Fuel Pump Question


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Jmicester24
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Fuel Pump Question

Post by Jmicester24 »



I replaced my fuel pump on my 99 1500 today and now fuel is not pumping. I jumped the fuel pump so i know it works.
(See attached photo) the black connector on top of the fuelpump assembly has power but as soon as I connect it back to the assembly there is no power. When I cranking the engine the clack connector has no power.

I guess my question is, is that connector suppose to behave in that manner?? If not, what could be the issue?
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Not photo from my bike
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Rambozo
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Re: Fuel Pump Question

Post by Rambozo »

Do you have a power filter fitted? (Only on Asp with CB or SE models)
Was your old fuel pump locked up or shorted?
If so, there is a chance you burned out a transistor in the ECU.
If you search here, there are topics on fixing that.
Does the engine start? The fuel pump will only run if the ignition is working.
Jmicester24
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Sat Nov 11, 2023 3:22 am Do you have a power filter fitted? (Only on Asp with CB or SE models)
Was your old fuel pump locked up or shorted?
If so, there is a chance you burned out a transistor in the ECU.
If you search here, there are topics on fixing that.
Does the engine start? The fuel pump will only run if the ignition is working.
I do not have a power filter.
The old pump was a bit too powerful for the bike, so I decided to change it. When put in the new pump that's when I noticed the symptons above.
My ignition works, as the bike still cranks when pressing the ignition button.
Jmicester24
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Re: Fuel Pump Question

Post by Jmicester24 »

Also is there a way to test to see if indeed I blew the transistor in the ecu?
Jmicester24
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Re: Fuel Pump Question

Post by Jmicester24 »

Jmicester24 wrote: Sat Nov 11, 2023 11:23 am
Rambozo wrote: Sat Nov 11, 2023 3:22 am Do you have a power filter fitted? (Only on Asp with CB or SE models)
Was your old fuel pump locked up or shorted?
If so, there is a chance you burned out a transistor in the ECU.
If you search here, there are topics on fixing that.
Does the engine start? The fuel pump will only run if the ignition is working.
I do not have a power filter.
The old pump was a bit too powerful for the bike, so I decided to change it. When put in the new pump that's when I noticed the symptons above.
My ignition works, as the bike still cranks when pressing the ignition button.
Here is a video of my issue.




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Rambozo
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Re: Fuel Pump Question

Post by Rambozo »

By ignition working I mean does it actually run?
If you jump the fuel pump for a few seconds it will fill the carbs. Then the bike should start and run for quite a while on the fuel in the carbs.
The fuel pump is not required to start the bike, just to keep it running. If the bike runs and you have no fuel pump, you probably have an ECU problem.
If the bike won't start, you may have a lack of spark problem and it would be normal for the fuel pump not to run in that situation.
The black wire goes right to the ECU.
BTW an LED test light needs so little power to light that you can get ghost voltage readings from normal transistor leakage current.
The fuel pump only runs when the ECU is sending pulses out to the spark plugs. It doesn't know if you are cranking or running, unlike other systems that run the pump any time you are cranking.
If you have a voltmeter, measure the battery while cranking just to get a baseline.
Jmicester24
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Sat Nov 11, 2023 8:45 pm By ignition working I mean does it actually run?
If you jump the fuel pump for a few seconds it will fill the carbs. Then the bike should start and run for quite a while on the fuel in the carbs.
The fuel pump is not required to start the bike, just to keep it running. If the bike runs and you have no fuel pump, you probably have an ECU problem.
If the bike won't start, you may have a lack of spark problem and it would be normal for the fuel pump not to run in that situation.
The black wire goes right to the ECU.
BTW an LED test light needs so little power to light that you can get ghost voltage readings from normal transistor leakage current.
The fuel pump only runs when the ECU is sending pulses out to the spark plugs. It doesn't know if you are cranking or running, unlike other systems that run the pump any time you are cranking.
If you have a voltmeter, measure the battery while cranking just to get a baseline.
I will try that this afternoon and report back. Thanks!
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Re: Fuel Pump Question

Post by Jmicester24 »

