Intermittent loss of power


Junior Member
Hello All

I have a 1980 Ericson 30+ fitted with a 2 cylinder 16 hp Universal marine diesel engine with 2200 hours on it. I have never had problems with loss of engine power until recently.

Initially the engine starts and runs normally and then for no apparent reason starts to slow down as if the throttle has been pulled back. The engine doesn't actually stop (so far) but it sounds a bit uncertain in terms of whether it will carry on or not and then after about 10 to 30 seconds speeds up again and runs normally for while. And then it slows down again and so on repeating the problem every 10 or 20 mins. This has happened repeatedly lately each time I have been out running the engine at higher rpm for more than maybe an hour.

It seems like a fuel flow problem to me so I changed the Universal's fuel filter (which was fairly new anyway) and replaced the 10 micron Parker Raycor water separator filter cartridge (also very new) and bled the system and ran it and all seemed well. (Neither of the used filters seemed dirty when I inspected them.) Anyway after running happily for several hours next time out on the water the problem started again.

Note Most of the rubber hoses between the fuel tank and the filters and the injector pump are in good condition (or new in fact) and there doesn't seem to be any fuel leaks anywhere. Also the electric fuel pump seems to be working OK from what I can tell. And the fuel in the tank is also relatively knew. A hand bulb in the line from the tank pumps fuel with ease through the system when I bleed it. So I don't think there is a blockage in the fuel line coming from the tank unless there is some gunge or dirt in the tank that is moving around and periodically partly restricting the fuel flow. During one of the loss of power episodes I removed the fuel filler cap in case there was some kind of airlock happening in the tank but this didn't seem to effect or remedy the problem.

So I am wondering if perhaps the injector pump is starting to fail intermittently. Does this seem possible or likely? Does anyone have any other thoughts on the source of this problem and ways to trouble shoot it?

Many Thanks Geoff

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
My troubleshooting book (Peter Compton's) says the most common causes of what you describe are air in fuel or defective injector(s). He puts injector pump far down list of likelies.

Wouldn't put too much stock in it, but at least it's something.

I once had an invisible crack in the casting of a 30-year-old Racor assembly that was letting air in. Very hard to discover. A pro advisor said to keep looking, because that's usually what it is. You can see a leak of fuel coming out, but not a leak of air going in.
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Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi Geoff,
I had very similar symptoms on our 1984 E30+ with the same engine last year. All filters and fuel line were good. Pickup tube in the fuel tank was clean. I had replaced the original Facet fuel pump four years ago. I couldn't find the problem nor could a local marine mechanic.

Then I read in Nigel Calder's diesel engine book to check for tiny air bubbles by removing the fuel line at the fuel filter on the engine and putting that end into a pail of diesel fuel; start the fuel pump--sure enough I had very tiny pinhead size bubbles which I traced to an air leak in the fuel pump. I did that by running a fuel line directly from the fuel tank to the pump and then into the pail of fuel thereby bypassing filters and isolating the fuel pump. We had tested the fuel pump for flow and it looked and sounded fine but Calder's test revealed the problem. It's amazing how a tiny air leak will disrupt the fuel flow and cause the engine to run erratically, sputter and eventually stall. I bought yet another different fuel pump and it solved the problem.

I was also told it could be the injector pump or the injectors but it wasn't. However at 2200 hours you should have the injectors serviced if that has not ever been done.

Let us know what you find. Good luck!
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Member III
I have spent more time than I care to admit covered in diesel and tracking down gremlins in my fuel system until I figured it out. The previous owner had replaced everything with new components but unfortunately did not implement several of them well which resulted in gremlins until I fully understood and remediated the system on my 30+.

Anything component before the first pump in the system is the vacuum side and if air is entering the system it enters on the vacuum side. Any component here can be suspect for air, small hairline cracks from an overtorqued fitting, air inside a fuel filter that wasn't bled properly, etc. Depending on the layout of your boat and system, bleeding the vacuum side can be very tricky. The fuel tank on these boats is at a low point in the system which makes purging air from the vacuum side difficult, but not impossible. Filling the tank to the top, unmounting components and getting them as low as possible while bleeding or filling them using a bottle or other device can help. I'd be wary of using a bulb like is in your system as they can often be a source of small air leaks.

