Injector pump failing?

[Glennosi]

Two symptoms of a failing injector pump?
1. We have trouble bleeding our MD21B. It bleeds fine through to the small nipples on the injector pump but now no fuel is reaching the injectors.
2. Previously when fuel does reach the injectors the engine has needed a long time cranking to start.
Engine performance is ok when it is running, no sputtering, misfires etc.

 

[Rappey]

Fuel lift pump worn ?

 

[Bilgediver]

See if you can find a fuel injection service place in your area. Some of those rotary fuel pumps are not easily available but a service centre may be able to sort it.

One thing you could try is to just slacken the discharge fittings on the pump as you try to prime it using the starter to turn the engine. You will have to also loosen the pipes on the fittings as well . This may allow air up the threads of the fillings if it retains a spring loaded discharge valve similar to the vertical non rotary pumps. I have very occasionally had to do this on my injector pump when the air in the pump would not compress sufficiently to lift the discharge valve against its spring. When fuel comes from all fittings tighten up. Avoid removing the fittings in case bits pop adrift

Un fortunately not much detail of these pumps in the Manual.

 

[Glennosi]

See if you can find a fuel injection service place in your area. Some of those rotary fuel pumps are not easily available but a service centre may be able to sort it.

One thing you could try is to just slacken the discharge fittings on the pump as you try to prime it using the starter to turn the engine. You will have to also loosen the pipes on the fittings as well . This may allow air up the threads of the fillings if it retains a spring loaded discharge valve similar to the vertical non rotary pumps. I have very occasionally had to do this on my injector pump when the air in the pump would not compress sufficiently to lift the discharge valve against its spring. When fuel comes from all fittings tighten up. Avoid removing the fittings in case bits pop adrift

Un fortunately not much detail of these pumps in the Manual.

Have loosened the pump ends of the

 

[Glennosi]

Have loosened the pump ends of the injector pipes and no fuel is present when cranking

 

[geem]

Have loosened the pump ends of the injector pipes and no fuel is present when cranking

Have you checked the fuel lift pump out first?

 

[Glennosi]

Have you checked the fuel lift pump out first?

Fuel lift pump is fine. Lots of bubble-free fuel arriving at injector pump.

 

[Bilgediver]

Have you checked the fuel lift pump out first?

I agree it might be wise to check the lift pump is delivering by disconnecting the feed to the Injector pump.

Remember that if your lift pump has a wee screw in the centre of its dome cover then there is possibly a filter basket inside. Check it is clean and replace.

Also make sure the throttle/speed lever is on full speed.

 

[DownWest]

If fuel is getting to the injector pump, but not appearing at the injectors, you either have an air lock (unlikely) or your pump needs looking at. Just had something similar with a rotary DPA, but it was not gradual, the HP section drive sheared. Rebuild cost was a bit eyewatering.

 

[penberth3]

.........Also make sure the throttle/speed lever is on full speed.

....and check the STOP control is at the RUN position - and hard on its stop pin, nearly there isn't good enough.