here is my problem..... i have a 98 e350 psd.
about six months ago, while at airport i left the headlights on and had dead batteries recieved jumpstarta and shortly there after in the mornings it just woulodnt start. the voltage needle will begin its climb to 12v then will dive to 6or 8 v and stay there even after the glow plugs finish cycling. this is just not enuf juice to start this motor..... to me it acts like some kinds slow draining short somewhere. if i jump start it it will run fine all day long. when it sits overnight it will rarely start the next day on its own. i have put 2 new batteries in and this helped for a few months....then i put a new glow plug relay in and it made no diferrence.
the vehicle was recently transported by ship to hawaii (3 weeks at sea) and there was no problems before arrival here or before the dead battery at the airport. these may be just incidental and not related.
the temps here are always 70 to 80 degrees and other posts that i have read re starting problems seem to deal with colder temps..... the wait to start light only stays on for 1 or 2 seconds in oregon it was 5 to 10 depending on temp,humidity etc. i really feel that there is a short somewhere but have no clue as to where to look....also diesels are new to me so i am not familliar with all the various sensors etc that may be the culprit......help!

 

Its possible that the alternator has some bad diods that will cause drain when sitting and just be able to keep up with charging. Also the starter may be warn out, like drawing too much power.
thats where I would go.

 

thanks for your input.....i really hadnt thought it could be a bad starter..... is there a good way to test for this... i read on another post about how the starter really needs to crank strong and fast. if over time this strength has deteriorated it would not be real noticeable to the ear.... i checked and it seems like this is one part that is easy to remove...as you may know the psd vans are hard to work on as many parts of the engine are inaccessable. how would i test the starter.. i think i will do this first and then the alternator. i was thinking of testing the glow plugs but it is not that easy on the van.
the relay seems to cycling. when i turn the key the voltmeter drops to 6-8 volts and drops steadily while cranking not to return. however when the wait to start light goes out if i wait about a minute without cranking i hear a click and the voltmeter rises to 12 volts... this must be the relay cycling off. but if i try to start it when it has this higher voltage it drops off as before and the batteries seem to be to weak to start the motor. if i jump it from a static battery it usually starts right up......