Member Contributer 5thave Posted October 14, 2021 Member Contributer Share Posted October 14, 2021 After 11 years as a pile of parts, I have my '91 back together, and I am ready to try starting it. I cannot remember what sound/noise I should hear from the fuel pump. Can anyone describe it? On first ignition-on condition there was no noise (fuel in the tank, but all hoses dry/empty. On engaging the starter I heard a rapid "Brrrrrp" followed by a little pop, and silence. Little to no fuel entered the filter, so I imagine the pump was still dry at this point. There is no visible damage, and all fuses are intact, but the fuel pump no longer makes any noise when ignition is on or when I engage the starter. After giving time for fuel to feed by gravity, I can confirm fuel in the rear float bowls (cyl. 1 and 3) but front float bowls seem to be dry (cyl. 2 and 4). I guess I need a fuel pump to move the fuel up front. 1. What should I hear from the pump? 2. When should I hear it? - when ignition is switched on? - when starter is engaged? Thanks folks! Link to comment Share on other sites More sharing options...
Member Contributer Captain 80s Posted October 14, 2021 Member Contributer Share Posted October 14, 2021 Pump only "pumps" when it is being cranked or it's running. I highly recommend you unplug the relay and jump the harness side to prime your system. Or crank and crank and crank. I install a toggle in parallel to prime my system at will, like after winter storage. And to get me home when the relay fails. Link to comment Share on other sites More sharing options...
V4 Rosso Posted October 14, 2021 Share Posted October 14, 2021 You should hear the fuel pump make sort of a rattling noise after turnnig on ignition until floatbowls are filled and fuel lines are pressurised. The sound you diescribed as "Brrrrp" sounds like the starter motor relay in conjunction with a bad/not fully charged battery. The bike runs on gravity feed without problem. Link to comment Share on other sites More sharing options...
Member Contributer Captain 80s Posted October 14, 2021 Member Contributer Share Posted October 14, 2021 2 minutes ago, V4 Rosso said: You should hear the fuel pump make sort of a rattling noise after turnnig on ignition until floatbowls are filled and fuel lines are pressurised. The sound you diescribed as "Brrrrp" sounds like the starter motor relay in conjunction with a bad/not fully charged battery. The bike runs on gravity feed without problem. Negative. This is a 91. Low pressure pump that only operates when cranked or running. (If it's not modified to eliminate the Fuel Cut Relay) But I agree it sounds like his battery is low. Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted October 14, 2021 Member Contributer Share Posted October 14, 2021 On my 86, the fuel is very reluctant to move through the pump when the lines are reconnected, and the pump itself can get an airlock. I now routinely disconnect the pump outlet and add a hose to a bucket, then put a jumper in the pump relay wire and turn the ignition on until I get a nice steady fuel flow. Then ignition off, remove the jumper, reconnect the delivery hose and the system is fully primed and working. When the ignition is switched on, the pump may give one little thump. Then when the engine is running (or the relay is jumpered) the pump will run steadily until the lines are full and some backpressure is reached, then the pump stalls out until the float valves re-open to let more into the bowls. My pump gives a stroke every few seconds when the engine is idling. Link to comment Share on other sites More sharing options...
Member Contributer 5thave Posted October 15, 2021 Author Member Contributer Share Posted October 15, 2021 Great info! Thanks. I also found item number 32, here, which describes how to jump and prime the pump and carbs. I will try this today! Now to find a paperclip for jumping that circuit.... Link to comment Share on other sites More sharing options...
squirrelman Posted October 15, 2021 Share Posted October 15, 2021 ^^^ make sure the paperclip doesn't touch the frame or anything grounded. Link to comment Share on other sites More sharing options...
Member Contributer 5thave Posted October 16, 2021 Author Member Contributer Share Posted October 16, 2021 23 hours ago, squirrelman said: ^^^ make sure the paperclip doesn't touch the frame or anything grounded. Yup! For sure! By the way, this re-assembly is FINALLY using the engine I bought from you in Buffalo pre-pandemic. 🙂 I know the rear two cylinders are OK, but the front bank is not firing yet. I think it's a fueling problem: I will be taking the carbs off again for a re-inspection. Link to comment Share on other sites More sharing options...
squirrelman Posted October 16, 2021 Share Posted October 16, 2021 i'm glad to see you have it installed, but cranking the starter more than about 10 seconds on each attempt may cause overheating and damage it. it's important to allow cooling periods between trying to start, and a good idea to pull out the headlight fuse too. on an initial start, it often helps to bottle-feed carbs then wait half an hour before an attempt. best also to open each float bowl screw a bit to check that fuel has gotten in. i'm pleased to hear it run after sitting on a bench in my shop for about 3 years. be sure to poke a steel wire through the idle jets when you're cleaning the carbs................ Link to comment Share on other sites More sharing options...
Member Contributer 5thave Posted October 18, 2021 Author Member Contributer Share Posted October 18, 2021 Yes, I checked the float bowl drain screws on rear cylinders #1 (left) and #3 (right). These had plenty of fuel. I am able to reach the drain on #4 (front right), which was dry. Any tips on how to reach the inward-facing drain screw on #2 (front left) carb? I can't seem to get a long screwdriver in there from the right-hand side of the machine because the thermostat housing is in the way. Any tips or ideas? I guess I am taking the carbs off again, and will check over everything once more, then re-install. Hopefully I can hear it run before the cold weather shuts down operations again (the wife wants to park in the garage and this means moving crap around and I lose my working space 😕 ) Link to comment Share on other sites More sharing options...
squirrelman Posted October 18, 2021 Share Posted October 18, 2021 if you stored the carbs upsidedown sometimes float needles may stick to their seats and won't allow fuel in. Link to comment Share on other sites More sharing options...
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