v6 fuel flow

[j_martin]

I have a 88 150SR4 engine losing power at wot. I put in a fuel pressure gauge between the filter and the carbs and documented 5 psi at 4500 rpm, rapidly degrading to 0 at WOT, with engine flameout of course.

I replaced the filter and it ran well all the way, with fuel pressure 5 lbs or more at WOT.

This is the second time, so I cut open the filter and looked at it. It is a relatively course screen, and there didn't seem to be anything in it.

What am I missing? Why would replacing a good filter increase fuel pressure?

Thanks for the help in advance.

 

[gss036]

Re: v6 fuel flow

Do you have a seperate water/fuel separation filter? If not, you need one. Rebuild the fuel pump, real simple and cheap. While you are working in that area, check the clear oil/fuel lines, they tend to get brittle and will break. That does not set off any alarms until you have engine damage form lack of oil./lube.

 

[j_martin]

Re: v6 fuel flow

I don't have a water seperation filter. I just put a kit in the fuel pump. It still had rubber check valves in it.

I think this 18 year old motor needs to have the carbs gone through, and all the oil, fuel, and bleed lines replaced with new. The line from the tank (Poly) has already been replaced. The filler hose and vent system will also be replaced.

I just pulled the last 10 gallons out of the tank into clean containers, and I'll put it all through a lab quality filter funnel to see if there's any debris in it.

Thanks for the help.
John

 

[gss036]

Re: v6 fuel flow

Can you pump the primer bulb and keep the engine running? Maybe sucking air somewhere?
I am running a 1989 Merc 200 hp and have never had the carbs apart, but I do run SeaFoam doing a decarb process every year. You can find the instructions in the FAQ, that might help. I have a tank that holds 115 gals of fuel and once in a while I will put in a quart of Mystery Oil, comes in a red platic bottle. Could bbe your carbs are dirty.
I have a seperator filter and replace annually unless I start getting a little surging, ususally because of excessive water in the filter, then I change as need, I also carry and extra filter on the boat but have never had to do an on water change. I run strictly on saltwater.
I have read some reports about the fuel causing problems in some fuel tanks, like disolving the material, but I think they are fiberglass type tank on whalers, maybe too much alcohol?