Jmicester24 wrote: Sun Nov 12, 2023 12:21 pm
Rambozo wrote: Sat Nov 11, 2023 8:45 pm By ignition working I mean does it actually run?
If you jump the fuel pump for a few seconds it will fill the carbs. Then the bike should start and run for quite a while on the fuel in the carbs.
The fuel pump is not required to start the bike, just to keep it running. If the bike runs and you have no fuel pump, you probably have an ECU problem.
If the bike won't start, you may have a lack of spark problem and it would be normal for the fuel pump not to run in that situation.
The black wire goes right to the ECU.
BTW an LED test light needs so little power to light that you can get ghost voltage readings from normal transistor leakage current.
The fuel pump only runs when the ECU is sending pulses out to the spark plugs. It doesn't know if you are cranking or running, unlike other systems that run the pump any time you are cranking.
If you have a voltmeter, measure the battery while cranking just to get a baseline.
I will try that this afternoon and report back. Thanks!
I jumped the pump to fill the carbs and the bike ran!
I then put a multimeter on the black wire while cranking the bike and it read 0.50 volts!!
That would point to me having an ECU issue correct??
If so, what would be the best way to fix it? Order an ECU off Ebay? Or try to fix it like the link below.
viewtopic.php?p=72687#p72687
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Re: Fuel Pump Question

Post by Rambozo »

If the fuel pump had no power while the bike is running, you have a bad ECU. Replacing or repairing is up to you depending on your skills and desire.
BTW testing while just cranking is not always reliable on this model because of a number of ignition issues and voltage drop while cranking. That is why I asked for the battery voltage while cranking.
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Sun Nov 12, 2023 7:44 pm If the fuel pump had no power while the bike is running, you have a bad ECU. Replacing or repairing is up to you depending on your skills and desire.
BTW testing while just cranking is not always reliable on this model because of a number of ignition issues and voltage drop while cranking. That is why I asked for the battery voltage while cranking.
Sorry, the battery was at 12.8 volts and while cranking I dropped to 10.2 volts.
If not the ECU what else could be the issue?
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Re: Fuel Pump Question

Post by Rambozo »

First thing, charge the battery or replace it. At 10.2 the ECU won't work right. I'm surprised it even starts without doing the let off the start button trick.
This is a super common issue with the 1500 and in my opinion a Honda design flaw. With low voltage you can't reliably test the ECU. Maybe there is nothing wrong with it.
Jmicester24
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Sun Nov 12, 2023 9:22 pm First thing, charge the battery or replace it. At 10.2 the ECU won't work right. I'm surprised it even starts without doing the let off the start button trick.
This is a super common issue with the 1500 and in my opinion a Honda design flaw. With low voltage you can't reliably test the ECU. Maybe there is nothing wrong with it.
I actually replaced the battery about 2-3 weeks ago. I will charge it tonight and repeat the test after work tomorrow. I will report back.
What voltage should the battery be while cranking?
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Sun Nov 12, 2023 9:22 pm First thing, charge the battery or replace it. At 10.2 the ECU won't work right. I'm surprised it even starts without doing the let off the start button trick.
This is a super common issue with the 1500 and in my opinion a Honda design flaw. With low voltage you can't reliably test the ECU. Maybe there is nothing wrong with it.
After a night of charging the battery was at 12.9 and while cranking it was 10.8. I also ordered an ECU of f ebay. Hopefully it should be here end of week.
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Re: Fuel Pump Question

Post by Rambozo »

10.8 should be enough. I believe the cut-off is 10.5 or there abouts. It depends on how dirty the connectors are as to what the actual voltage at the ECU and the coils is.
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Mon Nov 13, 2023 7:00 pm 10.8 should be enough. I believe the cut-off is 10.5 or there abouts. It depends on how dirty the connectors are as to what the actual voltage at the ECU and the coils is.
I am going to pull the ECU tomorrow in preparation for the one I ordered from Ebay. Is there a way to test it once it is off the bike??
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Re: Fuel Pump Question

Post by Rambozo »

Testing off the bike would be a lot harder. Basically, you would need to build a bike simulator.
Did you get an ECU from the same year?
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Mon Nov 13, 2023 10:18 pm Testing off the bike would be a lot harder. Basically, you would need to build a bike simulator.
Did you get an ECU from the same year?
It is from a 1993. Do you know any place where I can find this part circled in the photo? What is the name of that part? I would like to attempt to fix the other and use it incase this issue happens again.
Also, would it be beneficial to put a 3amp fuse on the black wire going to the fuel pump?
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Re: Fuel Pump Question

