I'm trying to track down my no-run problem (bike runs and revs up while starter button is pressed, dies otherwise), and I've gotten myself a cheap fuel pressure gauge set. Here's what I've got:

Hooking it up between FPR and return on tank gives me 0psi(????), but hooking directly up to the pump gives me about 90psi, which falls to about 70. The pump seems to hold pressure after you let off the starter just fine.


It seems to me that the pump's relief valve may be an issue (as probably also is the fuel filter, which is marked Made In W. Germany). That said...Is this really going to cause a no run situation?

FissionMailed wrote:
Hooking it up between FPR and return on tank gives me 0psi(????), but hooking directly up to the pump gives me about 90psi, which falls to about 70. The pump seems to hold pressure after you let off the starter just fine.


It seems to me that the pump's relief valve may be an issue (as probably also is the fuel filter, which is marked Made In W. Germany). That said...Is this really going to cause a no run situation?

0psi on the return line is expected as there should be no resistance to the flow back to the tank.

The place where you need to know the pressure is between the fuel pump and the injectors, as that is the pressure that pushes fuel through the injectors. The FPR bleeds off excess pressure by returning fuel to the tank.

Did you test pressure from the pump with the fuel rail still connected, or by putting only the gauge on the pressure line? You need to use a T piece so the pressure gauge is an addition to the system, not replacing the fuel rail.
Haynes manual says working fuel pressure is about 36psi, with the pump's safety valve opening at 68psi. Close enough to the 70psi you got.

Under normal circumstances, the pump's own pressure relief valve would never come into play because the FPR would keep the line pressure below the pump's cutoff value. If the FPR is faulty and doesn't release excess pressure, the pump's internal one would then come into play. This could also happen if the fuel filter is blocked, as the pressure doesn't get through to the FPR.

Bill

Could be electrical?
Someone may have to correct me but, when you release the starter button, the pump is then powered by a different part of the electrics.
Think contact cleaner on the multi pin connectors to the boxes under the tank. Or one may need replaced.
Pumps generally work or don't work. 
That fuel filter should be replaced. They can completely block up.
Personal experience there.

OK, I figured I'd still get 36psi just after the regulator. I get it...I do get 36 when hooked up before the fuel rail, however.

The fuel pump turning itself off is an issue I cannot seem to solve.

IT'S ELECTRICAL!
Common K problem. The starter button only powers the pump to start it. Then power comes from either the fuel injection or ignition. Can't remember which.
Do a search on the forum.

The fuel pump will run while there is an earth supplied from the ICU to the FI relay and that earth will continue for 1.5 seconds after you release the start button or will continue on while there are pulses coming from the Hall Effect sensors which trigger the ignition.
The problem you have IS electrical and not fuel pressure related.

Hey, just trying to narrow things down by testing what I can, before I start throwing parts at it.

So thinking ignition module is bad, possibly? I know that the bike does spark on all 4 cylinders. The connections have all been DeoxIT'd.

FissionMailed wrote:Hey, just trying to narrow things down by testing what I can, before I start throwing parts at it.

So thinking ignition module is bad, possibly? I know that the bike does spark on all 4 cylinders. The connections have all been DeoxIT'd.

Glad the fuel pump pressure is confirmed as OK.

If you are getting spark on all cylinders, its obviously not the Ignition unit. As the others have said, the problem is electrical and related to the fuel injection computer under the seat, or a relay or connection.

While a problem with the computer is not impossible, with any computer controlled vehicle it is far more common for it to be a sensor, a relay or an electrical connection. Even when people have replaced the computer, its likely the process of disconnecting and connecting the new one has made a better connection, so resolving the problem.

Bill

Got two ideas to check here: fuel pump relay (should probably just replace it, pretty cheap and just a standard 4 pin relay, right?), and the ground connection from the ignition unit to the relay(should test and make sure there isn't a break in the wire).

Is this the proper way of thinking here?

FissionMailed wrote:Got two ideas to check here: fuel pump relay (should probably just replace it, pretty cheap and just a standard 4 pin relay, right?), and the ground connection from the ignition unit to the relay(should test and make sure there isn't a break in the wire).

Is this the proper way of thinking here?

Yeah you're on the right track doing that but I think it is a 5 pin having 2 terminals for output connections. Don't start throwing parts at it as they can very quickly become a money pit.
To find electrical faults you need to take a very cautious and systematic approach and work through each part and section of the wiring one bit at a time and you will find the problem.

