1990 F350 4x4 7.3 IDI

[Will L.]

That trail of bubbles is exactly the normal sign of sucking air/ air intrusion. Search it out, if you cant find it install clear tubing on the incoming side from liftpump to ip. No bubbles into IP, bubbles only out means leaky gasket in the IP- occasionally rebuild of the IP is needed.

If dreams came true... someone would make clear viton tubing that is uv resistant. Then I would use that as my fuel line in every location on the truck. Instant diagnostics at a glance.

 

[n8in8or]

Start it from a 5 gal can. With that must rust there is no reason the fuel lines are innocent including IN the tank.

1 - good idea, thanks!
2 - that's funny, this isn't much rust in Michigan!!! You down south guys have it so good.

 

[n8in8or]

That trail of bubbles is exactly the normal sign of sucking air/ air intrusion. Search it out, if you cant find it install clear tubing on the incoming side from liftpump to ip. No bubbles into IP, bubbles only out means leaky gasket in the IP- occasionally rebuild of the IP is needed.

If dreams came true... someone would make clear viton tubing that is uv resistant. Then I would use that as my fuel line in every location on the truck. Instant diagnostics at a glance.

Thanks Will. This is my first time actually having to diagnose a diesel in depth. The Hoe has pretty much always been good to me - especially once I ditched the PMD.

 

[Will L.]

Rust. Rain. Snow. Cold. All these make believe words you guys talk about are so funny sounding.

Next you'll put them all together in one story. "It got so cold the rain turned to snow and started to rust my truck." Haha.

Follow WarWagons idea. Easy and tells you quick what's up.

 

[WarWagon]

1 - good idea, thanks!
2 - that's funny, this isn't much rust in Michigan!!! You down south guys have it so good.

Well there are places for sale out west... You just have to put up with like 100 degrees starting, oh, like now. And it's NOT a dry heat as the monsoon season wets things down and still gets you 115 degrees the next day.

Fans and AC compressors running flat out plus a serious temperature derate of engine power is the only downside.

I have yet to "shovel" heat.

 

[n8in8or]

Well there are places for sale out west... You just have to put up with like 100 degrees starting, oh, like now. And it's NOT a dry heat as the monsoon season wets things down and still gets you 115 degrees the next day.

Fans and AC compressors running flat out plus a serious temperature derate of engine power is the only downside.

I have yet to "shovel" heat.

Yeah, move out west - sweat all the time and be closer to bad influences Will and War Wagon. Good plan......

 

[n8in8or]

Primered the trans tunnel to prepare the floor getting coated in bedliner. I also accidentally primered part of my barn floor

I then decided to pull the fuel sending unit out of the tank after WW's comments and knowing that it's a typical problem area on these trucks. Well not only is it not the problem, but it's also in better shape than most!! Typically that shower head looking pickup is rotted off of these. Even so I'm going to mod the pickup so I don't have to worry about it failing in the future. Time to start rigging up fuel lines at the IP so it will run on a 5 gallon can I suppose.

 

[WarWagon]

What kind of lift pumps do these have if any? Every inch of line is suspect.

 

[n8in8or]

What kind of lift pumps do these have if any? Every inch of line is suspect.

They have an engine-driven mechanical lift pump that is driven by the cam - just like any old-school gasser engine. Not ideal obviously. I am suspicious of the lift pump, but rather than throw more money at it I will try to methodically test each component and narrow down where the air is getting in.

 

[ak diesel driver]

I've seen the 6.2 lift pumps suck air but still pump fuel fine.

 

[n8in8or]

I've seen the 6.2 lift pumps suck air but still pump fuel fine.

I've been searching for that info in relation to the IDI and I have been coming up fairly empty-handed. It sounds like it doesn't really happen, but in my gut it feels like it could happen. Testing will tell the tale.

 

[n8in8or]

I took the inlet fitting off the IP tonight so I can get a conversion fitting tomorrow. Looks like I missed an o-ring earlier. It kind of looks suspicious too, being all hard and stuff. Well I'll start by plumbing the IP straight off of the 5 gallon can and work my way back from there and see what I find. It should give me an answer fairly quickly.

Question: will it matter if the return circuit is still plumbed to the gas tank? Should I also plumb that to the 5 gallon can? I'm talking about the entire return circuit too, not just the IP return. Thanks.

 

[Will L.]

Do both to the 5 gallon can to be sure. I still rack my brain on fuel return being able to mess it up, but it does.
Then if it cleans upmand runs perfect, use the truck's return system and the 5 gallon supply. If that is good, the return circut should be ok.o

 

[n8in8or]

Do both to the 5 gallon can to be sure. I still rack my brain on fuel return being able to mess it up, but it does.
Then if it cleans upmand runs perfect, use the truck's return system and the 5 gallon supply. If that is good, the return circut should be ok.o

Thanks Will

 

[n8in8or]

Made some progress this weekend.

I got three coats of Herculiner on the floor of the cab. It's still pretty wet in the pics, but you get the idea. I had been thinking about doing this on the body too, but now I don't think so. I'm looking at the John Deere Blitz Black now instead.



I also started troubleshooting my air instrusion problem. I first tried running the fuel can straight to the IP, but it just wouldn't fire. I tried getting it primed, but it just wouldn't go. So instead I bypassed the filter housing and ran the lift pump straight to the IP. The lift pump is still drawing from the truck's fuel tank. I also have the return to the fuel tank bypassed - I have the bypass line run to the can under the hood. This configuration seems to have made an improvement so far. I've let it sit for over an hour a couple times and it starts better than it had been. Oh I also did the mod to the fuel pickup so I don't have to deal with that in the future. If it starts well tomorrow after sitting overnight then I'll start adding parts back in the system and see what one adds the problem.



Finally I started working on the Dana 80. I got it dug out of the stash and then cut the old spring perches and shock brackets off. Still a bit of grinding to go....

 

[WarWagon]

The return just keeps air from allowing the fuel to drain back to the tank. Leaks in return mean purging air out on next startup hours later. This is why the return goes to the same tank even when testing.

You might put a 12v test light on the IP in case it isn't randomly getting voltage to fire for some reason. (The 88 next door had an issue with this.) The air bubbles is a big problem to solve first.

 

[n8in8or]

The return just keeps air from allowing the fuel to drain back to the tank. Leaks in return mean purging air out on next startup hours later. This is why the return goes to the same tank even when testing.

You might put a 12v test light on the IP in case it isn't randomly getting voltage to fire for some reason. (The 88 next door had an issue with this.) The air bubbles is a big problem to solve first.

Ok. Hooking the return line to the truck's tank will be the first thing that I hook back up and then I'll go from there. Thanks.

 

[n8in8or]

The truck started up well after sitting overnight so I decided to plumb the filter housing back into the fuel supply. If it keeps working well, then it was either the connections at the filter or IP or it was the strainer on the sending unit. If it acts up again then I'll start probing the filter housing. The heater sounds to be a typical problem for air intrusion. Oh I also plumbed in the sending unit for the old fuel pressure gauge that came out of the Tahoe so I can add that in soon.

I also took some pics of how the floor looks after 2 days of dry time.

 

[WarWagon]

Don't need a rubber floor mat looking that good!

 

[n8in8or]

Don't need a rubber floor mat looking that good!

Thanks! That's the idea.