only starts at half throttle...?

[waikaremoana]

hi, new to these engines & have a starting problem..
-by the way the engine is in a boat.

new batteries, new mech lift pump, new starter.

needs about 2 x 10 secs of cranking but then starts & will run with lots & lots of white smoke but only if throttle position is at half or more, as soon as you let the throttle go it will stall.

then it takes about 20 secs of more cranking to get the same result.

wondering if this could be a result of air in the lines or a bad IP?
or perhaps bad injectors?

any help would be most appreciated
cheers
www.waikaremoana.com (http://www.waikaremoana.com)

[Subzilla]

I learned to try the simple stuff first. How fresh is the fuel filter? A clogged one can cause the extended starting.

Usually a bad IP will be gradually cause decreased performance. Air in the lines will also cause these symptoms but will usually purge themselves after a minute of running.

Others here will certainly chime in with more suggestions. You've found one of the best sites for GM diesel knowledge. Welcome and let us know what happens.

[Robyn]

Install a clear plastic line on the fuel return line at the top of the Injection pump and run it to a suitable "SAFE" container.

Get the engine running and allow it to run for a fair time so you can observe the return line.

There should not be any air in the return.

Place a loop in the line and keep the loop about the height of the engine so the line will fill with fuel and you can see any air coming through.

If there is loads of bubbles, you need to find out where its getting into the system.

ZERO AIR IS PERMITED

NO air means that there is a very real likelyhood that the IP is shot.

The Mechanical injector pumps dont have near the complex issues that the electronic ones do BUTTTTTT they do wear out and can have troubles

Also as mentioned, make sure you have good fuel flow to the engine from the tank.
Plugged filters have made a fool out of us all at one time or another :rolleyes:

Injectors can cause issues but generally they wont all go south at once and the thing will run, maybe not perfect but will run.

Boats can run into "waterin fuel issues" and over time if allowed to get to the engine will ruin the injection system.

Large fuel water separators is the order of the day with sight bowls so one can see whats in there.

Keep us posted


Robyn

[waikaremoana]

cheers for your input guys but maybe i should give you a few more details...
i have the clear fuel line on the return from the IP, no air bubbles in there.
new filter & housing, new water seperator filter & housing (with clear sight bowl) so not clogged & no water

with the fuel line disconnected from the IP the elec fuel pump sprays out a good stream - like a garden hose...

would too much pressure from the electric fuel pump cause the IP to lock?
bugger all fuel comes out the return & i would have thought there would have been quite a bit...

cheers