fuel pump widget?

Beamer · 1 fuel pump widget? Mon Mar 19, 2018 11:27 am

Beamer

Platinum member

Number of posts : 291

Hi,

can someone tell me what this little brass thingy hidden in a threaded hole is in the bottom of the fuel pump?

( top , right in photo)

This brand new Bosch pump, which I've only just bought has started making an awful noise. I think this widget should be centrally placed. Wondering if that is an indication of the problem.

TIA.

Crazy Frog · 2 Re: fuel pump widget? Mon Mar 19, 2018 11:41 am

Crazy Frog

admin

Number of posts : 5045

This widget must be the high pressure relief valve.
It doesn't seem that it's seated correctly. Try to pull on it with a pair of long nose pliers, and see if it goes back flat.
The noise must be the fuel pressure leaking from there.

Beamer · 3 Re: fuel pump widget? Mon Mar 19, 2018 12:06 pm

Beamer

Platinum member

Number of posts : 291

Thanks, I was guessing it was a release value. What I thought was a threaded hole is a spring.

The noise I heard is consistent with a fast tak-tak-tak that may result from it clacking open and shut. Yesterday I had trouble getting home because the hoses kept popping off in the tank. At first I suspected a blocked fuel filter ( despite it being nearly new ) but I just replaced it and still have the over pressure condition. The old pump, which I put back in thinking the new one was defective, is leaking at the crimped top end. All this points to a serious over pressure problem. At that least means the old pump isn't dead, yet , and the new pump is probably not defective after all. Glad about that.

I guess I need to strip off the air box, flow meter etc to get at the fuel pressure control valve. Arg !

Do these things often go wrong? I've not heard of that before.

cheers.

Crazy Frog · 4 Re: fuel pump widget? Mon Mar 19, 2018 12:38 pm

Crazy Frog

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Number of posts : 5045

Beamer wrote:Thanks, I was guessing it was a release value. What I thought was a threaded hole is a spring.

The noise I heard is consistent with a fast tak-tak-tak that may result from it clacking open and shut.
The "tak-tak-tak" noise can come from the one way valve on the return line (This valve is directly mounted on the front of the tank.

Yesterday I had trouble getting home because the hoses kept popping off in the tank. At first I suspected a blocked fuel filter ( despite it being nearly new ) but I just replaced it and still have the over pressure condition. The old pump, which I put back in thinking the new one was defective, is leaking at the crimped top end. All this points to a serious over pressure problem. At that least means the old pump isn't dead, yet , and the new pump is probably not defective after all. Glad about that.

I guess I need to strip off the air box, flow meter etc to get at the fuel pressure control valve. Arg !
YES you will have to investigate an over pressure. Before starting to dismantle the airbox, first check that the hose coming from the throttle body and going to the fuel regulator pressure valve is not disconnected at the throttle body.

Do these things often go wrong? I've not heard of that before.
Yes they do.

cheers.

Beamer · 5 Re: fuel pump widget? Mon Mar 19, 2018 1:07 pm

Beamer

Platinum member

Number of posts : 291

thanks for the tips.

The vacuum tube with the spring protection is in place and maintains a depression when I suck on it. Good idea though I had not thought of that.

There is no return flow to the reservoir there seems to be a blockage after the injector ramp. I think this may account for the dastardly split I previous had between pump and filter. Presumably a fabrication weakness and that was the weakest link at that time. As I fix things the next weakest link gives out. I've only just found out that it was a pressure problem all along.

Looks like I need to strip the air box etc. Very annoying.

Thanks for the help.

Beamer · 6 Re: fuel pump widget? Mon Mar 19, 2018 1:37 pm

Beamer

Platinum member

Number of posts : 291

Is there anything that can be serviced/cleaned on the press. regulator, or is it just a case of replacing it?

thx

Point-Seven-five · 7 Re: fuel pump widget? Mon Mar 19, 2018 1:41 pm

Point-Seven-five

Life time member

Number of posts : 4171

Please excuse me, but my psychic powers are running a bit low today, so I can't discern what model or year your bike is.

In any event, if it is an early model you may have a plugged check valve in the return line. It is screwed into the bottom of the tank where the return line connects.

