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Chris,
Don't tie in to the ECU too early. The ECU needs to know the engine is running or it will turn off the fuel pump. That is a safety feature in the event of an accident so the pump does not continue to pump fuel in case of a fire. So it needs an engine running signal. I noticed the cruise takes a similar signal off the number 6 coil. The ECU has two choices. The tach signal or the #6 coil signal.
I'm just trying to tie both of your problems together if it is possible. What if there was an issue with the #6 signal and you moved something etc. and now have the signal at the cruise but not at the ECU? I wish I knew for sure where the ECU got the engine running signal from. Can anyone say for sure? Is it the #6 coil. (It's at the ECU) Is it the tach signal? (It's also at the ECU) Chris I think you get my drift. Before you dig in to the ECU be sure the ECU has an engine running signal. Without that the ECU says "Engine not running , I won't turn on the pump." I think the reason the bike continuous to run after you take the jumper off is either it siphons or gravity feeds the carbs slowly. Especially if the tank has lots of gas in it.

Edit: Did a little more investigating. If you turn the key ON, the pump should run for a second or two. OFF, then back ON the pump should run for a second or two. OFF..then ON and the pump should run for a second or two. Does it do this? All above is correct but this feature makes sure the bike has fuel to start only.
 

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Discussion Starter #22
Thanks for the information and the comments are duly noted.

The fuel pump doesn't prime (run for a couple of seconds) when switching on the ignition or when repeating this routine, this is why I suspected the wiring in the first instance, and now the ECU itself.

I have already striped down the ECU and removed what I believe to be the faulty transistor. It didn't cost much from Ebay, so if it doesn't work, no problem. On the other hand this could be the answer to the issue!
 

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The 88-89 bikes had the fuel pump relay which cycled the pump on with key on. 90-up bikes the pump is powered only with engine cranking or running.
 

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snip...
Edit: Did a little more investigating. If you turn the key ON, the pump should run for a second or two. OFF, then back ON the pump should run for a second or two. OFF..then ON and the pump should run for a second or two. Does it do this? All above is correct but this feature makes sure the bike has fuel to start only.

Redwing, I'm pretty sure the fuel pumps after the 88-89 do not run for a couple of seconds after key-on. Then after those years were modified to have a vacuum petcock, that feature was deleted. It is of no use with a vacuum operated petcock in the gas line.
 

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Guess I'm too slow... DriverRider got in ahead of me with that tidbit.
 

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Chris,
Don't tie in to the ECU too early. The ECU needs to know the engine is running or it will turn off the fuel pump. That is a safety feature in the event of an accident so the pump does not continue to pump fuel in case of a fire. So it needs an engine running signal. I noticed the cruise takes a similar signal off the number 6 coil. The ECU has two choices. The tach signal or the #6 coil signal.
I'm just trying to tie both of your problems together if it is possible. What if there was an issue with the #6 signal and you moved something etc. and now have the signal at the cruise but not at the ECU? I wish I knew for sure where the ECU got the engine running signal from. Can anyone say for sure? Is it the #6 coil. (It's at the ECU) Is it the tach signal? (It's also at the ECU) Chris I think you get my drift. Before you dig in to the ECU be sure the ECU has an engine running signal. Without that the ECU says "Engine not running , I won't turn on the pump." I think the reason the bike continuous to run after you take the jumper off is either it siphons or gravity feeds the carbs slowly. Especially if the tank has lots of gas in it.

Edit: Did a little more investigating. If you turn the key ON, the pump should run for a second or two. OFF, then back ON the pump should run for a second or two. OFF..then ON and the pump should run for a second or two. Does it do this? All above is correct but this feature makes sure the bike has fuel to start only.
If the ECU wasn't getting that signal the engine would not run. It doesn't receive that signal anyway, it puts out that signal.
 

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Redwing, I'm pretty sure the fuel pumps after the 88-89 do not run for a couple of seconds after key-on. Then after those years were modified to have a vacuum petcock, that feature was deleted. It is of no use with a vacuum operated petcock in the gas line.
I had a 94SE and a '98SE.

both of them worked exactly the same.

Key ON, pump runs for 2 seconds and stops.

Key OFF, and back ON, it will run for 2 seconds and it will stop.

IF the oil pressure comes up, then the fuel pump will be turned ON until the key is OFF, or the BAS is activated.

