Excessive fuel pressure

[gorskined]

Hello as previously mentioned long time 356 and early 911 guy (things with carborators) first time working with a turbo and cis....
So my motor is a freshly rebuilt 76 3.0 row turbo all new guts. Basically stock with a k27 raptor turbo and a long neck Ic..... when the fuel pumps are on they sound more high pitched and my pressure off the fuel pumps go straight to 95 psi in about 2 seconds after the wur.
Takes about 4 to 5 seconds then the pressure eventually equalizes with the system pressure 95psi .... My wur has the adjustment nut but turning it doesn't make any difference in fuel pressure after the wur. So I'm assuming I need to send the wur out for a rebuild correct... If i understand what I'm reading the wur regulates system pressure... Not sure why it's called the warm up regulator. Its full time job is to regulate system fuel pressure..


Regards Ned

[reclino]

Warm up regulator sets control pressure. There is another pressure regulator in the fuel distributor that sets system pressure.

[Alan L]

It is a warm up regulator because it drops the pressure on cold start up - richens the mixture. Then it raises it as the car warms up = warm up regulator. Usually to around 3.6 bar.
Where are you measuring your fuel pressures from? Is the car actually running? It won't run with 95 psi WUR pressure.
Alan

[gorskined]

No the car won't start

[gorskined]

I am measuring the pump pressure just after the fuel filter it's an in line strainer with a gauge. The wur pressure is measured
just after the wur. looking at the top of the wur the left hand
port. And yes the isolation valve on the test gauge is open.

[matsuzaka]

CIS injectors are not electronically fired, they’re opened by pressure and I think 95lb pressure is normal.

[Alan L]

Can you post a pic of your measuring set up?
If you are measuring WUR pressure correctly, then there must be a fault in the WUR disc - closed system. The Wur works by squeezing a diaphragm/disc as a partial opening and that opening alters with temp to alter the WUR pressure. It is set by spring compression - which is the adjustment you talk of. I haven't got my head right around what could cause this , assuming measured right - but sounds like a restriction in the WUR. There is also a filter/screen inside the main port of the WUR - I am guessing it is the port you are using to measure from - looping thru and back with the gauge and valve? The screen is under that port (not the one that feeds the WUR pressure to the Fuel head. You could try checking that screen is not blocked. Dunno if that will give you zero pressure or max, until I see what you are doing.
What is the history -was it running before rebuilt? Anything done to WUR?
Alan

[Alan L]

Right - been a while since I did one - needed to refresh the brain.
You break in to the line between the FD and WUR - either connecting end will do. But I find the fitting on the WUR easier. If that really is showing system pressure, then it suggests no fuel is able to move thru the WUR adjusting disc. Which means most likely the blocked screen or the disc is totally crudded. Go for the screen first.
Alan

[Bucketlist]

When I first bought my car, an SC with the '76 3.0l Turbo motor I had similar problems. My System and control pressures were way off but somehow the car ran. The first thing I found was a clogged screen in the fitting where the fuel goes into the wur, I pulled the wur and cleaned it out which helped. The second and probably a rare problem was the needle was missing from the System pressure regulator. I bought a new one and had to modify the spring because a new one is nla. The third was the idle mixture screw in the fuel head was screwed all the way in and seized. After lots of soaking I was able to break it loose. Now I was at a point to make some progress. I pulled and cleaned my injectors, replaced my front fuel pump and had my wur rebuilt by Brian Leake. I did a few other mods like a cone air filter and added a CP gauge at the wur and in the dash so I didn't have to pull the intercooler to make adjustments.
There is no telling what a PO might do to a car before you get it so these are just a few things to check along the way. Good Luck!

[gorskined]

Follow up... I had the car briefly running early in the year with some issue so I pulled the motor. This is why I noticed the difference in the fuel pump noise. New twin bosch 044 and all new an 6 fuel lines... I also have the cone filter and 7 new injectors. The fuel head was rebuilt....
So after sitting the car will fire off for a second then die. If I pull a plug it's soaking wet. I removed the wur and took it apart.. it looks bran new but no filter screen and it has benn retro fitted with the adjustment screw that makes no difference when i turn it. But i did notice the main m plunger with the Allen head connected to the diaphragm the retaining collar nut is loose. I tightened it put it together no difference... BTW the car sat for 20 years before i got it broken studs. It's not a real 930 it's a wide body 80 sc... I watched some video on rebuilding the wur they mention that setting on the main diaphragm is critical. But no one mentions a starting point see pic of loose nut... they say be sure to measure and be sure to put it back together with the same
Setting. I. Pretty sure this could be the problem does anyone have a starting point for the settings... I dont mind sending it out to be rebuilt. But I do enjoy working on The cars and eventually understanding how the systems work..

