Fuel pump issues

Hi all

I was riding home last night, cruising at 85 - 90 mph when she coughed and spluttered to a standstill. I checked the fuses, all OK, still no joy then I wiggled the connectors going to the fuel pump and tried turning her over again and da da, she spluttered into life and I continued for another 59 miles no probs at all. The question is....is this a known issue with older high milage pans or just one of those things which hopefully will be OK now. I removed the connectors and blasted the whole lot with switch cleaner and a nylon toothbrush, and put new connectors on, while I was at it I sprayed out the fuse boxes as well.

Ta in advance

Darren C
Canterbury UK

Forgot to add...She is a 1995 ST1100AS model with 70k on the clock and tuned up to race spec lol

Do a search for fuel shutoff valve problems/removal. Likely that.

Here's a current thread....https://www.st-owners.com/forums/showthread.php?152786-Help!-ST1100-dying-on-the-road-fuel-contamination-or

How much gas did you have left in the tank ?? Sometimes with a low gas level, the pump may get hot and fail.

Next time it happens, turn the ignition off and then on and listen for the fuel pump to run for a few seconds ( prime ). Each time you turn the ignition from off to on, you should hear the fuel pump run for about three seconds and then shut off.

You may have a faulty fuel pump, besides a possible shutoff valve problem. Sometimes they are intermittent.

Jim Van said:

Each time you turn the ignition from off to on, you should hear the fuel pump run for about three seconds and then shut off.

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Same when you flick the KILL switch from OFF to ON (that's how I "prime" my ST's after winter-hibernation ;-) )

OK, there was about half a tank of gas so it shouldn't be a run hot problem. I have noticed how much quicker she is now, hardly have to blip the throttle and it takes off which makes me think the problem was with the contacts on the top of the gas tank which I cleaned up like new. I cannot actually hear the pump running it's so quiet but it is pumping up OK. How does it work? Is the pump on all the time or is there a sender circuit from the carbs which activates it?

Edit* Reading that other link I think I'll tear out the vacuum valve thing just to be sure. I've ridden her today and no problems apart from where all the coolant is disappearing to which is rather worrying!!!

Darren C said:

I've ridden her today and no problems apart from where all the coolant is disappearing to which is rather worrying!!!

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Look at the overflow hose by the rad cap, check that it isn't split, or plugged. Take the cap off when cool and insure the passage to the overflow tank hose is free of gunk.

Darren C said:

OK, there was about half a tank of gas so it shouldn't be a run hot problem. I have noticed how much quicker she is now, hardly have to blip the throttle and it takes off which makes me think the problem was with the contacts on the top of the gas tank which I cleaned up like new. I cannot actually hear the pump running it's so quiet but it is pumping up OK. How does it work? Is the pump on all the time or is there a sender circuit from the carbs which activates it?

Snip .......

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Once the bike starts, the pump runs continuously.

kiltman said:

Look at the overflow hose by the rad cap, check that it isn't split, or plugged. Take the cap off when cool and insure the passage to the overflow tank hose is free of gunk.

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Its not that, a week ago I noticed the expansion tank was empty and consequently a bit of air was sucked up into the cooling system, took half the bike apart to get to the rad cap, bad design!!!, and put about half a pint of water in to top up. I then ran the engine to get the coolant to flow out and put the cap on so as to make sure there's no air in the system. Topped the tank up to the Max line and all OK but the Level is dropping everyday and I have to top up about 300ml coolant. God knows where its going, coolant clean as is the oil, no steam in exhaust or drips on ground, I'm thinking if its dripping onto the top of the crankcase as its a V4, it would evaporate before dripping onto the road. I need to get a UV light and some of that dye you put in the coolant which shows up under UV

I wouldn't think a coolant leak would have much to do with the engine stopping- I could be wrong, it's happened before. in my own case I had my bike dying when..the tank was half or lower , AND when the ambient temps were high and high fuel demand (freeway riding for long periods-60-75 mph). first move to nail this down is to check the shut off valve. pretty easy to bypass and check that first. the fuel pump is submerged so I doubt if it's heat build up...more like the pump is getting weaker and unable to lift the fuel up to the carbs. thankfully the fuel pump is rather easy to R&R. regrettably a pricy Honda part. there have been others who have substituted other pumps for the ome- with varying results...... gotta ask..where IS "Cent."?

the_gr8t_waldo said:

I wouldn't think a coolant leak would have much to do with the engine stopping- I could be wrong, it's happened before. in my own case I had my bike dying when..the tank was half or lower , AND when the ambient temps were high and high fuel demand (freeway riding for long periods-60-75 mph). first move to nail this down is to check the shut off valve. pretty easy to bypass and check that first. the fuel pump is submerged so I doubt if it's heat build up...more like the pump is getting weaker and unable to lift the fuel up to the carbs. thankfully the fuel pump is rather easy to R&R. regrettably a pricy Honda part. there have been others who have substituted other pumps for the ome- with varying results...... gotta ask..where IS "Cent."?

Click to expand...

Cent is the olde name for Kent back in Anglo Saxon times

Thank you Darren...hopefully I'll make the connection, next time I trip over that one.