I understand the fuel rail pressure is 36psi. To test, a gauge is fitted to the line coming from the tank.
Question: has anyone put a permanent gauge or pressure switch on this fuel line?

I have run gauges on diesel truck lines to monitor fuel pressue.

As the k75 dies while going down the road you know if it is fuel or not, handy.

Be nice to rule this out as you coast to a stop!

I haven't heard of anyone putting a permanent fuel pressure gauge on their bike.  Usually, if the tank has fuel and the pum is running you will have fuel at the proper pressure. 

The pumps are pretty reliable, most problems are on start up after very prolonged idleness with bad fuel in the tank.  A bike that is used regularly will rarely have pump problems.  Same with the pressure regulator, I cannot recall many problems with them showing up on the forum.

I had one fitted to my fuel cooler unfortunately the cooler only really worked at 80 KPH +. I needed it to work around town in Queensland summer traffic. I removed it and found another solution. It did think it looked cool. I occasionally think about reinstating it.
Regards Martin.

There are aftermarket replacement adjustable fuel pressure regulators that can replace the OEM one and also have a pressure gauge on them.

 

When I built 'Big Block' I always intended to use an adjustable fuel pressure gauge/regulator. Here it is eight or nine years later, nestled beneath the four K&N pods on the ends of the under-tank throttle bodies, still going strong. I'd initially thought I might play around with various pressures, since the exhaust and the far less restrictive intakes were 'opened up' as compared to stock, but set it back to stock after a while as it ran best there.

I was thinking a pressure activated switch teed into the fuel line with an idiot light in view whilst riding. If the bike quit, before you stopped rolling you knew if you had fuel pressure or not. Nice to know where to start looking when you have a non runner on the side of the road! Thoughts?

Easiest(and cheapest) way to confirm fuel delivery is to open the tank and look inside.  You can immediately identify an out of fuel situation, and by cranking the starter and watching for fuel coming back through the fuel return line see that the pump is functioning. 

If you meet those two conditions, the odds are pretty darn good that the engine is getting enough fuel to run.

A little tricky while moving down the road.
Being new to these bikes your suggestion to check the fuel return line for fuel is an important one.

If you are moving down the road the engine is probably getting fuel.  That is the easiest proof of all.

I'm sorry point. I guess I didn't explain this very well. I'll try again.

These 80 year old bones are motoring along at 110km per hour on a bright and sunny day. All of a sudden the bike dies and I am losing speedl I look at the idiot light I put in to monitor fuel pressue, if on the problem is fuel, if not On I know I have fuel and can rule fuel supply out. Over the years I've been stuck on the side of the road looking for answers.
Cheers

I have recently had issues - three separate ones in fact - with fuel pressure. So being able to check it was very useful. Post 7; .75's is spot on. If you can see a healthy flow of fuel returning into the tank then it's unlikely that pressure is an issue. These don't run on monster pressure. This method worked fine for me whilst head-scratching.
For info the three problems were:
1: Blocked fuel filter (down to me, that one)
2: Cracked contact in the fuel sender flange (float-type sender, where the wires for the pump and sender enter the tank) The crack was inside the moulded plastic bush pressed into the square metal flange. Led to varying high resistance and intermittent current to the pump. Much head-scratching. Still can't figure out what would have caused it to crack but, one of the other contacts for the fuel sender cracked also leading to wacky fuel gauge operation for a while. Anyone else come across this?
3: Bad fuel hose. I bought so-called 'submersible' fuel hose (oohbay of course) when building the bike. Had lots of lovely writing on the side; 'J30 submersible ethanol' and all that. 3 years down the line it's soft, floppy and starting to swell. The hose clips seem to need constant tightening to the point where they will start to cut the rubber. The rubber outer is also starting to show signs of delaminating. Google confirms that there is sub-standard stuff out there. This hose seems okay in external applications - I think it is the rubber outer layer that suffers when exposed to fuel so I am careful to wipe it dry when disconnecting the tank etc.

PS: I was going to search the forum to see if this issue has already been noted, but my browser gave a warning that the 'form wasn't secure' ?

