1985 6.9IDI not starting

I have a 1985 F350 Crew Cab 6.9 Diesel - C6 Auto.

I have replaced any and all rubber in the fuel system lines. Installed new Orings and fuel return line kit on the injectors. New mechanical lift pump with an inline electric pump before the water separator. 8 New Genuine Motorcraft ZD-1 Glow plugs. Glow plug harness is all good and tests out great. 12V at the controller end and 12V all the way thru the fusible link ends to the glowplugs. All 8 ends are fine.

New glow plug controller although I have it set up on a switch (in cab) to warm up/activate the glow plugs.

Truck rarely, if ever, starts when "cold" ......first start up of the day. I live in Texas and this truck does this on an 80°F+ day. I'd hate to see how hard it starts on a cold day of 30°F. But when I plug in the block heater and it gets up to 130°-140° it will start with no problem.

New fuel filter as well. Vented fuel cap.
New injector pump.
All solenoids are working in the injector pump. I can hear them clicking and making noise when they are connected and disconnected.

Try starting fluid, if it starts right up, it glow plug related, once started does it restart easily?

Sometimes it will and
sometimes it won't start with the quick shot of that. When I have done it that way the glow plugs have not been "on" as I know that is the way you break stuff unnecessarily.

But it always fires with the block heater connected and will always restart after warm.

Glow plugs or glow plug controller. Lots of fake Motorcraft plugs., I changed over to cdd manual glow plug set up.

@raeasler : Not just GP issues, include air intrusion / vacuum in the fuel lines, particularly if you don't know its history. At nearly 40 years of age - the fuel separator is likely to be a problem - can't tell you how many times I've concluded it was the last fix needed... After doing all of what you did - and a lot more, the Separator turned out to be my primary issue. Replaced mine with a Racor 45 marine unit.

The return line kit is a just starting point for air intrusion. Bubble testing the rest of the lines is another method, though mine did not show the "keeping vaccum overnight" as being the issue. Made sense when I thought about the vacuum leak issue in relation to the typical 30 to 40 degree overnight temp changes... Good thread here on another member's journey with the separator, with photos - mine is also documented there. Can't remember if there are DX links, in that thread or not - they should be easy to find.

I can personally attest to fake ZD-1 GPs - and that they are more prevalent than you would expect. I've found them just about everywhere, even RockAuto. Link here to my post (with photos) on my experience with examples, there should be other links/posts in that thread to chase as well.

Some of the other things I would note: Bench test the GPs. New out of the bag doesn't mean good, make it a habit to test them prior to putting them in - and keep a log of the readings and where each GP+reading went... I keep two additional sets: 1) a new set, and 2) a used but "test good" set. The more you drive your ZD-1's - the more time you should spend hunting a spare set... others have rightfully noted it doesn't take eight good GPs to start the motor... but four likely is not enough... I shouldn't need to say this: do NOT let someone else wrench / supply your GPs.

I also made certain I was using the right starter (the wrong unit will not spin fast enough), the correct units are 50% more $$ and sensitive to overheating. That I had good batteries (went the $$ optima route), and I replaced the entire set of battery/starter/ground cables with 4-0 copper.

My '85 typically starts on the first turn after cycling the GPs three times - even after three to six months or a winter of sitting. Sometimes it takes pulling fuel all the way from the tanks... note the pressurizing button on the Racor units - it is very, very handy.

Keep us in the loop.

Old Goat said:

Have had it set up with same ZD-1 Plugs maybe 5 + years.

Click to expand...

Yep. Mine has been on the same set of ZD1As since June of 2018.

Old Goat said:

Forget the original GP Controller as used on 83 - 86, They are know to stick in the on position (as i have read) and burn out the plugs.

Click to expand...

The actual original one can stick on because it was mechanical. The updated replacement version is solid state, it can only fail "off"

The fatter silver is original mechanical.
The slimmer black is solid state.

Mine is the Black one that came on the truck and didn`t work. It is still screwed in, they can break off unscrewing them, Then you have another problem getting the broken off piece out of the Head.

I had read that, and at PNP various times, tried to remove 3 of them, two broke off and one came out.


Goat

Old Goat said:

Mine is the Black one that came on the truck and didn`t work. It is still screwed in, they can break off unscrewing them, Then you have another problem getting the broken off piece out of the Head.

I had read that, and at PNP various times, tried to remove 3 of them, two broke off and one came out.


Goat

Click to expand...

The one in the RV was black too and suddenly quit working after I owned it several years. I just unplugged the connector and ran a manual button on the relay/solenoid.

I wonder if they bothered to soak it with anything before trying to remove it.

If it were to break off, you can either go to manual only or change to 7.3 style, leaving the broken piece in as a plug.

That was me pulling the 3 different Controllers at PNP. No I didn`t spray anything on them, wanted to see if they would or wouldn`t come out.

And I did wire it up manually, works great.
Thought about going with the 7.3 set up. Even bought a new IHC one off E-Bay, and later found a new one at PNP, then the more I read and thought about it, wired in the Toggle and works every time. No light to watch/worry about, or stressed out how many times it clicks or doesn`t etc....
Also with manual I can activate the plugs when really cold after it starts to get her to smooth out, or get over her coughing spell to just run.


Goat

Old Goat said:

That was me pulling the 3 different Controllers at PNP. No I didn`t spray anything on them, wanted to see if they would or wouldn`t come out.

And I did wire it up manually, works great.
Thought about going with the 7.3 set up. Even bought a new IHC one off E-Bay, and later found a new one at PNP, then the more I read and thought about it, wired in the Toggle and works every time. No light to watch/worry about, or stressed out how many times it clicks or doesn`t etc....
Also with manual I can activate the plugs when really cold after it starts to get her to smooth out, or get over her coughing spell to just run.


Goat

Click to expand...

The way 6.9 works too, at least based on how I wired up my manual button, the key wasn't required to activate the plugs. That was useful with the electric fuel pump. No need to make the pump run while the plugs are heating.

The 6.9 controller would activate after running a time or two until it got warm enough from idling.