1990 7.3 idi stalling under load

[Makohunter]

Hi everyone new to site. I have a 1990 Ford f350 crew cab dually 5-speed manual transmission running into severe problems climbing any type of incline truck stalls and craps out. On flat and level roadway truck starts idles fine revs up to $2,800 RPMs $3,000 RPMs no problem as soon as the load is put on it dies. I replaced the fuel filter and the lift pump and still no solutions.any feedback or suggestions what I should look at next would be greatly appreciated.

 

[IDIBRONCO]

Welcome. Based on what you've said, I would guess that you have a fuel pick up (shower head) in a tank that has fallen off. When you're on pretty level ground, what's left will be lower than the level of fuel in the tank and your engine will run just fine. As you start going up a hill, the fuel sloshes to the back of the fuel tank. As it does this, the fuel moves away from what's left of your pick up tube which basically lowers the fuel level in the tank. Now this is assuming that you've only been experiencing this on one tank. Both shower heads may have fallen off too. A good way to check this is to fill the tank (or tanks) that you're having issues with and then drive the truck on the same roads. If it's the shower head (s), then the truck should keep running fine with a full tank since the fuel level will still be above the bottom of your pick up tube. The fuel level that I'm talking about from the pick up's point of view. The pickup is on the same incline as the truck while the top of the fuel will still be level with the earth. I hope I didn't confuse you with this explanation.

 

[Makohunter]

Thanks for your response my truck has two tanks and both are totally full unless the fuel pickup tubes on both tanks fell off simultaneously I do not think that is the issue since the truck will run fine and idle on level ground when I say an incline I'm talking three degrees maybe four at most so I'm pretty sure it's not the fuel tank but we'll check I'm thinking high pressure fuel pump?

 

[gandalf]

Your truck is a 1990 IDI? It sounds pretty well stock from what you've said. These trucks have never had a high pressure fuel pump. The lift pump, the fuel pump, maxes out at around 5psi. It will pump lots of volume, but at a lower pressure.

Perhaps you're referring to the injection pump. That does produce a high pressure as it distributes fuel to each cylinder. It's possible that it may be partially plugged, I guess. Just to rule that out I'd suggest a fuel conditioner which will clean the IP. It's cheap enough, and may solve your problem. I can't remember the name of the best conditioner, but some one will come along who does, and give instructions for that specific product.

 

[lotzagoodstuff]

If it was me, I’d change the fuel filter right now and carefully cut open the old one and see if/what it’s full of. On a newer OBS truck the fuel filter light would tell you if your filter is plugging, but I don’t know the brick nose trucks of your vintage very well.

You could also think about installing a Gagr abs measuring fuel pressure while you are driving it. It’s not terribly hard to put a gauge on and measure your fuel pressure, but I’m with IDIBRONCO here: I would bet you either have a plugged filter or maybe a weak lift pump that isn’t letting enough fuel through when you have high demand. Blowing air through the lines back to each tank would ensure you don’t have any debris blocking anything too.

Good luck and welcome to the site

 

[nitroguy]

When it dies, crank it and open the schrader valve on the fuel filter stack. If you're getting air out, fuel starvation supply is your problem.

On Red Fred, I had this problem. The valve on my tank stuck shut and was creating a vacuum in the tank when fuel delivery was really flowing. Lower loads wouldn't show the issue. I replaced my whole tank because of other issues, but I think it was the rollover valve on the top of the engine, or breather, or something like that that was clogged.

Might worth a look.

 

[chillman88]

When it dies, crank it and open the schrader valve on the fuel filter stack. If you're getting air out, fuel starvation supply is your problem.

On Red Fred, I had this problem. The valve on my tank stuck shut and was creating a vacuum in the tank when fuel delivery was really flowing. Lower loads wouldn't show the issue. I replaced my whole tank because of other issues, but I think it was the rollover valve on the top of the engine, or breather, or something like that that was clogged.

Might worth a look.

You know, if that's the case it wouldn't be a bad idea to take the fuel filler caps off to test that theory.

 

[IDIBRONCO]

If it was me, I’d change the fuel filter right now and carefully cut open the old one and see if/what it’s full of.

The truck has a new fuel filter and a new lift pump.

 

[Farmer Rock]

Your truck is a 1990 IDI? It sounds pretty well stock from what you've said. These trucks have never had a high pressure fuel pump. The lift pump, the fuel pump, maxes out at around 5psi. It will pump lots of volume, but at a lower pressure.

Perhaps you're referring to the injection pump. That does produce a high pressure as it distributes fuel to each cylinder. It's possible that it may be partially plugged, I guess. Just to rule that out I'd suggest a fuel conditioner which will clean the IP. It's cheap enough, and may solve your problem. I can't remember the name of the best conditioner, but some one will come along who does, and give instructions for that specific product.

Kerosene is better than any in the bottle cure,just be prepared to change the fuel filter again because it deep cleans everything from the tank to the injectors so the junk from the tank will clog the filter.Use a 40% kerosene to 60% diesel mix.As for the truck,does it start hard when hot?If so pour some cold water on the injector pump (ip),and if it starts better,that tells you for sure that it's a bad ip....it sounds like you are driving it unloaded,so if you have a trailer you can hook it up to,try some heavy towing on flat ground,that way you know if the angle of the hill is causing poor fuel pickup,or the truck lacks power.Has there been a noticable lack of power in general?

Rock

 

[riphip]

Get a bottle of Hot Shot Diesel Extreme, fill fuel filter, pour remainder in both tanks. Crank and run for about 5 minutes and turn off. Let it set overnite and run it like you stole it the next morning. That stuff will burn the skin off your arm. Will clean out everything.

 

[captainjerry001]

I had to take my 1992 F350 to the shop for removal and reinstallation of a fuel tank and replacement of the fuel hose inside the tank. The old hose was cracked and it let air into the fuel line when the tank was down to 1/4 level. The new hose in the tank fixed the problem.

 

[Makohunter]

Thanks for all the replies. It wound up being the O rings on the injectors. A bunch of them were brittle letting sir get sucked into the system. $50 buck replacement set & good to go. Thanks to all!!

 

[nitroguy]

Glad it got figured out!