Primary Fuel Pressure Regulator

[Slammer]

Hi.
I have had a lot of problem with fuel pressure. What I see now is that the PPR seem to be blocking the return from the WUR, so the control pressure and primary pressure are the same.
If I take the return line from the WUR, off the fuel distributor fuel are flowing and the values looks ok. If I turn the PPR out far enough the fuel will flow. Turning it in again it stops. Do anybody have an idea what could lead to this?
The return line to the fuel tank is open.

[Bitsyncmaster]

When I had both pressures the same, it was my WUR was bad. But check your WUR inlet screen to see if it's clear.

[David T]

Very common for the WUR aka Control Pressure Regulator (CPR) to fail. If you search the internet there are ways to fix it or you can send yours out for repair. The Primary Pressure Regulator (PPR) doesn't typically fail that way, when it fails you have hot restart problems. Try to put the PPR back to the setting you had, even if it is off a little bit it should be OK and you can fine tune it after you get the CPR fixed. Make sure the return line to the tank is not blocked, kinked, or plugged up again. Many of the problems with the fuel system start in the fuel tank. Make sure it is clean, all of the boots are still rubbery, everything is in proper position, and the pump is good especially if you are still using the OEM pump set-up.

[Michael]

I will just say that my Dgo WUR and FD fixed a lot of issues with my car.


When I pulled and resealed the intake a few months ago, that's when I experienced true rock solid cold start up and idle. I would trust this car anywhere now.

[Slammer]

I put the Dgo WUR in last year. The fuel flows fine out of the WUR, it can,t pass the fuel distributor for some reason. The return hose/pipe to the tank is open.

[Ron]

I put the Dgo WUR in last year. The fuel flows fine out of the WUR, it can,t pass the fuel distributor for some reason. The return hose/pipe to the tank is open.FWIW- There is a small passage between the FD's port for the CPR/WUR line and the return to tank port. A piece of old PPR o-ring got into the passage on 1669 and made it act as you describe (CPR/WUR couldn't bleed off fuel to get proper control pressure).

[Slammer]

FWIW- There is a small passage between the FD's port for the CPR/WUR line and the return to tank port. A piece of old PPR o-ring got into the passage on 1669 and made it act as you describe (CPR/WUR couldn't bleed off fuel to get proper control pressure).

That's about what I thought.
Any way I can get to that passage without dismantling the hole thing?

[Ron]

That's about what I thought.
Any way I can get to that passage without dismantling the hole thing?Yes. Remove the PPR, CPR/WUR return hose, and the FV-return to tank hose from the FD. Then you can see/figure out where the passage is. All return winds up in that corner...

[Slammer]

Yes. Remove the PPR, CPR/WUR return hose, and the FV-return to tank hose from the FD. Then you can see/figure out where the passage is. All return winds up in that corner...

That's what I did. Everything looked fine, until I put the PPR back. It was blocked again.
Decided to try another FD, and it seemed ok except the pressure was to low. I then added shims to get the pressure up, but ended up with the same problem. Took out some of the shims, and the control pressure was back.
So is it possible to get the engine to run properly with 3,6 bar primary pressure?

[Bitsyncmaster]

That's what I did. Everything looked fine, until I put the PPR back. It was blocked again.
Decided to try another FD, and it seemed ok except the pressure was to low. I then added shims to get the pressure up, but ended up with the same problem. Took out some of the shims, and the control pressure was back.
So is it possible to get the engine to run properly with 3,6 bar primary pressure?

I don't think 3.6 bar would ever run the engine properly. With only 52 psi primary pressure and your control pressure at 50 psi it just would never run right.

[Slammer]

I don't think 3.6 bar would ever run the engine properly. With only 52 psi primary pressure and your control pressure at 50 psi it just would never run right.

So what can I do? what causes this problem? 2 different FD's behave the same.

[Bitsyncmaster]

So what can I do? what causes this problem? 2 different FD's behave the same.

Maybe your fuel pump can only provide 3.6 bar. Make sure it gets 12 volts at the fuel pump. You can dead test the PSI but mine pegged my 100 PSI gauge.

[Slammer]

Maybe your fuel pump can only provide 3.6 bar. Make sure it gets 12 volts at the fuel pump. You can dead test the PSI but mine pegged my 100 PSI gauge.

I can get the pressure up by adding shims, but then the primary and control pressure will be the same. I'd like to test the pump if I had the right connector for it.

[Ron]

That's what I did. Everything looked fine, until I put the PPR back. It was blocked again.
Decided to try another FD, and it seemed ok except the pressure was to low. I then added shims to get the pressure up, but ended up with the same problem. Took out some of the shims, and the control pressure was back.
So is it possible to get the engine to run properly with 3,6 bar primary pressure?No, that's way too low.
Something odd going on here -- I'm with Dave, your pump is too weak, routing wrong, ???70624

[Bitsyncmaster]

No, that's way too low.
Something odd going on here -- I'm with Dave, your pump is too weak, routing wrong, ???70624

Yes check that hose routing. I was helping another owner with lambda problems and it turned out a hose was connected wrong.

[Rich]

I don't think 3.6 bar would ever run the engine properly. With only 52 psi primary pressure and your control pressure at 50 psi it just would never run right.

Agreed.

The Tech Info Manual calls for "Primary Pressure checking value" at 4.9-5.5 Bar. The setting value is 5.1-5.3 Bar.

On page 60

3.6 Bar isn't even close.

[Slammer]

70625

I can get the pressure higher, but then the control pressure will be the same.

[Ron]

In that case, I would get the pressure up to ~5.2 bar. Then try plugging the port for the WUR/CPR return line at the FD and putting the return line into a bucket or similar...

WUR/CPR??

[Slammer]

Tried to add shims today, and got to 5 bar maximum, and no return fuel. I believe the high number of shims are creating the problem with the return.

70636

So I measured at the pump, and it was 5 bar there also.
Took the pump unit out, and wonder can I replace just the pump or do I have to do the complete unit?
This is the John Hervey unit.

70637

[Bitsyncmaster]

Tried to add shims today, and got to 5 bar maximum, and no return fuel. I believe the high number of shims are creating the problem with the return.

70636

So I measured at the pump, and it was 5 bar there also.
Took the pump unit out, and wonder can I replace just the pump or do I have to do the complete unit?
This is the John Hervey unit.

70637

So it looks like your pump is bad. If it can only do 5 bar with zero flow, it would be even less when engine is running. The fact you get no return fuel says the pump can't do any more. A lot of us are using the standard GM pumps. Mine is from a Tahoe. Take those shims out when you try a new pump.

[Ron]

^+1^

[Slammer]

Thanks!!
I'll try that.