Engine stalls, fuel issue Detroit 4-71. Simple troubleshooting?

[zigzag930]

I had a man working over on the port side of my engine room this week and he was "crammed" in the area where the fuel lines come off the Floscan Homogenators/Pulse Dampers and connect over to the fuel pump.

The motor has been running perfectly up to that point, but today when I started it to heat it up (oil change time) the engine stalled out and would not restart. It slowed way down and then died. I had this problem once before on both engines when I first bought the boat. The fuel tanks were loaded with growth at that time and both filters completely clogged causing both engines to shut down.

So I was taught a method to prime the engine which works great. I disconnect the return fuel line at what I believe to be a fuel cooler and attach a vacuum pump (like used for oil changes) to that flange. By pulling a vaccum, fuel gets sucked through the entire engine, fuel pump, etc. When I crank the engine it will start and flow clean fuel into my vacuum pump's bucket. Shut down, reconnect and all set.

Well this time, I can not seem to pull fuel. I have changed the Racor (which was pretty clean anyway) and pulled the turbo/check ball/etc and verified no blockage. Refilled the Racor with fuel, opened the in/out valves and still can't pull any fuel through the engine. So I disconnected the fitting on the output side of the fuel pump. Still can't pull fuel. By the way there is 1200 gallons of fuel in the forward tank, so I'm not empty and the starboard engine is also running on that tank just fine.

So, I'm thinking there is a kink somewhere (due to the work just done in that approximate area) or there is some other blockage.

A few questions for the experts here. First if the fuel pump went bad, would that prevent me from pulling fuel through it? Second, if anyone is familiar with the FLowScan 7000 series, they have two pulse dampers and two homogenators (one set for flow to the engine and one set for flow from the engine). Could these be blocked up like a filter might do?

Thanks to all for any suggestions and assistance.

 

[SKYCHENEY]

Can you pull a vacuum or does it just pull air? And if you can pull vacuum with no fuel or air, then there has to be a restriction such as a kinked line or blockage. Are you sure that guy didn't shut off a fuel valve someplace? Trace the entire system and make sure.

 

[Captain Ralph]

Fuel valve open?

 

[zigzag930]

I can pull a vacuum, but only seeing a small amount fuel, mostly air.

I believe there is a restriction possibly caused by my 'helper' leaning on and bending the rubber to metal fitting on one of the many connections between the fuel selector and the engine.

There are no fuel shutoff valves except the on on top of the engine (at the final fuel filter). It is in the open position, but I closed it just for S&G to see if it made a difference.

 

[Captain Ralph]

I can pull a vacuum, but only seeing a small amount fuel, mostly air.

I believe there is a restriction possibly caused by my 'helper' leaning on and bending the rubber to metal fitting on one of the many connections between the fuel selector and the engine.

There are no fuel shutoff valves except the on on top of the engine (at the final fuel filter). It is in the open position, but I closed it just for S&G to see if it made a difference.

You don't have supply / return valves?
Usually placed in a location so to get bumped often with out notice?

 

[zigzag930]

Yes, I have supply and return valves for each engine.

Both engines are set to use the same tank for supply and return, however I did attempt to switch the port engine to another tanks just to be sure it wasn't a tank issue. Problem remained, so I switched back to the main tank.

 

[SKYCHENEY]

Sounds like you're pulling air from somewhere. Like you said, it may be a hose or fitting.

 

[Captain Ralph]

There is nothing in the FlowScan devices that could cause a shutdown of flow.
It may take a while but air will slowly move thru the gear fuel pump. I am sure the pump has not gone bad.
Maybe try to draw fuel before the fuel pump.

If you are drawing a vacuum and hand pump locks up, I can only guess a fuel line has been crushed closed.

If you are drawing a vacuum and hand pump never gets hard to move, you are drawing air and a fuel line is open or damaged.

What was your tech working on back there?

 

[zigzag930]

Tech was working on a leaking seachest which is in a miserable location. We had to find a guy small enough to squeeze into that spot as it required someone virtually double-joined.

On the 58LRC there is a seachest in the ER on the rear port side that is blocked by 5 or six hoses including large raw water intake, engine exhaust, generator exhaust and a few smaller hoses. We removed the exhaust water injector hose and the tech was able to work his way into that space. Applied JB waterweed and some 4200 and believe we have the leak under control.

Unfortunately this area he had to squeeze into has the fuel supply and returns right where he had to crawl over.

I will be looking at this closer on Friday when I can get back over to the boat. Will get some hose adapters to try pulling vacuum at several locations until I can isolate the problem.

My biggest initial questions were 1) will fuel pull through the fuel pump if it's somehow failed (which I agree is highly unlikely) and 2) if the FloScan could possible be causing this issue. Thank you for answering those two question.

 

[whoover]

I remember Mr. Clarkson having his flo scans apart a few years ago and he cleaned alot of junk out of it. It's worth searching his posts to check it out. Some about " no maintenance required".

Walt Hoover

 

[Fanfare]

Both the Flowscan "in" and "out" units have a canister attached. They are probably pulsation dampers of some kind. Whether they ever need maintenance I do not know but it seems possible. I don't remember anything in the installation instructions mentioning this.

 

[Captain Ralph]

On the FlowScan cans themselves, is a decal, "Not A Filter, Do Not Remove" .

 

[JD5652]

I had Floscans on a previous boat for over 10 years... never had to maintain anything. I did replace them once due to them being damaged ... but they are simply an open vessel with a predesigned flow pattern.

I guess if you had "gunk" get into them, then you might need to clean them, but I never had that expereince.

 

[drburke]

I had a similar issue.

Those "do not remove" damper canisters had accumulated some water and rusted a pinhole leak, which bubbled in air only under operation.

My mechanic said the FloScans are sensitive to any upstream leakage, so perhaps your tech bumped one and dislodged something.

DAN

 

[whoover]

Doing The Required Maintenance Or Service That Isn't Required But Really Is

This is Mr. Clarksons story on flo scans

Walt Hoover