Has anyone has a faulty fuel ressure regulator, my K1 is running rough , measured the fuel pressure and the pressure reading is jumping around but the average of the swing seems to be around 30 psi, according to the books this should be 36 psi. What are your thought or experiences of this?  Many thanks.

Have you measured on both feed and return  and got same readings

No, I took the reading from the rear of the fuel rail and the tube to the pressure regulator. Fuel flow though the rail looks good so do not have any indication of a blockage within the rail. Thank you for your reply

My thinking was to prove,pump and internal pipes are all good before stripping the RETURN VALVE down

Yes I agree but should have added the background. I have checked to pipes inside and outside the tank all good. Vacuum pipe to FPR good too.had a new pump and filter 3 months ago. All had been good for 3000 miles of my ownership then suddenly started to run badly loss of power won't rev cleanly.Always starts on the button, no problem. As new things go wrong, fitted new Mahle filter, then a known good pump. Fitted new rubber caps on the vacuum take off pipes.
Just bought but not yet fitted a new set of plugs, original look good. Have bought a good used TPS and have a replacement FPR that I will fit last dues to it being a pain to get at. I purchased a fuel pressure gauge results as I mentioned in my first post. Really fed up that I can't use my K1. Maybe someone could throw a light on for me. Being the 16valve bike it has first generation motronic ecu.

The return line from the FPR where it goes into the tank can crimp over especially if it is non OEM. The OEM one has the bends molded in, the non OEM relies on the quality of the hose. And even good quality hose can collapse at the bend due to hot weather. The supply hose from the tank to the rail should also be checked for crimping.
Regards Martin.

Fuel pressure regulators do wear out, here's a picture of the internals of one that failed.



The ball should be captive behind that centre washer thingy.

Paul.

Thank you Paul, would love to find my one is faulty as I need to find the fault of my poor running.

Remove the hose to the FPR from the rail. Connect your replacement FPR to a hose returning through the filler cap opening, as a temporary measure to see if it then runs normal.

daveyson wrote:Remove the hose to the FPR from the rail. Connect your replacement FPR to a hose returning through the filler cap opening, as a temporary measure to see if it then runs normal.

Daveyson, what a simple way to do it. Obvious really, but would not of though to do it that way.  Cheers. thanks a lot.

OK,  good luck with it.

When you say it bounces around, if that means say 36 to 25ish, maybe the regulator is good (considering that the pressure fluctuates, and also that it doesn't exceed 36) from these forums fuel problems are often caused by the electrical plug to the tank.

After a run, unplug the vacuum hose from the throttle body, if there is fuel or moisture leaking out the vacuum hose, you don't need to do the FPR test, you just need to replace it.

Check that it is easy to blow through the filter. A new filter that has broken temporary end caps can absorb moisture from the air over time, swelling the element but probably good enough at idle.

Here's another tip that seems so obvious, but that I never would have thought of.

https://youtu.be/X9yX4wpAAbQ

daveyson wrote:Here's another tip that seems so obvious, but that I never would have thought of.

https://youtu.be/X9yX4wpAAbQ

Never heard of that before. Brilliant!
I might give it a try when I get the opportunity. Cheers


I'm not familiar with the K1 but I'm pretty sure that all 4v Motronic models run at 43psi.
The earlier 2v Jetronic is 36psi.

Holister wrote:I'm not familiar with the K1 but I'm pretty sure that all 4v Motronic models run at 43psi.

The BMW K1/K100 4V manual indicates 2.5 bar/36.25psi.

Replaced the TPS with another used one still running rough. Can get the bike to rev on the road if I am very gently with the throttle opening any more than a small continual increase bogs down the engine, getting really fed up not to be getting any further with this fault. Changed the new fuel filter that was easy to blow through with another new Mahle filter, no change. Tank spotless inside. Injectors? Would this really just come on and make his engine run poorly without any blip of full power any time?

Who know any good K mechanic I can turn to? I'm down in Essex near the Dartford Crossing.

When  you replaced th TPS, did you set the idle position?  There is a function in the Motronic that when you ground one of the pins on the diagnostic plug lets you precisely sync the TPS to the throttle butterflies.  It's a very important setting to have a correct mixture across the range of throttle openings.

No. I checked the Clymer book for TPS replacement  and no mention of that, can you direct me to any relevant information of how to do that please.  Thank you for your reply.