LTD Won't Stay Lit

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kjmarti2
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Re: LTD Won't Stay Lit

#46

Post by kjmarti2 »

gltriker wrote: Sat Nov 07, 2020 11:14 pm Buy or borrow one of this type low pressure fuel pump test gauge set. tumb2

https://www.amazon.com/Lisle-20300-Vacu ... B000CODRFO
Ordered. Will test the fuel pressure when it comes in. It should be high if it's moving that much fuel, but good to have a number.
Barrie wrote: Sun Nov 08, 2020 10:54 am What I don't understand is how a (mechanical) pump can generate too much pressure. Is it the wrong type?
I'm as confused as you are. It's a new OEM pump. I don't really know what to do other than replace it.
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Re: LTD Won't Stay Lit

#47

Post by gltriker »

kjmarti2 wrote: Sun Nov 08, 2020 7:38 pm
gltriker wrote: Sat Nov 07, 2020 11:14 pm Buy or borrow one of this type low pressure fuel pump test gauge set. tumb2

https://www.amazon.com/Lisle-20300-Vacu ... B000CODRFO
Ordered. Will test the fuel pressure when it comes in. It should be high if it's moving that much fuel, but good to have a number.
Barrie wrote: Sun Nov 08, 2020 10:54 am What I don't understand is how a (mechanical) pump can generate too much pressure. Is it the wrong type?
I'm as confused as you are. It's a new OEM pump. I don't really know what to do other than replace it.
I could not remember how fuel discharge pressure was regulated in a low pressure mechanical fuel pump.
I reckoned the 2 check valves were independently responsible for , fuel inlet into the fuel pump, and then fuel outlet from the pump. But then how is the outlet fuel pressure regulated?

Google and Wikipedia gave me a generic answer.
In part, the Wikipedia article provided this information.

"The return motion of the diaphragm to top dead center is accomplished by a diaphragm spring, during which the fuel in the pump chamber is squeezed through the outlet port and into the carburetor. The pressure at which the fuel is expelled from the pump is thus limited (and therefore regulated) by the force applied by the diaphragm spring."
Last edited by gltriker on Thu Nov 12, 2020 3:59 am, edited 1 time in total.
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Re: LTD Won't Stay Lit

#48

Post by Track T 2411 »

Volume does not necessarily equate to pressure, either. Just saying...
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kjmarti2
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Re: LTD Won't Stay Lit

#49

Post by kjmarti2 »

Ok I am finally done sulking and cursing this project and I'm ready to do something about this fuel problem. I wanted to do the fuel pressure test tonight but I don't have a T-fitting for the fuel line, so I'll pick one up tomorrow (hopefully) and get that done soon. Hopefully it's pretty insightful and I just have a bad fuel pump.

I decided to take the fuel pump off the Phoenix which I know works and do a fuel volume test on it while installed on the LTD. It looks like the fuel rate of that pump is about half of what the other fuel pump was putting out, but it's still double what the manual calls for. I think this is probably ok though if the fuel pressure is right due to my limited understanding of how fuel moves through the carbs. I'll report back once I have fuel pressure numbers.
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Re: LTD Won't Stay Lit

#50

Post by gltriker »

You don't need to T into the hose.
Just push the tester hose onto the outlet fitting from the fuel pump and crank the engine over.
You will know almost immediately what the operating fuel pump pressure reading is. tumb2
Cliff

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
http://www.ngwclub.com/forum/page/ST :oldies

RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
"I'd rather Ride than Shine" -RAT tumb2 Me Too!!

Cliff

'75 GL1000 home built trike; http://www.ngwclub.com/forum/viewtopic.php?f=30&t=39996
October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

previous rides:
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kjmarti2
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Re: LTD Won't Stay Lit

#51

Post by kjmarti2 »

gltriker wrote: Fri Nov 20, 2020 8:16 am You don't need to T into the hose.
Just push the tester hose onto the outlet fitting from the fuel pump and crank the engine over.
You will know almost immediately what the operating fuel pump pressure reading is. tumb2
Fuel pressure looks good with the pump ported over from the Phoenix, I'm getting 2.3 psi or so at crank speed which is what the manual says is correct. So I concluded that if the problem was solely the fuel pump, the bike should run perfect if I ran with this one.

