Some questions on the fuel system layout for a '97 F-350 PSD that lost power and now won't start... I apologize for the length, but I want to make sure I've identified the right pieces before I go tinkering.

I accidentally ran the rear tank dry, ran about 150 miles on front tank, filled both tanks, ran about 100 on rear tank, then power just disappeared and engine ran rough- like a gasser with a bad miss. Immediately switched to front tank (full), no change. Limped home, now won't start. I changed the fuel filter, no change. After changing filter, had an obvious fuel leak dripping off the back of the engine until I really tightened down the fuel filter cap- that seems to have stopped the leak. No unusual gage readings, tach seems right (ie, CPS probably OK).

Ken suggested fuel pump, Matt Rajewski suggested checking the fuel pressure regulator screen. I've found the pump, pressure regulator body, and pressure test port. Now here's where I need some additional help:

**Matt said the pressure regulator screen is on the inside of the fuel bowl, high and right. I assume he meant "right" when standing in front and looking towards the rear. High on the "vehicle left" inside the fuel filter bowl is a port which appears to go into the pressure regulator body. This seems to fit the description. Is that what I'm looking for?

**Does the pressure test port on the fuel regulator directly indicate the fuel pump output pressure? Or is there a screen between the pump and test port that could be clogged and result in a low reading even though the pump itself is fine?

**What pressure should I expect when cranking without a start, say 300 rpm? (if it won't start, "40 psi at idle" doesn't help!)

**Any other typical, obvious signs of a bad fuel pump?

**Is there something in the tank selector valve I should be checking?

**Another suggestion I got is to put some low-pressure air into the engine compartment end of the fuel supply line to "backflush" the supply line and tank pickup screens. Does this sound reasonable?

**Fuel Routing. I'm looking at my Haynes manual and comparing to what I've seen in the engine compartment. Does the following description sound right:
1) Tank selector valve is somewhere under the truck. I'm assuming that the lines from tanks and to engine are obvious.
2) Feed line from selector valve goes to top of fuel pump, entering front-left-top of pump.
3) From front-right-top of pump to upper rear of fuel filter body. I'm guessing there's a port in the body here.
4) The outside of the fuel filter element is pressurized but unfiltered. Fuel flows from the outside to the inside of the element.
5) Filtered fuel comes out of lower rear of fuel filter body, to bottom-front of fuel pump body.
6) Fuel exits bottom rear of pump body through banjo bolt, through tubes to inside rear of cylinder heads, & eventually the injectors.
7) The fuel pressure regulator releases unfiltered fuel from the fuel filter body. Released fuel exits from top rear of regulator, goes through short little rubber hose to metal fuel line, then back to tanks.
8) Here's something that stumps me- there are two hoses connecting the front inside of each cylinder head with the top front of the pressure regulator body. What are they? Return to regulator? Additional pressurized feed to the injectors? Something else?

A source for a much better service manual than Haynes (factory?) would be a great help for the future.

Thanks for any help!

 

Yes its on the drivers side up high in the bowl. It feeds the regulator body assembly.

Yes it does tell you what the high pressure side is doing. There are no screens or anything. That much crap shouldn't have got through your filters anyway.

Well I don't know exact numbers on this one but anything over 20 would be good in my book. That's what mine fires on when cranking.

Well you can nail two with one stone here. If you blow air back through the lines, you will be able to have someone listen to which tank your selected and see if they can hear air coming out. As long as that's happening most likely its okay. Oh and blowing air back is fine to do.


As far as the fuel system, well that sounds about right. If I were you I would check and see if you have any fuel pressure at all. If not I would go with a fuel pump. That little black piece of plastic that runs down the middle of your filter is where most of the fuel for your second pump comes from, It has a one way valve in it so the pressurized fuel from the bowl can go into it. Also some fuel gets recirculated by the regulator and that fuel runs out of the regulator in a metal line and connects down on the bottom of the bowl. The two lines that run into it are returns from the heads, and they both run into the regulator and that's how it maintains pressure.

 

Thanks for the additional info, Matt. Multi-stage pump with the filter between stages, recirculation back to the regulator- not a system to play with at random.

I pulled the filter cover & filter, and took some Q-tips to the regulator port. Got out some black gunk, and a couple of small shiny metal particles, about the size of small sand grains. Used both end of 4 Q-tips before the Q-tip came out clean.

Bad news is no effect- still can't start it. Got some white smoke the first time I tried cranking, then little or nothing. Not even getting a sputter out of the engine, so I'm leaning towards a "lack of fuel" diagnosis.

