New to me 89 F250 7.3 surging when cold

[Zachatola]

Im new to the site and am also new to diesels. I acquired a 89 F250 7.3 ZF5 and it runs pretty good all in all, however when cold it surges and almost dies (sometimes does) when cold. It will start right back up but surges until its warmed up a bit and then all the sudden it stops surging. I tried driving it the other day while cold and while holding the throttle at a fixed place it would almost die then just jump up in rpm then repeat the process, then all the sudden it just stopped doing it and ran just find the rest of the time i drove it.

Im new to diesels and am doing a lot of reading about where i might pin point the problem but have not figured it out yet. Any ideas where i could start looking? It almost seems like a cold start high idle issue, or something like that. Again sorry for the ignorance with diesels, id like to learn more so i thought this would be a good place to start.

Thanks for any insight or info

 

[IDIBOBS]

High idle working? Might be cold advance? How does it start? Are the glow pigs working well

 

[Nero]

Sounds like you have either an air intrusion issue, or a sticking governor in the pump. Or both.

Try running a lot of fuel cleaner through the pump to un-gum it, and look into fuel return cap replacements, chances are that is where the air is getting into

 

[Zachatola]

High idle working? Might be cold advance? How does it start? Are the glow pigs working well

It starts great, especially when plugged in. Im not sure if high idle is working properly or not, what RPM would i expect to see when its properly working? The glow plugs in my experience have been working good, it takes a little to get it started when its cold out and it hasnt been plugged in, but i have been able to get it going.

Sounds like you have either an air intrusion issue, or a sticking governor in the pump. Or both.

Try running a lot of fuel cleaner through the pump to un-gum it, and look into fuel return cap replacements, chances are that is where the air is getting into

So if i was getting air intrusion would that basically be like a vac leak? Check for cracked hoses, things like that?

Any recommendation on a good fuel cleaner for diesels? I've used stuff for gas motors but im sure there are specifically engineered ones for diesels.

 

[Nero]

Air intrusion on the fuel side.
Air can get in between the mechanical lift pump, filter head, and injector return lines, and will cause surging until it purges out.

As for fuel cleaners, I personally recommend power service. You can either add it to your tank, or take off the filter at the engine and fill it up. Start engine, let it run for a little to fill the pump up with the cleaner, then shut er down and soak overnight. Then drive it like you stole it, really exercisesthat pump.

Some people will suggest atf, ive heard the cleaning packages can be too much for the pumps with newer atf formulas. Some will say it works just fine. But its an option.

 

[IDIBOBS]

Hot warmed up idle should be 650 ish. High idle should be 750-800

 

[Zachatola]

Air intrusion on the fuel side.
Air can get in between the mechanical lift pump, filter head, and injector return lines, and will cause surging until it purges out.

As for fuel cleaners, I personally recommend power service. You can either add it to your tank, or take off the filter at the engine and fill it up. Start engine, let it run for a little to fill the pump up with the cleaner, then shut er down and soak overnight. Then drive it like you stole it, really exercisesthat pump.

Some people will suggest atf, ive heard the cleaning packages can be too much for the pumps with newer atf formulas. Some will say it works just fine. But its an option.

Great info, I really appreciate it. Ill look into some power service. As far as Air Intrusion into the system, how would air be getting in? Cracked line, or a loose fitting? Something of that nature? I know that the fuel gauge doesn't work on the truck but i am guessing thats an elec issue, or possibly a pin hole in a float problem.

 

[Nero]

The metal fuel line from can pump to filter head, metal line from pump head to injection pump, and all fuel return line caps have rubber gromets or o rings. They dry out as they get old. The rubber lines between each cap and filter head vent can also let air in too.

 

[IDIBRONCO]

or a sticking governor in the pump.

This is my first thought. Along with the fuel cleaner.

what RPM would i expect to see when its properly working?

It is adjustable so it might not be at the "proper" RPM.

 

[Zachatola]

The metal fuel line from can pump to filter head, metal line from pump head to injection pump, and all fuel return line caps have rubber grommets or o rings. They dry out as they get old. The rubber lines between each cap and filter head vent can also let air in too.

Is there a O ring kit or something you guys might be aware of that i can source these O rings? Also i see there are a bunch of different "injector caps" all seem to be plastic. Is there a better brand than not to go with? I see some Delphi ones, and some off brand versions too.

Next question is how to restart the truck after replacing all these lines and O rings and stuff. It will introduce air into the system and ive always heard that getting a diesel started if you run it out of fuel is a major chore. Do i need to do something to get it started again other than just maybe some extended cranking?

Also is there any difference between an 89 and 90? Im not sure what year this pickup is. door tag says 11/89

 

[Nero]

That one on the title will probably be labeled as model year 1990. No real differences.

As for the return kit,

7.3 IDI NA & Turbo Return Line Kits

This is a genuine Delphi return line kit made in the USA and upgraded with our own viton o-rings, designed and tested to perform the best with the current quality dry diesel fuel as well as WMO, WVO, and other kinds of alternate fuels used in IDIs. This kit is the updated "late" 7.3 design...

classicdieseldesigns.com

For bleeding the air out, leave all the line nuts half a turn loose, and crank until fuel squirts out all of them. Then tighten all nuts, and she'll fire off.

 

[IDIBRONCO]

Toy will probably need to know what return line set up you have. Earlier ones had 3/16" hoses with barbs in the middle of the caps. Later ones had 1/4" hoses with barbs that are on the edge of the caps. It will make a difference as to how well they attach to your hard lines.

 

[Zachatola]

I finally had a chance to work on the ranch truck this weekend and did not find any wet injector return hats (so im thinking they are good at this point) I did however find that my lift pump was not getting fuel to the filter. I replaced the lift pump with a napa unit (apparently made by carter) and after a lot of messing around finally was able to get the truck running. My filter light went off and the truck seems to run and start good. I have however discovered that my fuel level gauge often swings from all the way full to empty at random times. Based on what ive researched it looks as though the level indicator is routed through the fuel tank selector valve? Correct me if im wrong but when the unit goes completely Full it is a short? on the level wire? From what i can tell the selector valve appears to be working and changing tanks, but i have no idea how much fuel is in each tank. The rear tank often shows about 1/4 tank so im wondering if that sender is working properly it doesnt seem to swing like the front tank does.