8V71TI shut down at cruising speed. Please help!

[Thelog]

I knew this day would come, but I hoped it wouldn't be after just three months of owning her. While heading back to the marina today, after running the boat (1978 46C) for about twenty miles, my starboard 8V71TI shut down. I had it synchronized at about 1700 rpm when I heard the starboard engine start to lose rpm. It continued to do so slowly and smoothly for about twenty seconds before shutting down. Attempted restarts would get no more than a sputter like she wanted to start again. I proceeded to change the primary filter (Racor 1000 series 10 micron) and cleared the entire canister of the old fuel. Filter was last changed about two months ago and appeared slightly dirty, but not too bad. After that, the engine ran for about five minutes with full power before shutting down again. I then changed the secondary filter and switched fuel tanks to the center tank which was running the gennerator. Since then, the engine turns over very quickly, but there is no life at all. It's worth mentioning that there was no smoke at all during the run. There is also absolutely no smoke while turning the engine over now. Any thoughts would be greatly appreciated! Thanks as always! I am very mechanically inclined, but brand new to diesel ( I do have the shop manual though)...

 

[MikeP]

Definitely fueling. Personally, I think I'd start with checking to ensure there were no vacuum leaks in the fuel intake line from the tank through the Racor. Do you have separate primer pumps? IMO, they are invaluable for these engines, both for quick restarts on filter changes as well as ensuring there is a good, solid flow of fuel initially. Although these motors/fuel pumps are allegedly "self-priming," in reality it takes a long time to actually achieve that and fairly often, you can run out of battery before the engines will actually prime themselves.

If no primer pump, break the fuel line between the Racor and the engine and hook up a Mitey Vac or something like that and see if you can pull fuel through the filter with no bubbles. FWIW, a Mitey Vac is a handy tool for all sorts of uses/troubleshooting.

If there is no vacuum leak in the fuel intake system, put another set of filters on and see what happens. It could be that you have very dirty fuel. My previous boat had fuel that was so bad on one occasion that it would totally clog a filter in 20 minutes of running. It took me two days of fuel polishing with a homemade polisher to clean the fuel/correct the problem!

 

[Tim Powell]

Mike
Fuel pump? I would believe if it just died slowly and without smoke it is external. What Mike said is the most likely place to start.

 

[SEVEN]

I agree with Mike as well. Do you know how old the fuel is? Has it been polished? If not get it done, change the filters after polished and try again. Good luck.

 

[skater]

I would look for an air leak. Start with the racor gaskets and o rings. I had a similar problem and it was an o ring for a plug in the racor bowl. It sucked air in, and the engine ran out of fuel. The primer pump would not work because the fuel was too low in the racor and could only suck air. It could also be the o ring for the racor drain cock.

 

[Salty Dame]

Maybe a twisted quad ring on the Racor lid. If they are mounted high it won't show a leak.

 

[rwappleton]

I'm with everyone else here you have an air leak in the system. I chased one on the genny for 6 months. Would run for anywhere between 2 minutes and 2 Hours and just quit. Mike's plan is the best. Minor fix in terms of money but major PIA looking for good luck.

 

[saltshaker]

Sure does sound like a fueling issue. How low was the tank when she shut down and have you run it that low before? You may have a bad gauge or pick up tube on that tank if it didn't read low. If you did starve it of fuel, it will eventually prime but as mentioned it can take a while. You can crack a return line and see if she's pumping fuel well or sputtering air. Not sure if it really helps but I have fracked a return line to aid in bleeding the system and the engine started right up.

 

[Tim Powell]

Sure does sound like a fueling issue. How low was the tank when she shut down and have you run it that low before? You may have a bad gauge or pick up tube on that tank if it didn't read low. If you did starve it of fuel, it will eventually prime but as mentioned it can take a while. You can crack a return line and see if she's pumping fuel well or sputtering air. Not sure if it really helps but I have fracked a return line to aid in bleeding the system and the engine started right up.

Jack got it I had a pick up in the aux tank that had come apart no fuel was comming sucking air only.
Invest in priming pumps would be a good long turm investment you are going to rum out of fuel at some time!

 

[Thelog]

Thanks to all for the responses! The Mityvac is on order with Amazon. I do not have a priming pump, but will be looking at getting one for sure. I have been running the mains on the rear tanks (starboard and port respectively) and the generator on the forward tank. When I purchased the boat three months ago, the tanks were all half full. I had them topped off shortly after that and they are at the half way point again now. I will be rebuilding the Racors completely this weekend. As far as chasing the leak from the tank to the engine, if I unscrew any of the fittings, is there a specific thread sealant I should use when replacing them? Also, yesterday I wouldn't crank the starter motor for more than thirty seconds, then I would let it rest for about five minutes between cranks. Can I crank for longer without damage? Should I let it sit for longer too? I have never worked with that size starter before. Thanks again!

 

[rsmith]

You need to bleed the system to get the air out. Fill the filters with fuel before you close them up. The secondary filter is after the fuel pump. If you don't have those stoopit spin ons you can leave the lid of the secondary loose and crank the engine until you have fuel pouring out the top of the filter.
One other thing there is a float ball in the Racors that shut off fuel flow if their is water in the filter these balls can get stuck. I'd kind of bet on that.

