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Discussion Starter #1
Hello all, am new to the Ducati world and the forum. Recently bought a 2004 ST4s with 18.5k miles from a friend and 500 miles later it became a dead duck. It was purring along in the mountains and the motor immediately and without warning died, as though someone had used the kill switch. After that the bike would crank but gave no hint of wanting to start. Dash display was normal with no check engine or other sign of trouble.

So, I tore into it; my background is I have been wrenching on cars bikes and other stuff for 50 years or so and did a stint as a mechanic in a Guzzi shop.

To cut to the chase, it has no fuel pressure to the injectors, verified by inserting a T fitting with fuel pressure test fitting into the rubber fuel line that runs to the injectors (labeled Out on the bottom of the tank) and connecting the fuel injection pressure gauge. The pump cycles briefly after first turning on the key but nothing registers on this known good test gauge.

It looks like the tank internals are accessed by removing the plate on the underside rear of the tank. I do have the means to test the pump again once it is out of the tank but have a few questions:



  • Is there anything besides an issue with the pump that could cause this problem, e.g. the pressure regulator?

    If it is the pump, has anyone heard of them failing in such a way that the pump motor runs but no pressure is generated?

    Do these pumps typically fail at this sort of mileage?

    If it does turn out to be the pump is there a better alternative than the Ducati sourced pump?

    If you have removed the pump access plate for any reason, does its sealing gasket have to be replaced or is it of the reusable type?
Thanks in advance for any comments or suggestions.
 

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I would bet the the fuel line inside the tank either split or popped off. This is a common issue. Open the filler cap and look inside when you turn on the key. There should be a slight motion of that gas...if you're getting splashing or swirling then the hose is off/split.

The line inside the tank is high pressure submersible fuel line (about $25 per foot at NAPA). Look in the "equivalent" parts post on the top of the ST section and order several a couple of the large o-rings for the fuel flange. I get them from McMastarr Carr for about $0.50, Ducati sells them for about $10 each :surprise: They are typically single use and have a tendency to slice upon install.
 

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Discussion Starter #3
Mike, you were right. While I was waiting for my post to appear I took the flange out and found the hose had popped off the pressure side of the pump. The hose appears to be in good condition but I suspect whoever connected it didn't get the hose and clamp below the barb.

I went ahead and reattached it and since the O-ring looked good and I didn't have a new one I greased it and put it back together but it broke so I will order a couple. The SM does say to use a new one...

One design element of the flange that does not impress me is that the two bosses that the vent hoses attach to are tapered upward and not barbed. After thinking that I had put them on well I tested by tugging on them and one easily came off even though the clamp was maxed out. I shoved it on further and they now pass the tug test but it is not a good design. It would not be a good day if those came loose while riding
 

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I agree that the design is weak. Usually, if you use a quality fuel injection clamp you won’t have a problem. My flange doesn’t have a barb...I was considering filing a groove around the nipple, but with the good clamps I haven’t had a problem (44k miles). One member safety wired his down.

Glad to hear that was the problem...relatively easy fix! Make sure there are no sharp edges to cut the o-ring...another member found this was the case on his tank. A little bit of sandpaper to the rescue.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #5
The clamps look to be good/factory; not the cheapo US band clamps where the screw threads are in the clamping band. If I get them to pass the tug test it should be good.

I ordered the 5 pack of rings from McMaster Carr, supposed to be here Thursday. Much easier using the website instead of the catalog I had to use back in the day when doing industrial plant maintenance.

In the meantime, I need to finish draining the tank (didn't know about the drain plug earlier) and will inspect the o-ring seating areas. Any recommendation on sealant for the drain plug? I was thinking Permatex Form-a-gasket.
 

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Discussion Starter #6
Also, I tried finding the o-rings referenced in the equivalent parts sticky on Amazon and came up empty when searching on the p/n and O-rings.inc...
 