If it's not air it sounds like the injectors or fuel quality. It doesn't take much air to stop one of these motors but small amounts (micro bubbles) can cause stumbles.

Injectors are an inexpensive replacement item (and you can have them rebuilt if you so choose.) That's enough hours that if they're original, they've seen a lot of fuel flow by them :)


Contributing Partner
Sounds like air in the fuel. I had a similar thing. Troubleshooting eventually showed a crack in the body of the Racor filter. As the Racor heated up the miniscule crack enlarged and allowed air bubbles into the fuel. I found the crack with a magnifying glass. I know a couple of others that had the same problem. One had his fuel injector pump rebuilt at great cost. It wasn't the problem. It was the fuel filter. All of these filter bodies were older. It's now on my bucket list to replace every 5-6 years. Cheap insurance. Also, it could be a loose fitting or a hose with a leak. I used the bucket with diesel in it and a length of fuel hose troubleshooting method. I started at the tank disconnecting parts and bypassing them. Between the Racor and the fuel pump, the engine started running well. Luckily, these little engines don't use much fuel so the bucket doesn't have to be large. Adding a valve at the top end of the temporary fuel line will keep a good column of fuel in the bucket hose which makes purging easy. Also the fuel pump will circulate the fuel and return the bubbles to the tank.

Good luck.


Junior Member
Many thanks everyone who responded so quickly to my request for advice. It seems to me that I have a small amount of air leaking into the system somewhere between the tank and the fuel pump based on what you guys have said so I will start with that possibility and work on it from there.

Cheers Geoff

PS an extra thanks to Christian Williams for putting me onto Zerk Fittings as a method to fix my leaking rudder post which I asked about a while ago.

Keith Parcells

Contributing Partner
I agree that the hand bulb could easily be the source of air bubbles. Why don't you try removing it and replace it with a barbed hose adaptor? See if that does it. If not, you could always put it back.
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Junior Member
All good thoughts so far, but I would check first for a clogged tank vent. It's cheap and easy to do.

Hello All,

To those of you who offered some great advice for trouble shooting my intermittent loss of power problem I thought I would just close the loop by letting you all know how things went.

I decided that a small air leak in the system (that several of you mentioned as a good possibility) between the tank and fuel pump was the best place to start. So I started with the simplest first Step and after checking all the fuel line connections for integrity and refitting and securing their clamps again I tested the boat out on the water and low and behold the intermittent power loss problem occurred again.

So it was back to the dock for Step 2 to try pumping fuel via the electric fuel pump into a bucket to see if I could see any tiny air bubbles indicating an air leak somewhere between the tank and the pump.

In order to inspect and get at the fuel pump more easily I removed both the drain hose under the sink and the alternator. In the process of removing the alternator I lightly touched the wire connecting the fuel pump to the wiring harness and the wire just fell off. On inspection the wire was badly corroded and had been hanging on by just a couple of strands (out of sight) within the wire connector and easily broke when I touched it. So it seems that the fuel pump had been intermittently switching its self on and then off as the wire moved slightly with the movement of the boat from time to time.

So after cleaning up the wires and reconnecting them in a new fitting I started the engine and took it out for another quick test run and had no problems.

Also this weekend was a long one here in BC for BC Day so I took the boat over to Gabriola Island for three days (50 nautical mile round trip) and had no more problems after running the engine at various rpm for a considerable number of hours so I think the poor corroded connection was the simple source of the problem.

Hopefully this solution may be a help to anyone else who has a similar problem. In hindsight checking the electrical connections to my fuel pump was an obvious place to start to make sure it was functioning properly first before even changing the fuel filters or any thing else.

Thanks Geoff