mishar

Easy way to check the pump is to switch wires from the right one to the left one (some extra wires will be needed). If it is OK car will run at least up to 3500 rpm.

When engine is off, or links broken, flaps are opened. Vacuum actuators are closing them for the low range (up to 4480 rpm). So if links are broken low end power will be lower, but it won’t be any huge difference. Just a bit like a turbo lag.

You have regular filter, so pressure regulator is at the engine. If everything else is OK you should check fuel pressure.

mishar

Not likely. Pressure is same all along the rail. In order that there is some pressure drop there should be significant resistance along the rail, but as it is short, quite large cross section and slow flow there is virtually no resistance.

Projekt 8E

Actually, I think I will do that first then. I'll switch the wires tonight and try it out. A very simple and effective test. that is less time consuming than running all new vacuum lines (which appear to be ok from multiple visual inspections).

Do you or anyone else know if there is a valve for checking fuel pressure from the fuel rail? I looks and all I can see is what I believe is the regulator on the driver's side rail.

Vicl

Well... I do not think that would be as easy to switch the pumps. The easiest way to check the pump is to see if the car will run when you have let say 20 litres of gas in your tank. When you start the car both pumps will be working and each pump responsible to transfer excess of the fuel to the other side. So, if tank is full the second pump will be off in 30 sec or so. Only passenger side pump will be working. When it needs more fuel (3000 RPM and up) the direr side pump will kick. If driver pump is not working the engine is not working for a long time when the fuel is low. The reason is following: Passenger side pump will transfer all fuel to the driver side and if driver side is not working then engine shuts down.
It is hard to diagnose such issue, but it may be pressure regulator.

Projekt 8E

I just ran the car down to about 15 miles left on the tank last week so the car does function with very little fuel left. I wonder if it is possible that the driver's side fuel pump is dying a slow death, therefor producing enough power to transfer fuel but not enough for adequate supply under high RPM full load?

mishar

It doesn't work like that at all. Right side pump is in charge for all fuel transferring and car works perfectly to the last drop of fuel. Left pump works at the startup in order to build the pressure ASAP and it kicks in at high rpm.

Projekt 8E

Ok guys, I wired up the driver's side pump from the passenger's side harness. The car ran ok. I revved it a few times and it never cut out. So I decided to take my jury rigged setup on the road for some passes. It ran all the way up to red line, still with the same throttle cut back. The strange thing though is that the intake g/s went a little crazier than normal I think, before it cut throttle.

Here' the spot on my log I'm talking about.

<img src="http://www.canyonero.com/files/1362794095.PNG">

It isn't too far off from what has been happening in other logs, but the other interesting thing is that bank one, which on the lambda test block was running at near 20%, which is considerably lean. Now it went down to 9.4 as seen on the right side... which I think technically is barely in spec.

I just cleaned my MAF and am about to put it back in. We'll see if that changes anything. I think for now though I can safely say the driver's side fuel pump is functioning.

Projekt 8E

Ok, so the final tally for the night holds some progress. Tonight after playing with the fuel filters, I have learned some interesting facts. 1. if they both aren't plugged in, it won't read a fuel level at all. With only 1 fuel pump running on each side, I was able to run the full range of RPM.

I swapped my ignition coils 5 and 8 to see if the knock moved. So far it hasn't registered anything related.

At the same time, which might have been stupid, I cleaned the MAF with MAF cleaner. It immediately responded with better results on block 032 for the lambda readouts. Everything was perfectly in spec.

Now I can get up to 4400 RPM before the throttle cuts. The other thing I noticed now is that the g/s under full load was bouncing from 110 to 160 roughly on occasion. Is it normal for that to happen like that? It seems like it is getting more and more out of control. I'm starting to wonder if the MAF is the cause.

Projekt 8E

I spoke a little too soon. On my way home from working on the car I really ran it hard on the highway. I couldn't get out of 3rd gear still. It held there over 6K RPM for about 15 seconds before I finally called it quits. If I would have manually shifted it, I could have kept going I'm sure.

But it still holds true that my throttle loss is up in the 4200 RPM range still. So it is better. I also got a lean code (p1128) for Bank 1 as well as knocks on cyl 5 & 6 this time. Presumably from the hard run. At least the car is telling me something now. The p1128 is either MAF, o2, or injectors.

If anyone can confirm or has any logs of a 4.2L at wide open throttle through 2nd and 3rd gear, I'd like to see how mine compares. I'm still curious about the intake g/s jumping all over the place. I'm not sure if that is causing an issue from a faulty MAF or if the car is doing that because it is adjusting the timing.

I think I made progress today though.

mishar

Can you please elaborate this? Is your gas pedal to the floor? It is in automatic and won't shift at 6K?