1987 6.9 IDI Losing Prime Overnight

[idiBen]

I'm troubleshooting a cold-start issue on my 1987 F250 6.9 IDI. The truck starts immediately when cold, runs for about 2–3 seconds, then dies. After that, it takes several crank attempts before it will start and continue running. Once running, it runs perfectly with no issues. So far I've replaced the injector return lines, return caps, O-rings, injectors, glow plugs, and glow plug harness.

After the truck sits overnight, the fuel filter head appears to lose prime. When I depress the Schrader valve on the filter head before starting, I get no fuel at all. After cranking and getting the truck running, fuel is present at the Schrader valve. I'm now investigating possible air intrusion around the fuel filter head and the fittings shown in the attached photos. These seem like potential sources for air entering the system and allowing the fuel to drain back overnight.

I found this older thread discussing the fuel line olives and related fittings:

https://www.oilburners.net/threads/where-to-get-the-fuel-line-olives.67503/

Since that thread is over 10 years old, I'm wondering if there is a current source for these parts. Has anyone recently purchased these fittings or olives, and if so, where did you get them? Also, has replacing these fittings resolved a similar air intrusion or drainback issue for anyone?

Thanks.

 

[Nero]

You can get the olives here

Olives and Viton O-rings for a fuel system seal up.

russrepair.com

Several vendors also offer kits to switch from hard lines to a JIC fitting flex hose to delete the olives.

 

[Clb]

You sound like you are on the right path, the return system is awfully touching if you bump it into it it's prone to leak, this get worse as they age sometimes.
Lube the lines before and after fitting the olives.
Threaded fittings, use rectorseal on the non olive side as some teflon based sealant is going to break down in diesel...
Good luck and welcome to the site.

 

[Jesus Freak]

There's a check valve in the mechanical fuel pump as well thats prone to go bad.....

 

[Olds64]

Make sure your mechanical fuel pump hasn't gone bad. I've had several go south on me and pump diesel into the crankcase. Just keep an eye on your oil level.

I finally went to an electric fuel pump.

 

[Clb]

Dang Chinese

 

[scsmith42]

On my 90 model, I was getting air intrusion in several places. Check valve in the Mechanical pump had gone valve bad, injector caps or problematic, and the O-ring seal around the heating element in the top of the fuel filter was also leaking.

Once I addressed all three of those items, I no longer have a problem with fuel draining down overnight.

I don’t know if you’re 6.9 has the same fuel heater in the top of the filter housing as the 73, but if it does you might want to check and replace those earrings or the heating element itself.