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Discussion Starter #1
Hi all, looking for some quick help diagnosing a hard/no start…

Long story short, I’m on a 2,500 mile road trip from CA to Glacier National Park, Yellowstone, and back home to CA and my truck is giving me some serious issues.

Currently in West Glacier, MT.

The truck in question is a (early) 99 F-250 7.3, ZF6. 3 years and ~15k miles on a reman engine from Promar, new injectors at the time of engine install. Pretty sure the HPOP is original (250k miles), the engine did not come with a HPOP, but we’ll come back to that.

Engine has an HP tuner, Garret GT38 turbo, 4” exhaust turbo to tip, AFR cold air intake, but stock injectors so we’ll call it a “mild” build.

The issue is a hard/no start when hot. When cold (and I mean cold, it was 35* in West Glacier MT this morning), it starts like normal, so I think we can rule out glow plugs.

Once started it runs great. You’d never know there was an issue. I’m towing a 9k pound trailer and we’re blasting over mountain passes like they aren’t even there (monitoring EGT’s of course). It might have a rougher idle than normal… but I can’t tell if I’m just looking for an issue and convincing myself it’s there… if it’s rougher than normal it’s not significantly so.

When hot it literally will not start. Cranks and cranks and cranks, sputters a bit, will not start. Hit it with some starting fluid, starts right up and as I said previously, runs great thereafter.

I took it to a mechanic in town here around West Glacier, MT and he diagnosed the issue as pressure regulator on the HPOP, and replaced that. I spent an hour with him in the shop “helping” and the scanner tool showed the regulator wasn’t closing when starting, we could see on the scanner the ICP was only getting about 300 PSI when trying to start, so we figured it wasn’t building pressure so it seemed reasonable to replace. The rest of the diagnosis came out OK – ICP readings we’re normal once running, and again, once running, it was/is great.

The HPOP pressure regulator may have helped (it’ll actually start on its own now but with LOTS of cranking), so its possible that was also an issue, but clearly wasn’t the cure.

Since it starts well cold after sitting overnight I figure it isn’t losing fuel pressure prime and likely not HPOP pressure for that matter?

As I mentioned injectors are newish so hopefully not the issue… and not smoking on start up or normal use, but maybe?

Would a “tired” HPOP cause a hard start when hot?

Other ideas?

Thanks in advance!
 

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Did you change the ICP or the IPR?

Try poring some ice cold water onto the IPR when the engine is hot and see what happens.
 

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Discussion Starter #3
Thanks for the reply.

IPR was just replaced with little / no changed.

ICP seems to be reading as normal. Have also tried unplugging which should put the computer in limp mode and "force" a reading of 700 psi. That's my understanding anyway.

So I don't think it's either of those things.
 

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Was the IPR a motocraft part or aftermarket? That can make a big difference. Does the truck fire up when you have the ICP unplugged?
 

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Discussion Starter #5
The replacement IPR was not Motorcraft. Beggars can't be choosers so what whatever the local mechanic here got from Napa.The one that was in there may have been, I have it so I guess I can look for a logo or something...

Unplugging the ICP does not make it start any better / faster. Tried that with both the old and new IPR.

ICP reading while cranking is ~ 300 PSI (with ICP plugged in), not enough to start. Once running it gives a normal ~500 at idle and upwards from there on throttle.

ICP unplugged showed ~700 on the OBD scan tool, as expected, but again, did not make it start any better / faster.

The thing I can't quite wrap my head around is the engine runs amazing. Like I said I was pulling a trailer up grades without issue, good boost, good throttle response, great power... you'd never think anything was wrong, once it was running of course.
 

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Sounds to me like you have a leak in the HP oil system, potentially an injector o-ring.
If you're looking at ICP data only, you're only getting half the picture. You also need to look at IPR duty cycle at the same time. If the IPR duty cycle is abnormally high, that will pretty much confirm you have an HP oil leak. It may eventually get so bad that it will not run correctly, even if you do get it started.
The reason you can get started when cold is that the oil is thicker and can't get out the leak as fast as when the oil is hot.
The oil pressure monitored by the ICP needs to get up to 500 psi before the PCM will activate the injectors. Starting fluid (definitely not recommended as it may cause damage or personal injury) gets the engine turning over faster, which lets the HPOP build pressure faster. Oil volume delivered is basically a direct function of the HPOP RPM (turning faster = more oil volume, which overwhelms the leak path letting the pressure build.)

on edit: A Ford dealer should have the capability to test for leaks. It involves isolating each head HP oil line while monitoring ICP and IPR duty cycle.
 

