965: fuel pressure regulator replacement

[Martin123456]

My fuel pressure regulator is broken and so i am looking for replacement.

regulator: Bosh 0 280 160 765
car: V90 3.0 132kW 1998
engine: B6304S2
engine control unit: Motronic 4.4

I looked everywhere, but cannot find it - its not in stock anymore.

https://www.skandix.de/en/spare-part...0-765/1052148/


Do you guys know where to find new one ? Or maybe some appropriate replacement ?

From what i have found out so far, replacement regulator needs to have 3 bars (43.5 psi)

[Laird Scooby]

The picture you've shown is one for a 760 V6, the correct one looks somewhat different :

https://www.rockauto.com/en/catalog/...regulator,6124



Here's the one that is shown in the Skandix pic you found, fitted on a V6 :



https://www.rockauto.com/en/catalog/...regulator,6124

The Rock Auto listing for the 760 part.

Would be helpful if you can post a pic of your existing unit for positive identification.

[Martin123456]

I dont understand what is wrong with the link/picture i posted. My existing regulator is Bosh 0 280 160 765. That picture and skandix page shows exactly that.

But here is actual picture of my regulator:




I tried that rockauto.com web catalog to check V90 1998 and its a bit weird. It says PR161 is a replacement, but clearly, that regulator looks differently
https://www.standardbrand.com/en/eca...=PR161&view=bg

Yes, that PR71 for 760 looks like what i have, but it has different pressure. only 36psi
https://www.standardbrand.com/en/eca...ype=p&search=s

[Laird Scooby]

Here you are, one in stock with the part number you quote :

https://www.autodoc.co.uk/bosch/677413

Just re-checked, no stock available!

There seems to be a mismathc between the part number and description/photo. The one i linked to on Rock Auto that looks the same should do the job for you as it's also 3 bar.

It's annoying when part numbers get deleted.

[Martin123456]

yeah, thats my problem. original Bosh regulator is out of stock everywhere.

Originally Posted by Laird Scooby

The one i linked to on Rock Auto that looks the same should do the job for you as it's also 3 bar.

You mean that PR71 ? that is only 2.5 bar
spec: https://www.rockauto.com/en/moreinfo...=1288706&jsn=8

[Laird Scooby]

Originally Posted by Martin123456

yeah, thats my problem. original Bosh regulator is out of stock everywhere.



You mean that PR71 ? that is only 2.5 bar
spec: https://www.rockauto.com/en/moreinfo...=1288706&jsn=8

Good point Kev, i hadn't noticed that!

@Martin123456 - in what way is your current FPR broken?

[Martin123456]

Originally Posted by Laird Scooby

@Martin123456 - in what way is your current FPR broken?

Well, it leaks. Membrane is probably ripped or something. As a result, engine revolutions are not steady when on idling, they go up and down. I think its because control unit has problem to inject the right amount of gas because of wrong pressure.

[Laird Scooby]

Originally Posted by Martin123456

Well, it leaks. Membrane is probably ripped or something. As a result, engine revolutions are not steady when on idling, they go up and down. I think its because control unit has problem to inject the right amount of gas because of wrong pressure.

You've confirmed it leaks by removing the vacuum hose with the engine running i take it then?

A split vac hose would cause similar symptoms. What is cold starting like?

[Martin123456]

Originally Posted by Laird Scooby

You've confirmed it leaks by removing the vacuum hose with the engine running i take it then?

Exactly. But even when not removed, i can smell gas when hood is open.

Originally Posted by Laird Scooby

A split vac hose would cause similar symptoms. What is cold starting like?

i checked it along with whole intact and everything looks fine. Of course there may be something else wrong as well, but FPR leaks for sure, so i have to replace it anyway.

Cold starting is fine - even revolutions are pretty steady until engine warms up. Then they starts to go little bit up and down.

[Laird Scooby]

Originally Posted by Martin123456

Exactly. But even when not removed, i can smell gas when hood is open.


i checked it along with whole intact and everything looks fine. Of course there may be something else wrong as well, but FPR leaks for sure, so i have to replace it anyway.

Cold starting is fine - even revolutions are pretty steady until engine warms up. Then they starts to go little bit up and down.

Just to confirm, when you pull the vac hose off the stub you get fuel leaking out of the stub?

Usually if the FPR fails and is leaking fuel out, the system pressure drops as the fuel leaks into the inlet manifold and evaporates overnight. This means there is no fuel present to fire the engine as soon as it turns so makes me doubt the FPR is faulty.

Also if the uneven idling doesn't happen until it's warm (and hence is dependent on the Lambda sensor) it implies again the FPR is working ok. The fuel/engine management runs open loop while cold until the Lambda sensor has heated up sufficiently to give an output.

There is at least one other possible cause, the first/main suspect would be the CTS - Coolant Temperature Sensor. There should be two, one for the gauge and the other is for the ECU/engine management system and that one can fail telling the ECU that the engine is colder than in fact it is.
As such it is trying to run richer and the Lambda sensor will tell the ECU it's running too rich so the ECU will back the mixture off but because of the over-rich running it backs off too much so the engine falters. Then it over-corrects and continues on this cycle, causing uneven idling.

The second possible cause could be the Lambda sensor is failing and giving too low an output - this again causes the ECU to "correct" the mixture by enriching it too much and it goes into the above excessively rich then lean cycle as above.

If the present Lambda sensor is 10+ years or 100k+ miles old then it is definitely suspect.

However, one thing at a time. If the FPR isn't leaking then look at the CTS assuming the temp gauge reads ~ halfway once warm and doesn't drop on the open road at 50-70mph.