Anyway, good morning everyone ('cept Charlie of course)

Suzi Q wrote:
Anyway, good morning everyone ('cept Charlie of course)

morning mate 

bit late in the am here ...7:30 pm abouts the temp is 3 deg c and heading lower ...fast ...this morning was -7 c 

hmm  however i have seen some of the issues discussed here over the last few years ...and normally i wouldnt disagree with almost all the comments ...but i have noticed  a couple of weird issues that maybe relevant 

1>  not long ago (couple of years ) poor old gerty was suffering from surging issues trying to maintain a nice "country 100 kph " (just add 10 % ...or so ...lol) 

turned out that the old corrolla fuel pump had started to decay after 40 something years of operation ..(recovered from an 78 model some 10-12 years ago ) and now gerty some 150,000 + klms further along the path. (bloody oddo gears lost the plot after 246,000ks ) so lost count there for a few years .

 turns out that the brushes - armature were starting to draw way too much current ...and had burned tthe contacts on the under tank power connector ...even after i had changed it during the fuel pump exchange for 1/4 inch spade connector assembly ( much higher contact rating than the 2.1 mm pin - socket arrangement) as usually fitted .)

anyhow replacing the fuel pump and connector solved that particular issue ...might note that i changed all fuel lines at that time also for 30 r 8 external and 30 r 9 internal .

2> a local enthusiast with a hybrid k100 engine in a k1100 frame ...rt - lt style  was suffering similar issues . but the pump seemed to be ok ...with no evidence of connector issues being burned ...etc ...lets call him steve 

under acceleration or back off normal apparent operation , just at maintaining speed steadily ...like sitting at highway or inner city speeds was the issue noticed .

installed new fuel pump and internals  with no real fix upon testing 

turns out the fpr was only letting about 2 bar pressure load the system .  i removed and crushed the fpr either side of the vacuum line ...thus compressing the spring mechanism to the diaphragm-seat of the fpr ...which brought i back up to about 2.7 bar ... which seemed to sort the issue more than some what .


here we are  a year and a bit later and the issue has returned again to the same machine  so a replacement has been put aside for future repair , 

but other considerations should be assessed

is the AFM actually tracking correctly ? ...has the fuel hose deteriorated and lodging particles of rubber into the filter ..as well at the fpr .??

points i would like to make from experiences 

just because there is fuel returning to the tank ...doesnt confirm correct fuel pressure

the connector going to the fuel pump , under tank , could be corroded and limiting current ..(also affected at running temps)

bloomin spec on fuel lines have no actual real relevance with chinese manufacturers  supplying crap standards for major(usually respectable suppliers )  in relation to fuel standards


if fitting internal lines make sure that the outer sheath is a mixture of PE insulation over the rubber piping as well as the radial reinforcement of the core ...so 30 r9 or higher should be sought ...


get the AFM to someone who can service the electrical bits and pieces ...at least know enough to be able to test it PROPERLY ...often the contacts going to the board from the external connector block are corroded and give erratic readings ...besides the wiper loosing carbon track ...

check the coils for cracks ...they can start to jump over when traversing inclement weather or elevation changes

and make sure you deoxit the hall sensor connector cables under tank  ...in fact all connectors in the ignition - fuel supply schematic 

just some thoughts .......   good luck !!!

Spent some time since the last post, on the fuel system, owing to several different problems. I fitted a fuel pressure gauge which, for ease of installation, is teed into the line from the tank outlet to the LH end of the fuel rail. I have tested this gauge with a proper fuel pressure gauge and it is accurate enough. 
The fpr that's been on the bike since it was built 3 years ago gives 29-31 psi. It oscillates on the gauge, presumably because the fpr is pressuring & releasing cyclically. When the engine is revved the pressure on the gauge rises to 33 psi or so. This rise is 'normal' since the vacuum connection the the inlet manifold ensures that the fuel pressure tracks the inlet manifold pressure and, opening the throttle increases manifold pressure. (Or, if you prefer, opening the throttle reduces manifold vaccuum - same thing)
What isn't correct is the fuel pressure, it should be 36/37psi. So I tested two other fprs. All are original items, from various K bikes over the years. The reason for this post is that all three fprs gave the same 29-31 psi reading. And, this is the same reading the Charlie mentioned in the previous post. So, maybe, as these fprs age, the springs weaken?
Anyway, I solved the problem by fitting an adjustable Malpassi fpr. This oscillates on the gauge, but with more amplitude that the OE fprs - about 4 psi altogether. When running, I have adjusted it so it oscillates between 34 & 38 psi.

Good update post Suzie Q, and good to see you back too.

Probably not a big deal but I think even the oscillation can be reduced as well. I can't remember the name of the post but it was reduced in that case by taking the vacuum for the fuel pressure regulator from all the throttle bodies, not just the last one.

Going back to the original post, I think a pressure gauge on the dash is a good idea. If your brick rolls to a stop and the fuel pressure is good, that eliminates a large part of the fuel system as the problem.