Truck Started not Starting Right Away..

[Silver Burner]

For the last few thousand miles, it doesn't matter how cold the weather got (except for the one day in central Oregon when it was -7), the truck would fire up no problem after a 10 second or so wait on the controller. In the last 500 miles though, it has gotten hard to start right away. It still burns for a 10-12 second run followed by that quick flicker on the wait to start light, but it'll just turn over a few times, catch, then immediately die. Then I'll wait 30 seconds or so, run the cycle again, and crank probably 10-15 times until it finally catches. When it does, it acts like it's running on 5 or 6 cylinders for a few seconds before they finally all start firing and it calms down and runs like the perfect truck it's been. My question, *** is going on? Do I have an air leak in the fuel lines somewhere? I did verify at the top of the fuel filter assembly that the lift pump is working with a home made air valve attached to a hose running to the bleeder. Cranking the truck produces a bunch of diesel out of the line. Any help would be appreciated.

 

[Brianedwardss]

Air in the lines. If you don't have any fuel leaking around your injector caps, pull the little brass check valve off the filter head. It's the little fitting that the return line clamps to on the filter head, right next to the bleeder. Pull it off and see if you can see daylight through it. You shouldn't be able to, it's designed to flow one way from the filter head to the return line. It may just be stuck open

 

[Silver Burner]

So I took apart my fuel filter assembly, checked that check valve and sure enough it's wide open. tried running some pb through it to see if I could clean it up and get it working again, but it seems to be stuck open for good, so I guess I'be be replacing it. I also figured for the hell of it I'd take apart the water separator and all the little fittings on it, clean everything up and make sure there were no leaks there either. It's currently sitting on my garage floor full of Howes to see if there are any leaks. When I pulled the fuel filter this morning it was a good half inch from the top with fuel. Definitely getting air in there.

 

[Brianedwardss]

Well atleast it's an easy fix! I think they're $20-$30 at the dealership. I payed $34 w/rush shipping a couple months ago.

 

[Brianedwardss]

Your's is a '91, and that's the changeover year for check-valve size. 7.3l's from '88 to '91 had a 3/16" check valve, but late '91 and up had a 1/4" check valve. I'm not 100% sure, but I'd guess that you measure the return hose size that's clamped to it.

Part Numbers:

Early 3/16" check valves: E8TZ9K061A
Later 1/4" check valves: E9TZ9K061A

A little ways down this page on Oregon Fuel Injection, you can order 'em:

http://www.o-f-i.com/index.php?pid=12#FUEL_&_OIL_FILTERS_O.E.

 

[Silver Burner]

How on earth does a stuck check valve cause so much air and the level of diesel to drop in the fuel filter??

 

[Brianedwardss]

Well, hard to explain. I know on big rigs, an easy way to tell if ya had an air leak was that the fuel in the filter was about 1/4 down from the top, not full to the brim. Our fuel filters are the highest thing on the engine fuel wise, and that's the reason all the air flows to the filter. That check valve keeps the air from getting in, which also keeps the fuel prime. Some folks replace that check valve return line with a clear one to see what kind of air they're getting. (air while running, air while sitting, air while cranking, etc.) I'm guessing on yours it's just a small seep from one of the caps, but I'd look at the fuel tank selector valve and see if it's shiny at any of the plastic connections, as they have o-rings in them that can cause air

 

[johneich]

The check valve in a lift pump can get weak, when this happens diesel will follow gravity and go downwards sucking air into the filter check valve, we can tell this is happening by a fuel filter that is less than full. This is why its important to have an air tight system, gravity is always going to try and pull our diesel back to the tank, any air leak will allow that to happen, if there is no air leak then the gravity won't let the diesel flow, there is a scientific explanation I can't think of right now but its like putting a straw in a drink and then putting your finger on top of the straw and lifting it out of the drink, the fluid stays in the straw until you remove your finger which is letting in air.

Also remember, you can have an air leak where there is no diesel leak, air is easier to leak than a fluid.

 

[Silver Burner]

I've got the 1/4" check valve in mine, but the build date on the truck is 10/90, so it's not a late-build 91. I assume someone replaced it with the larger one at some point in the past

So now I need to figure out the check valve on the lift pump and the plastic fittings on the fuel selector valve. Wish it wasn't a monsoon outside right now....

 

[johneich]

I don't think you need to check your lift pump check valve right now, I just edited my last answer above, read it again and see if what I added makes sense.
John

 

[Brianedwardss]

My last air issue, I first installed a return line kit, didn't cure it. I replaced a couple fuel lines with rubber and verified the other plastic ones were good, nope still got air. I replaced the mechanical lift pump, nope! Then Mr T on here mentioned the check valve... Once I did that, my truck hasn't burped on a start-up since.

 

[Silver Burner]

Just ordered the sucker from MacKenzie Ford for about 22 bucks. I'm a little worried that I won't get the right part though. I told him I had a 91 7.3 and what part I needed. he started punching stuff in the computer and then asked me if I had a Powerstroke! I was thinking Dude, *** are you doing working in parts at Ford?? I went through the pictures he brought up with him and I think I have the right thing ordered, but the guy was a bit Slooow, so I guess I'll just wait and see.....

 

[Silver Burner]

Got my check valve today and replaced it. Truck was a typical ***** to start, but I let her run for a while to get good and warm and I'll let it sit overnight and see if she starts up tomorrow. Hopefully it's all fixed up now! BTW, here's a couple pics of my new crew. Never did get them up before.

You must be registered for see images attach

You must be registered for see images attach

 

[SparkandFire]

Nice looking truck! Hopefully you got your hard-start issues resolved!

 

[rockchuk]

In turn hard to start

Well I took the plunge and also own a 7.3 IDI motor. This site is a wealth of info. Aleady did the clutch rod end revamp using the tech article.


Does anyone have a pic of where this check valve in on the filter housing? I only see a fitting for the return hose on the filter housing. That in turn runs down the driver side of the motor ( hard line) then goes through a check valve and on to the fuel tank.
Thanks
Chuck