount bracket on the drivers side.

What injectors did you fit? A direct replacement, exact same part number?

The problem with the VL was easily fixed by shoving a piece of wire into the tank return line and pushing it off inside the tank then they sold the car. I do know the earlier cars had an earth issue with the o2 sensors and you got no codes but pick it up by viewing the spped activity of the swinging o2 output. You could clearly see there was one much faster than the other. I'll be interested in knowing if all plugs are running rich.

Charlescrown wrote:The problem with the VL was easily fixed by shoving a piece of wire into the tank return line and pushing it off inside the tank then they sold the car. I do know the earlier cars had an earth issue with the o2 sensors and you got no codes but pick it up by viewing the spped activity of the swinging o2 output. You could clearly see there was one much faster than the other. I'll be interested in knowing if all plugs are running rich.

immortality wrote:Bad earths can cause all sorts of issues.

What injectors did you fit? A direct replacement, exact same part number?

Thanks immortality, I had watched recently a YT where a mechanic or motor electrician showed what a bad earth along the MAF lines would potentially look like. It doesn't seem yet that I am having signs of such an issue on that line going from my oscilloscope display. But I can't yet be 100% confident it is alright until I test it further.

I am not 100% sure where some of those earths are that you mentioned? I might need to take a pic of where I think they are tomorrow and just confirm with you. I know of one near or behind the battery area which I think from memory the fuse box utilises. There is also a thin one at the back of the engine near or on the inlet manifold. Another is on the front of the engine where the heater pipe mount is which I think is what you refer to as the tensioner area? Not sure about the "back of the passenger side head as well as the main earth down on the engine mount bracket on the drivers side". The car is at the age of now expecting to have earthing issues.I did recently have a drivers door light switch earthing go bad which was causing the fob remote to not always operate.

The injectors were the OEM part numbers. "6 X GENUINE BOSCH FUEL INJECTORS HOLDEN COMMODORE VT VX VY V6 0280 155 777".
What dwells on my mind after watching hours of YT videos ( sometimes to much wrong knowledge can be a curse), is it doesn't seem to be an injector issue. Well not excessively bad that is. While trying some cheap China eBay ones prior to the genuine. I had a couple of the china ones that leaked almost straight away. Where there was fuel flowing out the exhaust manifold. Though the engine still idled reasonable ok. As it sort of does currently idle and run ok except fuel excess usage and exhaust smell of fuel. But I cant see or even smell fuel fumes in the engine area (I am almost immune to petrol fumes though, which makes it hard to know for sure).

I am tonight preparing a fuel pressure and injector tester so tomorrow (weather permitting) I hope to check fuel line pressure, injector functions and get some sort of resolution to the injector status of health.

Charlescrown wrote:The problem with the VL was easily fixed by shoving a piece of wire into the tank return line and pushing it off inside the tank then they sold the car. I do know the earlier cars had an earth issue with the o2 sensors and you got no codes but pick it up by viewing the spped activity of the swinging o2 output. You could clearly see there was one much faster than the other. I'll be interested in knowing if all plugs are running rich.

Ah. I think I know a little more clearly the line you are referring now. I am confident they are all clear from tank to canister and tank to engine. As I blew the internal fuel pump / tank breather valve (not sure of the correct term) off the fuel pump when I was clearing them with the compressed air. Hence, the need to drop the tank and resolve the pump issue earlier in the week.

It has turned too cold and wet this evening, but I plan to do the checking of the plugs tomorrow along with the fuel pressures and injector tests.

How old are the O2 sensors?

Depending on how old they are and how badly they have been flooded they may be stuffed.

immortality wrote:How old are the O2 sensors?

Depending on how old they are and how badly they have been flooded they may be stuffed.

Less than 1 month (approx). First things in a flood of parts I have now changed trying to resolve the issue. Keeping in mind though that many parts I have just replaced, were still the originals from 2004 when I purchased the car. I only changed them because I had no real way to bench test them so replaced them as a process of logical elimination. They are reporting as too rich with a swing to get there after closed loop is active. I did briefly get some ideal fluctuations on a test drive recently. They seem to be responding ok from what I can tell. They were not cheap either, from AutoPro.

The thing that annoys me most, is not knowing the actual cause, yet. Other than the excess fuel richness issue, the car is actually performing on road quite reasonably.