Fuel system woes

[Diver Down]

I apologize for the long post but I'm in need of some troubleshooting advice on a fuel system problem with one of my 8v71s.

I assume the fuel flow is typical for our old Hatts with 8v71s: tank to Racor filter to fuel pump to secondary filter (on engine) to heads. I just dismantled and thoroughly cleaned the Racor and replaced both filters. Here's the problem: engine starts easily but only runs about 1.5 minutes and then shuts down. It appears that fuel is not moving through the Racor filter because I don't see the color change in the bowl that I would expect to see as fuel from the tank replaces the new fuel put in the unit when the filter was changed. Also, I don't see any bubbles or other movement of fuel in the bowl. Generally, the pressure guage on the discharge side of the Racor reads 8-10 (psi?) but now runs up to about 25. Sounds like a blockage, but where? If it was on the suction side of the Racor (i.e. between tank and Racor), wouldn't the engine suck down all of the fuel in the Racor before shutting down? I haven't disconnected any hoses yet but could it be a bad fuel pump? If so, how would that explain the high pressure on the discharge side of the primary fuel filter?

I'm not a diesel mechanic and any suggestions will be greatly appreciated.

[captddis]

I bet the check ball is in backwards.

[rmatt]

If the problem existed before you worked on the system, then check the vent. If it started after you worked on the system re-evaluate what you did.

[bostonhatteras]

The guage on the racor is for inches of vacuum. The higher it is the less filter life you have left. A pressure guage can be inserted after the secondary filter, usually right on the filter head. For me 0-10 vac is normal on primaries and 25-65 psi is normal at the secondaries. Can't help more than that because I don't have racors on the mains. Just simple DD spin ons. I've never had an issue but I keep the tanks clean.

[SKYCHENEY]

I bet the check ball is in backwards.

As Dave said, check the Racors. It sounds like there is a blockage there, most likely the check ball.

[bigbill]

did you shut off the fuel valves to service the system? make sure the valves are open, also change tanks to see if anything changes.

[Bob Bradley]

Had a problem a couple years ago when a chip of crap lodged itself in the inline fuel shutoff valve upstream of the Racor. Start debugging by using your fuel manifold to isolate it to a line vs a tank problem. That will eliminate the vent line as a potential cause.

[Pascal]

You said the engine starts and run for a shirt while, are you implying you can get it to restart again? If so how, manual priming?

Racors gauges are vacuum not pressure. Remember the Racors are on suction side, there is no pressure just suction. A high reading indicates a blockage, likely in the Racor since that's what you worked on. Disconnect the Racor outlet and slip a piece of hose on the Racor fitting, the use a hand on pump pull fuel in the Racor. See what happens. If you can, the the blockage is between the Racor and the fuel pump. If not, then it s either the Racor or the line to the tank incl valve or pick up, unlikely thiugh

[Boatsb]

Although stated to be unlikely there are many instances of clogs between the pickup screen and the filter inlet. Put suction on that part of the system and see what comes out. If you get resistance and minimal fuel you have your answer. If you get clean fuel easily move to the next link. As Dave and others said there is a blockage. Isolate it and you'll have the answer.

[Diver Down]

Disassembled and cleaned the Racor 3 times with no fix to the problem. Then installed a rebuilt kit and everything is now back to normal. I suspect the aluminum check ball was getting stuck in its seal.

[bobk]

Mike, You probably ought to rebuild the other one too. My filter life was about 500 gallons or so based on vacuum gage before I rebuilt. Since then, I'm at 1500 gallons and still have good vacuum. I'm about to change them just to see what the filter elements look like.

Bobk

[Boatnut]

Disassembled and cleaned the Racor 3 times with no fix to the problem. Then installed a rebuilt kit and everything is now back to normal. I suspect the aluminum check ball was getting stuck in its seal.

Hey Mike,

Glad to hear you got the problem resolved, and it seems like it was an easy fix. Thanks for letting us know how you made out.

[luckydave215]

Mike, You probably ought to rebuild the other one too. My filter life was about 500 gallons or so based on vacuum gage before I rebuilt. Since then, I'm at 1500 gallons and still have good vacuum. I'm about to change them just to see what the filter elements look like.

Bobk
Wow, you guys must be getting dirty fuel, or maybe it's all the southeast humidity encouraging algae growth.
I get 4~5 fuel fills (6-8 thousand gallons) between filter changes, and even then I do it just because, as vacuum is still OK.

[bobk]

Wow, you guys must be getting dirty fuel, or maybe it's all the southeast humidity encouraging algae growth.
I get 4~5 fuel fills (6-8 thousand gallons) between filter changes, and even then I do it just because, as vacuum is still OK.

My number was per filter, 3000 gallons total, and like I said, it's still well in the green, I just want a look to confirm all's well.

Bobk

[bigbill]

dave, you are getting that amount of time out of your filters because you are burning that amount of fuel, and keeping it fresh.
i'm sure most of these boats don't burn near that many gallons in a season.