RicK G wrote:The fuel pump will run while there is an earth supplied from the ICU to the FI relay and that earth will continue for 1.5 seconds after you release the start button or will continue on while there are pulses coming from the Hall Effect sensors which trigger the ignition.
The problem you have IS electrical and not fuel pressure related.

I have looked at the wiring diagram and agree with what you say about the earth being supplied from the ICU.  What you say about the Hall Effect sensors makes sense also.  I was wondering if the vacuum switch is also used to determine when the engine is running. It would be fairly simple to jump out the vacuum switch to see if that is the problem.

I don't think the vacuum switch does much about telling if the engine is running at all ...I believe it used to be wired to the injection control computer under the seat so has little to do with the icu (ignition control )

just as a note ...if no pulses are received from the hall effects ...the icu will not keep the fi relay engaged for that 1.5 seconds ....please don't ask me how I know ...

good luck

I'm almost positive this is an issue where, somehow, the Hall effect signal is not being received after the starter button is released. I just don't see how this can happen when it knows when you inject fuel and when to spark- as proven by how it can rev as normal while the starter button, (fuel pump), is engaged. Right? Is a partial failure of the ICU really possible?

The diagram, and this issue, are giving me a headache.

there was a member  that delved into the icu and found the issue ... that he had ...a bit of soldering and perhaps a replacement component solved this for him .



so I just think that its a not an unheard of issue

for some of us the icu and other electronic gizmos are a not go situation   but perhaps if some one has a spare it could prove disprove the fault at hand

just what I think

The vacuum switch connects ICU pin 15 (violet/green) to earth.
Violet/green goes thru a connector under the tank.
Would be worth checking both the wiring from ICU to vacuum sw and also the function of the switch.

Also, just a thought but the TPS idle sw may be perm closed. You said in your prev thread that it wouldn't rev over 2k. Try removing the TPS connector to test.

I actually took the TPS sensor out, cleaned it, and reinstalled/readjusted it. No effect. Unplugging it does nothing- actually one of the first things I tested.

What's odd is that it got WORSE after I threw new plugs on- before it would idle badly, not above 1500rpm or so, but now it won't run unless you hold the starter button down. They're NGKs (d7ea maybe? Boxes aren't handy this second, it was a type y'all recommended )and I kept the old resistor caps on them. I can verify all are sparking and the wires are not mixed up.

Looked up the vacuum switch- appears mine is already disconnected as three of the TBs have vacuum caps on, number four has a line to the FPR.

This bike is rough to diagnose. If you guys could only see what the previous owner did to the relay box (hint: none of the relays are factory, most of the wiring isn't either) you'd understand my troubles

FissionMailed wrote:..... three of the TBs have vacuum caps on, number four has a line to the FPR.

That's how it should be

That vacuum switch was discontinued from around mid 85 and a good thing to as it was about as useless as tits on a frog.
I think it was used to richen the mix at low vacuum which wasn't needed.
Result is to remove it insulate the wire if necessary and feed it to the rubbish bin.

The vacuum connector is disconnected (no effect on my issue, which I figured)

So let me ask this- how much resistance is acceptable to ground? I'm getting about half an ohm from the ecu connector to ground on the battery.

0.5 Ohms doesn't surprise me considering the length of wire involved. That type of contraption usually run on less than 12v (usually 5v) so I wouldn't consider it to be a problem. Check how much the meter reads when you put the leads together, those meters often read 0.5 or close.

Half ohm is what I consider to be within the measuring accuracy of most digital meters a dead short.  With the current from the ECU measured in mA the voltage drop in that wire is going to be near zero.  

The ECU grounding is good.

You say that the wiring has been 'customised'.
I have had problems with the K I've just bought and believe that's where the problem lies.
Does the bike have an alarm or immobilizer?
I've just discovered a very old one on mine and its coming out.
Can I suggest that you post a list of what you have already checked.
The guys here love a challenge, sad, I know.
If we all knew what has been checked, it may speed up a diagnosis.

FissionMailed wrote:The vacuum connector is disconnected (no effect on my issue, which I figured)

So let me ask this- how much resistance is acceptable to ground? I'm getting about half an ohm from the ecu connector to ground on the battery.

What I understand is the vacuum sw was normally open and the vacuum from the TB would close the switch grounding pin 15 of the ICU signaling a change in the ignition advance curve. 
In removing the vacuum sw it was recommended to insulate the connection back to the loom.
Pin 15 is not normally grounded. The ICU is grounded permanently thru pin 1.
If the vacuum sw was terminated properly you should have no continuity from pin 15 to earth. Your meter should indicate open circuit. 
0.5 ohm just means you have a closed circuit. You'd get pretty much the same reading if you put your meter probes together.

