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Fuel pump wiring loom.
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Moto GP Alien
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    Posted: 27 Jul 2025 at 18:42
My Gen 1 engine stopped abruptly today. I cycled the ignition switch and noticed the fuel pump wasnt priming. Cycled it again and the bike started. I rode it for about 5 minutes, then had to stop for a pick up. About 20 minutes later the bike wouldnt start again, and again , no fuel priming. After a minute or so it started and got me home, running faultlessly for 30 minutes. I had this problem a few years ago, it'd only do it the once for a couple of years and I carried out the side stand bypass mod at least 12-18 months ago and thought that had cured it, until today. 
Once home I checked my bypass wiring, con checked it while wiggling the wires and found no fault. I also raised the tank and con checked the pump wiring at the connector while moving the pump wires and couldnt fault it. I also checked out the pump relay and couldnt fault it. I swopped the fuel pump relay with the engine stop relay just to see what happens but I'm pretty sure the fault lies in the green wire in the resin block of the pump base plate, a known failure point.
I see the oem Aprilia pump loom is NLA, but there seems to be an after market offering for about £125, has anyone fitted one of these to their bike?
The alternative is to dig the resin out and repair the wire. If anyone has done this, what did you use as the resin substitute?
People say I don't know Jack Sh1t; but I do, he lives next door.
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On mine I didn’t have to remove enough resin to pose a leak issue. I filled the hole with araldite just to secure the wire really. 


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I don’t o ow there was an aftermarket offer g 

But £125!!!


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JB Weld should do the trick, it's completely fuel resistant once cured.
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Yep, £125 is steep. It seems to be offered by a German bike shop. They don't say whether they still join the wires in the resin block or they are continuous. What were Aprilia thinking of when they connected the wiring like that?
I found a thread on AF1 where someone experimented by putting some JB Weld in fuel and it softened up. It seems Caswell might be the way to go.
Has anyone used Loctite 518 on the main seal as per the manual? Last time I had the pump out I used a thin bead of aircraft fuel tank sealant outside of the seal but now retired I can't get any more.
People say I don't know Jack Sh1t; but I do, he lives next door.
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Just talked to Griff. The loom for sale, which APW also sell, is for Gen 2s only. The only option for Gen 1s is to repair the original. I've found that aircraft fuel tank sealant which I used on the top of the resin block and around the base plate o ring, PR1440, is available online. This is used as avgas as well as avtur tank sealant and is ethanol resistant. About £60 for 125ml, so is a viable alternative as a resin substitute. When I remove my pump I'll get a good idea as to how it has held up with pump fuel.
People say I don't know Jack Sh1t; but I do, he lives next door.
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Are you going to mod wiring to make the joint external?
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Originally posted by legend88 legend88 wrote:

Are you going to mod wiring to make the joint external?

After digging the old resin out, I'll see if there is enough slack to bring the joint to the outside of the base plate and put the join there. If not, they'll be soldered and heat shrunk and put back into the new sealant. This will still be better than standard. The wiring has a fuel proof outer, so I'd need to source and buy some if I was to completely replace the wiring and this would mean a joint in the tank to re use the oem pump connector. I've already been into the tank once to replace the filter. I want this to be the last time I go in there again, if possible.
People say I don't know Jack Sh1t; but I do, he lives next door.
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Originally posted by Administrator Administrator wrote:

On mine I didn’t have to remove enough resin to pose a leak issue. I filled the hole with araldite just to secure the wire really. 


