Universal M320

[Bill Shep]

My engine starts normally, runs fine for approx. 4-5 minutes then suddenly dies. After cranking it will restart, run for a few minutes and then suddenly die again. I've replaced the fuel filters, have plenty of fuel to the injection pump, getting plenty of fuel out of the injection pump (for a time anyway, until it dies).

Any ideas on what might be causing this?

 

[jssailem]

Bill
Diesels are not that complex. Electricity to start them. Fuel to keep them running, Coolant to cool them down so they run a long time.
You say you changed the filter/filters. Which? A wild stab of a guess with out more info, is you have air in the system from the filter change. Air trapped in the filter has not been replaced with fuel, or a seal/compression washer was missed when you reconnected a fuel line or filter line. You say your getting fuel to the injectors, but were all of the fuel lines bled?

I'd look at the connections you loosened to change the filter/filters and confirm they have any washers that are needed (some fittings use a copper compression washer) and that the connections are firmly tight. (not strip the threads tight). Check the filters for any air in the system (Racor filters often have a sight glass). If your fuel system has a vacuum gauge check to see that the system has a bit of vacuum. No vacuum means you have an air leak.

post back your discoveries.

 

[Bill Roosa]

Yes, air in the lines. Bubble gets carried to the pump where it air locks it. (air compresses pretty well and liquids do not!!). Stop the engine and the bubble moves by gravity to some plumbing BEFORE the injector pump and at a HIGHER level that the entrance. High spots like this are the bane of diesel fuel system and their owners.
bleed, bleed, bleed, bleed, bleed and then bleed some more
or
re-plumb once you ID the air trapping part so you can actually bleed it in one attempt.

 

[Benny17441]

Bill's got it. Air trapped in the line. Don't know what engine make you have but some models can be a challenge to bleed. Some have added electric fuel pumps and others even a hand squeeze ball pump..

 

[Bill Shep]

I checked all fuel lines for cracks/loose fittings and found none. I then took the fuel line from the tank off and placed it in a jug of diesel. The engine then ran fine so apparently there's gunk in the tank and/or suction tube.

 

[jssailem]

Bill
When gunk builds up in the fuel tank occasionally it will plug the pick up tube. Temp solution blow out the tube, add a product like "Bioborjf Fuel Microbiocide". It's a temp solution. Most effective will be to clean the tank. And polish the fuel by filtering it.

 

[Sprega]

PO of "Miss Izzy" had the same problem. Removed the fuel tank and had it steamed. It been fine since.

 

[Bill Shep]

Thanks John

 

[LakeOntario270]

Check that your fuel filter is tight and not sucking air.

 

[Bill Shep]

10-4, they are both good and tight.

 

[Donnybrook]

Most likely, fuel pickup tube in the tank is clogged. The 90 degree elbow coming out of the tank is a good place to find an obstruction. You can take the fuel line off the injector pump and place it into a container. Run the pump and check the output.

 

[dcapn88]

If your diesel tank is difficult to clean, (i.e if you have to cut 6" holes in each baffled area), here is a work-around: use a portable-plastic tank (like the Moeller 6 gallon), and either fill it at a gas-station/fuel-dock or transfer (with a bulb-pump) from your regular tank as needed; (I highly recommend you filter with a cleanable (glass-type) filter and remove water, like with a "Mr. Funnel", as you transfer). You can run the return line into your existing tank, (or T it into the transfer hose downstream from the bulb-pump...this will minimize the need to re-fill the plastic tank..you may need to add fittings for the transfer and return fuel lines). I did a similar sytem on my previous boat and am in the process of doing it again on my latest boat, bot 1980's vintage. If I ever get around to re-building my regular tank, or just cutting holes and scrubbing then I will have this plastic tank system as a back-up system for under $100.

 

[dcapn88]

Since most pick-up tubes are near the bottom of the tank, where most of the gunge lives, you can try measuring the depth of the tank (through the fuel-sender mounting hole), then make a new pick-up tube...that is shorter..(by maybe an inch(?) that will mount at the sender hole (you, of course, will no longer have a sender..unless you make another hole-mount for the new pick-up tube). This will allow you to get fuel that is less contaminated and thus increase the time between changing filters.
Another short-term remedy for a plugged pick-up tube is to temporarily reverse the bulb-pump and rapidly pump air back through the tube, hopefully clearing some of the gunk back from the pick-up.

 

[Jim 5757]

OK Bill...we have the M3-20 in our Morgan 28. According to the factory manual, it is "self bleeding". We have never had any problem other than a few restarts after changing filters or completely emptying the tank for cleaning.
One thing you might try is to disconnect the fuel line from the secondary filter outlet and - with the ignition switch on - run the filter outlet into a clean jug. I get approx. 1 gal/min this way and it seems to be a good way to verify you're getting enough fuel to the injectors. If all that's OK, it's time to look elsewhere... fuel quality, compression, air...

 

[Jim 5757]

Just thought of something else... what's your idle RPM?