Fuel pump math


Information and questions on GL1500 Goldwings (1988-2000)
  • Sponsored Links
Post Reply
User avatar
754
Posts: 88
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Fuel pump math

Post by 754 » Thu Feb 07, 2019 4:54 pm



Can someone confirm my math for me. I have been fighting with my wing the last few months. It just won't run well especially at idle, and will not high idle at all. I checked the fuel pump output twice. At the carbs the pump put out 9oz of fuel in 5 seconds. Closer to the tank like the book says it put out 10oz of fuel. Is that sufficient out put for it? I know that the carbs are absolutely clean and set properly. Just trying to rule out everything I can.

Thanks,

Travis


1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

Rodzim
Posts: 29
Joined: Sun Oct 07, 2018 1:24 pm
Location: Smyrna, ga
Motorcycle: 1994 gl1500 se

Re: Fuel pump math

Post by Rodzim » Thu Feb 07, 2019 5:04 pm

9oz i 5 sec is enough for a chevy 350 at full throttle. Its fine. Make sure the pressure is not too high

User avatar
MikeB
Posts: 2364
Joined: Fri Dec 04, 2009 12:54 pm
Location: Tacoma, WA
Motorcycle: 1998 - GL1500 Aspencade.
2003 - GL1800A

Re: Fuel pump math

Post by MikeB » Thu Feb 07, 2019 7:12 pm

The service manual says to route the pump outlet line to a beaker.
Turn ignition switch ON, let fuel flow into a beaker for 5 seconds, then turn the ignition off.

Multiply the amount in the beaker by 12 to determine the fuel pump flow capacity per minute.

Fuel Pump Minimum Flow is 640 cc (21.6 oz)/minute.

9 oz for 5 seconds times 12 is 108 ounces (266.1 cc)/minute.
The book calls for 21.6 ounces/minute. Right off hand, I'd say it is not a fuel pump delivery problem.
MikeB
Tacoma, WA, USA

User avatar
bluthundr31
Posts: 294
Joined: Tue Jul 11, 2017 11:43 pm
Location: Morgan Hill, CA.
Motorcycle: 1991 GL1500 Interstate (Cinnamon Beige)

Re: Fuel pump math

Post by bluthundr31 » Thu Feb 07, 2019 8:33 pm

If this is that Carter pump from a couple months ago, sounds like its working as it should.

Do you get much of a response using the knurled knob in front of the gas cap to adjust the idle up or down?

Could there be a leaky/cracked vacuum hose issue now?

User avatar
754
Posts: 88
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: Fuel pump math

Post by 754 » Sat Feb 09, 2019 10:08 am

bluthunder31 yes it is, it's the same pump and person. After I first got this bike running it always ran very rich. The plugs were black (not soot covered), but just black. It also had a surge I was trying to fix. Last September I replaced that bad pump with the one that's in it now and it seems to still be working well. The bike starts right up, however it's running very poorly at idle or high idle. I know that the carbs are perfectly clean, I just cleaned them last week (pulled out everything that comes out, cleaned and blew out every possible passage, no diaphragm holes, all jets perfect, float height is also correct, vacuum hoses all tight too). I also replaced the carb isolators, the 2 90 degree hoses on the front of the intake manifolds (that go to the check T valve), and all of the small vacuum hoses as well. The only vacuum hoses I have not done are the ones down in the bowels of the engine. Since then it just will not run like it should. I set the pilot screws at the manual suggested 2 turns out and am wondering if that is just too much. I lost the piece of paper that had the original pilot screw settings written on them (I assume they were not messed with before, the screws had no covers on them and I can't confirm those previous settings were right or not). If memory serves me correctly the pilot screws were much less then 2 turns out, possibly one turn to maybe 1 and a half turns out max.

Also a new question, what should be the initial settings for fresh clean carbs? 2 turns on the pilots per the manual, that I know for sure. Anyone that cleaned their carbs before do you remember how the link bar on the front fit? Should it drop right on with both throttle plates closed for idle or do I need to adjust them open some and reset the link bar? There is not much information on setting them up after cleaning.

Thanks again everyone.
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

User avatar
AZgl1800
Posts: 1503
Joined: Thu Oct 30, 2008 2:46 pm
Location: Lake Oologah Indian Territory USA
Motorcycle: '02 GL1800

Re: Fuel pump math

Post by AZgl1800 » Sat Feb 09, 2019 11:36 am

Have you removed the carbs and lifted up the rubber diaphragm below the carbs, and inspected the vacuum lines there?

the big one the makes a severe 90° left turn to the left side of the engine, is very prone to cracks... I had to replace that one on my 94SE

Also had to cut off about 3/8 inch of the vacuum line that goes to the nipple between the 2nd and 3rd cylinders on the left bank. that line was cracked also.
~John

User avatar
754
Posts: 88
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: Fuel pump math

Post by 754 » Sat Feb 09, 2019 11:52 am

Yup have looked at and replaced those hoses.
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

User avatar
754
Posts: 88
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: Fuel pump math

Post by 754 » Sun Feb 10, 2019 11:37 am

I just wanted to bring this back to the top. This morning I was able to confirm I have no vacuum line leaks on my 1500. I used my home made EVAP smoker and tied directly into both the right and left intake manifolds and I did not see any visible leaks. Are there any other base line settings for these carbs, out side of the pilot screws? Do the throttle butterflies need to be open any at idle or do they need to be fully closed? Is there a way to bench test the carbs and their systems before they a put back on?

Just trying to work this problem out.

Thanks guys.

Travis
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

User avatar
terryt
Posts: 247
Joined: Mon Jul 23, 2012 4:52 pm
Location: United Kingdom
Motorcycle: 1979 gl1000 trike
1989 gl1500 trike

Re: Fuel pump math

Post by terryt » Sun Feb 10, 2019 2:59 pm

You have checked fuel rate adjusted the pilot screws checked all the hoses. Have you balanced the carbs.

User avatar
bluthundr31
Posts: 294
Joined: Tue Jul 11, 2017 11:43 pm
Location: Morgan Hill, CA.
Motorcycle: 1991 GL1500 Interstate (Cinnamon Beige)

Re: Fuel pump math

Post by bluthundr31 » Sun Feb 10, 2019 3:40 pm

FUEL, , ,AIR, , ,SPARK!!! In the correct amount, this is all you need for it to run well.

Sounds like you're satisfied that the fuel portion is pretty solid, ,
Sounds like you're satisfied that the Air (vacuum) portion is solid, ,

I'm thinking that the Spark portion is the next "system" that you should consider giving attention to. Examine the plug wires, spark plugs and the coils next. You might want to dive into the timing belt too to check the "alignment" and the tension/wires to the coils.

User avatar
754
Posts: 88
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: Fuel pump math

Post by 754 » Mon Feb 11, 2019 6:04 pm

Hey all, I learned some things yesterday. I have my wing running better than it has in a while. After looking over the carbs I decided to readjust the throttle plates. I adjusted them to be more open than they were. After that readjustment it ran to high as it is supposed to do. I did notice that I seemed to have some fuel coming from one of the overflows. Guess it may be a hung float or needle. I know that they are adjusted properly (that was one of the first things I checked). The remaining issues are probably from that over fueling. I also noticed that it seems that the 2 turns out for the pilot screws is a bit much. My wing seems to be much happier at one and quarter to one and half turns out. I hope to get these remaining issues sorted soon. My CB750 is due for a top end rebuild that I want to finish before riding season.


1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

Post Reply