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Discussion Starter #7
Sounds to me like you have a leak in the HP oil system, potentially an injector o-ring.
If you're looking at ICP data only, you're only getting half the picture. You also need to look at IPR duty cycle at the same time. If the IPR duty cycle is abnormally high, that will pretty much confirm you have an HP oil leak. It may eventually get so bad that it will not run correctly, even if you do get it started.
The reason you can get started when cold is that the oil is thicker and can't get out the leak as fast as when the oil is hot.
The oil pressure monitored by the ICP needs to get up to 500 psi before the PCM will activate the injectors. Starting fluid (definitely not recommended as it may cause damage or personal injury) gets the engine turning over faster, which lets the HPOP build pressure faster. Oil volume delivered is basically a direct function of the HPOP RPM (turning faster = more oil volume, which overwhelms the leak path letting the pressure build.)

on edit: A Ford dealer should have the capability to test for leaks. It involves isolating each head HP oil line while monitoring ICP and IPR duty cycle.
Thanks for the reply. I think a leaking injector is the most likely cause.
 

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Discussion Starter #8
Well the plot thickens. I bought an injector o-ring kit at Napa in town here and pulled the valve covers, expecting, almost hoping, to see an obviously leaking injector. They all look perfect from the youtube videos I've watched. Oil comes out of the little drain at the top and there's no obvious oil squirting all over the place...

So any other thoughts?

Really appreciate the numerous fast responses!

I took a short video, its at the end of this album

 

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By chance have you looked at the fuel filter to see if it is black? If so the oil is getting into the fuel system via the injectors.
 

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By chance have you looked at the fuel filter to see if it is black? If so the oil is getting into the fuel system via the injectors.
I have a 02 doing the same exact thing. I have a ISSPRO gauge on my High OIl pressure. Mine started out just like yours with longer hot starts and then to having to use either when warm. Now it will not start at all. When mine would run it ran perfect except I could not build over about 1,800 psi ontil I let off of the throttle and then it would jump to 3,100 psi for an instant. I am sure it is a o ring on an injector.
 

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You wont see a leaking o ring just by looking under the valve covers. You are going to have to pull them out.
 

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Discussion Starter #12
Truly appreciate the replies.

This is becoming a nightmare... My wife and I have been trying to enjoy our vacation so we've been driving the truck around during the day for sightseeing and hikes and such and I've been gathering parts and wrenching at night...

Any and all help, thoughts, opinions, ideas, are appreciated!

By chance have you looked at the fuel filter to see if it is black? If so the oil is getting into the fuel system via the injectors.
I replaced the fuel filter today, here's a pic of the old filter. I would describe it as dirty but not black, thoughts?



New filter seems to have no affect whatsoever on performance.

I have a 02 doing the same exact thing. I have a ISSPRO gauge on my High OIl pressure. Mine started out just like yours with longer hot starts and then to having to use either when warm. Now it will not start at all. When mine would run it ran perfect except I could not build over about 1,800 psi ontil I let off of the throttle and then it would jump to 3,100 psi for an instant. I am sure it is a o ring on an injector.
So I got a Scan Gauge II on it today, bought from local AutoZone. Very similar to what you describe. Running hard WOT, uphill (not towing), I get about 1700 PSI on the ICP. When shifting gears (manual trans) it briefly spikes as high as 3400 and immediately drops when getting back in the throttle under load.

You wont see a leaking o ring just by looking under the valve covers. You are going to have to pull them out.
I was under the impression an obviously bad o-ring would be spitting oil and would not return oil out of the "exhaust" port on the top side? Thoughts on that?
 

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Discussion Starter #13
Today's update, as touched on in the previous post.

Replaced fuel filter for good measure. No affect on performance.

Bought a Scan Gauge II and now have real time readings on ICP and IPR.

A few data points...

Cranking, I never saw more than 190 PSI on ICP. Clearly not enough to fire.

After starting with a little ether, truck runs and drives great (which has been the case). At idle, ICP is high 400's, which I think is normal?



As mentioned in the previous post, running WOT, uphill (not towing), the truck is pushing 20 PSI boost (on a new mechanical gauge that I believe to be accurate), I only see about 1700 PSI of ICP. I gather it should be higher? When I shift (manual trans), it briefly spikes into the 3's, I saw 3400 once, and then settles back to ~1200 and builds to roughly 1700 at peak.

The IPR reading is weird on this gauge. I was under the impression that this should be a reading from 1-100%. However this gauge shows 0.6 at idle (see above), and spikes to 6.0 flat at the same WOT run previously mentioned.

So... we're back to the start... for one reason or another the high pressure oil system doesn't seem to be building enough pressure... As the injectors are relatively new and not obviously leaking (I don't think), and there is no smoke, and I don't think signs of oil in the fuel system (see fuel filter pic) is it possible the HPOP is on its way out? I'm pretty sure its original at 250K miles. I'm the 3rd owner of the truck so hard to say for sure.
 

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You are correct about the IPR reading. It should read about 14 with the key on. You may have the wrong program for that read. The icp needs to see 500 to start so the low read you have is a problem. 1700 at Wot is way low.
 

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Dont see a filter pic. Was it black? Like I said before. You wont see a bad oring unless you pull the injector.
 

