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HALP! I just renewed everthing on the fuel pump assembly, all the hoses, the pump, fuel pressure regulator, fuel filter, external hoses, metal qd's, and the timing belts. Also got rid of the charcoal cannister and put a y-adapter in for the vents.

It started quick and nice on the first turn. The problem is, it bogs on the bottom, and backfires a little when I try to rev up. I have to keep my hand on throttle to keep it running at idle. If I let go, it'll shut off in about 30 seconds. I was extremely careful to make sure I didnt pinch any hoses. It takes some effort, but once I get it up over 3-4k rpm it seems to be fine.

I've read some about the TPS stuff, but I didn't touch the TB's except to remove the old fuel lines and replace them. I used oetiker clamps and there are no leaks.

What I'm wondering is, could putting in the new pressure regulator have screwed up the TPS setting? If thats the case, I'll just put the old one back on. Only reason I replaced it is because it looked cruddy. I did not use a stock ducati reg. It's one that was mentioned on another thread that's for a 2000 VW Jetta.

Also, if I run it with the gas cap open there is some fuel sputting near the top. I was thinking this is coming from the air separator.
 

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Discussion Starter #2
UPDATE: I took it for a spin to fill it up as I read some other post talking about air in the line after a new pump install. No joy on that. It's completely fine up top though. Once I got over 3k, I took it up to 10k and it pulled hard. The exhaust seemed to get overly hot too. Like, my butt and right leg were warmer than normal which makes me think it's running lean. I'll probably pull the plugs to see if their ashy or not. Check for spark..etc.

Still curious though if the fuel pressure reg change could cause the tps settings to be jacked.
 

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The fuel couplings (quick connects) are known for being very problematic with starting, running, cutting out, etc... When I read the description it sounded like the same thing that I had going on with me. I bypassed the fuel inlet shutoff valves on both sides of the fuel line going out(line to fuel delivery). All my problems went away. I choose to do this only after trying to replace o rings and it not working. It would start and run fine and then suddenly start to die. I have been running it like this now for about a month now without any more drivability issues.

I am curious, why did you make all these changes? And why ditch the charcoal canister?

Eric
 

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If you put a Y piece in the emissions canister hoses you have
now got a free flow of air from the tank vent to the two
take off points on the throttle inlet stubs ?,
This could be causing your poor lower throttle/idle response.
Blank the two hoses/pipes off individually and vent the one from the
tank with a longer hose/pipe or connect it to the overflow tank vent
that runs down to the front nearside alternator case.

brian.
 

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Discussion Starter #5
I am curious, why did you make all these changes? And why ditch the charcoal canister?

Eric
I got the bike at a low price with no maintainence record. Timing belts are a given. I had problems with the gas lines because the p/o tried to replace them, used the wrong hoses, and missied one that was rotting. I had the small return line inside the tank split. When I got in there, the fuel pump had evidentally been sitting in water as it was really corroded. I absolutely hate getting gasoline on me, so I wanted to make sure everything in the tank was renewed so I didnt have to get in there again for a while. The quick couplings were just a mod that I saw everyone doing and looked like a good idea while I had it apart. I had to change the external fuel lines too in order to get the male qd's to pop on. The cannister was corroded as well and since it's not required, I removed it.

If you put a Y piece in the emissions canister hoses you have
now got a free flow of air from the tank vent to the two
take off points on the throttle inlet stubs ?,
This could be causing your poor lower throttle/idle response.
Blank the two hoses/pipes off individually and vent the one from the
tank with a longer hose/pipe or connect it to the overflow tank vent
that runs down to the front nearside alternator case.

brian.
There are two vents that come from the tank. One of them went to the cannister, and the other went to the street. I put a Y in there to connect both of those into one that goes to the street. For the throttle stubs, I saw another post where a guy put vacuum plugs over them. I picked up a box of misc. vacuum plugs from O'Reiley's. I did this instead of using screw blanks for the inlets so if I need to balance the TB's at some point, I'll be in business.

So, the way I hooked it up, is that what you meant, or are you saying I should hook one of them up to the engine somewhere?

Also, thank you VERY much for your replies!!!
 

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Only reason I replaced it is because it looked cruddy. I did not use a stock ducati reg. It's one that was mentioned on another thread that's for a 2000 VW Jetta.
Hmmm. Assuming that changing the external fuel lines (not sure why you did this? Did you use correct fuel hosing everywhere?) and timing belts didn't introduce a problem, I'd look closely at this and put the stock pressure regulator back in. I've personally never heard of anyone using a 2000 VW Jetta fuel pressure regulator in a 748.
 

