How much of a high pressure oil leak?

[Matt Saunoras]

Would those little 4mm Allen plugs on top of the oil rail cause?

I've got an 07 F-450 bucket truck here with what looks like a fairly recent jasper engine in it. Towed in for a no start hot after it was shut off and parked for 10 minutes. I get it, fires right up cold, get my EOT up to 220, shut her down and it lights right back up every time. Can't verify it.

However when I let it sit overnight the next day it was slow to build ICP cold, still started but took about 3-5 seconds of cranking to do so. I have seen dummy plugs cause this but I was hesitant because of how new the engine is. Plus pulling the right valvecover with the PTO laying over it made a 20 minute job into a 2 hour job. I couldn't even get the ICP sensor out so I wound up air checking from the left side initially.

But of course I did hear an air leak under the right side and when I did finally get the cover off I found that little plug on top of the oil rail was loose and the O-ring blown out.

Has anyone ever seen this and if so could one of these little bastards ever be the sole source of a no-start? I actually had a pack of these plugs stashed away and when I replaced it I couldn't hear any more leaks.  Checked standpipes and dummy plugs on both sides and all were good. 

[Keith Browning]

Yes. I used to see a lot of these plug seals blow out on 4.5L engines in the LCF commonly cause a no start. I have also seen these fail on 6.0L engines too but only once or twice. They can act similarly to a worn standpipe or block off seal especially with regard to the no start when hot condition. And I am confident you will inspect everything whilst you are in there.

[Matt Saunoras]

Thanks Keith.  I'm satisfied for now that there are at least no more leaks under the valve covers.  I'm going to put it back together and see what happens. 

[Chase]

I had one on a 6.0 E van once that was blowed out.

[Matt Saunoras]

So far so good, truck starts fine hot and cold, ICP climbs steady like it should.

[Bruce Amacker]

Look at an IPR/ICP graph while starting up. A happy healthy 6.0 will spike to 40ish% IPR while building ICP, if it flatlines high at 85% to build ICP something is wrong. We've had this in class and used it for diag on intermittent no-start/hard start situations to verify the complaint and verify the repair after replacing a part.

 

 

[Matt Saunoras]

The bottom screen shot is what I always look for but many times I've seen the top one and I agree that indicates a concern. I most definitely had a long crank cold that looked like the top.