How old is the fuel filter? Is it the same one from December when you had the loss of power?

 

Are you using the new FPR housing & stock spring I mailed you?

 

Fuel filter in the bowl is only a couple months old, it looked clean and showed no signs of contamination 3 weeks ago when I rebuilt the bowl. The frame rail filter tested good, there was no change in pressure readings when I bypassed it versus running straight through it (assuming my FP gauge is working), and that is the same age as the bowl filter.

I am running the FRx and the 61-65 psi spring that came with that. I wasn't able to find plugs for the heads so I have been unable to flip it out for the FPR and spring you sent. I will look again tonight at work, otherwise maybe its something I/we can get in SF.

Also, my arm is still pretty much worthless so I don't think I could flip it out by myself today.

Baatzy

 

If you power loss was gelling related and you have the same OEM fuel filter still installed - I would swap that out before the drive home. The wax drop out can stay in the filter. Don't let the FP go lower than 45 psi.

Edit: I think I have some plugs for the fuel rails

 

I'm still thinking this as well.

Sous, you have the same setup (FRx & Stock fuel bowl). What pressure are you seeing?

 

I do not have the FRx, but do have a stock fuel bowl and fairly new filter. My fuel bowl has not been rebuilt, but it currently does not show signs of leaking.

I am seeing right around 65 PSI steadily throughout the power band and idling. The only time the FP drops is when the glow plugs are warming up and the fuel pump shuts off. As soon as I go to start the truck, it is steady right about 65.

I still think this is a sending unit problem, for these reasons.

All other parts have been verified to be working and in good order. The truck runs and idles fine with no sign of fuel starvation.

The FP drops and returns erratically without explanation. ISSPRO tech told me that some 7.3 diesels will kill a FP sending unit, some won't. I was sent a new sender and the adapter I linked earlier which restricts the flow of fuel to the sender and all is fine now. Just like the guys that have installed the 90 degree bend and have had no problems, the fuel is being restricted just enough to provide a safe operating condition for the sender. I think the sender on the Baatzy's truck was damaged early on and is not acting right any longer.

I would put a call into ISSPRO and talk to them. You will probably have to leave a message, but they got back to me within about 12 hours and were very reasonable and sent me a new sender and the adapter the same day.

Just my thoughts, I will continue to follow this thread though.

 

Sounds good Sous, we'll swap in a known good sending unit when he drops by this week.

 

Keep us posted. If I were a betting man I would put some cash down on the sending unit being the culprit.

 

At the time, Rich, we discovered that the plastic foot on the pickup tube in the tank was crumbling into small pieces, and a bunch of that crumbled crud had been sucked up with the fuel flow and was packed into the elbow of the hard tube at the top of the tank right where it bends through the stamped steel plate.

 

I read about early failures of sending units that used a straight adapter, favoring a 90* adapter to get the sending unit in a non-horizontal position.

I have the FRx and recently replaced my fuel pump, but still drops too low fuel pressure.

Since then I have replaced my alternator and haven't gotten back into it yet.

Of interest is when I was calling about the fuel pump specs, the drop in output is very significant with just a small voltage loss (about 30%, IIRC). That is one suspect I have but haven't tested yet.

Be sure to test the voltage at the fuel pump if you're running into this problem.

You could also have some air going through your sender/gauge. With the FRx, it might never make it to the injectors, simply passing through the rails and back through the FRx to the tank.

Anyways, since you guys are going "all in" to find and fix the problem, figured I'd throw in my suspects for your consideration

 

Baatzy, has there been any updates to your FP issues?

 

There has, life has been pretty hectic since Rich and I got together on Thursday. I am currently watching my food be carried across the restaurant, when I get done and get to my gate I will break it down into what we found.

Baatzy

 

We are looking forward to it, hope your flight was/will be good.

 

So we dove into it Thursday and after a long day we finally found the issues. The first was the FPR was not working correctly, allowing the truck to build up 80+ psi with the glow plugs off and truck running. We aren't sure what caused this yet. It may have just been a faulty/misplaced spring, but I didn't notice any issues with the spring location when we took it apart. I will have to look into this more, but for now I am back to the stock FPR instead of the FRx until I figure out what to do.

The second issue was with the standpipe deal in the middle of the fuel bowl. When I rebuilt the bowl I never lined up the window on the inner part of the tube with the window on the outer part of the tube. This caused my pressure drop I was experiencing. That's my own fault, I should have known better. However I looked back through the documentation of rebuilding the fuel bowl, and I haven't been able to find anywhere where it mentions lining those windows up, so kind of a two fault deal. To remedy this I plan on gutting the internals at some point in the future. I should have looked at the bowl first, as I had just rebuilt it. All in all, it was a stupid easy fix, but it gave us a run for our money at the beginning.

I really want to thank Rich for taking his afternoon to help me get this figured out. He dove right in and helped me chase the issue down. He made sure we got it figured out and were good to go even though it took us quite a bit longer than we both thought it would.

My flights have been going well. I spent last Friday at a job interview, and yesterday and today traveling and having another interview. Today's was in a salt mine under Lake Erie. Made me feel kinda guilty thinking about all the rust that stuff causes....



Thanks,

Baatzy

 

I have not done the FRx mod, but it seems that the spring needs to be dead on or there are problems. I remember another member installed it and was seeing 100 PSI.

As for the center post in the filter housing, I think that is only there to stop the fuel from getting to the engine without a filter installed. I have seen where some people remove it completely if I am not mistaken. In all of the pictures and threads I have read about rebuilding the fuel bowl I cannot remember one where it mentions the "windows" or ports in the stem.

I guess I would have lost my bet on that it was a faulty FP sensor. I am glad you guys got it figured out and it is not too costly of a fix.