Crazy Frog · 8 Re: fuel pump widget? Mon Mar 19, 2018 1:42 pm

Crazy Frog

admin

Number of posts : 5045

Beamer wrote:Is there anything that can be serviced/cleaned on the press. regulator, or is it just a case of replacing it?

thx

NO. It's a sealed unit.
But....
If you are ready to remove it, you can always try to remove the small hose from the throttle body and blow some compressed air into the fuel regulator. Sometimes, it work. Don't go over 20PSI otherwise you could blowup the hose. They are not made to sustain high pressure.

Crazy Frog · 9 Re: fuel pump widget? Mon Mar 19, 2018 1:48 pm

Crazy Frog

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Number of posts : 5045

Point-Seven-five wrote:Please excuse me, but my psychic powers are running a bit low today, so I can't discern what model or year your bike is.

In any event, if it is an early model you may have a plugged check valve in the return line. It is screwed into the bottom of the tank where the return line connects.

I second your statement .75
I cannot see that happening, but it's easy to check. You just have to remove the return hose and unscrew the valve from the tank. As I was fed up to listen to the "tak-tak-tak", I removed the ball and the spring from it.
Somewhere on the forum Sidecar Paul had removed the valve too and inserted a tube going to the top of the gas tank (Internally). This way, the gas is not pouring when you remove the hose.

92KK 84WW Olaf · 10 Re: fuel pump widget? Mon Mar 19, 2018 2:01 pm

92KK 84WW Olaf

Life time member

Number of posts : 7897

Possible the two front pipes on the tank are connected wrong way round?

Regulator sitting in my parts box....you only need bottom half of the airbox off to get in there. The lower half has two usually seized Allen bolts down to the top of the engine.

But check your vacuum lines. Early Ks up to some time in early 85 have one at the front as well [my RT is 84 and has one], to a fuel pressure sensor. Don't worry about the sensor, it does nothing. But the vacuum line needs to be good or else plugged with a cap same as the vacuum take offs.

Loss of vacuum will give you over pressure.

Did you buy a genuine Bosch pump....?

Beamer · 11 Re: fuel pump widget? Mon Mar 19, 2018 2:10 pm

Beamer

Platinum member

Number of posts : 291

1985 K75C

I've got the thing off, so I'm going to give it an hour in the ultrasonic cleaner and maybe some gentle heat. Not much to loose at this point.

I've already established that there is a blockage before it gets back to the tank.

I have some Carburaigle hosing that is good for 10 bar, that will allow be to give enough to open it up if it's not completely jammed.

I'd guess it's just a spring loaded valve, is that right?

cheers.

92KK 84WW Olaf · 12 Re: fuel pump widget? Mon Mar 19, 2018 2:20 pm

92KK 84WW Olaf

Life time member

Number of posts : 7897

I don't get how there can be a blockage except for a broken up fuel pipe as they can disintegrate. After that I'm thinking something misconnected.

Beamer · 13 Re: fuel pump widget? Mon Mar 19, 2018 3:18 pm

Beamer

Platinum member

Number of posts : 291

I had all sorts of crap in the tank when all this started, so a blockage is possible.

How does "something not connected" result in no fuel return? If I have 4-6 bar from the pump, it should blow off and return something, right?

OP:

This brand new Bosch pump, which I've only just bought has started making an awful noise.

92KK 84WW Olaf · 14 Re: fuel pump widget? Mon Mar 19, 2018 4:46 pm

92KK 84WW Olaf

Life time member

Number of posts : 7897

I took it from the post that although you had pressure there is also no fuel is returning to the tank. If you disconnect the return pipe at the front of the fuel rail and pressurise the system you should get a spray. Messy but its a quick check.

There is also a mesh filter for the pump........as well as the metal fuel filter.

Crazy Frog · 15 Re: fuel pump widget? Mon Mar 19, 2018 4:53 pm

Crazy Frog

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Number of posts : 5045

If the fuel pressure regulator is blocked, nothing will go back to the tank.
To compensate, the built in high pressure regulator on the pump will release pressure in excess of 66PSI.

