I have an early 99 F250 7.3. It slowly started taking longer to start. Then it would start while cold, but not hot. When it warmed all the way up, it wouldn't idle.

I have changed injectors with know good injectors. I have changed the CPS and IPR. I have checked all wiring. I can put a scanner and watch the Injection Pressure. When cold, it jumps to around 3000 and when revved, will jump to around 4000. As it sits at idle, the pressure starts dropping and will eventually fall to around 400 and quit. I can still rev the engine and increase to the mid 1500 or so, but when idle will drop off. I do not have any oil in my antifreeze or antifreeze in my oil. I am not losing any oil or antifreeze or have any blowing from my dipstick tube or antifreeze reservoir. Right now I am suspecting the HPOP. Any other ideas before I order a new one?

 

Also forgot to mention new fuel pump. New PCM and no chips installed at this time.

 

You are seeing 4k HPOP?

Pull the valve covers and watch the truck idle when warmed up.

While your watching the HPOP also watch the duty cycle...

I had an injector issue where the truck would run cold, but once up to temp it would die. Injector was bleeding oil so much that the HPOP could not keep up.

 

I replaced my injectors with a set out of my son's 2000. They were working fine in his and worked great in mine but with the same starting issue. I have since swapped them back to my original, because he sold his stage 1s. I can still give that a try, but I have my HPOP out at the moment debating on putting in a new one.

btw, I also put in all new seals in my HPOP with no effect.

 

Well its hard to say if its the HPOP or not without the Duty cycle...

You put new seals in the IPR or in the HPOP?

Have you done anything to the IPR?

 

[QUOTE=ggirten;10736413]... When cold, it jumps to around 3000 and when revved, will jump to around 4000. As it sits at idle, the pressure starts dropping and will eventually fall to around 400 and quit. .../QUOTE]

You are seeing 3000 psi at idle? Last time I saw a truck with 3000 psi at idle it was also showing 3-4% duty cycle and it turned out to be fuel supply issue. We cleaned the screens in the tank and the IC pressure and duty cycle returned to normal and truck ran fine.

Does your truck still have the mixing chamber and screens in the in-tank pickup assembly? If so, you might want to get a 5 gallon can of diesel and plumb it to the feed side of your pump to see if the engine runs differently. It's something simple to check before you decide to purchase a new HPOP...

Like Joe said...it would be nice to see IC pressure and duty cycle at the same time to help resolve your issue.

Hope this helps.

 

I don't recall the duty cycle, but it is high. Over 60 at times. Unfortunately, I can't start it right now until I put the HPOP back in. The pressure dropping as it warms up is what concerns me. Once it is in the mid to low 400s, it then will not idle. I have replaced seals on the IPR and ICP as well used 2 different IPR and a different ICP. They were out of if nephew's truck that was running, but he blew the motor and replaced it with another.

 

If it was over 60% the pump is more then likely shot.

 

I have been working on this for quite a while and that is where I think the problem is likely to be, but wanted some other opinions first.

Thanks

 

Probably not a fuel issue then. 60% is pretty high.

Have you tried unplugging the ICP to see if it makes a difference?

 

Yes, no difference.

 

Well, my daily driver lost some teeth on the timing chain gear, so my truck will have to wait until I get that one going. Hopefully only a week or so.

 

Finally broke down and bought a new HPOP. Trucks runs great, starts easy. Back to the way it used to run. :

 

What HPOP did you go with,stock or aftermarket?

 

First test ur glow plugs/gpr, then get u new batterys, starter, altenator...then dig in to other things.