She bucked and now wont start

roosterdiesel

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What I did notice while cranking it the oil pressure needle never moved. One dealership thought it could be the base oil pump but another one said they never go bad.

When I replaced my HPOP line and messed up a fitting it blew the line back out. I didn't notice the oil on the ground since it was dark. The needle moved after the reservoir was filled but it still wouldn't fire since one line wasn't connected. The gauge on a 7.3L is an on/off switch...6psi in the reservoir and the needle comes up.

Low pressure oil pumps do fail but not like yours. You may have a cracked pickup tube or the the tube broke completely which has happened before. If that's the case you will have to pull the engine.
 

sagebel

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My factory oil pressure guage does not move until the truck is running. Pull the juice out completely. Fuel coming out a loose fuel bowl cover will not confirm a HPOP issue. You can hook up a guage to one of the oil rails on the head to verify HPOP pressure while cranking. I think you need about 600 psi to start the truck.
 

roosterdiesel

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On an engine in good running order the gauge won't show anything until it fires, it fires before the reservoir gets pressure. In a no start situation you will see the needle come up after cranking a bit if the LPOP is doing it's job.

If you don't believe me disconnect your main harness on the driver's side VC and crank to your hearts content, the needle will move and it won't start since there's no voltage going to the injectors.
 

bushpilot

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Not sure, porbably not, as a line could be cloged or something to that effect, but I could be wrong.:dunno

operationally the 7.3 isnt all that different from the 6.0...HPOP drives
and fires the injectors.

the fuel pump just gets the fuel outta the tank and up to & thru the
filter and onto the injectors...anywhere along the lines there could
a problem...including not having enough oil pressure from
the HPOP (500psi...is whats required on the 6.0l w/ a regulated
maximum pressure just below 4000psi)

on the 6.0L the fuel pressure is regulated to around 60psi (and
i recall simular pressure requirements on the 7.3l)

doesnt the 7.3 have an IPR & an ICP too...(either one of these
could, i would think, cause starting or running issues)

heres how the ICP works/impacts starting on the 6.0L (perhaps
itll help trouble shoot DPerkins truck) -->


ps60_061_Electrical_Components.jpg
 
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DPerkins

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Thanks guys for the info. I had one of the dealers tell me if the truck will not make base oil pressure the control loops will put the truck in a no start mode. He suggested I put a manual oil pressure guage on the truck. My manual showed the sender port being behind the fuel filter on the high pressure reservoir. I did this and cranked the truck for probably a minute and a half and the neeedle (on the mechanical) never budged. That is why I suspect a low pressure problem.

So I set out to replace the base oil pump which really isn't too bad. Just ran out of time yesterday having to let guys off for new years. My concern is when I got the base pump out, both gears looked pretty nice. No big damage at all, just some slight surface finish wear, so I am doubting this is the problem.

What is really throwing me off is the lack of any codes or check engine lights. Sure do hope I can figure this out without letting my local dealer have his way with me!
 

bushpilot

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again i dont know the 7.3, but the 6.0 needs a minimum of 500psi oil
pressure from the HPOP to start...
 

roosterdiesel

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Actually the pressure sender is on the top of the reservoir, what you pulled was the oil temp sensor which is fine. Was there any oil in the reservoir?

How did the front cover look? Is it grooved? The way it stumbled a few times then died leads me to think the pick up tube is cracked or broken, usually happens where the tube is brazed to the mounting flange. I don't think you can see this without removing the pan which takes pulling the engine. If the new LPOP doesn't produce any PSI in the reservoir you've got a problem with supply to the LPOP.

If the LPOP doesn't fill the reservoir, the HPOP can't produce the 500psi needed to fire. Not sure what "control loops" the dealer is talking about since the ECM doesn't even monitor oil pressure. It monitors injection control pressure which is zero if the LPOP isn't supplying the HPOP.
 

DPerkins

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Yeah that is the way he described it, no base oil pressure = no high oil pressure = no injectors. I just would think if this was the case some kind of code would throw. He said is was extremely rare to lose the high pressure pump but had seen a few low pressur pumps go. He also said to remove the filter and make sure the check valve was still in tact and functioning. All that looked good.

Didn't really check for oil in the high pressure reservior, just removed the sender and put my mechanical gauge in. No oil pressure. My manual said even though the sender was on the high pressure side, it should still see the low oil pressure reading, which makes sense. I didn't even see the manual gauge needle wiggle while cranking. We have a number of race cars which they want you to dry crank to build oil pressure prior to starting. I was expecting to see the needle come up at least a little but it didn't.

Sure hoping I don't have to have the engine pulled!
 

roosterdiesel

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Just to make sure...did you pull the sensor labeled EOT in the pic or something else? If yes and no oil leaked out then you have an empty reservoir. THe res. is low pressure, only thing high pressure is in the rails and HPOP lines from the pump to the head.

You may want to check pressure on the rotating assembly, test port down my the oil filter. If no pressure there with the new LPOP you aren't getting oil to the LPOP.
 
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