addo wrote:Gauge readings vary enormously. Best approach is to take a middle cylinder warm engine reading off a car that's demonstrably running well and use that as your reference. I suggest any gauge ought to show between 180 and 220 pounds hot, but you need to also understand how the gauge should move as it approaches max pressure.
I may be visiting David this weekend so if he has a compression gauge we may be able to measure one of the front cylinders of his V6, which could give a reference figure....
Fuel pressure is easier to read with the manifold vacuum lead plugged, then there's no idle pressure drop. My observation of FPRs is that the rubber fails progressively; the usual first symptom is hard starting after sitting as the pressure no longer holds up in the fuel rails.
Yep, that was going to be one of my tests, comparing the pressure with the vacuum line to the regulator connected and disconnected.
I don't believe you have yet subjected the car to real "load", from what you've described. There's a long way between looking at data with the throttle open and putting 450kg in it (which it will handle easily in good health) and dragging off up a hill. This tests fuelling, cooling, throughflow much more validly.
Maybe so, but the point of my test was to see whether it was running lean or rich at WOT at low rpm where the car has been struggling for power and pickup for months, and the result is that it is running lean when it should be rich. How lean I don't know since the oxygen sensor is narrowband...it could be very lean indeed. It also has at least 20 degrees of torque reduction retard in the same conditions.
If it's stuck in a lean condition with 50% - 100% throttle at only 1500rpm when it should be rich, there is no way its not going to be lean on wide throttle at higher rpm when even more fuel is required - that's just a bit harder to test safely when driving on the road without a data logger or better realtime display than a Lexia. The way I see it there is a major fuel shortage under load that is present even during low rpm demands, and that needs to be fixed first.
It's a shame I can't graph rpm, throttle opening, oxygen sensor reading and ignition torque retard together on a graph - if I could go for a varied test drive and log all of those to look at afterwards I could easily confirm what I suspect across a wider range of engine load.
What I did with one experiment was to weld in a 1/8" NPT (female) steel bung ahead of the converter, on the passenger side. This gave me a pressure takeoff point and it required no removal of any items to establish. My error with the next step was to use soft solder on the copper tube - silver solder or braze would've been smarter! What is screwed into the female port, is a 1/8 NPT to hose barb fitting, with about a foot of copper tube (coiled) mounted on it. Your pressure gauge can then be fed by ordinary "rubber" hose clamped onto the copper end - the copper is long enough to dissipate critical heat levels.
Yeah, the adaptors I've seen show an adaptor with a flexible metal tube at least a couple of feet long before it goes to the gauge to isolate it from the high temperatures, so I would use something like that.
If the measurements show a problem with the pressure I'll inspect it to make sure its the right one. (And since I think the manifold has to come off to get at it, I'd check the compressions while I have the inlet manifold off)
I imagine that the pressure would sag during each injection pulse, what that would do for drivability I don't know. It must be there for a reason or it would have been left out to save money...