Both of those bikes had the vacuum petcock and both worked just like they are supposed to.

I had plenty of experience with the '98. the fuel pump on it went bad, and I did a lot of testing for flow trying to figure out if it is the pump, or something else.

Jumper the fuel pump B+ terminal to 12V and the fuel pump will run forever. But, if it is OEM hookup, it will only run for 2 seconds key ON unless the engine starts and oil pressure comes up.
 

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I had a 94SE and a '98SE.

both of them worked exactly the same.

Key ON, pump runs for 2 seconds and stops.

Key OFF, and back ON, it will run for 2 seconds and it will stop.

IF the oil pressure comes up, then the fuel pump will be turned ON until the key is OFF, or the BAS is activated.

Both of those bikes had the vacuum petcock and both worked just like they are supposed to.

I had plenty of experience with the '98. the fuel pump on it went bad, and I did a lot of testing for flow trying to figure out if it is the pump, or something else.

Jumper the fuel pump B+ terminal to 12V and the fuel pump will run forever. But, if it is OEM hookup, it will only run for 2 seconds key ON unless the engine starts and oil pressure comes up.
So the engine running signal is oil pressure? I kind of look at the schematic and did not see that but I don't doubt what you say. My old Vega worked like that. When the bearing wore out and oil pressure dropped it would die at a stop sign when the engine would idle and the oil light came on. Good to know and Dave, I learned another thing. :)
Mike
 

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I had a 94SE and a '98SE.both of them worked exactly the same.Key ON, pump runs for 2 seconds and stops.Key OFF, and back ON, it will run for 2 seconds and it will stop.IF the oil pressure comes up, then the fuel pump will be turned ON until the key is OFF, or the BAS is activated.Both of those bikes had the vacuum petcock and both worked just like they are supposed to.I had plenty of experience with the '98. the fuel pump on it went bad, and I did a lot of testing for flow trying to figure out if it is the pump, or something else.Jumper the fuel pump B+ terminal to 12V and the fuel pump will run forever. But, if it is OEM hookup, it will only run for 2 seconds key ON unless the engine starts and oil pressure comes up.
I can assure you oil pressure has nothing to do with fuel pump running parameters as there is no oil pressure signal wire to ECU and fuel pump battery (+) supply comes directly from ECU.
 

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Well I wish someone would make up there mind! :ROFL: How about the vacuum signal? That is there. :raspberry:
 

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90-up bikes the pump is powered only with engine cranking or running.
You are exactly right for my 1999. Not key on. Bump the start button and it runs for 2 seconds or so. If you start the engine it runs until you shut it down. Where does it get the signal?
 

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Redwing, I'm pretty sure the fuel pumps after the 88-89 do not run for a couple of seconds after key-on. Then after those years were modified to have a vacuum petcock, that feature was deleted. It is of no use with a vacuum operated petcock in the gas line.
My 1988 has a vacuum operated petcock. As I understand it (and I'm not positive) the petcock spring is just strong enough to stop gravity from feeding fuel to the engine. With the pump running it will over power the spring and pump fuel even with the vacuum line disconnected. Only meant to stop gravity feed so no hydro locking.
 

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Redwing, I'm pretty sure the fuel pumps after the 88-89 do not run for a couple of seconds after key-on. Then after those years were modified to have a vacuum petcock, that feature was deleted. It is of no use with a vacuum operated petcock in the gas line.
My 1988 has a vacuum operated petcock. As I understand it (and I'm not positive) the petcock spring is just strong enough to stop gravity from feeding fuel to the engine. With the pump running it will over power the spring and pump fuel even with the vacuum line disconnected. Only meant to stop gravity feed so no hydro locking. Heard from some who ran there bikes with the vacuum line off. It ran but not properly at higher RPM.
 

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Well I wish someone would make up there mind! :ROFL: How about the vacuum signal? That is there. :raspberry:
Pretty sure it's the pulse generator signal that operates the fuel pump output. That is the only input signal that tells the ECU the engine is turning. If it had a fuel pump relay the ignition pulse to the coils output would operate it.
 

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Discussion Starter #35 (Edited)
An update for all who have similar problems.

Replaced transistor, as per attachment, and the 'old girl' fired up and ran at first attempt.

For the little time involved in stripping the ECU down, and the relatively low cost of the replacement part, well worth the effort!

