Volvo MD2030c

[Runaway]

I have one of my MD2030 engines that suddenly started putting out black smoke at high rpm and will not rev past 2000 rpm in gear. Starts normally and runs clean up to 2000. It then smokes and misses if further throttle is applied. I have changed the fuel, both fuel filters twice and the injectors. As soon as you lower the throttle it runs smooth and clean. When I first started to trouble shoot it it would run 2400 under load and drop to 2100 and start missing then go back to 2400 rpm and run smooth. It runs at normal temperature. We suspect fuel pump issues? Any ideas? Is there a timing advance that could have failed?

[Runaway]

Originally Posted by Runaway

I have one of my MD2030 engines that suddenly started putting out black smoke at high rpm and will not rev past 2000 rpm in gear. Starts normally and runs clean up to 2000. It then smokes and misses if further throttle is applied. I have changed the fuel, both fuel filters twice and the injectors. As soon as you lower the throttle it runs smooth and clean. When I first started to trouble shoot it it would run 2400 under load and drop to 2100 and start missing the go back to 2400 rpm and run smooth.

It runs at normal temperature.

[barnakiel]

Air filter OK?

The boat is powering or at the dock (gears not engaged) too?

If fuel lines/filters are fine, if the prop is clean and the transmission not obstructed in any way, I would think perhaps some issue with the high pressure pump.

Before going for the big one, check out the small (lift) pump too. Their partial failure sometimes leads to odd behaviour of the whole system.

You can also undo the injectors and give them a basic visual test in situ.

b.

[Runaway]

Underway 2000 then it misses in neutral revs higher but still the same where it misses until you reduce throttle. You hear the engine tap when it misses like it is firing too early. The injectors are new from Volvo. Does the pump have variable timing or fixed? I am looking at the high or pickup pump as you stated. I have had broken fuel regulation springs in the past that caused problems.

[Runaway]

I did also replace the fuel filter. It runs perfect until 2000 rpm. Then black smoke with a heavy miss. It appeared that the injector furthest from the fly wheels was slightly discolored. I guess that is #3. Just not sure how the system works.

[Runaway]

I did mean to say I changed the air filter as well. I have not changed the exhaust manifold.

[Tellie]

I'd suspect and inspect the exhaust manifold or perhaps a possible fouled prop first before fooling with the pump.

[Runaway]

As it has the same symptoms in and out of gear I do not think it is a prop issue. I have a new riser exhaust I will be installing. It sounds like at a certain rpm one cylinder fires too early making the engine miss, slow down and smoke. Upon backing off the throttle it is clean and smooth.

[Runaway]

We have done a compression check and the pressure is good. We are now removing the high pressure injector pump and sending it to be tested.

[barnakiel]

High pressure pump off and to a service point. A regular service check will tell you if this pump has any issue.

Once all the do it yourselve points are checked there is often little else to do than check the injectors and the pump next. But it does not sound an injector problem.

Misfiring at high revs sounds to me like a possible timing/pump issue but then again I am not a diesel mechanic.

PLS share the findings!

barnakiel