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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: tony101 on September 03, 2015, 08:19:17 AM
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Hi, can anyone tell me if I should hear the petrol pump 'whir' when I switch on the ignition on my 1990 K75 (non ABS). My bike would not start yesterday, I have plenty of fuel and there is a spark but no fuel. When I press the starter button the engine cranks over nicely and then when I release the button the fuel pump makes a noise. But when I watched a video on youtube about changing the fuel filter, albeit on a K100, it mentioned that you should hear the pump 'prime' when the ignition is first switched on, mine does not make a sound when I switch the ignition on.
Any advice where to start looking for the problem? Thanks
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greetings...
k75... ignition in run position... kill switch in run position... you should not hear the fuel pump run until you press the start button...
with ignition in run position and kill switch in run position... what all works... head light... horn... turn signals... brake lights... dash lights... what have you done to it recently... tell us more...
you can start looking here... (http://www.motobrick.com/index.php/topic,5067.0.html)
j o
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HI, thanks for the reply. Other than put two new discs and pads nothing! I have been away for a week, so when i got back I started it up and it fired straight away with no problems, then come the next morning to go to work, it just would not start. Everything else on the dash is working (gear indicator, neutral light etc) and all lights work, it has a new (ie less than 2 months old) odessey battery and is turning over easily
Thanks for the link, that looks excellent..looks like i have my weekend in the garage planned out now!
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Check the fuel pump power connector. It's where the right-rear of the tank meets the seat meets the frame.
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Check the fuel pump power connector. It's where the right-rear of the tank meets the seat meets the frame.
I had the same problem as you, and this was the cause. If the connection isn't secure enough, the cables will come loose. Then the fuel pump no worky worky.
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Sadly the connection is good and i can hear the pump working. Next on the list is to check the fuel pressure...but need to get a manometer first, unless anyone knows a way of checking without one?
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Did you install a new fuel filter?
I think the bike should idle even if fuel pressure was low.
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Hi, can anyone tell me if I should hear the petrol pump 'whir' when I switch on the ignition on my 1990 K75 (non ABS). My bike would not start yesterday, I have plenty of fuel and there is a spark but no fuel. When I press the starter button the engine cranks over nicely and then when I release the button the fuel pump makes a noise. But when I watched a video on youtube about changing the fuel filter, albeit on a K100, it mentioned that you should hear the pump 'prime' when the ignition is first switched on, mine does not make a sound when I switch the ignition on.
Any advice where to start looking for the problem? Thanks
I will always start by changing the plugs as my first step in dealing with turns over/no start issues, even if they look good, and are relatively new.
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Sadly the connection is good and i can hear the pump working. Next on the list is to check the fuel pressure...but need to get a manometer first, unless anyone knows a way of checking without one?
Not sure a manometer will have enough range, fuel pressure will be in excess of 35psi....... need a regular pressure gauge.
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I don't know shit from shinola but. You say you got spark. And you can hear the fuel pump working. I would pop off the hose from the gas tank where it connects to the throttle rail, point it in a safe direction, like in a bucket or something, and see if it pukes gas when you crank it over? if not pop off the fuel filter in the tank and try again?If still nothing comes out, I would replace the fuel pump and filter. Like I said I don't know much, and this game is all new to me, so this could be a very unwise procedure unbeknownst to me. I accept no responsibility for anything that may happen! Do so at your own risk. I HAVE NEVER DONE THIS BEFORE MYSELF!!!!
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Fuel injection typically has a minimum pressure to function properly.
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Fuel injection typically has a minimum pressure to function properly.
I did not know that. :dunno2: Thanks!
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Fuel injection typically has a minimum pressure to function properly.
For the K75, it's 2.5 bar IIRC.
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Here is a random thought... Have you considered popping the vacuum plugs and the vacuum regulator hose on the TB's, and adding fuel or an aerosol based engine starter fluid. Doing it one by one will let you know if the individual plugs are firing. Doing all of them at the same time and letting it run for a second or two until it quits will let you know if everything is firing and your timing is right. If it does that, then you know it's a fueling issue.
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Well i could be worth a try, as i have discovered i have fuel getting to the injector rails. So it looks like its time to delve into the electrics :o(
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Ok, so i've done some probing and i have some 'interesting' readings with the voltmeter. So:
Battery reading 12.54v
Pin 4 of Jetronic should have 12v - I only have 7.6V
At pin 30 of Starter Relay I get 12.3v
At Pin 87 of Starter Relay I get 10.33v (when starter depressed)
and at Starter Motor I only get 10.1v (when starter depressed) - starter turns over nice and fast though.
