Looking for some help/advice

91 F-250 7.3L

First problem: It is cold up here much of the year (minnesota) and when I start the truck I get plenty of engine rattle. In the past once it warmed up everything was fine. In the last year though... I generally warm it up about 5-10 minutes but when I take off (gently) I get terrible valve clatter. It will not go away and as soon as I get the RPMs up the oil pressure begins to drop, worst case almost to zero. The longer I drive it or the warmer it is outside the less pressure drop I get but it is still a problem at higher speeds. However, if I turn the truck off for as little as 10 seconds then start it again it is a smooth as silk and very little oil pressure drop at high RPMs. Any ideas? Sticking by-pass valve in the oil pump? The problem seems to be getting worse as time goes on.

Second problem: I don't drive the truck real often in the winter but try to run it about once a week. Last week it ran fine but two days ago when I tried to start it was very hard to start ( four plus hours on the block heater) and once started ran very rough (seemed to be missing) and poured out gray smoke. Idled for probably fifteen minutes then tried to drive it but the problem didn't go away. Shut off and restarted several times, same problem. Now I can't get it to start at all even after putting it in the insulated garage for two days and plugging in the block heater. It usually starts within 1 second under these conditions. Bad injector? but why so bad? Multiple injectors? Injector controller? How would I test?

Thanks

mnmark

 

First thought that comes to mind is the oil is all jelled up from being cold. I would change the oil to a synthetic like Rotella and see what happens. If that doesn't fix it, than I suspect something is clogging the oil pickup tube. Perhaps some debris is in the pan. Like maybe one of those seals that you have to remove from the quart jug of oil when you put oil into the engine. Somehow it accidentally ended up going into the engine and now it's floating around in the crankcase.

 

Thanks for the ideas. I don't think jelling is the issue since I am already using Rotella and have problems even at cool temps like +10-20F. No oil should jell at that temp.


I did suspect debris on the screen or in the tube except that it is a problem every time I start it at low temps and is seldom a problem after shutting it down warm.
Thanks again

mnmark

 

are you sure the rattle is the valves and not the timing advance sticking? a rich dose of lubricity/stanadyne fuel additive may help. Low oil pressure may be the sending unit acting up too. Get a mechanical guage and hook it up. The hard start problem may be fuel draining back, get a return line repair kit from injection shop or international to see if that helps you out. The block heater will take a few hours to aid in starting if glow plugs/relay is acting up. When the cold weather starts, the crazies start too.

 

Blinder12:


Thanks for the suggestions. The timing advance might be an issue. Is there a connection between timing advance and oil pressure because the two issues are connected in my truck? The engine is noisy when the oil pressure drops and is quiet when the oil pressure stays steady.

I have not heard of a fuel drain back problem before. Can you explain a little so I can troubleshoot? I did read some other threads about leaving the drain on the fuel filter open and that caused poor starting and smoking. I think you are on to something.

I do suspect I have a glo plug issue. Does anyone have a troubleshooting procedure or can recommend a good shop manual for this engine?

Thanks

mnmark