Warm starting a 7.3

I have read many posts about Cold Hard Srarts on a 7.3(1996 F350 auto) but mine starts up great cold its when you drive it 20 miles and shut it off and try it 10 min later it dosent want to start. It acts like its starved for fuel and will start after a mininte of cranking and its off to the races. If the truck sits 20 to 30 min it will start right up with no problem. To answer some questions I have traced the fuel line for defects, Has new fuel filter, cam sensor, back pressure sensor, oil temp sensor, T stat and temp switch, glow plugs and G plug relay. Oil and filter have been changed and has good oil pressure I even put a new throttel padel sensor in and still have this problem. The truck only has 82000 miles on it and this dosent make any sence to me. Has anyone had this problem or have any idea what it could be? I am at my witts end! Bandit

You probably have a worn bore in the fuel shut-off selenoid in your injector pump. When it sits for a while the heat it soaks up from the surrounding engine causes it to sieze in the bore and it wont allow fuel to flow. when it cools, it can move again.
Try this: next time it wont start, carefully pour some water(have a gallon jug's worth) on the selenoid cover on the top of the pump with the key on and listen for a slight "Click", once you hear that (or if you dont, but have dumped the entire gallon out), crank it over. If it starts, youve discovered your problem, heat soak on a worn pump selenoid.

Maybe a rebilder will replace just that part for you, or complete rebuilt pumps are about 400.00 on ebay. OR, you could throw a couple of gallon jugs of water in the box.............

On these 7.3 there is no injector pump only a high pressure pump that pressureises a commond fuel galley in the heads to each injector and is fired by the cam sensor. I am thinking its something electrical that when its hot after shutoff is not opening up in the fuel system when you try to start it. I just dont know what. Bandit

I thought it was 97 or 98 they went to the HEUI injectors and turbo.

Try pouring water over the fuel rails maybe?

I know that on our old AC tractors, if you shut them off (or stalled them) hot and needed to restart them hot, you had to pour water over the pump.

Could the high-pressure oil pump be going bad? Could you try cooling it off with a gallon of water?

I dont think so, Because if it was bad the truck would not run good once started and run 60 mph down the road. I still think its electrical in nature. Bandit

had a 94 & 95, those models had a problem with the glow plugs wiring in the valve covers and to the fire wall. needed to be replaced around 75k+ mileage, they wound melt causing malfunctions, if not fire in wiring. just a thought, maybe connected. another thought, maybe inside the fuel tank something is getting sucked up to clog fuel pick-up tube, then after sitting, picks up again.///also log-in to
FTE [ford truck enthusiast] look at their discussion sties. maybe has heard/had same problem. good luck.

Yup, I read that as a "1993" 7.3, the old Navistar IDI engine. THOSE engines had their injector pumps right up front where you could easily access them.
The key is that if you crank it (circulating cooler fuel up to your pump) it will eventually operate and allow fuel to flow and your engine to start.
You have to find what ever electrical control shuts off your fuel supply on your Powerstroke and cool it down (or attempt to verify or overide the ignition switch voltage).
I assume that once up to normal temperatures if you shut it off for a few minutes( to fuel up or run into a store) it will start as it should, but only if you let it heat soak a bit it will have this problem?

When I changed the glow plugs and relay I put new valve cover gaskets and new wiring under the covers, So I dont think that is it. I have wiggled every wire plug off cleaned it and pluged it back in, and still have the problem. I realy dont know what to think. Bandit

We have a late 94 F 450 with the power stroke and it was like this shortly after we bought it in 96. We had it to 2 dealers a few times including 2 weeks at the one dealer. That dealer replaced the high oil pressure pump regulator. That worked for awhile and then we took it to the other dearler after it started not starting when hot. They upgraded the computer to a 96 and replaced all the injectors. Other than small stuff that has been working for more then 10 years. Glow plug releys are a constant problem with several new numbers over the years. We have upgraded the turbo and the pipe from the turbo to the cat. That made it a lot more fun to drive. One other upgrade was to take out the 5.13 rear gears and install 4.10. That helped the fuel milage.Our is a 19 foot rollback truck with a 5 speed trans. You might want to take it to someone that can read live info when it is hot and won't start. You will likely find the problem that way. HTH.

Two things you can try. First is when it won"t start hot, unplug the ICP sensor. It"s the 3 wire sensor on the left head near the front. If the ICP (injection control pressure) is below 500 psi, the injector driver module will not activate the injectors. When you unplug the sensor, the module will default to 1250 psi and activate the injectors. If it starts when you do that, replace the ICP sensor. The other thing is check the IPR (injection pressure regulator) electrical connector. The IPR is the round thing down low on the driver side of the H.P. oil pump with a 2 wire connector on it. The IPR is nothing more than an electromagnet over a valve that is open at rest. The higher the duty cycle on the IPR, the higher the ICP pressure. I have seen many IPR"s that the connector seals deteriated and corrosion has caused problems. If the IPR does not close, you have no ICP. There are 2 different IPR"s used back then. If you find you need one, have your VIN# with you. One is $300, the other is $600 last time I checked at your local Ford dealer. If you"re lucky, you can replace the IPR connector for a lot less $$. The connector is kind of pricey since it"s part of the Navistar wire harness and they used GM wiring connectors. All that stuff went through the roof when GM went bankrupt.

I was just thinking aloud. I went to school with a guy whose 7.3 just shut down on him one day. He had someone with a trailer come to drag him home. Looked over the motor, pulled the dipstick, they dumped a half gallon of oil in it, and Doug drove it home.

I will have to try this in the morning when I drive to the farm. I have been doing alot of reading and this seams to be an odd problem to have on this truck. Hopefuly it will be something simple and nothing major to fix. Thanks for the infomation. Bandit

I gave her a try checking the ICP and the IPR with no luck, Still was hard to start when it was good and warmed up. This thing is driving me nutts! It has to be something simple. Bandit

You need to find out whats out of spec. That's going to require a scan tool that will read live data. If it was base mechanical, it wouldnt start easily cold. You're lacking either high pressure oil or voltage most likely. The 7.3 isn't known for high pressure oil leaks, but it's possible. Does it regularly use some oil? There are orings on the injectors that can leak. The oil will get into the fuel. Since there is no return line from the heads, you probably will never see it in the fuel.

It dosent use any oil, it leaks a very small amount, has 1500 miles on the oil change and I dont see a change in the oil. Tommorow I am taking it to a guy that has a engine analiser and with the Navistar 7.3 service manual I bought I hope we can figuar it out. I will let you know what we find. Bandit

May be a stupid answer,but I have had like problems with WIX fuel filters.They don't seal well enough(not the same size as Motorcraft) and with the heat will let a trace of air leak in.Wix makes a lot of WILL-FITS.Just something to look at maybe.

Had the guy check it today and found 2 problems, 1 it has 2 bad o-ring on 2 injectors and 2 the oil I got was CJ4 not CF4. He said the newer API oils (15W40) are hard on older powerstrokes because they thin down to easey and said to us CF4 sae 30W when it gets above 50 degers. I changed the oil sofar so go but the sets of o-rings are on back-order for a week or so. So I guess I will have to limp her along for a while. Bandit