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If you want to actually TEST the pressure regulator, what you can do is put together a fuel line with a tee in it. Two ends of the line mate to the lines coming out of the tank so you form a loop from the fuel tank output going back into the tank return line. From the tee, attach a pressure gage. Turn the key on to make the fuel pump prime and read the pressure on the gauge. Compare it to the spec in the manual (I forget what it is off hand). If the fuel pressure regulator is not working right, you'll see the wrong pressure on the gauge. Other issues could also cause problems (blocked fuel filter, fuel line off inside tank, etc.) but this will give you more info to work with. I did this when I was trying to diagnose fueling issues. You can buy all the parts to do this from McMaster-Carr, for example.

You might have junk clogging things in the fuel lines if you had rotting hoses in there previously. Maybe the fuel injectors...? I've had similar problems after my bike sits for a long time and varnish builds up in the injectors. Running injector cleaner usually clears it up, but if you have debris instead of just varnish, that could cause problems injector cleaner wouldn't fix. It would depend where in the fuel supply loop the bad hoses where.
 

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Split fuel line in the tank. Replace it. Common issue.


"Also, if I run it with the gas cap open there is some fuel sputting near the top. I was thinking this is coming from the air separator."
 

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Discussion Starter #9
Split fuel line in the tank. Replace it. Common issue.


"Also, if I run it with the gas cap open there is some fuel sputting near the top. I was thinking this is coming from the air separator."
All of the fuel lines are new. I double checked that I have vacuum caps over the stubs on the TB's. I thoroughly flushed the tank out of debis before I put it back together. I think Im going to try putting back the original fuel pressure reg first to see if that fixes it. Opening the gas tank will be next if that doesn't work.
 

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Just an update. I pulled the tank today, and the spark plugs. Both plugs had gray film on them, it's running lean as I suspected. This also explains a little why my ass and right leg were getting so hot. I swapped the original weber fuel pressure reg back into the tank.

That's about as much gas smell as I could stand today. I'll put it back together tomorrow and see how it runs.
 

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To check for a leak in the tank just open the cap and turn on the ignition.You don't have to start the bike. When the pump primes watch for fuel turbulence or a stream spraying in the tank. You shouldn't see anything, but if you do then a line is split, a connector is loose, the fuel filter is split... etc.

When I first got mine a hose was split. When I opened the tank and primed the pump a 4 foot jet of fuel shot straight out of the gas cap and across the front of the bike, narrowly missing my face. Pretty obvious there was a problem haha.
 

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Well, I've put the tank back on, after putting the stock FPR back in. It seems to be running okay now. I warmed it up, but haven't had a chance to ride it yet due to the thunderstorms here in Kansas City. I can't imagine that there are any split hoses in there.

I just replaced everything inside the tank with Gates SAE30R10 hose and crimped them down with oetiker clamps. When the tank only had 2 gallons in it, there was a little sputtering at the top, but that has to be from the air separator. It's a really small amount, and it's seems to be coming from about where that would be.

However, it would be really cool if someone with a 748/916 with a not so full tank would start their bike with the cap open and let me know if they have the same thing. I'll post a video of it once I get some of the gas out of there.
 

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BIG smile on my face right now. Just went home for lunch and got the bike. It ran awesome! Idle was at 1500 w/ the fast idle on, and right at 1000 with it off. No bogging and smooth power all the way up to redline. I still think it might be running a little lean as my ass got a little warm, and it's only a 3 mile ride. So, I may turn the mix screw out just a smidge until I can check it out with DucatiDiag. Just ordered my cables today. :D
 

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What do you think ended up being the culprit? I just replaced all of my lines, metal quick connects, had to switch everything over to a new fuel pump base plate (cracked the old one trying to get part of a plastic QC out), and a new low fuel level sender. My condition is identical to yours, barely runs if I can get it to start at all. Very laggy to rev up and seems that the exhaust gets very hot.

I just got the injectors back from cleaning and balancing (RC Engineering) and now the bike doesn't really want to start at all.
 

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Discussion Starter #16
It was running funky and missing on the low end. Up over 5k it was fine. I had put an aftermarket fuel pressure regulator in, and also removed the charcoal canister. There was nothing really wrong per se with the original pressure regulator, I did it just because I was replacing everything else. I think the new FPR was not letting enough fuel through at idle, and removing the canister probably leaned it out further. Anyhow, I put the original FPR back in the bike and that mostly fixed the problem. It reved okay after that, but it still seemed to be running a little lean. So, I turned the idle pot on the ECU to richen it just slightly. I think it was the combination of those two things that made it run right.
 
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