Got part through Ebay at the following link: http://www.ebay.co.uk/itm/160937383031?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT, but I'm sure there are similar places to obtain the part in the US?

Thanks to all who gave me some useful advice.
 

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It aint rocket science
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As I understand it (and I'm not positive) the petcock spring is just strong enough to stop gravity from feeding fuel to the engine. With the pump running it will over power the spring and pump fuel even with the vacuum line disconnected. Only meant to stop gravity feed so no hydro locking. Heard from some who ran there bikes with the vacuum line off. It ran but not properly at higher RPM.
Very true that the 1.5 psi the OEM pump delivers will keep the valve somewhat open. Anyone can test this for themselves by starting engine and removing petcock vacuum line, you will be waiting a long time with engine idling for the carbs to run dry as in a tankful of gas.

Whether the pump pressure alone can open the valve from fully closed without the vacuum assist during engine cranking for starting who knows and is of no consequence to me anyways.

Not so much for hydro lock as any flooding fuel level in bowls gets dumped overboard when upright with the 1500 carb design but in cases where unattended machine tips over that a tank of gas cannot leak out as a fail-safe.
 

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Simple things changed over the years so not every 1500 works like every other 1500.

My 88 1500 the pump will run just flipping the key on and off and not cranking or anything. Also with engine off I can fill the carb bowls just flipping on off the key. 88 does have a vacuum petcock also I'm pretty sure.
I did this to fill the carbs for push starting after I let the 88 sit a long time after that deer hit it.
However, I can also just turn on the key and use reverse without the engine running on the 88. My newer 1500's like 95 and 99 reverse will not work unless engine is running. Sometimes it's simple changes like that which can make things confusing.

I'm sure somehow Honda decided it safer for reverse to NOT work if engine not running, I consider it rather dumb and a problem at times, also unsafe!
What if 1000lb bike dies and it needs to be rolled backwards up a little hill to get out of a road??? One thing to not have a reverse at all on a bike, but if it does have reverse then it should work!

Sure was nice with 88 to be able to back up a hill a little then roll to start it (since my idler gear was busted and had to always roll start).
With 95 and 99 it's a pain that if they sit a long time and hard to start I just have to keep cranking on them till they do start or battery goes dead. I have to back up a hill in my drive to get out but then I can roll a long long ways down hill to roll start if I wanted/needed, but of course cannot do that since the engine has to be running to back up!

Again it's nice the 88 reverse works without engine running. She been sitting well over a year and I'm sure will be hard to start! SO I can roll her down a little hill at the shop and if she don't start then just back up the hill a bit and try again. If I get the battery a bit low just swap batteries and charge up the low battery while using the other full charged battery.
 

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This is some good to have information on the ECU repair. Looks pretty simple to fix if that is your problem.
Thanks for posting that info.
 

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Chris,

Thank you so very much for coming back and reporting EXACTLY what fixed your bike.
So many folks just get it fixed, and disappear from the forum.

Now, we have a documented reference for folks who also have severe non-starting issues to look into.
You got a goldstar and a bookmark >:)



An update for all who have similar problems.

Replaced transistor, as per attachment, and the 'old girl' fired up and ran at first attempt.

For the little time involved in stripping the ECU down, and the relatively low cost of the replacement part, well worth the effort!

Got part through Ebay at the following link: http://www.ebay.co.uk/itm/160937383031?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT, but I'm sure there are similar places to obtain the part in the US?

Thanks to all who gave me some useful advice.
 

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Rick

Glad you are skilled enough to accomplish what you did with the replacement of the transistor. By far I believe you are one of the few that had gumption to try this fix.

I have read the posts and wires to the fuel pump go hot for a second while turning the key to run. Never heard or felt my pump run at all. I have an open circuit at the fuel pump wires. I tried running straight from the battery to the plug of the motor and nothing. Should of jumped around spinning madly. So unless I get something said in reply to surprise me regarding the fuel pump motor, I know I need a new fuel pump.

Fussed with the tank itself inside and managed to get a better flow the petcock hole in the tank. Trying the vinegar effect to clean the inside out the best I can.

I did get it running for a minute on full choke with air pressure at the sending unit location. I had to use starter fluid but it did run like that couple times. Have not been able to start it up again.

Rick
 
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