I have an 89 7.3 IDI. It came with a donor van for my 84 E350. I installed it about three years ago. I have no prior history. I has always started easy and run smooth. However, if it ever ran out of fuel, I had to bleed the air from the top of the filter. The supply pump is electric so I don't have to crank the engine for that. I then had to crank it for maybe half a minute and it would start very rough.

Well, cold start it now behaving like there is air in the system and I have to go thru the process above. It starts as easy as it ever did, apparently on the fuel that is in the pump, and then dies. But then it starts OK as long os it stays warm.

Does this make any sense?

TY
Ray

 

Sounds like the classic "air leaks in the return lines" symptom. An air leak will let your fuel all drain back to the tank overnight. Classic symptom is that the rig fires right up, then dies after maybe a half second and has to have the air purged outta the lines (usually by cranking it for 90 seconds in 15-second bursts, but you've got a better way) before firing up and running .

Look for damp spots on the return lines -- especially those little short segments that go between the plastic fittings on each injector. That's the part of the system that gets subjected to heat cycling the most.

The "right" way to fix this is to get a return lines kit and you're good to go for another 15 years. The "fast/cheap" way to fix it is to replace the fuel-stained piece of hose (5/16, if I remember right) and soldier on until the next bit springs a leak. Your call!

 

I already have a kit. I guess it is time to put it on.

TY
Ray

 

Visit....... http://www.intellidog.com/dieselmann/idi.htm read about air leaks.

 

Did not find any sign of leaking. I am replacing the O rings, plastic fittings and hoses, just because. It is a lot of fun on a van.

Fuel cannot drain back to the tank because the supply pump only flows one way.

Ray

 

If air leaks into the system it can return to the tank through the return lines.

 

I did not find any leaks, but I created one. One of the plastic fittings would not seal. I tried a variety of old and new fittings and O rings. I finally put a thin O ring in with the two normal ones, I didn't have any fat ones..

So I have replaced the stuff that might fail someday, but still don't why it starts and stalls.

In the meantime I replaced the schrader valve with an electic operated from the cab. Right now it goes to a catch can.

 

So I should shut of the return line when the engine is off?

Ray

 

I dunno if this will give you any ideas but just in case ... it's copied and pasted directly from dieselmann's InDirect Injection page 2 (http://www.intellidog.com/dieselmann/idi2.htm). There's a bunch more good stuff there -- well worth the read.

Here's the clip:

