Lonely ST1100 struggling to revive

Joined
Feb 10, 2013
Messages
92
Age
61
Location
Colombia
Bike
1993 ST1100
Hey guys,

You may remember me. I'm the Colombian biker who went down back in may. Details here: https://www.st-owners.com/forums/showthread.php?152842-Lonely-ST1100-down-(pics)-rebuild-vs-naked-vs-scrap&highlight=mauricio

Here she is back up on her feet after a thorough restoration (absolutely no new plastic. Even the mirror covers were rebuilt):

IMG_6396.JPG
IMG_6398.JPG

But unfortunately, not for long. The ride back home after four months at the body shop, ended like this:

IMG_6427.jpg

Half way through the ride coolant temp went through the roof. At that time I was loosing power. Promptly killed the engine, coasted to a stop and waited for a couple of minutes. When I tried to restart she didn't fire. Arrived home on piggy back and the following day, removed the restored plastic. Pump wouldn't prime when opening the switch although it does happily hum away with a direct 12V feed from battery. Tested for 12V at positive pump connector, switch open. Nada. Tried removing the fuel cut off relay and shorting blue with brown and black with brown at the connector. Still doesn't prime. BTW, the petcock valve was removed and bypassed many years ago.

Brown is the feed to the pump. Black comes from the coils. Blue comes from the ICM. Green is ground. So I looked for 12V on blue and brown, switch open. No cigar. As a last resource I ran the pump from the battery for a while until the fuel filter was full. Started right away. Let her run to test fan. With pump unplugged it would soon starve (revs drop). Hot wire from battery to pump brings it immediately back to life which confirms pump is fine. So I decided to connect all the default wires back to the pump and relay and much to my surprise, it kept running like a champ. 12V at the pump connector. Pulled the relay while the bike was still running and got 12V at both the blue and black wires. Weird.

Got hot again and no fan (that's another story) so I killed the engine. A while later, again no go. Once more, won't prime. No voltage at pump or relay connector.

Any ideas?

Thanks!

Mauricio
 
Joined
Jun 3, 2006
Messages
3,514
Location
British Columbia
Bike
2021 RE Meteor 350
WOW, heck of a good job on that restoration, Mauricio! Everything looks good as new, from the pics.

How about a broken wire somewhere in the circuit, or a corroded connector?
 
Joined
Feb 2, 2009
Messages
2,303
Location
Dahlonega, GA
Bike
2018 NC750X
STOC #
7666
After sitting for so long during the restoration... check and clean the ground connections. I believe there is a major point near the alternator.... remove the bolt and clean the terminals, apply a little dielectric grease and re-secure. Might want to clean major wire bundle connectors with contact cleaner and then lube them with dielectric grease also. Be sure to service the main connector (the big red one) in front of the battery. Hope this helps.
 
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maubur
Joined
Feb 10, 2013
Messages
92
Age
61
Location
Colombia
Bike
1993 ST1100
Not too bad. Looks nice but you can still pick out a couple of flaws. Mirror plastic is thinner than original and there's a hidden tie wrap pulling one of the panels so it lines up with the black side pocket. All in all I'm pretty pleased.

I'll follow your suggestions although I think this is more serious than just bad connections. Visual inspection shows no rust or suspect connections. The fan does run when I unplug the thermostat wire on the left side and ground it. I had the radiator overhauled while the bike was at the shop and it was painted. Funny thing is the fan ran as expected once the engine got hot when I first installed it at the shop. Not anymore.

I'm fearing the Ignition Control Module might be shot. I understand power goes from this module to the fuel relay and I'm not getting any voltage there. Or maybe it's the ignition switch?

Keep'em coming please.
 
Joined
Mar 20, 2016
Messages
1,202
Location
Auckland, New Zealand
Bike
2005 ST1300
STOC #
8901
So than fan worked, now it doesn't, and when the bike gets hot, the voltage to the fuel relay drops out. Maybe these two are related? Perhaps the fan switch is causing some unwanted circuit when it is switching at temperature?
 

