Whelp, this isn't sounding too good...
Just got a call from the shop I took it to - one of the few local commercial Diesel shops. They've done their basic checks and it's looking like it's an issue either with the HPOP itself or the anti-drainback valve in the HPOP. I guess I wasn't too far off with my hunch that it's not getting fuel.
Should know more later today, but I really don't want to imagine the size of the bill if it's the HPOP...
Bummer man.
In reply to BoxheadTim :
W T F did you turn it off?
NEVER do that until you get to your garage. I don’t care if you do get yelled at, it’s the rules, the law, I’m in California,...whatever.
In reply to A 401 CJ :
Not quite sure what you're getting at. Why would I leave a vehicle that's never had a problem restarting idling outside a shop, unless I really, really wanted to have it stolen?
The shop has made progress and I should know either later today or tomorrow morning if they fixed the issue.
Good news, it wasn't the HPOP. Plus, injector pressure is good when everything is running.
Bad news, the main oil pump was well worn and the suspicion is that with the engine hot, the oil was too thin for the worn main oil pump to feed up enough oil into the HPOP. They've replaced the main oil pump and we'll see if that fixes the issue.
I'm hoping that the bill isn't so big that I can't afford to race this weekend 
.
Still no luck 
. HPOP reservoir is being fed again with the new oil pump in place but it’s still not firing.
This is beginning to look like a very expensive bust.
BoxheadTim said:In reply to A 401 CJ :
Not quite sure what you're getting at. Why would I leave a vehicle that's never had a problem restarting idling outside a shop, unless I really, really wanted to have it stolen?
Just keep adding fuel and pay some kids to look after it :-)
i thought you had said that it failed to start at a filling station after you’d gotten it started with the CPS and you were waiting on your second tow. My bad. Didn’t read close enough.
In reply to A 401 CJ :
That was the second failure, but the idea was to test if I’d fixed the issue or not. That why I went to a gas station a mile from home. Figured it’d be better if it broke there than 200 miles from home while towing.
On a serious note, and I think it’s already been said, it’s not unheard of to get a dud CPS. I would try a third before anything else. It sounds like the chumps are stumped at the diesel shop...which doesn’t surprise me these days.
A 401 CJ said:On a serious note, and I think it’s already been said, it’s not unheard of to get a dud CPS. I would try a third before anything else. It sounds like the chumps are stumped at the diesel shop...which doesn’t surprise me these days.
Agreed. From my reading when I had the 7.3 I would only use real Ford/Motorcraft CPSs for that reason. There's a lot of interplay between some of the ignition signals and what the computer will/won't power up if those signals are missing. At this point it's a cheap thing to try before you dig in any further....assuming they haven't got it completely disassembled already....
They're pretty deep in it by now, well past checking sensors and the like.
I was only posting the Cliff Notes above, but from the phone calls I had with the shop's owner, they did start with testing the obvious stuff like the CPS and the various other sensors known to give trouble. I'm not sure they're stumped (yet), but it's certainly a more unusual failure mode. The whole diagnostic ladder looks something like this:
The reason that both the shop and I are pretty confident that it's not an issue with the usual electronic suspects is that the truck starts up when the engine is cold and runs fine even when hot until you turn it off. It's only on the hot restart when things go haywire.
At this point I asked them to stop their diagnostic journey if the pressure regulator doesn't fix it as I have to put a price cap on the diagnosis/fixes given the age and value of the truck.
The interesting side question is what prompted the failure of whatever component is causing the problem. The weekend before the failure, it was happily towing my trailer for a good 500 miles with no issue. I do suspect that the additional load from the long distance tow may have triggered the problem, but I'm still curious how this happened.
I am not confident in this shops abilities. A 7.3 Powerstroke is not a complicated vehicle. Sounds like they are in the "throw parts at it" mode.
The whole "thin oil and worn pump not filling the HPOP reservoir during hot restart" is very suspect, since the HPOP reservoir should be full at start, and if the worn pump was not able to keep the reservoir full on a warm restart it would also deplete during regular driving, faster actually than at start because of greater RPMs causing a greater demand on the high pressure oil system.
The only reason your HPOP reservoir would be empty at start would be a failed check valve allowing oil to drain back into the crank case or a massive external leak. It wouldnt matter cold or warm start, since the oil during a cold restart was warm at one time and would have drained back when warm. You would still see excessive crank times cold or warm but if your HPOP reservoir was empty during start you should see the truck start and run fine just with an extended crank time, maybe some misses at first but they would clear up after 15-20 seconds.
Pretty sure you nailed it by watching the high pressure oil and duty cycle during hot restart. Sounds like a failing hpop regulator or the high pressure oil sensor is on its way out. Simple test is to unplug the high pressure oil sensor and see if it starts, that will force the pump into default high pressure mode and it will pop off. Or it wont.
They are throwing (some) parts at it, agreed.
How confident am I in the shops abilities?
Well, they're supposed to be one of the better Diesel shops around here, at least accordingly to some people I trust. Unfortunately "one of the better shops around here" is a pretty low bar in general. There is also the small matter of me not having the time or tools to dig into the truck right now, so I had to have someone else work on it.
Now that you mention it, the truck has always needed a bit of cranking when it sat around for a while (like, a few weeks), so I'll double check with them that they did have a look at the HPOP reservoir's drainback valve. But never anything like it suddenly needs right now when hot.
Also if what they say was true about the reservoir not filling it would be very easy to fill the reservoir using a turkey baster through one of the plugs on top (or hell, with the top cover off) and spin it and it should fire right up.
These things do have some notoriety for a bad harness after a while so even changing hard parts may not solve it if its intermittent electrical connections in the harness. Especially around the HPOP oil sensor, these fail and oil gets into the wiring. However, my old-old 2002 7.3 (first one) was driven 60k miles with no problems with what the internets would tell you was a bad HPOP oil sensor.
Another thing to check if the HPOP oil system was open or had air introduced is an air bubble under the hpop sensor. This can be tested by unplugging the sensor, truck should start right away. If it does, crack the sensor loose while running, let it bleed a little oil, and retighten it.
To expand on my original post, the HPOP reservoir should be full after running unless the drain valve was allowing it to leak back into the crank case. If it was empty, the truck wouldnt run at all, and if the pump couldnt keep up with the HPOP you would have spun a bearing or done other damage.
So even with supposed thin oil/weak pump, the reservoir would not be empty at start, unless the truck was ran really hard right at shutdown and you were not supplying enough oil. This again could be double checked by adding oil to the HPOP reservoir right after shutdown or monitoring the level with the engine running and the top cover removed. There is a gear in there, but you should be able to see oil level with the cover removed, even if you have to shut the motor off and take a quick dipstick check of oil level in the HPOP reservoir with a screwdriver or similar.
In reply to 93gsxturbo :
Thanks for the knowledge above, I have a feeling this is going to come in very handy.
The shop just called, problem was traced to a faulty HPOP regulator. They replaced it and the truck apparently is a happy camper again.
I shall celebrate this by taking the truck to the tire shop (my NA Miata needs new shoes on the spare wheels). Let's hope that the next post in this thread isn't "at the tire shop, waiting for a tow".
Made it to the tire shop and back, I was even confident enough to put some additional stops in to run some more errands. So far, so good.
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