Is this you Spoonz? How much more resin did you have to dig out to get to the other end of the wire? Looking at the photo shows the bottom of that resin block, how did you finish the repair?
What Araldite did you use?
People say I don't know Jack Sh1t; but I do, he lives next door.
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From memory it was about half way to make a join. The picture I posted was actually my friend Chris’s bike who had the same issue as I didn’t take pics. I used the 2 part araldite rapid which is fuel/heat etc resistant.  I think Chris grafted in another loom but he is no longer with us so I can’t ask him what it was unfortunately. 
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Thanks for the info Spoonz.
Was yours a full failure or an intermittent fault? 
It seems a pain to have to go into the fuel tank again for a fault that might be else where i.e the fuel pump relay or a wire fault else where (I have swopped the pump and engine stop relays over).
Did you manage to get an indication that wire was definitely at fault or did you go in to cut your loses?
People say I don't know Jack Sh1t; but I do, he lives next door.
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Because I was aware of others having the problem I knew where to look. It was very intermittent initially with small cut outs which I didn’t immediately connect to the pump. But eventually the pump would sometimes not run even stationary but would start if I lifted the tank. I could only prove the fault once the pump was out and I could meter the wiring and see an open circuit if I wiggled the wires. 
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Thumbs Up
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Bugger...removed the pump and dug out the resin block, only to find the wiring joint still well soldered and in one piece.
I ended up cutting the wire and I reckon I can re solder them outside of the tank, there seems to be enough slack in the wires. As I need to replace all the resin, Ill probably go with Caswell sealant.
But it means the cutting out fault isnt due to this bit of wiring.
People say I don't know Jack Sh1t; but I do, he lives next door.
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Starting to get the pump sorted now. Bought some fuel resistant wire and heat shrink. This will allow me to take the 2 wires through the resin block without a joint there. The pump live I'll crimp in the tank and heat shrink it. The fuel level sensor wire will be all one piece. Today I re potted the resin block...what a faff. Luckily I bought some viton sheet and made a thin plug to go into the bottom of the block as the Caswell sealant is very runny. I also heat shrunk the wires where they exit the block to provide extra protection and punched 2 holes in the viton sheet for them. Just got to wait for the sealant to cure now and going to leave it a week before any fuel goes near it.
One thing I noticed was the 3 wires from the pump base plate were very hard and brittle, must be due to the heat from the engine over time. Makes me wonder what state the rest of the wiring near the engine is in.
People say I don't know Jack Sh1t; but I do, he lives next door.
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I ended up fitting a complete new loom on my 2000 rsv because of the wiring going brittle.
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Originally posted by 426hemi 426hemi wrote:

I ended up fitting a complete new loom on my 2000 rsv because of the wiring going brittle.
Hoping I dont have to go there.

This is the resin block with wires going straight through without a joint. I mixed the Caswell in a glass container; the stuff left in it appears rock hard.
People say I don't know Jack Sh1t; but I do, he lives next door.
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There was numerous other connections and plugs going brittle and I found a complete new loom so had it swapped out and had better connections for the power commander and quick shifter etc done at the same time.
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I seem to remember Garin having injector loom issues on his Tuono from deteriorating wiring. Given its proximity to the engine it cooks nicely cooked
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Luckily it doesn't appear to affect the copper core, the outer insulation goes solid and any movement causes it to crack. My pump harness near the white plug is nice and soft, the closer it gets over the engine the stiffer it gets. With the resin block re wire I've replaced all the hard insulated wires.
People say I don't know Jack Sh1t; but I do, he lives next door.
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Originally posted by Spoonz Spoonz wrote:

I seem to remember Garin having injector loom issues on his Tuono from deteriorating wiring. Given its proximity to the engine it cooks nicely cooked


Yep several sections of the loom had be repaired due too brittle wiring, but after 16yrs and 40k, its not new anymore !

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My Caswell repair didn't take, despite clinical preparation.
Leaked down the side of one of the wires through the sealant.
Decided to cut my loses and bought a Gen 2 pump harness from Griff.
It fits the Gen 1 pump flange but needs the wiring modifying. It has 4 wires through the resin, the 2 extra ones are both earth's. They're redundant as Im keeping the original earth set up. Done the pump, just got to join the original connector to the harness, then another leak check.

Edit: All done, working and leak free.
What a pain in the @rse that was.
People say I don't know Jack Sh1t; but I do, he lives next door.
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