[reclino]

Is your return line obstructed. You say new an6 fuel lines. I would check with compressed air that the return line through the tunnel to the tank is not plugged.

[gorskined]

Originally Posted by reclino

Is your return line obstructed. You say new an6 fuel lines. I would check with compressed air that the return line through the tunnel to the tank is not plugged.

Good point but No obstruction. . I ran a recirculation loop with a big filter to try and clean up the old tank finally gave up and replaced the tank then ran the loop with the new tank and pumps to be sure the lines were clean. I'm amazed the amount of fuel those pumps can move

[Alan L]

Have you removed the fitting on the WUR where the line to the FD connects (the hard line to the FD).
Have you unscrewed that fitting from the WUR? The screen lives under there, and has caused the symptoms you describe.
Alan

[gorskined]

Originally Posted by Alan L

Have you removed the fitting on the WUR where the line to the FD connects (the hard line to the FD).
Have you unscrewed that fitting from the WUR? The screen lives under there, and has caused the symptoms you describe.
Alan

Yes actually there is no screen.

[RarlyL8]

If the return line is open and the control pressure is the same as the system pressure then it is likely that the WUR flow path is blocked. Is the adjustment screw on the top side of the WUR? If so then that is for cold control pressure only. If this engine has set unused for a significant amount of time the entire fuel system must be cleaned. Particulate matter will continue to wreak havoc on every component until it is flushed out. We can handle component rebuilds but the system must be clean before installing them or they will clog and fail.

[gorskined]

Originally Posted by RarlyL8

If the return line is open and the control pressure is the same as the system pressure then it is likely that the WUR flow path is blocked. Is the adjustment screw on the top side of the WUR? If so then that is for cold control pressure only. If this engine has set unused for a significant amount of time the entire fuel system must be cleaned. Particulate matter will continue to wreak havoc on every component until it is flushed out. We can handle component rebuilds but the system must be clean before installing them or they will clog and fail.

The entire system is cleaned the distributor rebuilt all injectors replaced. New fuel lines new fuel tank new fuel pumps new accumulator the only thing that hasn't been rebuilt was the wur. I did take it apart. Everything looks new super clean good diaphragms and gaskets.. Like it was just done with the adjustment mod and never used But as mentioned there was a loose nut on the alen shaft on the main diaphragm see picture a few posts back I don't know
Where to set it. Given the issue not sure what way to turn the alen shaft.... Did not make a difference when I just tightened the nut.

[Alan L]

The allen screw sets the pressure - winding it in hardens the pressure - pushes against the smaller inner spring and puts additional pressure on the diaphragm. I don't know there is any book setting from scratch. Suck it and see basically and tweek from there.
So to be clear, you unscrewed the union fitting from the body of the WUR - from that brown disc that has both input and output feed lines in it. And found no screen? There should be one. But the possibility then is the disc is clogged. That needs to come out to check. The bit the pin rests on.
Alan

[gorskined]

Originally Posted by Alan L

The allen screw sets the pressure - winding it in hardens the pressure - pushes against the smaller inner spring and puts additional pressure on the diaphragm. I don't know there is any book setting from scratch. Suck it and see basically and tweek from there.
So to be clear, you unscrewed the union fitting from the body of the WUR - from that brown disc that has both input and output feed lines in it. And found no screen? There should be one. But the possibility then is the disc is clogged. That needs to come out to check. The bit the pin rests on.
Alan

I had it apart its clean like it never saw fuel I actually have a old diesel cat injector with a fine mesh screen I installed in the wur .. So in lay man turns . Given my situation (over pressure) should I make the distance between the flat surface shown in the picture more or less? I don't mind trial and error as long as I'm going in the right direction. Again thanks for all the help.

[Alan L]

The spring in your pic has nothing to do with setting the pressures. That is the boost dump spring - which lowers the pressure (richer) on boost. The rubber gasket pushes down on it. You will have a port on the WUR above that - that hooks to your butterfly throat. That provides the boost sensor to the WUR. When it pushes down on that spring it relieves the pressure on the top two springs and the WUR metering disc.
On the other side of that gasket you should have two springs - an inner and outer. The inner sits on top of that allen key adjust basically - can't recall the exact configuration. When you tweek the allen screw it alters the pressure on the inner spring and the combined springs push a pin on the WUR metering diaphragm/disc - a stainless disc. You have had that out too? That configuration sets your operating WUR pressures. It does look like there is an obstruction in your WUR system somewhere - matter of finding it.
Alan

[Alan L]

I don't seem to have a factory pic of the 930 WUR. It is different to all the others - because of the boost dump function. So here is a rough sketch - generally from memory. May not be precisely right - but hopefully clarify what bit does what.
The metering disc is on the bottom side of the cylinder on top of the WUR with the two fuel ports.
Alan