1991 7.3 idi hard starting

[challenger]

I have a 1991 Super Duty F450 with the 7.3 idi. When I park the truck on level ground it takes an extremely long time for the truck to start. I have to hold my foot to the floor and maybe on the 9th cranking cycle it'll start. It doesn't matter if it's cold or warm out. I have replaced the glow plugs, glow plug relay, return lines with the "Ts" 2 new batteries, fuel filter etc...

Now here's the kicker, if I park the truck on a hill with the noise facing down it starts right up, I don't care if it's 5 degrees out it starts without it even being plugged in, Now I'm wondering if there is a check valve somewhere in the fuel system or could it be a bad lift pump.....any advice???

 

[Thewespaul]

Well once we know what engine you have then it will be possible to narrow down what the cause of the hard starting is. An idi and a powerstroke have very different fuel systems. If it’s a 1989 f-superduty then it will have an idi, in which case I would see if the fuel heater is leaking, that’s a common cause of drainback issues on these trucks.

 

[challenger]

I have also replaced the fuel filter and heating element

 

[sjwelds]

Does sound like a bad lift pump, also could be air intrusion. Run a hose to a can of diesel and to lift pump, see if it makes any difference

 

[challenger]

Thanks

 

[Thewespaul]

Do you have any fuel leaks when the engine is running? Check the inlet fitting in the back of the injection pump, there’s a olive seal in the fitting that will deteriorate and leak but not be very noticeable because of its location.

 

[challenger]

I checked all the lines for leaks including that one and it was not leaking. I do have new filter to injection pump seals which I plan on replacing anyway

 

[Oledirtypearl86]

How long does the wate to start light stay on when you hit the key you might have a few bad glow plugs that would cause a hard start mine at 30* f will stay in for 8 to 12 seconds that's a guess I've never timed it but some times it feels like forever


Oh and welcome to the site there is tons of knowledge here


Edit missed the part about nose down hill I'd say lift pump too or a air intrusion

 

[hacked89]

Once you have it started on level ground, if you shut it off and wait ~30-60 seconds. Does it start right up or with difficulty?

Sent from my SM-G955U using Tapatalk

 

[Joseph Davis]

check to see if you have a check ball on the return line to tank behind the left valve cover at manifold. the bi-metal valve get stuck open if you have a leak in the return line. But most likely you have an air leak in the fuel system return lines to tanks because fuel keeps draining back into tank after you shut her off; and air is getting in. This means no drops on the ground.

 

[challenger]

Problem corrected. I replaced the lift pump and the seals in the fuel line from the pump to the filter housing and the seals from the filter to the injector pump

 

[snicklas]

OK, That's enough. There was a mistake made and corrected. This behavior will not be tolerated here. Drop it and move on or earn a vacation. There should not have been 2 pages for me to have to clean up......

I'm glad the issue is fixed.