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Newb needs some 7.3ps cold no start help

total newb

total newb

senior jerk ass
Joined
May 19, 2020
Member Number
283
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2,725
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trinity center ca
So i am a drivetrain guy not a motor guy and know very little about powerstrokes in general, but i can search and read some other threads which has brought me to this point.



The problem,

When cold, been sitting for a few hours it will crank but not start. Regaurdless of ambient temp. 20-105*.
You can crank till she quits but wont fire. As much as i/you hate to do it, a lil huff of no no juice will fire it up.


In the last 2 years the full glow plug system was replaced, controler, harness/gaskets, relay and all 8 plugs.

Recent oil change.



1999/dec
300k miles and afaik no significant repairs or mods. Oe/stock on all other components.

Read a few threads here running down a few basics.

Icp "at least 500"
480+ while idle
20210819_205835.jpg
 
I thought maybe the lift pump but watched a few vids and checked a couple things and all seems good on the surface. Relay and fuses are good. Pump runs with power supplied.

However it seems like it may be weak but i may not be reading things right
20210819_205802.jpg
 
I did pick up a icp, fuel filter, crank sensor along with a airfilter but did not have time to install.

Read again later today to unplug icp and crank but did not have time to try it
 
What's your ICP while cranking when it won't start? The 500psi is to fire the injectors on start up, not after the truck is running. It's possible it's not building enough just spinning on the starter till you feed it the Cosby sauce.
 
check that upper hpo reservoir. It can drain back, or undersupply - various reasons.

ipr needs to be working

beware of a weak/tired hpop or lpop

you can press up the rails manually with a porta-power pump for a leakdown test.
 
Agreed. I’d check ICP pressure to see if the hpop is weak
 
If it's only when it's cooler, it's gonna end up being glow plugs.

If it's warm (>30*F) it's gonna be the ICP? I can't keep it straight. It's the dealie on the front of the oil rail on the Drives Side head... Look for oil under the electrical connector.

Do you have a pressure guage for the HPOP yet? ~$30 in parts get you one and you can test the HPOP. Pretty sure it's not that though, if the truck starts when warm.
 
If it does it regardless of ambient temperature forget about the glow plug system . 1 and 3 are on the same bank I would be pulling passenger valve cover and inspecting the UVCWH especially if anything other than motor craft was used when you did the glow plugs . Crank it and see if oil is coming from each injector downspout . If one of them has none coming out which I suspect one or three or both may be doing then verify proper power supply from the harness if it is good the poppet valve on the injector has crapped the bed and needs replacing . At 300k you’re way and I mean WAY overdue for a set of injectors . This obviously all doesn’t matter if your ICP pressures and HPOP aren’t in good order .
 
total newb said:
Where are you hooking the gauge and porta?
Click to expand...
There are a couple of hex plugs in each cyl head rail facing into the valley. One is the hpop feed. They use orb fittings I think.

Iirc, I put the gauge on one port, and press up though the other. I got a new porta-power at the time and loaded it with engine oil. Repeat for the second cyl head.

Mine held pressure overnight despite ongoing cold start problems. Warm was never an issue.
 
So wtf.
First crank after 12hrs sitting it fired. Shut it off and now it wont.

Here are some shots of cranked and while cranking
20210820_110909.jpg
 
And while doing all this the batteries went low, so i got the charger and hooked it up and now i see the d-side + cable end is shit and loose so i may be only pulling from 1 side worth a shit. Doh. :homer:


Batteries are interstate mdt what everthefuck is supposed to be in the truck, bought straight from interstate and not quite 1 year old
 
The ICP value (65.9) seems low. It should also start/run with that sensor disconnected. (front of driver cyl head)

I did not have usable electronic diagnostic equipment at the time for my '97... so I'm not in a position to compare values. :emb:

Easy to kill batteries with a stubborn PSD. Plus you have to keep that 10-11v(? ) threshold for the IDM. I had rewired with #4/0 cable and manual GP's by time it was this bad and I was troubleshooting this deep.
 
Those numbers say its not making icp to fire if that 65 psi was while cranking

Fuel pw is right and ipr % is right for idling, if thats while cranking the ipr should open up to raise icp till it gets to around 500pai

Was the 2282 psi icp and 35% ipr while idling ? Or with throttle,

Unplug the icp sensor and try if you havent already, that should default the reading to around 700 pai and it will crank and run

Without knowing the answers to above readings


Have you checked the nut on the back of your ipr sensor, make sure that solenoid is still bolted on.