Spoiler: it didn't. I haven't replaced the spark plugs yet which are pretty dirty so I'm sure they are contributing to the problems I'm seeing, but I'm not sure that can account for everything. While it did run better than with the other fuel pump, it will still die if I let off the throttle and it tops out around 3500 rpm in first gear. The engine doesn't sound right when it's revved up, like I'm not running on all cylinders or maybe it's misfiring. All the cylinders feel warm to the touch though. I'm going to run a compression test when it cools down to see if I get the same numbers as when I tested it out of the frame. Trying to come up with a plan beyond that but I have to admit I'm stumped here.

If there's a guru in the San Diego area that wouldn't mind helping me diagnose and fix this I'd be eternally grateful, I can pay with money or beer. I'm starting to think this issue is simply beyond my capability.
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Re: LTD Won't Stay Lit

#52

Post by kjmarti2 »

Maybe I damaged one of the delicate bits in the carbs by being too forceful during install? I could port over the set from the Phoenix to test that theory I suppose.
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Re: LTD Won't Stay Lit

#53

Post by desertrefugee »

No. Stay the course. Didn't you say it ran well with an external fuel supply? That tells you the carburetors are fine.
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kjmarti2
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Re: LTD Won't Stay Lit

#54

Post by kjmarti2 »

desertrefugee wrote: Sat Nov 21, 2020 2:35 am No. Stay the course. Didn't you say it ran well with an external fuel supply? That tells you the carburetors are fine.
I've only run it from the external tank in the garage on the center stand. It ran fine that way with this fuel pump as well. These issues only seem to really manifest under load when I'm moving. Although I seem to recall the slight misfire symptom still being present with the external tank at high rpm. I'd have to run it again to be sure, maybe I'll do that tomorrow.
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Re: LTD Won't Stay Lit

#55

Post by Fred Camper »

Recall the ignition system needs more energy at higher load so do not discount that if you feel your fuel system is solid.
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Re: LTD Won't Stay Lit

#56

Post by kjmarti2 »

For those still following: I learned a few things today. I can reproduce the problem on the center stand by revving up to 5000+ rpm after which the engine automatically throttles back to near idle by itself. If I let go of the throttle it then dies.

I think I can rule out the following:

- Ignition timing. I checked it, set it again, and double checked. No change.

- Compression. 135# all around installed

- Fuel system ahead of the carbs. Saw no change running from the external tank

- Charging system. Saw 15+ volts across the battery terminal while throttling

-Spark plugs. Ported over the plugs from the Phoenix and saw no change

-Coils. I get purple/blue spark on each when grounding

- Battery. 1 is new, the other is off the Phoenix. No change for either one.

-Advance unit. Spins freely, verified with cover off

The remaining suspects that I can see are:

-Carbs. Maybe I damaged a float or something on install

- Timing belts. I checked several times to make sure I was spot on, but it's still a possibility

-Dyna red wire. It's going thru the turn signal relay, could try moving it to the coil wire.

-Ballast resistor?

-Incorrect starter clutch install?

-The bike just doesn't like me?

- Anything else I'm missing??
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Re: LTD Won't Stay Lit

#57

Post by CYBORG »

Partially plugged fuel filter???
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Re: LTD Won't Stay Lit

#58

Post by Fred Camper »

Mine would miss when hooked to the turn signal but only during the blink. I installed an ignition relay and it has not missed a beat since.
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Re: LTD Won't Stay Lit

#59

Post by Shadowjack »

I can reproduce the problem on the center stand by revving up to 5000+ rpm after which the engine automatically throttles back to near idle by itself.

Sounds like you've drained the float bowls. How does it do when you connect the external tank directly to the carb inlets instead of to the fuel pump, and let gravity feed it?
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Re: LTD Won't Stay Lit

#60

Post by gltriker »

Sounds like it's just constipated. :(

Exhaust is the only system I haven't seen listed as a suspect .

One side is possibly severely restricted? Maybe both sides? Duct tape.

Choke cable adjustment has adequate dimensional slack in the fully opened ( knob pushed in) position ?
Last edited by gltriker on Sun Nov 22, 2020 12:49 pm, edited 4 times in total.
Cliff

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
http://www.ngwclub.com/forum/page/ST :oldies

RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
"I'd rather Ride than Shine" -RAT tumb2 Me Too!!

Cliff

'75 GL1000 home built trike; http://www.ngwclub.com/forum/viewtopic.php?f=30&t=39996
October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

previous rides:
1953 H-D Servi-car, naked, 1969-1978 (serial#53G1559 committed to memory!)
1980 CB900 Custom (triked) 1997-2003 .... R.I.P.
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