A buddy may have a fuel pressure gage I can use this weekend, and I'll try to get someone to listen when I blow back through the lines. I think I'm going to check prices on a new pump on Friday; if they're not too expensive I'll order one before I check pressure and lines. Pump looks about the same age as the rest of the stuff on top of the engine, so it's got some miles on it. If it turns out good, having a replacement on hand might not be a bad idea. Should probably get a serpentine belt as well.

This will teach me NOT to push the tank range!

 

Paddler,

Well I don't really see why the pump went bad just because you ran it dry. Possible that the lack of fuel in the secondary part of the pump might have caused some damage, its a piston type pump. The first part of the pump is a diapram lift pump, I don't see how lack of fuel would hurt it. Maybe some junk got in there and tore it up, hard to say. Make sure you try and check pressure first though before you buy one.

All your symptoms do point towards the fuel though. Anyway good luck.

 

I've replaced the fuel filter, cleaned out the pressure regulator intake screen, and blown out the fuel return line with compressed air. Actually blew some fuel out the filler pipe when I took the cap off.

With the block heater plugged in for about an hour, 65 degree air temps, and good charge in the batteries, still would not start. Seemed like it was on the verge of starting. I think I got SOME combustion- just enough to push the cranking rpms to 500 or so (300 seems usual). Fuel pressure gage on the test port on the regulator bounced between 30 and 50 psi on cranking. Decent cloud of white smoke from the tailpipe- larger than the black cloud I would get on a normal start, but not "enough to fill the parking lot" like someone else had. Also have a thin stream of white smoke continuing to waft out of the tailpipe for quite a while after I stopped cranking.

Tach readings match what the engine speed sounds like. I see the voltage drop when the glow plug relay kicks in, and the "wait to start" light works as expected. Air filter is new.

I was not able to get the tank-to-pump feed line off the pump to blow that out- but 30 to 50 psi at the test port suggests that I no longer have a fuel feed problem.

I'm stumped. Seems to have fuel, enough juice to crank to starting rpms, and warm enough that glow plugs shouldn't be an issue (even though I have no reason to suspect them) Time to tow the beast to the shop and let them handle it.

 

Check your injector control pressure (i.e. I.C.P.) you will have to have around 500 psi before the engine will start. You will have to get a scan tool with monitor capabilities to check this. Ive seen the I.C.P. stick open and cause the problem your having. I have also shot either into a cranking engine(glow plugs unhooked) and shocked the I.C.P. back into operation.

 

Paddler,

I agree with you about the fuel situation, seems to be working with 30 to 50 psi at crank.

I agree with z1express here about the icp, and ipr. Both of these dealing with your hp oil system, which has to be up to par to properly fire the injectors. Try unplugging the icp (drivers side top of the head three wires coming out of it) and see if it will run. Check the ipr also, its oring could have gone south.

Good luck

 

z1express , jdboy9, thanks for the input. Unfortunately, its over my mechanical head. I'm working outside, don't have a scan tool, or the technical literature to do anything with the output.

Got a shop appointment on Tuesday, and a tow arranged for the morning. I'm leaving Friday afternoon for a week of whitewater kayaking in West Virginia. Shuttle duty (carrying boats and paddlers to/from the put-in and take-out over "alleged" roads) is one of the reasons I got it, so it would be nice if the techs could fix it. Long bed, crew cab, and racks on the cab fills the bill nicely.

I'll post the diagnosis when the techs have it running again.

 

Paddler check e-bay for CD form manuals. they are about 10-15$

 

Finally towed the beast to a Ford shop about a mile down the road. Road is a strip-malled section of US 1, so I paid rather than tow-strap it behind my neighbor's truck. Interesting question- how does 6800 lbs stop with no brake assist? I didn't want to find out!

Shop said injector driver control module and cam position sensor and transducer. About $950 for the driver module, $165 for the CPS & transducer, $1,690 total out the door. Ouch!

Curiously, absolutely no problem in the fuel feed / pressure system. Running a tank dry about 250 miles prior was simply coincidental.

Didn't have time to do more than drive it home tonight, but it fired right up and sounded perfect. Probably will drive to and from the train tomorrow, because I'm taking it to Canaan Valley WV for a week of whitewater kayaking. 3 hours of highway, then a week of back roads (or reputed roads!)- don't want to be broke down in the boonies!

 

Paddler,

Good to hear you got it running. The symptoms these trucks show can usually turn out to be a different problem each time. That's why I have a scanner because I start with that and if I can't find anything wrong then I go to the easy stuff first and work till I find the problem. Sometimes it can be difficult, as we saw in this case.