Post by Rambozo »

That is a PNP power switching transistor. I can't make out the number to look it up. The replacement that was used was listed as a 2SB953A. That is an old number and not real easy to get. Mostly NOS on ebay. I typically buy from Digikey or Mouser, sometimes a local electronics shop, but they are getting hard to find. I would open the ECU and get the number and locate the datasheet to find a replacement. This is a simple design and won't be too picky. Any replacement with ratings in the same ballpark should be ok. Something 5 amps or better, high enough voltage, and speed isn't important.
A fuse would help, but the relay mod mentioned would be the ideal solution. While this does fail, if you search the forums, you can see it's pretty rare, so just fixing it should be good enough as long as you have a fuel pump that is close to stock.
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Re: Fuel Pump Question

Post by khspe2 »

I know that the 88 and 89 models ran the fuel pump off of a relay, and not through the ECU as it is done on the 90 and later model years. Would it be possible to just hook the fuel pump up to a relay and an in-line fuse, as suggested by others (with power only in the KEY ON position, but NOT repair the blown ECU transistor? Would other aspects of the ECU not work properly? I do not have sufficient electronics/circuit knowledge to answer this question.
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Re: Fuel Pump Question

Post by Rambozo »

The problem with that is you would lose all the safety features. This is setup so if the engine isn't running (like in a crash) the fuel pump shuts off. Also, if the bike is on its side the BAS also shuts the fuel pump off. The last thing you want is to be pinned under the bike in a crash while the fuel pump is pumping fuel out a torn hose while you wait for it to reach the hot exhaust or a sparking wire.
Almost every vehicle has some kind of safety for this. You could roll your own as there are fuel pump relays that get an ignition signal to run, some tie into the oil pressure switch as a run signal. Some get a signal from the alternator. Lots of ways to skin that cat. But you really do want something. As I said, the Honda system is pretty reliable so it makes sense to just fix it.
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Re: Fuel Pump Question

Post by Jmicester24 »

I pulled my ECU, I wanted to inspect it to see if I could see any damage to the board. I didn't see any visual damage. The component with the arrow next to it is the part that is damaged correct??
Also what is the Golden gel substance on the board?? It looks like honey! Haha
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Re: Fuel Pump Question

Post by Rambozo »

That should be it, but I would trace it to the fuel pump pin to be sure.
You won't know it's damaged until you test it. Depending on the circuit you might be able to test it in circuit, but it might have to come out as other components can interfere with testing. Some multimeters have a transistor test function, or you can just do a diode test from the base to emitter and base to collector. If you post the numbers on it, I'll pull the datasheet.
I'm sure it has a real name but I know it as hot snot. It's a kind of hot glue that dampens vibration to keep solder joints from cracking. Perfect for a circuit board on a motorcycle. The clear stuff like that is ok. If you ever see stuff that looks like butterscotch, that is a glue that becomes conductive as it ages and needs to go.
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Re: Fuel Pump Question

Post by Jmicester24 »

Rambozo wrote: Wed Nov 15, 2023 3:31 pm That should be it, but I would trace it to the fuel pump pin to be sure.
You won't know it's damaged until you test it. Depending on the circuit you might be able to test it in circuit, but it might have to come out as other components can interfere with testing. Some multimeters have a transistor test function, or you can just do a diode test from the base to emitter and base to collector. If you post the numbers on it, I'll pull the datasheet.
I'm sure it has a real name but I know it as hot snot. It's a kind of hot glue that dampens vibration to keep solder joints from cracking. Perfect for a circuit board on a motorcycle. The clear stuff like that is ok. If you ever see stuff that looks like butterscotch, that is a glue that becomes conductive as it ages and needs to go.
So I decided to attempt to solder a new transistor. I bought a pack of transistors and soldering iron from amazon. I cut off the transistor from the board and soldered a new one in its place. I put the ECU back on the bike and BOOM the fuel pump started working! Rambozo you are the man! Thank you! If you are ever in the Phoenix area let me know cus itll be lunch on me!
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Re: Fuel Pump Question

Post by Rambozo »

Glad to hear you got it sorted.


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