So my question today is, normally if the Starter Relay fails, does it stop working completely or do we think I have found my non starting problem? I note of interest looking back at the receipts from the previous owner that the bike seems to have had a starter relay every 2 years and the last one was fitted ............. 2 years ago!!
Anyone any thoughts? Thanks
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Pin 4 of the ECU is connected to several other circuits on the bike -- Pin 86 of the starter relay and pin 6 of the ICU. There are also two inline connectors through which the wires pass that could be corroded and introduce voltage drop.
First check the voltage at pin 86 of the starter relay with the starter switch depressed. If it is 12V, the voltage is being dropped across a bad inline connector.
Check and clean the 4-pin connector that joins the injector harness to the main harness, on the left side just below the tank. This connector is just like the fuel pump connector and can suffer the same degradation. Also check the 9-pin switch block connector on the right side of the tank. Lastly check the connector at the ICU located by the headstock under the tank. There seems to be enough voltage to engage the starter relay (since your starter turns), but there might not be enough to signal the electronics on the ECU and ICU.
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Ah I only have 7.6v at pin 86 of the relay, so it looks like the starter relay is the problem
Thanks for the advice rbm, i'll clean up the connectors you mention while the the tank is off etc. just for good measure
Time i think to order a new realy.
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Hold on. The relay may not be bad. It may be the other components attached to the same circuit that is causing the problem. Take a look at the schematic and think through the problem.
The output from the start switch is on pin 1 of the 9-pin switch gear connector. Then it branches out to three different components - the starter relay coil, the ICU under the tank and the EFI computer under the seat. Try eliminating all components from the circuit and plug each in to see their effect.
1) Pull connectors from the starter relay, ICU and EFI. Test the voltage at pin 1 of the 9-pin connector. If 12V, one of the other components is the culprit; if 7.6V the starter switch is the culprit. Confirm your suspicion by testing the voltage at pin 6; it should be 12V. If not, the problem is towards the fuse block.
2) Plug in only the starter relay. Test the voltage on pin 86 at the coil. If 12V, one of the other components is the culprit; if 7.6V the starter relay is the culprit.
2) Plug in the ICU and test the voltage. If 7.6V, the ICU is the culprit; if 12V either the EFI or the 4-pin harness connector is the culprit.
Wholesale replacement of parts in an effort to solve a problem without stepping through a troubleshooting procedure is wasteful.
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Morning, rbm thank you again for your advice looks like it may have saved me going down a dead end. OK today's readings are:
1) Pull connectors from the starter relay, ICU and EFI. Test the voltage at pin 1 of the 9-pin connector. If 12V, one of the other components is the culprit; if 7.6V the starter switch is the culprit. Confirm your suspicion by testing the voltage at pin 6; it should be 12V. If not, the problem is towards the fuse block. 12.16V and 12.15v
2) Plug in only the starter relay. Test the voltage on pin 86 at the coil. If 12V, one of the other components is the culprit; if 7.6V the starter relay is the culprit.10.49v
2) Plug in the ICU and test the voltage. If 7.6V, the ICU is the culprit; if 12V either the EFI or the 4-pin harness connector is the culprit.7.6v
So it is looking like an ICU issue, is it?
Can anyone suggest why i'm only getting 10.49v at the starter relay?
Thanks
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Strange. With just the starter relay in the circuit, you should theoretically read battery potential at pin 86, because it's not a complete circuit and no current should be flowing (therefore no voltage should be dropping). There is 1.6V being dropped across something that is drawing current but there is nothing in the schematic that I can see which would cause that drop.
When you connect the ICU and press the start button, you're telling the ICU to complete the ground to the starter relay. You should measure some voltage drop at the starter switch, maybe a volt or so, to account for the drop across the switch and within the wiring and possibly within the ICU. But not 4.5V.
If you change the procedure slightly, and for step 3 plug in the EFI computer rather than the ICU, do you again read 7.6V at the starter relay?
With all the wiring back in place, when you turn over the engine, do you get spark at the plugs?
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Well with the ICU unplugged but the EFI plugged in I get 10.3v. But i still get sparks at the plugs. So not sure at all where i am losing my 1.6v, it really is strange.
I can get another icu reasonably cheaply, so may try a secondhand unit and see what results i get with that fitted.