Need some help

[Michael]

A hint - when you remove and install this, if you have difficulty, remove the banjo bolts on the side of the fuel distributor. Actually you don't have to remove them, just back them off slightly. I've found that sometimes they go so far in they can hang up or nick the small o-ring. (Only one is really a problem but I forget which one.) Removing them all the way also gives you a place to carefully push it out or use compressed air. Don't go crazy with that or you'll be chasing parts all over the garage.

Not to nit pick, but wouldn't new seals be recommended once the banjo bolts have been loosened?

[Ron]

There is a 3rd o-ring (not shown above) on the push-up valve.
The pin you see inside the spring (above) is part of the push-up valve. The o-ring and another spring are on the other end of it, inside the carrier. You have to push back a retainer to remove a tiny C-clip and remove the carrier plug to replace it.

P-UpO-Ring.jpg
PPR AT REST:
PPR_Engine OFF.jpg
(See red arrow- The push valve o-ring holds control pressure when the engine is off.)
It does not come in the "hot start o-ring kits", last I knew...

[Bitsyncmaster]

There is a 3rd o-ring (not shown above) on the push-up valve.
The pin you see inside the spring (above) is part of the push-up valve. The o-ring and another spring are on the other end of it, inside the carrier. You have to push back a retainer to remove a tiny C-clip and remove the carrier plug to replace it.

P-UpO-Ring.jpg
PPR AT REST:
PPR_Engine OFF.jpg
(See red arrow- The push valve o-ring holds control pressure when the engine is off.)
It does not come in the "hot start o-ring kits", last I knew...

I think the O-ring at the very end of the piston is what seals rest pressure. I don't see what the function of that internal O-ring does.

[Ron]

I think the O-ring at the very end of the piston is what seals rest pressure. I don't see what the function of that internal O-ring does.

Hehe, I thought we were on the same page the last time this came up. Sorry, I'll try again.

Yes, it seals rest pressure for what would be primary pressure when the engine is running. BUT, there is a metering hole/restrictor passage (see D:01:08, Fig 7) connecting the lower and upper chambers (primary and control pressure) in the FD...
Like I said above, it's holds the control pressure circuit...

More:
"The push valve controls the return of fuel from something called the control-pressure regulator. You'll see more about the control-pressure regulator in 5. Control Systems. For now, all you need to know is that the push valve 0-ring shuts off fuel return from the control-pressure regulator to better maintain residual system pressure." ("Bosh Fuel Injection"; Chapter 5 "Continuous Injection - Theory"; Section 3 "Fuel System"; Subsection 3 "System-Pressure Regulator"; para. 4)

Later, the manual points it out as a source again:
ResidualLeaks-BOSCH .jpg

A bad "3rd" o-ring could allow it to leak back to the tank via the 2 yellow paths in the following pic:
PPR_Engine OFF2.jpg

[Bitsyncmaster]

Hehe, I thought we were on the same page the last time this came up. I'll try again

Yes, it seals rest pressure for what would be primary pressure when the engine is running. BUT, there is a metering hole/restrictor passage (see D:01:08, Fig 7) connecting the lower and upper chambers (primary and control pressure) in the FD......

More:
"The push valve controls the return of fuel from something called the control-pressure regulator. You'll see more about the control-pressure regulator in 5. Control Systems. For now, all you need to know is that the push valve 0-ring shuts off fuel return from the control-pressure regulator to better maintain residual system pressure." ("Bosh Fuel Injection"; Chapter 5 "Continuous Injection - Theory"; Section 3 "Fuel System"; Subsection 3 "System-Pressure Regulator"; para. 4)

Later, the manual points it out as a source again:
ResidualLeaks-BOSCH .jpg

It could leak as shown via the 2 yellow paths in the following pic:
PPR_Engine OFF2.jpg

Is there an open hole at the end of unit? If not where does that vent to?

[Ron]

The same place as the Primary bleed off...The two yellow arrowheads are drawn in the FD return-to-tank port, pointing to the tank.

The last pic is drawn funny- there should be a carrier and plug on the right end...and it doesn't show the WUR output port in, I.E., port for the WUR's return-to tank line.

Look at WSM D:01:08 to see the 3 ports (Primary Pressure in, Return-to-tank out, WUR output in). I'd post it, but what I have is too low res to see anything useful.

See?

[Michael]

Me reading the last few posts on this thread. I don't mind admitting when I am lost:

[Ron]

Found a better pic (but not much). Colors added.
Image1.jpg

[Ron]

Here ya go, found what I was looking for:

"In order to fully seal off the control-pressure circuit with absolute certainty when the engine has been switched off, and at the same time to maintain the pressure in the fuel circuit, the return line of the warm-up regulator is fitted with a check valve. This (push-up) valve is attached to the primary-pressure regulator and is held open during operation by the pressure-regulator plunger. When the engine is switched off and the
plunger of the primary-pressure regulator returns to its zero position, the check
valve is closed by a spring (Figure 17)."

Note the Decoupling Restriction Bore (Fig 16; 4), where primary and control join.
Image2.jpg
Note the 3 ports (Fig 17; 1, 2, 5*)
*This is from a 4 banger setup -- #5 will come in at 90° to the piston. instead of at the right end of the main bore.

[Bitsyncmaster]

OK. Now I see it with that last drawing. It was throwing me because the drawing was not representing what the PPR looks like. I knew the end of the PPR is a solid blocked fixture. It should have shown the #5 on the side of the drawing.