Fuel primer bulb collapsing

[shopmon2002]

I have a boat with a 2003 90 hp Merc. The fuel primer bulb goes flat after being run for a while and the engine looses power, which tells me the tank is not venting. It has a Perko filler cap with the vent line and fill line built in it. I'm not quite sure how this thing works. I mean, is it vented or not? It doesn't look like it is, but how else could the fuel system vent? Also, what is the anti-surge valve in the top of the cap and how does that work? I disconnected the vent line and it's clear of obstruction, so it almost has to be something to do with this cap and vent system, right? Thanks in advance!

 

[dingbat]

Re: Fuel primer bulb collapsing

Don't assume it's vent problem. It could be your anti-siphon is clogged or stuck partially closed. It could be the screen at the bottom of the intake tube is getting clogged up.

 

[rboating]

Re: Fuel primer bulb collapsing

could also be the primer bulb being weak..had that issue last summer on a outboard... replaces the bulb and all was well...

 

[shopmon2002]

Re: Fuel primer bulb collapsing

Ok, thanks. I guess I should run it with the fuel cap loose, and see if it happens again. Are you familiar with the perko surge valve and ventilation of the tank? How does it work(is it sealed or unsealed)?

 

[shopmon2002]

Re: Fuel primer bulb collapsing

Update...drained the tank, bad gas. Replaced with good gas. Replaced the fuel line, fuel filter, and the water fuel seperator filter. The boat does not have an anti siphon valve, but took the 90 degree valve at the tank off and cleaned.....really dirty. Ran the boat and the bulb went flat again! Opened the fuel cap to let it breathe, but it didn't help. Took the bulb off on one end and it was pushing fuel through when I pumped on it not attached to the engine side. The new fuel filter was pretty dirty again, but it is in between the bulb and the engine. Any suggestions????

 

[relocyo]

Re: Fuel primer bulb collapsing

Hmmm, I had this same problem, took me forever to figure it out, I saw you drained the gas, is it a portable tank or built in? Can you look in the tank? My problem was (portable tank) the stupid fuel gauge built into top of tank the plastic dipstick broke off and the fuel pump would suck it up to the pickup and flatten my bulb, maybe something to look for, how does the motor run like it is now?

 

[shopmon2002]

Re: Fuel primer bulb collapsing

It is a built in tank, and I cannot look in it. After the bulb went flat and the motor stalled, I disconnected the line in between the bulb and the engine. When I pumped it by hand, the fuel pumped nicely through it. The filter is in between the bulb and the engine and it was definitely dirty, but would this make the bulb flat? I would think that it has to be something stopping up the tank(vent restriction, clogged line/valve, etc.) It seems to me that if the filter was clogged, it wouldn't have the suction to flatten the bulb? Thanks

 

[chriswh86]

Re: Fuel primer bulb collapsing

what about pulming up an external tank for now, maybe using a jery can, see how the motor runs then, if it flattens the bulb or not.

If not, you know you have an issue with lines to your bulb and/or tank

 

[relocyo]

Re: Fuel primer bulb collapsing

Although im no expert, id bet you have an obstruction either IN your gas tank, OR in the pickup.... Dollars to cents.... To me it seems youve found the problem, its in the tank, hand pressing the bulb will not create the same amount of suction from a fuel pump running anything near planeing speed, I think the previous post,about hooking up a jerry can is the best way to go to ABSOLUTELY know its the tank... Just my .02 ...... Let us know how it works out...

 

[j_martin]

Re: Fuel primer bulb collapsing

An old fuel line can have the inner tube separate from it's support and collapse, blocking the flow.

Odds are good, though, that it's a plugged screen in the tank. I've also seen oil bottle foil seals in the tank get over the pickup and cause random blockage. That was real fun troubleshooting.

Crud in the tank isn't going to fix itself, and it seems to multiply if you try to filter it out. Sounds like a real serious cleaning, maybe even pulling the tank is needed. Been there meself once.

 

[shopmon2002]

Re: Fuel primer bulb collapsing

An old fuel line can have the inner tube separate from it's support and collapse, blocking the flow.

Odds are good, though, that it's a plugged screen in the tank. I've also seen oil bottle foil seals in the tank get over the pickup and cause random blockage. That was real fun troubleshooting.

Crud in the tank isn't going to fix itself, and it seems to multiply if you try to filter it out. Sounds like a real serious cleaning, maybe even pulling the tank is needed. Been there meself once.

I think you may be on to something. When I stated above that I had changed the fuel line, I only replaced the piece from the water seperator to the bulb, and another from the bulb to the engine. The piece from the tank to the seperator is original. Although it looks like a good hose from the outside, I do remember now that when I pulled the line from the tank to inspect it, a piece of inner tube was stuck to the valve. I remember thinking "Why did someone put an inner tube sleeve on the outlet before sliding the hose on?" I pulled the 2" piece of inner tube off, and reattached the hose. So, what you are telling me is that that inner tube is actually the breaking down of the hose itself, and this could be stopping me up? Does this have anything to do with ethanol fuel? If so, it makes perfect sense, because the previous owner of the boat let it sit up with ethanol fuel, which I had to pump out. I will remove the remaining piece of hose and inspect further for deterioration.

 

[relocyo]

Re: Fuel primer bulb collapsing

Spot on with the ethanol... Spot on...

 

[shopmon2002]

Re: Fuel primer bulb collapsing

Ethanol worn fuel line was the issue. Replaced and it runs like a top. Thanks for all the help!

 

[relocyo]

Re: Fuel primer bulb collapsing

Ethanol worn fuel line was the issue. Replaced and it runs like a top. Thanks for all the help!

Great to hear! Thanks for the follow up, to often we get a new person with a question, a couple hypothesis, and never hear back what worked and what didnt...

 

[Sturg81]

Good info guys. I have the same problem with my Suzuki DF225, 4 stroke. Runs and idles great, up to about 6 MPH. Then primer bulb collapses. Changed in-line (spin on) filter repeatedly. Also changed the primer bulb. Tested a fuel sample for water and/or trash at the primer bulb discharge, and contents of in-line filter, Clean no water. Have ordered new; A1 type 3/8" fuel hose, clamps, fuel tank pickup, and check valve. Knowing it's a 1998 fuel system, changing all completely.

 

[Sturg81]

I have a boat with a 2003 90 hp Merc. The fuel primer bulb goes flat after being run for a while and the engine looses power, which tells me the tank is not venting. It has a Perko filler cap with the vent line and fill line built in it. I'm not quite sure how this thing works. I mean, is it vented or not? It doesn't look like it is, but how else could the fuel system vent? Also, what is the anti-surge valve in the top of the cap and how does that work? I disconnected the vent line and it's clear of obstruction, so it almost has to be something to do with this cap and vent system, right? Thanks in advance!

Just a thought, If the tank was not venting, you should experience a problem when fueling (filling up). The air in the tank must be displaced as the tank fills, which would not be possible with a plugged vent. My guess is an obstruction inside the tank, or checkvalve, or collasped fuel line. all of which are prior to the primer bulb.

 

[WIMUSKY]

Just a thought, If the tank was not venting, you should experience a problem when fueling (filling up). The air in the tank must be displaced as the tank fills, which would not be possible with a plugged vent. My guess is an obstruction inside the tank, or checkvalve, or collasped fuel line. all of which are prior to the primer bulb.

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