Another thing to check is the ipr solenoid for cracks, and the connector

I think you already know this, but dont replace icp with anything but genuine motorcraft, and watch out. Ebay and amazon sell chineese clone motorcraft shit thats really cleverly done.
 
Makes me suspect the IPR. If you unhook the hpop lines, what pressures does the hpop build while cranking?



When I went through this, it was the hpop, but I did all the same things you're doing first :lmao:

I also replaced the ORB fittings with JIC fittings. Now I can get a hpop line anywhere. 16", with a 90* flare on one end.
 
It has been cranking faster and starting easier since i fucked with the battery cable. So i think it just boiled down to not pulling from both batteries more than anything else.

But i live in a pissant town and work long days so i havent had a chance to pick up the icp im going to swap or a new cable set
 
Pt_Ranger_v8 said:
If it's only when it's cooler, it's gonna end up being glow plugs.
Click to expand...
BS
he says the temperature range in the OP: 20 to 105
7.3 DI absolutely will start at 20F without waiting for the GPs to do their thing

it'll crank for a bit, but it ain't no IDI where it won't pop over without GP at 90F
 
u2slow said:
My 95 and 97 PSDs proved that to be BS.
Click to expand...
before they all died the rust death whenever they'd come in at work nobody waited for the GPs
you needs you some fresher batteries or cables or a starter

always funny how you hop into whatever the new engine generation is at the time and immediately notice how quickly the starter spins the motor over
easy to forget that even IDIs turned over that quick at one time
lots of times even reman starters don't quite do it, because the ground path is through the corrosion pitted motor case and endcaps that are covered in paint
 
[486] said:
before they all died the rust death whenever they'd come in at work nobody waited for the GPs
you needs you some fresher batteries or cables or a starter
Click to expand...
Good tips, but nice try. Lots of work done to electrics on each. GP's very necessary... except maybe a couple months in the summer you can bludgeon them into starting with enough cranking.
 
A 7.3 has to have everything working 100% to start correctly.
You need to have enough cranking RPM, just 20 RPM slow and the cam tone wheel may not trigger the cam sensor and that's what tells the PCM to fire the injectors.
So the batteries need to be good, starter spinning the correct RPM, sometimes the start corrodes between it and the bellhousing causing a bad ground resulting in slower crank speed.
Glow plug system need to be working.
Oil temp sensor needs to be correct, that how the PCM know engine temp because it doesn't see coolant temp. So if the oil temp is off the PCM may not turn on the glow plugs.
ICP sensor can effect the running and starting of the engine, I've had no-starts caused by aftermarket sensors. then I've seen all kinds of other problems caused by aftermarket sensors. IF you didn't get the sensor from the dealer it's garbage, ebay is FLOODED with counterfeit shit that claims to be OEM, I've even been stung with this shit before.
Now the most expensive problem, and probably the #1 most common problem I see these days is the injectors. If the injectors are worn and don't have enough clearance to exhaust the oil it's not going to want to start and that in 90* weather. Then if you do get it started it'll run like shit, probably won't rev up until the oil gets some temperature in it so it flows out the injectors better.

There is a "band-aid fix for 7.3 injectors and I've done it a few times with excellent success. Look up 7.3 injector shimming on youtube, this does work and is a cheap band-aid then there are shim kits on ebay with the tools for under $100
#1 rule on basically all diesels is to use OEM parts, aftermarket shit is just that, shit, I can't tell you how many guys I've seen think it'll work for them then they have to buy it again and throw that Chinesium shit in the dumpster, I'll bet I see somebody have to buy a second set of injectors at least 2-3 times a year. I just had a 6.0 in that somebody put internet injectors in it and they had to do the job again.
That's all that comes to mind right now, I probably missed a few things but if all that stuff is right a 7.3 will start right up in the coldest winter mornings without being plugged in.
 
So i finaly got a new cable installed. Wasnt quute a perfect match but it was correct where it counted.

Spins much faster and starts much better.

So thanks for all the help and infos.
 
u2slow said:
Good tips, but nice try. Lots of work done to electrics on each. GP's very necessary... except maybe a couple months in the summer you can bludgeon them into starting with enough cranking.
Click to expand...
just looked up the climate for vancouver and it doesn't even get all that cold up there, wierd that it gets both way hotter and way colder around here. Shit sucks. I want normal temperatures, dammit
 
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