Stall after starting (especially after hot-soak/cool-down) then hard start
Air intrusion into the fuel supply system. Usually, the source of the fuel leak can be determined by the time from when the engine starts to when it stalls. On 6.9 engines with a firewall-mounted water separator, the engine will start and run for upto a couple of minutes before any air which may be in the separator reaches the injection pump. The 6.9 water separator is prone to leaks, both fuel and air. The best cure for this is to replace the OEM seperator with an aftermarket one (much cheaper--$30-$60 vs. $180), or remove it and its hoses and connect the line from the tank to the one running to the lift pump. Since it's not recommended to operate a diesel engine without a water separator, replace the fuel filter with the 7.3 type filter/water separator assembly. You can either purchase the header and sedimate bowl from Ford or a wrecking yard and install a new 7.3 filter. Another option is the Racor fuel filter/water separator kit. This kit contains a filter which fits on the original header and has a water sedimate bowl which screws onto the bottom (@ $35). The filter can also be purchased separately (@ $20), and you would want to keep a spare on hand as the replacement filter would not be available at your local parts store.
The 7.3 filter/water separator can develop fuel/air leaks at the fuel heater and restriced filter sensor or the filter drain (all three are servicable) and water in fuel sensor o-ring. The air bleed Schrader valve can leak on either filter.
The next common area for air leaks on both the 6.9 and 7.3 engines is at the injector return cap o-rings and hoses. This will cause the engine to stall after about 30 seconds of running if the air is able to travel into the fuel filter. On 6.9 engines the return line from the filter should be long enough to loop about four inches above the filter.
The 6.9 can be modified to have a check valve at the fuel filter return to prevent air from entering the filter. A 7.3 Econoline filter outlet fitting (E8TZ-9C402-A) can be installed in place of the original outlet fitting. An early 3/16" 7.3 filter return orifice with a "flapper" valve can be installed into the port ment for the E-van's restricted filter sensor.
On 7.3 engine the filter return orifice contains a check valve. This check valve is usually a rubber flap inside the fitting, and if this fails air is drawn into the filter as the fuel cools and contracts. This can be detected by removing the fitting and trying to blow through it from the hose barb end. If you are able to blow through it from this direction, it needs to be replaced. Seal the threads on the orifice with Loctite 515 Gasket Eliminator or PST. There are two different flapper valve orifices--3/16" and 1/4"--and the correct one needs to be used with the coresponding hose size or leaks may occur. Starting in 92 a 1/4" filter orifice was introduced without a flapper valve using a spring and plastic check ball. The spring-and-ball and flapper orifices are not interchangable; they have different headers. Also, the correct size return lines hose needs to be matched to the injector caps and the proper clamps used--not worm-gear, this will distort the hose; either OEM spring clamps or fuel injection system screw-and-band type. When replacing injector return o-rings on one injector, you should replace all on that cylinder head as they tend to leak after they have been disturbed. Use silicone dielectric grease to aid in reassembly and some times it helps to install a third o-ring between the return cap and injector line nut to keep the cap in place.
On the fuel supply lines at the filter inlet, filter outlet and injection pump inlet, there are seals which can allow air to enter the fuel system if they become deteriorated or dried out, even if there are no visible signs of fuel leakage. If there is a leak on the line between the filter and injection pump, the engine will seem to try to start, then become hard to start. Note that there are seals of the same type on the injection pump return line at the injection pump and at the return line collector fitting on the rear of the engine (some applications).
Less common areas for air leaks are the injection pump outlet check valve and the fuel lift pump, but both have been know to happen. Using clear hose on various sections of the fuel suppy and return systems can usually pinpoint the area of the air leak. Install the clear hose at the suspect areas, start the engine to purge any air, then allow to cool. Watch these hoses for large air bubbles or pockets when starting the engine to determine the origin of the air leak. Also allow the engine to come up to operating temperature to look for air leaks which may occur when the system is hot. These may migrate into the filter and cause a hard start concern.

 

If you have an electric pump and a pressure of 4-6 psi at the Schrader valve, there should be no air left in the system when you go to start it.....after 15 seconds of key on. Try this ... 15 seconds key on......turn off and right back on... watch the WTS light and go for the start when it goes out. If there is still a problem I would check the GPs are all working using a test light......

 

I have read the references posted here plus I have a couple manuals. For air in the system they all say to look for leaks in hoses and fittings. But it seems tp me that any leak large enough to let enough air in to cause starting problems would be large enough to leak enough fuel out to be noticeable. There are no fuel leaks anywhere.

I fiddled some more with the leak I created. It appears that the original O rings were two different sizes and the kit were all the same size. I used an original plastic fitting - which is slightly smaller - and selected two O rings. I had already added the third O ring before the last reference was posted. I seem to have the leak stopped.

I was not aware of the valve in the filter return line. That just might do it. The weather has been warm, so the glow plugs have not been on very long, so the air would not have had time to bleed off. I will check that.

Ray

 

An air molecule is much smaller than a fuel molecule.
So air will leak into the fuel system when the engine is not running through places that will not leak fuel out when the engine is running.

Since the fuel tanks are lower than the engine and fuel filter, if any air leaks in the heavier fuel returns to the lowest possible level, the fuel tank.

I am not understanding the third O ring.
There are only two grooves in the injector to put O rings in.

 

It goes on top of the plastic futting under the injector fitting. It holds the plastic fitting down, and provides a secondary seal between the two fittings.

I am on the road now. If I have some down time I'll look at the filter bleed antireversion.

I am dooing a long bleed cycle before start and that seems to be working.