Comberjohn wrote:You say that the wiring has been 'customised'.
I have had problems with the K I've just bought and believe that's where the problem lies.
Does the bike have an alarm or immobilizer?
I've just discovered a very old one on mine and its coming out.
Can I suggest that you post a list of what you have already checked.
The guys here love a challenge, sad, I know.
If we all knew what has been checked, it may speed up a diagnosis.

Comberjohn, you might find this thread interesting if you haven't already seen it. Similar thing.
https://www.k100-forum.com/t2307-k75-cuts-out-and-dies

No alarm or immobilizer from what I can tell. So far:

Spark has been tested as good on all 4 cylinders
Hall effect sensors both test fine when taken off bike
Coolant temp sensor was tested at the ECU connector at about 32*F and was fine (5500ohm, I think? It was in line with the K100 diagnosis bible)
Ground from ECU to transmission is fine, maybe .1ohm at most
3 injectors are fine, one at 17ohm even, not sure if that's enough to kill her
Removing TPS does nothing
Spark plugs are new D7EA with the resistor caps off the old bike (after replacing these, the bike ceased to idle unless starter button was held down)
ECU/ICU, hall effect, and ignition connections cleaned and DeoxIt-ized
AFM is a used unit that tests good (I think)
FPR is new, fuel pressure is good from pump and at rail

(after replacing these, the bike ceased to idle unless starter button was held down)

We met this here with a K75 and the problem was the multi pin connector under the seat. I moved to remove the battery and suddenly the problem disappeared. Take off, clean the pins [think you have done this], refit and tighten the little grub screw. If the pins are not connecting properly this will not show up on the meter. Even if they are clean each one must make a good mechanical connection in order to make the electrical connection.

There is another thread here from a few weeks ago and to the surprise of the forum experts the cause was found to be a relay which when replaced cured the problem. I cant remember if it was the load shed or starter relay.

Edit: no real corrosion on the ecu pins, I did remove the ecu from its holster to more securely attach the connector

Does anybody have the part numbers for the load shed and starter relays? Thinking I might just replace those no matter what

I don't want to throw parts at it, but I do want to ensure its reliability for a while- guys, I spent a problem-free year riding my bike every day, rain or shine, 100* down to single digits, and now I'm stuck with my mk6 GTI which I kinda hate, because I have little time to diagnose this crazy thing

I always go for the simple stuff first.
Can you clarify what exactly you did with the plugs?
Did you change the caps from another bike?
We've all done stupid things, have you checked the plugs are tight?

Sorry! Caps came off the old plugs, not bike. Were Champion plugs. I removed the old ones, put a very light dab of antiseize on the new ones, then installed them. The wires are on the correct coils. I did not gap them, are you supposed to gap these? I was under the impression that you weren't.

I will check and see if they are tight in the morning, and gap them as well- not sure that is my issue, but worth checking, of course.

Edit: and, of course, my battery is beginning to get weak. Before I continue on with this, would it be better if I got a battery charger or am I OK to jump start it off a non-running car and let it for for a few minutes to charge up? Is there a big difference?

just a question

did you install the ferules to the top of the threaded section of the plug tops ...some (or many ) ngk plugs do not come with them fitted at all these days

leaving a good old spark gap if you neglect them (THE LEADS ARE DESIGNED FOR A 5 MM FERULE ON TOP OF THE PLUG )  the 3 mm threaded tops leaves a gap if not fitted .
sometimes this is unnoticed ...at first   but may contribute to failures 

just a heads up !

FissionMailed wrote:
3 injectors are fine, one at 17ohm even, not sure if that's enough to kill her
The standard Bosch OEM #0280150210 (number is stamped on the plastic section) has an impedance of 16.2 ohms. If the coil was shorting it would likely read less. I'd keep an eye on that injector anyway and if the impedance varies it may indicate a poor internal connection or an impending short.
What do the others read?

Spark plugs are new D7EA with the resistor caps off the old bike (after replacing these, the bike ceased to idle unless starter button was held down)
Would be good to know what SPs you had in there previously (not just the brand).
Gap should be 0.024 to 0.028 in (0.7 - 0.6mm)
What do you mean by "resistor caps off the old plugs" ? The resistor caps are the right angled metal caps with rubber inside which are a part of the the HT leads and as Charlie says you must have ferules screwed to the top of the SP for the cap to fit correctly.

