Riddle me this. Can this diesel manually suck fuel through an electronic fuel pump when the fuel pump has no power to it? Mine idles rough whether hot or cold on every start until I gun it a few times (to about 2500 rpm), then it purrs like a new one. My guess is that it can. Haven't checked the power to it when it is running, but it (the fuel pump) doesn't make a sound when you first turn the key to the on position. Where do I start if the pump isn't getting power?

 

Have you converted the truck to e-fuel? The stock pump is mechanical.

This is the stock pump located on the top of the engine, in front of the turbo.

 

Right, but the fuel pump has two lines/hoses. One runs to the filter and the other to the opposite side of the filter by way of what I am calling the high pressure fuel pump and to the injectors. It's the hp pump that is not getting power to it and I am assuming is the pump that pressurizes the injectors prior to starting the truck. (when the key is in the on position).

 

Mechanical fuel pump is low pressure and high pressure pump, two stage. Fuel is sucked into the mechanical pump from the tanks and is pressured to about 5PSI. From the pump it goes into the fuel filter then back into the mechanical pump where it is pressurized to about 50 PSI then out to the heads.

 

The fuel pump in the picture is the only pump on the truck. There is no electric pump on an OBS Powerstroke. The HEUI Injectors make the pressure to inject the fuel. The Stock fuel pump shown in the picture above is a two stage pump that pressurizes the fuel up to about 70 PSI. The rest of the magic happens inside the injectors via an intensifier piston and a (mechanical) high pressure oil pump (HPOP). I think the device you're talking about on the side of the fuel bowl is the Fuel Pressure Regulator (FPR).

Let's see if I can get some pictures to help us clarify what we're dealing with:

This is the FPR (yours may look slightly different since this one is a picture of an early model off a 94 or 95)


Here is another picture of the FPR from a different angle:



Here is a diagram that shows the flow of fuel through the fuel system on the OBS PSD:


And here is a good description of how the fuel and HPO systems work if you care to read up on it:
Ask a Mechanic - A deep look at the 7.3L Power Stroke

Edit: You caught me napping, Jim!

 

Also, regardless of the fuel pump location, on the side of the FPR there should be a black plastic cap that you can remove to reveal a Schraeder valve (like a tire valve stem). With the truck at an idle, you should be able to use a cheap stick style tire gauge to check the fuel pressure (use some rags to shield the area too as it can spray fuel when you remove the gauge). You're looking for 60 PSI or more at idle. Below that and it is possible that you have a fuel pump or FPR issue. The FPR can be shimmed to increase the pressure, but if it is really low, you may need to replace the pump.

 

Hey Nate, The 1st 2 pictures are a 96-97 fuel canister. On the 94-95 the fuel filter restriction sensor was on the bottom rear portion of the canister.

 

Yeah you're right. For some reason I thought I saw the black plastic strainer on the bottom of the FPR like the early ones had. I'm not sure what I saw now...

 

This will definitely give me a place to start. I have no doubt that I can search out the problem here with the help of this schematic and repair it myself. Actually, just found the hoses on the pump are shot (ta-da). Greatly appreciated guys.

 

Depending no which hose it is that is shot, that could be your whole problem right there! If it is the suction side of the low pressure diaphragm of the pump it might be sucking air and not getting enough fuel.

You can buy those hoses pre-cut from dieselorings.com or your Ford dealer (Riffraff Diesel has them too) or you can go to the parts store and buy a foot of each size (5/16" and 3/8"). Just make sure if you go that route that it is SAE30R9 rated (some places call it "fuel injection") hose. The cheaper SAE30R7 stuff is not rated for the higher pressures used on the high pressure side of the pump. I think 30R9 is rated up to 100PSI or something.

 

Got it! I'll cut em and save some money. Got some serious tranny issues coming up I think. A few times when I've gunned it hard to level the idle (from the fuel pump issue), the overdrive light flashes. The tranny shifts real hard, especially when downshifting and it is so sporadic in power while driving that it almost feels like when a car isn't firing on all cylinders, then finally kicks in and takes off, only this is consistent. I'll look through some other posts for tranny's to see if I can find some answers. Unless you know about this too. Thanks again.

Scott

 

Great info Nate! and others, but those photos really help me... since i have the canister in the pics..

 

If you really want to do a nice job get yourself some fuel injection type hose clamps like are in that first picture I posted. They don't have the holes in them that a typical worm style hose clamp does so they can really be cranked down without cutting into the hose.

Yeah I am not going to be much help on the transmission issue I am afraid. I haven't had reason to work on mine much (knock on wood)... This "gunning the throttle" you're talking about, is this being done while you're driving? If it is in park or neutral, I don't have any idea what it could be. If it happening while you're driving, my guess is that the PCM is sensing a transmission slip and that is what is setting off the blinking OD light. That light serves the same function for the transmission as the CEL light does for the engine. If the OD button has been blinking the PCM has stored a code and a good tranny shop should be able to pull that code for you. My gut tells me it is a slipping code, but without that code, we're pretty much just guessing.

Get the transmission codes pulled, replace those hoses and i post the tranny codes up in a new thread. There are a lot of guys on here that know a lot more about the transmissions (and really the rest of the truck as well) than I do.

 

Well, it finally stopped starting altogether and it just so happened that it was a cold morning (read on). Since I was taking it in for the tranny anyway, I figured I'd let them fix my "fuel issue" too. Luckily, my tranny guy is honest and told me he sends his diesel work to a one man shop and "he's very good". Long story short, the guy said that only two of the GP's are "kind of working" and replacing them will take care of the problem. After reading threads of guys replacing GP's on their own, I am glad I am having it done under warranty. Even the idea of having to remove a head to get a stuck GP out sounds like torture to me. Should be running today/tomorrow and off to the tranny shop. I can't wait to get this truck back and just drive it for a while. Just something about a loud, powerful Ford diesel ya know?