1998 Mercury 150-HP: VST Overflow Hose Squirting Fuel

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Author Topic:   1998 Mercury 150-HP: VST Overflow Hose Squirting Fuel

picflight posted 03-10-2014 12:59 PM ET (US)
I recently changed the electric fuel pump on my 1998 Mercury 150 HP EFI V6 2.5-liter. Prior to opening the vapor separator tank (VST), I did not notice any fuel squirting out upon priming until the bulb was hard. After I did the pump replacement, when priming for the first time I noticed fuel squirting out the hole each time I pressed the bulb; see picture, linked below.
I was able to start the engine, and everything looks normal at first glance. I have not tried priming using the bulb again before I get a definitive reason for this behavior. The service manual says that hose is the separator overflow hose. Should it be overflowing into the engine like that?

http://farm8.staticflickr.com/7314/13041845004_9931bea396_c.jpg
sosmerc posted 03-10-2014 08:35 PM ET (US)
With the engine running, there should be NO fuel coming out of that hose. If there is, it means the float inside the vapor separator tank (VST) is not set right, or there is debris under the needle and seat. I suppose if the VST is empty, and you pump too quickly on the primer bulb, it might be possible to momentarily get some fuel out of the overflow. But NEVER when the engine is running.
picflight posted 03-11-2014 12:30 AM ET (US)
It [i.e, the flow of fuel from the overflow hose] only happened when I initially pumped after putting the vapor separator tank together. There was no fuel coming out when I started the engine. I will try pumping again in a couple of days when I plan to install the lower unit and start it again.
I checked the float before I installed the VST; it was freely moving and clean.
sosmerc posted 03-11-2014 01:17 PM ET (US)
You will probably be ok. But if the engine at some point starts to smoke more than normal, or run a bit rough at low speed, just pull the hose off of the vst fitting and make sure it is not putting out any fuel.....it's just supposed to bleed fuel vapor.

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Author	Topic: 1998 Mercury 150-HP: VST Overflow Hose Squirting Fuel
picflight	posted 03-10-2014 12:59 PM ET (US) I recently changed the electric fuel pump on my 1998 Mercury 150 HP EFI V6 2.5-liter. Prior to opening the vapor separator tank (VST), I did not notice any fuel squirting out upon priming until the bulb was hard. After I did the pump replacement, when priming for the first time I noticed fuel squirting out the hole each time I pressed the bulb; see picture, linked below. I was able to start the engine, and everything looks normal at first glance. I have not tried priming using the bulb again before I get a definitive reason for this behavior. The service manual says that hose is the separator overflow hose. Should it be overflowing into the engine like that? http://farm8.staticflickr.com/7314/13041845004_9931bea396_c.jpg
sosmerc	posted 03-10-2014 08:35 PM ET (US) With the engine running, there should be NO fuel coming out of that hose. If there is, it means the float inside the vapor separator tank (VST) is not set right, or there is debris under the needle and seat. I suppose if the VST is empty, and you pump too quickly on the primer bulb, it might be possible to momentarily get some fuel out of the overflow. But NEVER when the engine is running.
picflight	posted 03-11-2014 12:30 AM ET (US) It [i.e, the flow of fuel from the overflow hose] only happened when I initially pumped after putting the vapor separator tank together. There was no fuel coming out when I started the engine. I will try pumping again in a couple of days when I plan to install the lower unit and start it again. I checked the float before I installed the VST; it was freely moving and clean.
sosmerc	posted 03-11-2014 01:17 PM ET (US) You will probably be ok. But if the engine at some point starts to smoke more than normal, or run a bit rough at low speed, just pull the hose off of the vst fitting and make sure it is not putting out any fuel.....it's just supposed to bleed fuel vapor.