You can buy this second hand starter relay or a new one from euromotoelectrics.com which has diodes to protect the electronics. The old ones don't.
But its easy to check it out first rather than buy a new one. It pulls apart easy enough. Clean the contacts. Test the coil etc. If one or both contacts are burnt ... chuck it.
Low battery voltage can damage a starter relay. Take your battery out and get it tested at a battery shop.

charlie99 wrote:just a question

did you install the ferules to the top of the threaded section of the plug tops ...

Terminology error on my part. Yes, I took them off the old plugs. I no longer have the old plugs to see what they were, beyond remembering they were Champion copper.

3 injectors read 16.1-16.2ohm, one read 17.

https://i.servimg.com/u/f38/19/15/72/20/20150210.jpg


This is the special equipment connector, right? There is no female side that I can see. Makes sense as my RS was stripped. The yellow plug next to it doesn't need to be plugged in anywhere, right

Also, I haven't done any electrical testing today, but I've got my battery charging (was right at 11.99v) and will do that tonight. I cleaned up all the relays and have got the starter one out- I test it by applying 12v to the positive and negative, I guess? Only 12v source I've got is the 4 AA battery rig I made for the hall sensor test

What is the non OEM fuse holder in the picture connected to?

Appears that my headlights have had a relay thrown on them. I have no idea what a 250V/10,000A time delay fuse is going to protect.

Modified wiring systems usually make some mysteries sooner or later.

What is the non OEM wire at the starter relay output for?

The round black connector is for extras, and it should be a white one down
there for the OEM alarm system.

Did you do anything else at the same time as the plug change?
Just sounds too much like a coincidence that something else would fail at the same time.
I thought I had a bad set of new plugs and it turned out that I'd put one of the injector blanking plugs on to the threaded part of the butterfly adjusters. One of the injectors was drawing in air.
Took a while to spot it.

Almost as good as not putting any of them back on and then wondering why it was running like a pile of sh!te.

Dai wrote:Almost as good as not putting any of them back on and then wondering why it was running like a pile of sh!te.

So, you were watching me!

FissionMailed wrote:Also, I haven't done any electrical testing today, but I've got my battery charging (was right at 11.99v) and will do that tonight. I cleaned up all the relays and have got the starter one out- I test it by applying 12v to the positive and negative, I guess? Only 12v source I've got is the 4 AA battery rig I made for the hall sensor test

NO. Test the starter relay by applying 12v to the connector terminals. You should hear the contacts click. Check continuity between the larger terminals terminals. The + & - ones on the outer.
If you can visually check the contacts, make sure they aren't burnt or worn down too much.

Kaptain Holister wrote:NO. Test the starter relay by applying 12v to the connector terminals. You should hear the contacts click. Check continuity between the larger terminals terminals. The + & - ones on the outer.
If you can visually check the contacts, make sure they aren't burnt or worn down too much.

I'm just going to say that I don't understand the mechanics of this. What am I supposed to do, exactly?

Also, when I changed the plugs (which I just pulled, verified they were gapped properly, and cleaned), I changed the FPR, as the old one was some junky adjustable aftermarket one. It tests fine.

The non OEM wire on the starter relay appears to be for the headlight relay setup

A few observations: the fuel pump sounds...odd, but it does continue to run for a second or two after the engine dies, which happens after you release the starter button.

Second, I began testing the ignition connector with my multimeter, and I find that the #1 pin ground is good, but pins 3/4 both give infinite resistance. This is wrong but seems odd. I'm reading with the key out and kill switch off. This is correct, right?

Has the Starter been given a tune up, Its used after its starting duties and may not be supplying that feature.

K75cster wrote:Has the Starter been given a tune up, Its used after its starting duties and may not be supplying that feature.

No, no work has been done to the starter.

FissionMailed wrote: but pins 3/4 both give infinite resistance. This is wrong but seems odd. I'm reading with the key out and kill switch off. This is correct, right?

You should measure 0 resistance to ground with connector connected.
With the Connector disconnected I would expect some resistance through
pin 3 (hall sensor negative) and infinity through pin 4 (shield).

On the other hand I don't think it's a good idea to measure through the hall sensor.

I thought measuring at the female ignition connector with an ohmmeter was exactly what I was supposed to do. Now I am entirely lost

If you following Bert's TS guide it seems to me that it's based on a connected connector.

I thought the same thing, which is why I'm totally lost as to how to go about the electrical tests. I can replace any parts I need to with no issues, but I need a guide that pretends I'm 3 years old when it comes to electrical stuff

If you measured infinity resistance to ground at pin 3 and 4 with the connector connected in post # 43 it's something wrong with your ignition ECU.