Norm

Vendor
Joined
Aug 26, 2007
Messages
350
Location
Chilliwack, B.C., Canada
Bike
KLR650
STOC #
8030
I'm in the throes of SWMBO's house renovations so will be a bit slow in response but happy to help.

Just as a starting point: the fuse box hasn't been much of an issue, so far as know, but the Main Fuse in the starter relay has been a frequent issue. I'd voltage drop that and try jumpering from the battery + cable to the red wire leading to the fuse box, from the ignition switch. I recommend that anyone who owns an ST1100, consider the Ignition Circuit Bypass Relay Modification to remove the Main Fuse and circuit from there through the ignition switch and back to the fuse box as a problem area.

One observation: people will often check voltage at a disconnected terminal and conclude that the circuit is good if the voltage is close to expected. The difference between an open circuit and one under load is a profound one and should not be ignored. A high resistance/corroded section can allow full battery voltage to be sampled through the section when there is no current flowing. With the circuit under load, the voltage drop could indicate an under load voltage near zero.

The voltages measured should be done with the circuit in operation, or in other words: by back probing the plug, or slipping a small wire into the connection, or piercing the wire insulation with bed-of-nails type devices.

It occurred that it may sound as thought I am sweeping in as some sort of savior and if so, not my intention and not my view, so I apologize. Just willing to help if can, if a bit when commitments are bit less.
 

kiltman

Site Supporter
Joined
Apr 27, 2013
Messages
3,280
Age
68
Location
Stratford, Ontario Canada
Bike
2002,ST1100ABS
STOC #
8826
For your overheating issue. Hook up an ohm meter to the thermostat sender. It's located under the radiator filler neck. (I made an adapter so one of the leads could plug into the sender or a lead with alligator clip will do.). Run the bike. The fan should kick in when the meter reads around 28 ohms and shut off around 31 ohms. If your gauge indicates in the red but the ohm meter is in the 30 ohm range, consider a bad ground near the steering head.
When you remove the gas cap is there a sound of air escaping? When my bike got hot, I would experience a vapour lock and the bike would shut down. Wait ten minutes and the bike would start again. I replaced the gas cap and haven't encountered the issue.
last summer I spent a lot of money on rebuilding the cooling system when it turned out to be a bad ground to my temp gauge, and a faulty gas cap.
 

Norm

Vendor
Joined
Aug 26, 2007
Messages
350
Location
Chilliwack, B.C., Canada
Bike
KLR650
STOC #
8030
That you have no indicated voltage at expected terminals, points more to an open circuit/failed component, than to corrosion of a connection, IME. A high impedance volt meter will read full voltage with almost nothing in terms of circuit quality.

When you tested voltage to the four relay terminals, was the testing with the relay plugged in/plugs all connected, or unplugged?
 
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OP
maubur
Joined
Feb 10, 2013
Messages
92
Age
61
Location
Colombia
Bike
1993 ST1100
Thanks for the advice guys.

Unless there is any chance that the fan and pump issues are related, I am working first on getting the pump to prime. I've checked all electric connections as suggested and they seem to be sound. The gas cap is venting both ways.

Norm, when I tested the relay terminals the relay was unplugged. I tested blue/yellow and black/white, the former coming from the ignition and the latter from the coils (according to the diagram). Engine off, ignition switch on. Red VM lead to the individual terminal at the relay plug and black to ground. No cigar. 0 volts. When I started the bike I got around 12V from both, relay still unplugged. Same happens at the positive terminal on the pump under the seat. When I open the switch I read no voltage at all. Pump won?t prime. Engine on and it gets a steady 12 volts with relay and all connections in place.

I tried shorting blue/yellow with brown/red at the relay connector in order to bypass it. Still no voltage at the positive pump connector when opening the switch. The brown/red wire has been tested for continuity from the relay plug to the pump and it checks fine. Then I tried shorting black/white with brown/red at the relay plug but again, nothing happened. Am I bypassing the relay correctly? Can this have anything to do with the ICM (Ignition Control Module)? I'm guessing if it was shot the engine wouldn't run, right? No spark. Maybe there's something wrong with the ignition switch?

Please bear with me guys.

Thanks.

Mauricio
 
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