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1999 R1100R hard starting


The Fabricator

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The Fabricator

I have a specific question.

The engine runs fine once it is running.

The engine sometimes starts easily and other times cranks a lot, fires, dies, fires and runs and then the exhaust smells rich, wants to die so I hold the throttle open so the engine spins to 2k or so for 10 to 20 seconds, then slowly lower the speed down to idle.

The 'choke' [fast idle] doesn't seem to affect starting. Some times the engine is hot, turned off for 10 minutes, then does not want to start.

This happens hot or cold.

I have checked the injector spray patterns and spark consistency and synchronized the TB's.

I have not checked the fuel pump pressure. The pump cycles on when the key is turned on, then stops after pressure builds up.

I have read about deteriorating fuel hoses inside the tank that will leak. I am wondering if this is a problem causing low fuel pressure at start up.

I would think if that a leaking hose would cause the pump to cycle on again to maintain pressure [engine not running]. It does not.

The question: Am I correct thinking the pump would cycle on to maintain pressure even when the engine is not running [key on] if a hose is leaking in the fuel tank?

[bonus Question] If the fuel pump could not build up enough pressure to reach the regulator pressure threshold, would it run forever?

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Afternoon Fabricator

 

 

The engine runs fine once it is running.--This would basically tell us the fuel pressure & flow is decent.

 

The engine sometimes starts easily and other times cranks a lot, fires, dies, fires and runs and then the exhaust smells rich, wants to die so I hold the throttle open so the engine spins to 2k or so for 10 to 20 seconds, then slowly lower the speed down to idle.--LOTS of possibilities on this one. What CCP is in your bike now??? You might have to eventually check the cold-to-warm resistance sweep of your IAT (Intake Air Temperature) & Oil Temperature sensors.

Any chance that someone has installed an Air Temperature spoofer in that bike at one time in the past?

Any chance that your bike is running extra wide spark plug electrode gaps?

What is the battery voltage DURING cold engine cranking? If low that can easily cause poor cold starting.

 

The 'choke' [fast idle] doesn't seem to affect starting. Some times the engine is hot, turned off for 10 minutes, then does not want to start.

This happens hot or cold. --What does the choke do on a hot idling engine??? Will applying the choke raise the idle speed considerably on a hot idling engine? If not then it needs adjusting. How about if you hold the choke lever ALL the way up in the manual "faster idle" position?

 

 

I have checked the injector spray patterns and spark consistency and synchronized the TB's.--This is a good place to start.

 

 

I have not checked the fuel pump pressure. The pump cycles on when the key is turned on, then stops after pressure builds up.-- This is good but pump doesn't stop after pressure build, it stops after a set run time (very short time) -- (there is NO pressure feedback to the Motronic so it has no idea what the fuel pressure is)

 

I have read about deteriorating fuel hoses inside the tank that will leak. I am wondering if this is a problem causing low fuel pressure at start up.-- Probably not, internal hose issues usually cause runability issues not starting issues. They will usually start with very low pressure as the Motronic sets a very rich command & it doesn't take much fuel delivery to start the engine.

 

 

I would think if that a leaking hose would cause the pump to cycle on again to maintain pressure [engine not running]. It does not.--It CAN'T cause a pump re-run again as the Motronic has no access to fuel pressure feedback. Initial pre-start pump is run on time not pressure feedback.

 

 

The question: Am I correct thinking the pump would cycle on to maintain pressure even when the engine is not running [key on] if a hose is leaking in the fuel tank?--NO!, see above posts

 

 

[bonus Question] If the fuel pump could not build up enough pressure to reach the regulator pressure threshold, would it run forever?----NO, see above posts.

 

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The Fabricator

DR. Thanks for your help.

 

What CCP is in your bike now???

I don't know what this means.

 

Spark plug gaps are probably ok because I had the out to check the spark consistency and I don't remember anything odd about them. [i have seen many spark plugs.]

 

No Air Temp spoofers or any thing. Very stock, low miles unit.

 

'Choke' lever applied does cause the idle to increase slightly. Holding the lever fully does cause noticeable idle speed increase. This performance seems appropriate. When I first got the bike, there was so much slack the lever didn't do anything. I adjusted it. Vacuum gauge on a 'T' fitting [pinch off to isolate one TB at a time] to synch.

 

IAT and OT sensor check not done. A good idea.

 

I thought about the battery charge state.. Just to be sure I charged it, checked voltage, after charging and after 'skimming off the surface charge' by burning the headlight for a few minutes. I don't remember the numbers as at the time it seemed appropriate. Can't say I checked the voltage while cranking. It was a long time ago [months] since I worked on it. Worth checking. I will. The cranking speed seemed appropriate.

 

I have my answer: The pump shuts off by a timer. No pressure feed back. Now that I think about it, I have never noticed a pressure sensor to ECU communication in my travels.

 

I will check the fuel pressure and other things.

 

 

 

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If it runs fine, it's probably not a fueling problem. I think you have a minor setup issue.

 

Have you synched the throttle bodies at idle and at off-idle?

 

The choke should raise the rpm to about 1800--2000 rpm when the bike is warm. Is that happening? Are you using the choke to start when the bike is cold?

 

"When I first got the bike, there was so much slack the lever didn't do anything. I adjusted it." That intrigues me. Typically if the choke isn't working it's because the lower throttle cables have stretched. I wonder if you over-tightened the choke cable and now it's holding the butterflies open. Are the throttle screws resting on the stops on the throttle bodies at idle? You can check it visually or listen for a loud "SNAP" on each side as you roll off the throttle.

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Morning Fabricator]

 

What CCP is in your bike now???

I don't know what this means. --CCP is the coding plug that tells the fueling computer what mapping to use. It's in the fuse box (see picture below). A LOT of old 1100RT owners removed the CCP as it sometimes helped lower the light throttle surging but it could effect engine starting on some bikes.

 

 

No Air Temp spoofers or any thing. Very stock, low miles unit. --Are you sure as some can be homemade & very subtle looking?

 

'Choke' lever applied does cause the idle to increase slightly. Holding the lever fully does cause noticeable idle speed increase. This performance seems appropriate. When I first got the bike, there was so much slack the lever didn't do anything. I adjusted it. --Try starting the bike by holding the twist grip to about 1/8 open, if that helps starting then you probably a need a choke adjustment.

 

Vacuum gauge on a 'T' fitting [pinch off to isolate one TB at a time] to synch.--That is a pretty crude way to balance the TB's as most vacuum gauges read in inches of mercury, 1" of mercury equals about 13.5" of H2o and we usually balance to under 2" of H2o so 2" of H2o isn't even a needle width on a standard vacuum gauge. This is just for education as it probably has nothing to do with your present problem. Just make a simple homemade U tube H2o manometer & balance using cross side vacuum bias not to atmosphere with a mercury gauge.

 

IAT and OT sensor check not done. A good idea.--If you can't find a smoking gun then you will probably have to do this at some time.

 

I thought about the battery charge state.. Just to be sure I charged it, checked voltage, after charging and after 'skimming off the surface charge' by burning the headlight for a few minutes. I don't remember the numbers as at the time it seemed appropriate. Can't say I checked the voltage while cranking. It was a long time ago [months] since I worked on it. Worth checking. I will. The cranking speed seemed appropriate.--You need to verify cranking voltage just to eliminate that.

 

I have my answer: The pump shuts off by a timer. No pressure feed back. Now that I think about it, I have never noticed a pressure sensor to ECU communication in my travels.--Yes

 

I will check the fuel pressure and other things.--Yes this needs to be eliminated.

 

 

lVjFALS.jpg

 

 

 

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