Beamer · 16 Re: fuel pump widget? Mon Mar 19, 2018 5:22 pm

Beamer

Platinum member

Number of posts : 291

Olaf wrote:I took it from the post that although you had pressure there is also no fuel is returning to the tank.

That's correct.

CF wrote:If the fuel pressure regulator is blocked, nothing will go back to the tank.

That is the assumption I've been working on since I noticed it was a pressure problem. The bike runs, so I know it's not before the injector ramp. That means either the regulator or the pipes either side. I can blow through the return pipe, so that's clear.

After an hour in the ultrasonic bath the regulator is shining like new. I'll see whether it works any better tomorrow.

Point-Seven-five · 17 Re: fuel pump widget? Mon Mar 19, 2018 5:59 pm

Point-Seven-five

Life time member

Number of posts : 4171

#19 on this drawing p/n 16 12 1 455 348 U.S. price is $8.62

An owner on the MotoBrick forum had a really ugly one come out of his tank last week. Was preventing almost all the return flow to the tank. If pulling the return hose shows lots of flow, this is your problem.

glennpm · 18 Re: fuel pump widget? Sun Mar 25, 2018 3:24 pm

glennpm

Silver member

Number of posts : 113

The brass post from your picture is part of the internal pump over pressure valve. Its like a needle valve. It should be centered in the hole.

If you decide to replace the pressure regulator, search by the Bosch number and you'll find some reasonable prices. I was searching a couple of weeks ago when I thought I may need one for my 87 K100RS. Bosch part #0280160200 for early K's but verify for yours.

Beamer · 19 Re: fuel pump widget? Sun Mar 25, 2018 3:43 pm

Beamer

Platinum member

Number of posts : 291

Thanks Glenn, that ref may come in handy.

The old unit seems very solidly locked closed. 1 hour of ultrasonic bath and even a hammer and screwdriver up its 'ole did not free it. I ended up swapping with a spare I had on a non running bike. Now blows off at about 2.3 bar.

Runs pretty well through out the rev range but still has a tenancy to stall at junctions. Very annoying.

Fiddling with the air flow meter bypass does not help much at all. With all the crap that went round I may have an injector which is a bit sticky at very low feeds. I'm going to have to dig a bit deeper.

Main thing is I'm mobile. Wink

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1 fuel pump widget? Mon Mar 19, 2018 11:27 am

Beamer

2 Re: fuel pump widget? Mon Mar 19, 2018 11:41 am

Crazy Frog

3 Re: fuel pump widget? Mon Mar 19, 2018 12:06 pm

Beamer

4 Re: fuel pump widget? Mon Mar 19, 2018 12:38 pm

Crazy Frog

5 Re: fuel pump widget? Mon Mar 19, 2018 1:07 pm

Beamer

6 Re: fuel pump widget? Mon Mar 19, 2018 1:37 pm

Beamer

7 Re: fuel pump widget? Mon Mar 19, 2018 1:41 pm

Point-Seven-five

8 Re: fuel pump widget? Mon Mar 19, 2018 1:42 pm

Crazy Frog

9 Re: fuel pump widget? Mon Mar 19, 2018 1:48 pm

Crazy Frog

10 Re: fuel pump widget? Mon Mar 19, 2018 2:01 pm

92KK 84WW Olaf

11 Re: fuel pump widget? Mon Mar 19, 2018 2:10 pm

Beamer

12 Re: fuel pump widget? Mon Mar 19, 2018 2:20 pm

92KK 84WW Olaf

13 Re: fuel pump widget? Mon Mar 19, 2018 3:18 pm

Beamer

14 Re: fuel pump widget? Mon Mar 19, 2018 4:46 pm

92KK 84WW Olaf

15 Re: fuel pump widget? Mon Mar 19, 2018 4:53 pm

Crazy Frog

16 Re: fuel pump widget? Mon Mar 19, 2018 5:22 pm

Beamer

17 Re: fuel pump widget? Mon Mar 19, 2018 5:59 pm

Point-Seven-five

18 Re: fuel pump widget? Sun Mar 25, 2018 3:24 pm

glennpm

19 Re: fuel pump widget? Sun Mar 25, 2018 3:43 pm

Beamer

20 Re: fuel pump widget?

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