BTW I had primer pumps and ripped them out its all a source for leaks. I keep a 2gal can of fuel in the ER to prime the filters. Simple and effective.

 

[piripucha]

Take a look at the lower part of the turbine of the racor filters, if you see bubbles coming out from it, you have an air intake from the tank to the Racor. Also drain the bowl completly, as it was mentioned before, if you have water in your fuel, the racor will shut down. I will like to mention that my 8V71TI came with a crossover line from the secondary filters. That way you can prime one engine with the other. Its a cheap solution you only need two valves and a hose . I hope this helps.

 

[Avenger]

As far as chasing the leak from the tank to the engine, if I unscrew any of the fittings, is there a specific thread sealant I should use when replacing them?

I can tell you what not to use: Teflon tape. Never Ever in a fuel system. You can use any paste or liquid type of thread sealant. Many OEMs use Gasoila which is a red varnish type of sealant.

You may do well to make up a length of clear tubing to temporarily replace fuel lines in the system. This will allow you to see if there is air in the system, and by moving it around you may be able to see where the air originates.

Also, yesterday I wouldn't crank the starter motor for more than thirty seconds, then I would let it rest for about five minutes between cranks. Can I crank for longer without damage? Should I let it sit for longer too?

Sounds like you are doing it right.

 

[davidwigler]

Take a look at the lower part of the turbine of the racor filters, if you see bubbles coming out from it, you have an air intake from the tank to the Racor. Also drain the bowl completly, as it was mentioned before, if you have water in your fuel, the racor will shut down. I will like to mention that my 8V71TI came with a crossover line from the secondary filters. That way you can prime one engine with the other. Its a cheap solution you only need two valves and a hose . I hope this helps.

Can you post pics of this crossover line? Sounds like a great idea if not too complicated.

 

[piripucha]

Sure I will go by the boat next wendsday (Therapy day !!) and I will post them by thursday. Its quite easy , on the secondary filter base you take out one of the plugs and put bal lvalve, I dont know the size, you do the same with the other engine filter and connect them with a hose. It also ussefull if you have to get some fuel for toping filters. Caution do not run with the valve open because the engine can not handle the reduced flow.

 

[Jasper]

Great advice in this thread.
I had repeated problems with the generator cutting out, then sporadic Port engine shut down. Had the fuel and tanks checked and they were in need of polishing. Yet the problem would happen from time to time. After a major fuel treatment done and this seemed to help, so I blamed the dirty fuel.
UNTIL: What happened to you occurred to me out in Moreton Bay. I did what I always do, change the Racor filter that is being used (have 3 a side), then primed it. For the first time I noticed one of the fuel line connectors was making a low hissing sound. Thanks to the prime pumps, got back to the my home by morning, removed the fuel line. Replace both connector and fuel line.
Never had a problem again...touch wood. I believe the fuel line joint/connector was always the main problem and over time it got worse and showed itself. In hindsight, I should have checked every hose and connector more thouroughly.
Make sure you take the advice above and especially Prime Pumps. They are invaluable!
Good luck!

 

[dottieshusband]

+1 to what rsmith said. I can't add to the fuel starvation issue, but starting the engine AFTER a fuel starvation event, now there I've been. I don't have a walbro priming pump, but I wish I did. I keep a 5 gallon jug of diesel on board to fill the racors and engine fuel filters. It takes a few gallons, and then still a bunch of cranking. If you've got good filter seals, and full canisters, and a good fuel pump, then it should at least try to start. Lot of valves in there to look at, racors, fuel manifold, etc. on the fuel pump, be aware that you have a CW unit and a CCW unit, they look different.

 

[34Hatt]

I had a sporadic engine shut down years back took a while to find the bottle cap in the tank that would get sucked up against the pick up tube
Know of two other boats that found tape stuck in their pickup tubes so if you don't find it right away !

 

[racclarkson@gmail.com]

1. DD recommends 30 micron filtration.
2. Change either Racors or secondary separately filling either with clean filtered fuel and allow whichever filter changed to purge air on starting.
3. Then do the remaining unit as above and you may not even notice a hiccup.

I've never needed to use a crossover feed by doing above, but it's nice to have one. Flush the residual fuel from the crossover circuit now and again. I do it before filter change to let old filters catch anything there.

 

[SKYCHENEY]

1. DD recommends 30 micron filtration.
2. Change either Racors or secondary separately filling either with clean filtered fuel and allow whichever filter changed to purge air on starting.
3. Then do the remaining unit as above and you may not even notice a hiccup.

I've never needed to use a crossover feed by doing above, but it's nice to have one. Flush the residual fuel from the crossover circuit now and again. I do it before filter change to let old filters catch anything there.

A 30 Micron primary Racor is not necessary. A 10 micron or even a 2 micron will work just fine. That is not the issue here.

Also, I have never had a problem changing both the primary and secondary filters at the same time. Changing them independently and going through the priming process twice seems silly to me. The issue here is probably an air leak, if the filters were filled with fuel after changing and it still wouldn't prime.