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7.3 cranks but won't start.

4372 Views 26 Replies 10 Participants Last post by  greenskeeper
Hey all, new to the 7.3 platform and have hit a wall.

A couple days ago I put all new o rings and fittings on the hpop because it was leaking, and after installing it, put oil into the hpop res, cranked it over and it started after a couple of seconds. It ran and idled fine for the first 10 seconds, then the motor started clacking really loud, and after a couple of seconds died on its own, it seemed like it wasn't running on all cylinders and it was shaking. I cranked the motor for longer this time and it started up and then died immediately. It started and died immediately about twice. After that, I checked the hpop res and it was basically empty. I added oil 1/2 inch from the top and it started, I tried revving it up but wouldn't go past 1500 rpm even with the pedal to the floor, no engine clack when I got above 1000 rpms, motor dies as soon as I let off the pedal, I did that twice. When cranking there was a consistent ticking sound coming from the motor. Next cranking runs I didn't fill the hpop res (reservoir was basically empty again when I checked) and the motor doesn't want to start anymore, just cranking with that ticking noise, and a CEL comes after about 30 seconds of cranking then turns off immediately when I stop cranking. Cranked it long like that about 4 times, and the same result, hpop res was always empty. It would try to start if fill up the reservoir but never does now unless I put oil in the res, but even then, it doesn't want to run. I eventually overfilled the engine, but I needed to change the oil anyways. Still the same thing with fresh oil.

I haven't checked to see if oil is moving into the reservoir while cranking, haven't had a second hand to check that.. But Im assuming oil isn't moving into the reservoir because it's always empty. I'm thinking it's possibly a bad lpop, ipr? but idk could be something else?, but that ticking/knocking noise while cranking is also concerning me. I also replaced the ball and spring in the valve to the right of the hpop thinking maybe that's why is was emptying. The motor ran well at times before I took the hpop off, the cel would come on at times if I got the rpms above 2500, the light went away randomly and wouldn't come back on unless I was above 2500 rpms. Just thinking maybe that was part of this issue? Any help is appreciated, I need my truck to run and really don't want to send it off to a shop, or pay tons in parts that won't help.

Link to video of me cranking it
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What year truck? Need to know that code to narrow it down.
What year truck? Need to know that code to narrow it down.
Its 1996 f350. Is it a obd2?
Yes but you'll need a scanner compatible with our trucks.

OBDII bluetooth adapter and ForScan app on your phone will do.
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Vid link does not work, how about posting to youtube, then posting the link here

Knock when cranking and no oil pressure, sounds like a rod bearing to me
Def should be oil in the HPOP reservoir if the engine has any oil pressure at all
the "gauge" sensor is on the hpop reservoir and trips at 5-7 psi

All you done is mess with the HPOP ? nothing else ?
and the engine ran fine before ?
just trying to get some context
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Vid link does not work, how about posting to youtube, then posting the link here

Knock when cranking and no oil pressure, sounds like a rod bearing to me
Def should be oil in the HPOP reservoir if the engine has any oil pressure at all
the "gauge" sensor is on the hpop reservoir and trips at 5-7 psi

All you done is mess with the HPOP ? nothing else ?
and the engine ran fine before ?
just trying to get some context
Here's the YouTube vid of the truck cranking. Actually sounds more like a knock than a tick.


When it was running okay, I had replaced the turbo pedestal o rings. I put new hpop lines and fittings on the hpop when I put new seals in. I do now remember the previous owner said he replaced the cps, turbo, and vacuum pump for the brakes.
Full send on the starter, nice.

So ran fine then you messed with it and now it won't start?

Sounds like you may need to recheck what you did.
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Try to read the code that is stored in the PCM... that would help tremendously with diagnostic.

HPOP loosing prime probably has something to do with the check valve assembly that you fiddled with.

The HPOP reservoir should have oil no lower than 1" from the top of the inspection plug.

Also by opening up the HPO system, it can take a lot of cranking and then driving to purge the air from the HPO system. With air in the HPO system you can get all kinds of funny noises and running conditions.

I'd suggest removing the valve covers and while cranking look for oil coming from each injector spout... no oil means the injector(s) isn't firing.

PS.... holy hell... try to limit cranking for 5-10 seconds at a time, otherwise you'll be buying a new starter sooner than later. Also have the batteries on a charger to keep them topped off while cranking a bunch of times.
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I got high flow hpop fittings from dieselorings, and the description said to remove those springs so I did. The old fittings were the exact same as the high flow fittings except that there were springs behind them. Could that contribute to my issue?
Try to read the code that is stored in the PCM... that would help tremendously with diagnostic.

HPOP loosing prime probably has something to do with the check valve assembly that you fiddled with.

The HPOP reservoir should have oil no lower than 1" from the top of the inspection plug.

