Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
FBH pump flow rate
Afternoon all
My FBH is playing up - again. Starts okay and produces some heat to the exhaust (although not much) and plenty of smoke but then shuts down. I have a GAP tool and get a variety of codes. Typically it is 02 (0X02) No start, but yesterday, just once, a new one, 139 (0X8B) Circulation pump interruption. It tries a number of fuel pump, glow plug cycles and then shuts down.
I have decarbonised the unit and it was working fine in the warmer weather on the GAP test cycle.
I thought that I would try to test the fuel flow so I pulled the diesel supply from the unit and measured the flow. On both the priming and the test cycle I found that the supply is weak but I do not have a comparator. The flow was just dripping intermittently (yeah - prostate, I know!) and both cycles produced less than a teaspoon of diesel. Have had a look around various threads but could not find a description of what is in the normal flow/volume range. I can re-run and measure the flow more accurately.
Grateful if anyone can advise on the expected flow and volume on these tests.
Thanks
16th Dec 2022 2:07 pm
Jimbob42
Member Since: 23 Mar 2022
Location: Leicester
Posts: 211
Mine does similar and I’ve done a fuel test which just spits a drip each pulse, speeds up when pump goes into higher demand.
16th Dec 2022 6:47 pm
Norfolk
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Thanks
I was expecting at least one drip per click of the pump. Mine is intermittent and with no pressure - certainly not a spit. I wonder if it a failing pump or blocked tube?
16th Dec 2022 7:52 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
You need to restrict the flow to get pressure, otherwise, measure the flow into a graduated tube and compare to spec. (around 65ml/min. max flow, subject to a few variables). The pump moves a specific amount per pulse, it's the pulse rate that varies the volume, the venturi in the injector provides a restriction and therefore the pressure. The output will also 'appear' different if a fuel damper is fitted.
Startup pulse rate is very different to run rate at 1/2 or full output.
16th Dec 2022 7:58 pm
Norfolk
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Thanks. Thought about the pump spec. but the speed varies through the programme and hence not possible to get a figure for the volume. Hence trying to get to the volume in cc produced by the GAP priming or test cycle. Will try again in the morning.
Would you expect the pump to be strong enough to push by a finger over the end of the pipe?
16th Dec 2022 8:28 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Never tried it and I wouldn't recommend it due to the problems subcutaneous hydrocarbons can cause.
Restricting the pipe (i.e. closing off with a hose clamp) will cause the pump to stop pulsing once the output pressure is suitably high. You do need to check if you have a damper fitted as this will change the characteristics of the flow - look for a grey disc on the outlet pipe of the dosing pump.
16th Dec 2022 8:34 pm
Norfolk
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Thanks. Will check in the morning
16th Dec 2022 9:33 pm
Motolab
Member Since: 18 Oct 2019
Location: Sleen
Posts: 1820
Just forget “the flow” of your dosingpump, since it is a DOSINGPUMP (or meteringpump) not a regualar fuelpump.
If they work, they work… if not, they are quiet and do nothing at all…
If there is no combustion, OR the resistance of the glowplug is wrong OR there is TOO MUCH diesel in the combustion chamber (due to deliberate priming mostly)
Diesel does not evaporate, like gasoline, so it stays where it is and the FBH will not ignite..
The heat you feel at the exhaust for a few seconds (or half a minute) is glowplug heat…
I had thousand’s of pierburg dosingpumps through my hands… as said they work or the don’t
If they don’t they do nothing.. (or have physical / mechanical damage)
Other non start issues can be blocked inlet or outlet by dust, spiderwebs or even windflow under the motorBest regards
Harold
Always looking for Pre '55's & Pre war British Motorcycles! knowing or having one for sale? PM please. I visit the UK 6 times a year
Ps. I edit my texts quite often, english is not my native language, so I will edit My “typo’s” etc.
16th Dec 2022 10:07 pm
Norfolk
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Harold
Thanks for this. Understand what a dosing pump is and how it works - or indeed does not. However, whether the diesel is supplied in a continuous flow or discreet pulses, flow = volume/time. The two Gap cycles have a defined time hence…..
Back to the point - checking flow rate answers two questions - the presence of a marginally failing pump or more likely a partial blockage in the suction or pressure pipes.
17th Dec 2022 9:36 am
Motolab
Member Since: 18 Oct 2019
Location: Sleen
Posts: 1820
i just wanted to give you a more plausible solution direction on your FBH problem... i.a. a NON starter..
ps.
we sold FBH's proffesionally for more than 20 years...Best regards
Harold
Always looking for Pre '55's & Pre war British Motorcycles! knowing or having one for sale? PM please. I visit the UK 6 times a year
Ps. I edit my texts quite often, english is not my native language, so I will edit My “typo’s” etc.
17th Dec 2022 11:37 am
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
This may help, or not.
Click image to enlarge
17th Dec 2022 12:14 pm
Norfolk
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Hi.
Yes - very helpful. I am at the bottom left - disconnect and observe fuel flow. I assume the box to the right is linked - check the fuel lines. Do you have a link to this or just the screen grab?
Thanks
17th Dec 2022 12:58 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Member Since: 02 Feb 2015
Location: Norfolk
Posts: 76
Brilliant - thank you.
"Disconnect fuel line from heater fuel inlet. Turn heater on and observe fuel expelled from fuel line. Does the pump expel fuel approximately 12 inches? (1-2 inches if pump is equipped with a damper)?"
Mine was just an intermittent weak dribble - this implies there should be a fairly forceful spurt. I will check the output from the pump before the pipe from there to the FBH.
17th Dec 2022 2:31 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Check if you have a damper fitted, also check the pump is getting full voltage and has a good ground.
The only times I've seen delivery issues have been with a seized pump due to lack of use and dirty fuel, the other one was with a damaged delivery pipe, caused by the monkey that replaced the clutch...
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