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Any recommendation on sealant for the drain plug? I was thinking Permatex Form-a-gasket.
Should be a copper crush washer, or one of the newer aluminium washers like the oil drain plug uses. I've had mine out a few times and have reused it. I know it's not the best practice, but I have not had a problem doing so and I haven't needed any sealant to make it work. Once it fell in to the same black hole that 10MM sockets tend to disappear in to. I used a copper brake banjo bolt washer. I can't tell you the size off hand, but I have the standard Brembo sized washers on hand and that was it. Working fine still.

I don't think you'll ever get the fuel line nipples to pass a tug test. Same as the top of the pump. If it's oem, it will have the same crappy no-barb nipple. With the correct size hose and proper fuel hose clamps, I have not had one pop off on me.
 

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Discussion Starter #8
Mine has a copper washer so I am going to flip it over and reuse it as that usually works well. It had some sort of sealant that was a whitish green in color that was more or less powder. I did have a cylindrical wire brush of the correct size to get it out of the threaded hole but it was a bit of a PITA.

Since the SM says to use sealant I used the Permatex sealant as that has worked good in the past on gasoline connections.

Has anyone fitted the drain with a petcock type of valve, like a Fumimoto? It looks like there is room if the valve is small enough and is a right angle configuration. It would make it easier next time I drain the tank.

I was able to get the hoses to pass the tug test but did not try the 'yank on it' test; pretty sure it would fail that. Under better lighting I see that the cast bosses for the vent hoses are not tapered as it previously appeared.

I pulled the hose back off the pump and I can see a vestigial sort of barb on the pump nipple (photo attached) so it would appear that if the hose is fully seated on the nipple and the clamp is sufficiently tightened the hose should not come off as long as it doesn't split or otherwise deteriorate. I don't know if this is the original OEM sort of pump or substitute.

I am the 4th owner and from what I can tell, the previous 2 owners didn't do much maintenance. The original owner is deceased and the bike was part of the estate sale, with no service records available. I do know it has been hot-rodded, apparently by a dealer who remapped the ECU to accommodate the open top airbox and carbon exhaust cans because it runs real strong.

Anyways, based on everything I've seen so far it looks like the hose was not properly secured to the pump nipple so there shouldn't be any worries going forward.
 

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That's exactly the description of what happen to me yesterday I ran my scanner tool and PO 352 ignition coil b primary/secondary high input warning lamp on came up if you haven't checked the DTC code please do and let me know also when I cycle the fuel pump and look into the tank it should I see any fuel moving around or would that be the tell that a line has split or come off the flange

06 ST3
 

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Discussion Starter #10
AFAIK, mine didn't throw a DTC; no trouble indicator on the dash, so your code is apparently indicating a second possibly unrelated problem, or your DTC condition is preventing the bike from starting.

I didn't try the 'look in the tank' test mentioned by Mike because I had already drained the tank and pulled the fuel pump mounting flange before I saw his post. I had opened the tank previously but just to listen for the 5 seconds of the pump priming the fuel injection 'rail' but it sounds like a good test for you to try.
 

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The pic you posted looks like the OEM pump. Not much of a "barb", but it holds if done up right. Maybe the stuff you saw on the drain plug threads was a bit of blue lock-tight. With Ethanol gas, I am not sure how normal sealants will hold up over time. I have used a stuff, looks almost like model glue, called Seal All. Comes in a yellow and red tube. Fixed a pin hole leak on my 916 tank flange bolt threads, that are different than the ST's threaded posts. 916 has crimped inserts that you thread bolts in to. Put little on the bolt threads, leak is gone. It's been a few years and the tank has been apart for filters, lines and a pump since. Good stuff if you want be sure those threads are sealed. Holds up to Ethanol.
 

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Do yourself a favor and pull the pump from the holder. After all you're right there! There's an inlet screen at the bottom and otherwise hidden. You want to ensure the screen is clean so as to allow the pump to efficiently take the fuel, pressurize it and pump it thru the filter and onward. Good luck.