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Discussion Starter #16
You are correct about the IPR reading. It should read about 14 with the key on. You may have the wrong program for that read. The icp needs to see 500 to start so the low read you have is a problem. 1700 at Wot is way low.
Thanks for confirming, I thought under load ICP should be high 2's....


Dont see a filter pic. Was it black? Like I said before. You wont see a bad oring unless you pull the injector.
The pic loads for me so not sure what the deal is, it's in this album:


I've already put the engine back together (drove the truck 70 miles around Glacier National Park) so too late to pull injectors... at least now...

Maybe I'm talking myself in circles. but the injectors are newer and there's no smoke... conversely HPOP (I think) has 250K on it... I'm leaning HPOP at this point.
 

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I've already put the engine back together (drove the truck 70 miles around Glacier National Park) so too late to pull injectors... at least now...

Maybe I'm talking myself in circles. but the injectors are newer and there's no smoke... conversely HPOP (I think) has 250K on it... I'm leaning HPOP at this point.
Injector o-ring leaks won't necessarily be squirting all over the place. If it's the top o-ring, it'll likely just ooze out and flow back into the crankcase. Leaky o-rings won't necessarily cause smoky exhaust.

It's probably NOT the HPOP. They rarely fail. I would plan on replacing the injector o-rings. I'm pretty sure that will fix it up.
 

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Discussion Starter #18
Thanks for the replies, can't tell you all how much I appreciate the help.

Today's (weird) update.

Drove 400 miles (towing a ~8k pound travel trailer) from Glacier National Park to Yellowstone. Same story, truck starts relatively normal cold, hot start with a couple blasts of starting fluid.

I checked the settings on the Scan Gauge and had the "math" setting wrong on the IPR. It now reads a max of 0.98, and as little as 0.10 at idle. So at least I've got that sorted. Hot idle is the same high 400's ICP and now 0.10 IPR.

From idle to heavy throttle the IPR reading slowly moves up, peaking at IPR. So my amateur reading of the gauge is that the computer is at least going through the "right" motions.

The first couple hundred miles were business as usual, under throttle, uphill, (towing), ICP would dip as low as 800 under heavy throttle, downshifting and revving up to 2k+ would usually get more like 1200 and the truck towed OK, though was obviously down on power. Cruising at ~60 on flat ground it would hold 12-1300, it would spike to 2k-ish under light throttle. Under heavy throttle it would consistently dip to 1k, very heavy throttle into the 900's or even 800 if bogged in 5th - like 1500 RPM.

We stopped for lunch in Butte, MT. Got back on the road and pretty quickly hit a gnarly grade, labelled 6% grade downhill with a 25 MPH big rig speed limit.

Here's where things got weird...

So we hit the grade, I downshift to 4th and get in the throttle and see 2K ICP! The truck accelerates quick, towing, uphill! I was beside myself... I shift to 5th, and accelerate, uphill towing with ~1500 ICP! This lasts for ~ 45 (glorious) minutes. I can bury the throttle at 60 in 5th gear, see 1500 ICP, and accelerate with reasonable EGT's. It feels totally normal. 4th gear HEAVY throttle is ~ 1700 ICP, compared to like 1200 max earlier in the day.

Then we got off the highway, I put the clutch in towards the end of the ramp, and the engine dies... started with some starting fluid, and its back to business as usual... noticeably under power, and never enough ICP. Downshifting and winding the motor to 2k+ is the only way to get adequate ICP and by adequate I mean ~ 1000-1200.

Under anything past "light" throttle the IPR reads .98, meaning, to me, it's trying to build max pressure, basically under any load. Which seems to make sense. So the computer at least thinks its trying to max out the pressure....

So... Given the glorious 45 minutes of power... Is it possible the injectors and HPOP are fine? Perhaps the IPR is faulty? It was just replaced, but...

Or maybe some sort of related electrical issue? ECU? HP tune?

Injector o-ring leaks won't necessarily be squirting all over the place. If it's the top o-ring, it'll likely just ooze out and flow back into the crankcase. Leaky o-rings won't necessarily cause smoky exhaust.

It's probably NOT the HPOP. They rarely fail. I would plan on replacing the injector o-rings. I'm pretty sure that will fix it up.
Thanks for your reply, good to know HPOP's are robust and leaky o-rings can be more "subtle" than I suspected - always learning!

Some interesting updates, see above.
 

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You are correct about the IPR reading. It should read about 14 with the key on. You may have the wrong program for that read. The icp needs to see 500 to start so the low read you have is a problem. 1700 at Wot is way low.
You were right, I had the wrong program in the Scan Gauge for the IPR, getting more normal readings now, see above. Thanks for the tip!
 

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I would still poor some ice cold water onto the IPR when you have a hot no start. It it starts then the IPR may be defective.

Sometimes things can test just fine once up and running and then give you problems trying to start.

Having a defective sensor or part right out of a new box isn't uncommon, and depending on where the part was purchased at I have seen where people have placed a cleaned up defective part back into a new box and returned it to get their money back.
 
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