Also by opening up the HPO system, it can take a lot of cranking and then driving to purge the air from the HPO system. With air in the HPO system you can get all kinds of funny noises and running conditions.

I'd suggest removing the valve covers and while cranking look for oil coming from each injector spout... no oil means the injector(s) isn't firing.

PS.... holy hell... try to limit cranking for 5-10 seconds at a time, otherwise you'll be buying a new starter sooner than later. Also have the batteries on a charger to keep them topped off while cranking a bunch of times.
Ah okay, good to know. Ill do that test sooner or later, probably when I get the lpop in. I just ordered it for the heck of it. Yeah I figured I was cranking too much, thats probably why I killed the other starter... oops.

Forgot to mention it would drain out even with the old check ball and spring. The old spring was shorter than the new one so I thought maybe that was the issue.
Had my Dad crank while I look in the reservoir, no oil moving into the reservoir at all. That knocking noise was the loudest in the top back area of the motor. The knock would go away slightly if I add oil to the reservoir and it would puff a couple of times, but wouldn't start. Just making updates along the way. Still need to get the codes. What's a good code reader again?
Looking in the reservoir while cranking should have got you an eye full of oil -- sounds like the LPOP is not working at all

FORScan Home -- ForScan
OBDLink® MX+ - Outstanding Bluetooth-Compatible OBD II Scan Tool -- Bluetooth - advanced CAN protocols
OBDLink® EX - OBD2 Adapter For ELM327 & FORScan -- USB corded
BAFX Products® - Wireless Bluetooth OBD2 Reader / Scanner for Android Devices -- Bluetooth
ShenZhen CheBoTong Technology Co., Ltd. -- vLinker
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Just ordered the bafx code reader, should get results by wednesday.
Looking in the reservoir while cranking should have got you an eye full of oil -- sounds like the LPOP is not working at all

FORScan Home -- ForScan
OBDLink® MX+ - Outstanding Bluetooth-Compatible OBD II Scan Tool -- Bluetooth - advanced CAN protocols
OBDLink® EX - OBD2 Adapter For ELM327 & FORScan -- USB corded
BAFX Products® - Wireless Bluetooth OBD2 Reader / Scanner for Android Devices -- Bluetooth
ShenZhen CheBoTong Technology Co., Ltd. -- vLinker

many thanks for those Links,
ordered the Kubota sealant just now, the rest is on my Gotta Do List.
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many thanks for those Links,
ordered the Kubota sealant just now, the rest is on my Gotta Do List.
First person on here that has said they are gonna use the Kubota stuff (y)

Little bit expensive, depending on where you purchase -- but really good stuff
There are likely other manufactures, but was the best I ever found in all my years -- the dealer I worked at Case-IH also sold Kubota so was easy for me to get
There are a lot of Case and Case-IH tractors with that stuff on the transmission surfaces

There is also a "runny" version that is the only sealer that would hold on a Case 2590 transmission housing -- tried everything that was available to me
3
First person on here that has said they are gonna use the Kubota stuff (y)

Little bit expensive, depending on where you purchase -- but really good stuff
There are likely other manufactures, but was the best I ever found in all my years -- the dealer I worked at Case-IH also sold Kubota so was easy for me to get
There are a lot of Case and Case-IH tractors with that stuff on the transmission surfaces

There is also a "runny" version that is the only sealer that would hold on a Case 2590 transmission housing -- tried everything that was available to me

Well,
I gotta be prepared to take care of things, the Right Way.
gotta little B7100 Kubota that runs like a dream, that is, when the glow plugs light up.... someone, or a little critter has mangled the wiring really bad....

Goldwing Motorcycles have aluminum blocks and heads, although I have never needed to remove the head off of one, they go 300,000 miles plus with just normal PM stuff.

and, my new toy is the '02 7.3L Excursion to pull my Toy Hauler around.
It is a retired Alpine, Tx fire chief's Battalion car. Manual hubs, stock AFIK.
Had to replace the exhaust pipe, and suspension parts, guess that is normal at 173, 000 miles.

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the Goldwing you can see in my Avatar..... I just gave that to my son August a year ago, after I suffered a heat stroke while riding it, decided it was time to hang up my spurs and let him enjoy it for the next 150,000 miles or so... with 80 birthdays behind me, I am lucky to be in good health.

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Hey all,

Just have a quick question...

Just yesterday I Replaced all my injector cups and o rings, I cleaned the bore, but I forgot put 620 loctite on the cups... I just saw a video this morning about using loctite, and looked on forums about using loctite and my stomach sank. Is it super crucial to have 620 loctite on the cups? I don't recall any loctite on the old cups when I pulled them. I'm replacing them because I have the motor out and want to reseal it. It would suck to have to buy new parts but if I should, then I will.

Thanks in advance.
You're going to have to redo that job.
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It sucks, but you don't want to risk damage to injectors and engine from fuel in coolant, etc. Bite-the-bullet ... Cheers!
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