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96 90hp 60 degree fuel issues

S

ss396fish

Contributing Member
Thanks for letting me in here! I have been sorting thru archive threads but decided to start over. My motor started running out of fuel pressure. It would run fine, and then stall. After pumping the too soft bulb it might run fine for days or weeks but problem has progressivly got worse lately to the point it's a bulb pumping every half mile. Checked everything from pick up in tank to engine, changed fuel lines, took apart tank swapping valve, anti siphon valves, checked primer bulb for proper check valve operation and if anything was in it possibly obstructing flow. Acts like vent problem so ran it without gas cap. I hooked up a fuel pressure gauge in carb line and had fluctuating pressure from 2/12 to 1lb. Book says at least 3lb. So looks like VRO. I checked pulse limiter, looked to be ok. Carb cleanered it anyway. This is 2nd go around with this deal so I have the pump that was taken off a few years ago. Me and my Dad who was a career auto mechanic and really sharp dude took it apart and could find nothing wrong with it except poppet screw a little bit looser than spec. Anyone know what causes the pump to fail? Not a moneybags and hate to spend $450 again if I don't have to. Thinking about putting tightened up old pump back on and see what happens. Damn OMC for shutting down the rebuild kits..... Thanks for any info
 
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Agreed , try the old pump.-----------Are you getting good pulses to the pump.-------Checked filters?--------Checked vapour seperator ?
 
I checked pulse limiter and upper crankcase fitting, both wide open. only filter is the built in one, appears clean. Manual says replace filter yearly but original looks like new. Snugged up the vapor seperator screws. Is there more to it than that? All I knew to do was look for leaks as far as that thing is concerned. Don't know how to test pump pulses. I do have service manual. I am just handy enough to be dangerous and although Dad is quite the mechanic this thing is all new to him. We're just feeling our way along . Sure would be nice to be able to afford to take stuff to THE MAN when trouble rears its head... And by the way, athough the pressure tested low there appears to be plenty of flow volume. Thanks to you all
 
Boobie said:
Try Master Tech Marine in Milton FL, 850-623-1197 for VRO parts.
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These guys seem to know their stuff and said although nothing was visually wrong with vro, the diaphram just gets old and slightly stiffer to the point crankcase pulses can't quite flex it anymore. Even though I hardly ever put corn gas in it. Kit on the way. Started to get pump without oil pump but often push my little floating house at around 1300 rpms for an hour or so and figure I might have more carbon and plug troubles so putting it back stock.
 
I believe it is a personal preference.-----------When you mix gas / oil yourself nothing can go wrong.-------------Other folks have a different opinion and want the convenience of not having to do any math / figuring.--------Some folks do not mind having the dealer do an annual check of VRO output / performance for a small ? fee..----------I know of folks that have installed new pumps at huge $$ on the advice of mechanic when there was nothing wrong with the VRO pump.
 
Any chance of the pump failing on the oil side with no warning like I had this time with the starving of fuel? Do have the warning gauge hooked up and apparantly warning signals working.
 
Any chance of the pump failing on the oil side with no warning
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Yes they can lean out from mechanical problems in pump and fail to give warning.....that's why it called a VRO(very risky oiling)
 
Still not enough fuel pressure!!! Don't seem to have enough pulse pressure. Had pulse limiter out and seemed to be open, sucking And blowing. Guy told me I could'nt move check valve with lung pressure that it was a protection device in case of backfire. Is that so? Gonna take it back out check hose for restriction, remove pulse limiter, and see if I get a stronger pulse straight from the crankcase. Unless I get a better idea from you guys...... Getting frustrated...
 
racerone said:
Agreed , try the old pump.-----------Are you getting good pulses to the pump.-------Checked filters?--------Checked vapour seperator ?
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Maybe should have listened to you a bit harder from the getgo. Assumed if there was a problem with the vapor seperator I would be able to see it without disassembly. Have got gasket on order but have not taken it apart yet. As far as pulses go, don't know how much is enough. Sure don't feel like much with my finger over the hose....
 
My simple advice is often ignored , folks do not want to trouble shoot.---------Want the instant fix !-----------The pulse limiter is a protection device to prevent over pressure of the pump.--------------The pump would explode from a violent backfire in the crankcase if that were to happen.-----------------Post the results of a compression test first.
 
Will check compression as soon as I have time to go get gauge at Dad's. Kinda hard to believe there is problem there as good as it runs and sounds when it's getting fuel....
 
Only by inspection and trouble shooting will you get / find a path forward !!-------The pulse limiter is NOT a check valve.----It is a flow fuse.------------Too much airflow and it closes.
 
racerone said:
Only by inspection and trouble shooting will you get / find a path forward !!-------The pulse limiter is NOT a check valve.----It is a flow fuse.------------Too much airflow and it closes.
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Been inspecting my ass off! Had pulse limiter off...twice. Seems to be WFO. Not sure how the pulses are supposed to feel but seem kinda weak. One guy said that was probobly normal, that it was'nt a big hit but an accumulation of little ones that did the work. Whatduhyathink?
 
I guess it is time to learn what a ---" flow fuse "-is.---------Yes they are fully open when you blow one way or the other.---------A flow fuse CLOSES when there is too much flow.
 
racerone said:
I guess it is time to learn what a ---" flow fuse "-is.---------Yes they are fully open when you blow one way or the other.---------A flow fuse CLOSES when there is too much flow.
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I got that. What I don't know is how strong the pulses are supposed to be. Just trying to understand the friggin thing....
 
The VRO is driven off the vac and pulse pressures. There is a check valve in VRO inlet that does go bad along with air motor cover leak or crack. This unit only pumps when you hear it "click", this is when then spring drives the diaphragm home. You will have weak pressure cranking it to test but pressure increases as RPM increases.
 
faztbullet said:
Make sure top of vapor separator is not warped it can cause this.....
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Got the new gasket. The vapor seperator chamber and the top for it are not absolutly perfect but they sure look like they match up very well. The chamber being a little convex and the lid about the same concave. I would think the gasket would make up any differance there might be. Only talking a few thousands here, just barely lets light under straightedge... Any harm in a bit of RTV, black permatex or something? I understand too much could get to needle & seat. That gasket ought to be a wee bit thicker..
 
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...or a light hand with a file?... or some kind of gas resistant string in bottom of gasket groove?... Think maybe top of vapor seperator is flater than I first thought. Still seems like pretty close match. New lid 60 bucks, tired of spending money. Afraid insurance company might go broke if I don't send em all I have...
 
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