BTW, how'd you get home? I always fear this fault when on a trip in the middle of nowhere. I think I'll start to stash a spare "O" ring for such a disaster!!

Steve
 

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That's exactly the description of what happen to me yesterday I ran my scanner tool and PO 352 ignition coil b primary/secondary high input warning lamp on came up if you haven't checked the DTC code please do and let me know also when I cycle the fuel pump and look into the tank it should I see any fuel moving around or would that be the tell that a line has split or come off the flange

06 ST3
James,
You should hear a slight gurgling sound with the gas cap open. But if there's a WHOOSH sound with a lot of activity, then either the pressure line is off the pump, or it's split open.
 

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Discussion Starter #15
@Dan, the new printed SM I received today refers to coating the threads of the plug with 'thread locker' so you are probably right about it being Locktite. The copper washer is apparently intended to do the sealing but an extra layer of security in using something that locks the threads and seals would be wise.

I'll look for Seal All. The Permatex I used can be cleaned up/thinned with alcohol so I no longer think it is the best substance to use for this application. I only run premium but that doesn't guarantee there will be no ethanol from every premium pump/hose.
 

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Discussion Starter #16
@Mike, I wasn't able to siphon all of the gas out of the tank and had to stand the tank on its nose to keep gas from running out when I pulled the pump flange. It was then I found out about the plug so I took it out with the tank on its side and was able to drain every last drop. I'll probably spend some time looking for a petcock that would be reliable and safe in this application. Fumoto makes nice oil drain petcocks but they don't list anything for gasoline.

Never had to deal with this on the Guzzis, just hook a hose to the petcock and drain it into the gas can.
 

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Discussion Starter #17
Do yourself a favor and pull the pump from the holder. After all you're right there! There's an inlet screen at the bottom and otherwise hidden. You want to ensure the screen is clean so as to allow the pump to efficiently take the fuel, pressurize it and pump it thru the filter and onward. Good luck.

BTW, how'd you get home? I always fear this fault when on a trip in the middle of nowhere. I think I'll start to stash a spare "O" ring for such a disaster!!

Steve
Yes, I am going to clean that screen; it is mentioned in the SM.

I was riding with a Harley buddy and there was no cell service so I got to ride bitch back to town. I hope I never have to repeat that experience. Besides the pillion perch being uncomfortable he didn't have enough air in the rear shock and we hit some pretty good pavement breaks where the road had started to slide down the hill. The obnoxiously loud exhaust would not have been so bad if I had used my earplugs.

After I got back to town I called the buddy that sold me the bike and took him along to help push the bike into my trailer.

If I had known this was a relatively common issue I would have previously pulled this apart and checked it. It's one of those things I would rather deal with in my well equipped garage than out on the road.
 

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@Dan - are you using the Seal-All Gas Tank Sealer version of the product?
This stuff.

https://www.amazon.com/Seal-All-380112-Contact-Adhesive-Sealant/dp/B008VK0JS4/ref=sr_1_3?keywords=Seal-All+Gas+Tank+Sealer&qid=1564654146&s=gateway&sr=8-3

So far I've only used it for sealing the flange bolt threads I mentioned. Looks like it has a lot of uses. The reason I bought it was that it was advertised to hold up against gas, oil and solvents. True statement so far. My intention was to use it as a troubleshooting aide to be certain the leak I was having was what I thought it was, those tank flange bolt threads. If using this to seal them stopped the leak, I was going to use Caswell sealer to line the tank. I have the kit to do it. The Seal all worked so good that a quick temp repair has lasted several years now. I guess I'll get around to using the Caswell sealer at some point...
 

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Discussion Starter #20
Thanks. I looked on line and they make several versions including one for patching gas tanks. Walmart sells the one you bought online but they didn't have in the local store so I bought it across the street at O'Reilly's. The o-rings are supposed to show up today so I'm going to pull the drain plug, measure the size/threads and reseal it with Seal All after I clean the Permatex out of the hole.
 
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