Running fine, now won't stay started

[jastutte]

96 discovery. has been running great. stopped to drop off my son. when i climbed back in it would crank and fire up then stumble and die. it keeps on doing this. will turn over and start then die.

have pressure at the rail. not sure what pressure, but i did get spray from the access at the rail. spark is good. air is good.

i have been having occasional rich and lean conditions. strangely enough, it will run perfectly, 13 mpg around town, then for one small trip run rich then run lean next time. i know this from monitering short term fuel trims.

what should i check?

grounds?

is there a way to test the cam sensor or the crank sensor? would either sensor cause this no start?

thanks,

180,000 miles, new o2 sensors, new maf

 

[jastutte]

little update:

truck sat for half hour and then fired right up. when she fired up the valves on the passenger side were clacking like mad. really loud. eventually they quieted down. drove home no problem. turned her off and then fired her up again. no problem. deciding to live dangerously, i used the disco for the rest of my running today. been running and starting just fine.

is it possible a valve got jammed open or closed and this i what would choke off the engine?

anyway, going to change the oil tomorrow and use some rotella T.

 

[Lake_Bueller]

With that many miles, I'd take the time to drop and clean the oil pan while you're doing an oil change. The clacking is usually related to low oil pressure. Sludge on the bottom of the pan can plug the oil pick up and cause the low pressure.

 

[robertf]

You can check the positioning sensors with a oscilliscope, not much else.

I think its the crankshaft position sensor. the cam sensor won't keep it from running but the crankshaft sensor is the heart of the system.

you should check for spark and fuel injector signals when cranking . Only if you have neither it is the crank sensor.

 

[ptschram]

Having just gone through this with a DII, it might well be the CkPS, they can be tested with a voltmeter, set to millivolts range.

That said,w e really need a pressure reading from the fuel rail to KNOW if the pump is good.

 

[jastutte]

i'll test the fuel pressure this week.

the strange thing is that the truck is running fine again and there is no more clacking from the valves since yesterday and the truck drove great all day long with the exception of the one no start. yes, that is an awkward run on sentence. must be the porter for breakfast.

 

[robertf]

Having just gone through this with a DII, it might well be the CkPS, they can be tested with a voltmeter, set to millivolts range.

That said,w e really need a pressure reading from the fuel rail to KNOW if the pump is good.

true, but thats a yes/no, can't see data dropping with a mv meter.

 

[ptschram]

true, but thats a yes/no, can't see data dropping with a mv meter.

Vantage FTMFW!

http://buy1.snapon.com/products/diagnostics/Vantage.ASP?partno=EETM300f&dir=catalog

 

[crown14]

Uh massively sticking exhaust valves needs to be suggested.

 

[ptschram]

Uh massively sticking exhaust valves needs to be suggested.

At 180K, there isn't enough left of the cam lobes to open the valves:smilelol: