on my 97, about 2 months ago, i replaced the CAM sensor because it starting shutting off intermittently and that seemed to resolve the problem. Yesterday, drove it about 8 miles and it shut off. I went ahead and replaced the CAM sensor as it wouldn't recrank. 30 minutes for the changeout and it fired back up. Drive it 1 mile and it shut off again.

Decided to pull the fuel filter and change from the back tank to the front tank (both over 3/4 full). when i pulled the fuel filter, the bowl was only about 1/4 full...shouldn't it be at least 1/2 or more even with displacement? My dad was with me so i had him turn it over while i had filter removed to see if it'd fill up. Nothing...just an occasional bubble.....no fuel leaks anywhere in the valley or around the pump or under the truck.....so i replace the filter, let it sit 15 more mins, and it cranks right back up...goes 2 miles...shuts off again.

let it sit 15 more mins, cranks back up and drive it to it's destination a few miles away. Cranked up several more times that day with no issues.

each time, the eventual "turn off" was a gradual turn off where it seemed to be losing fuel pressure as well as power obviously until i'm guessing the fuel bowl ran just about dry.

fuel filter looks good and replaced this spring. less than 5K on it

any thoughts/suggestions besides replacing the fuel pump? any posssibilty the new CAM sensor is bad too? going to go ahead and replace the fuel filter as well just in case. Water separator didn't seem to have anything in it when i tried it first...very little came out

I need to make a 3 hr trip with a load with it next week and don't want to be sitting beside of the road waiting every 15 to 20 minutes for it to recrank to only go a couple of miles.

Thanks much for any suggestions -- you guys have been great in the past helping me!

 

only warning light i got was a fuel filter light came on twice on 2 out of the 4 cutoffs. It may have came on the other 2 but i didn't notice. No check engine lines or "water in fuel" light either

 

oh and CAM sensor is motorcraft part from ford dealer - had my experience with trying the others one out -

fluids all full -- oil less than 2K on it since last change - 190K miles

since it appears to happen when the truck gets "hot" (not overheating) - could i have a HPOP issue? maybe IPR or FPR? i've read on here that when the mechanical fuel pumps fail, they usually leak but this one isn't and the valley is dry

the only common theme i can figure out with my issue is it occurs after the truck has gotten hot and runs for 10 to 15 minutes and if you let it sit for 15 minutes, it will recrank. Replaced the CPS twice now and the issue still occurs intermittently. Sometimes, you can run it for an hour trip and it doesn't shut off though. thinking i should check the fuel pressure on idle at the fuel bowl? should be about 50psi?

if the trucks shuts off and the bowl won't fill/overfill upon turning motor, do i have a fuel pump issue, maybe a screen somewhere?, or does a certain sequence have to happen for the PCM to work with the CPS to make the fuel pump work with the cam?

thanks for any ideas/suggestions - my truck is over on an island in the outerbanks so i'd like to bring any possible solutions back with me as there are no parts stores where i'm going to work on it!

 

The first thing you need to do is check your fuel pressure. At idle, you should see 55-65 PSI at the fuel pressure regulator. You can use a standard sick style tire pressure gauge and check it at the shrader valve on the driver side of the fuel bowl. There is probably a black plastic cap on it now. Use a rag or something down in there as it may spray some fuel on you when you pull the gauge off. It sounds to me like you have a bad fuel pump or there is an issue with the fuel supply (fuel lines, tank selector valve, tank pickup, etc).

 

The fuel pump is mechanical. It just happens to be driven by an extra lobe on the camshaft. There's no electronic/electrical control to it; when the engine is turning, the pump should work. The CPS has nothing to do with fuel pressure. The PCM only uses the CPS to determine injection timing, and to feed the tachometer.

 

Thanks guys - so my logic is correct that when i get a "no start" and i have the fuel filter pulled and i'm looking inside the fuel bowl, if my dad is turning the motor that i should see that bowl filling up?

couple of follow-up questions:

do these mechanical fuel pumps sometime fail intermittently like this?

is there any nice thread or pics on how to change the fuel pump on the 97?

any special tools, words of advice, etc when changing it out in a remote location? will have to bring everything with me so want to be prepared

thanks!

 

Yes, your logic is correct. The bowl should fill while you're cranking.

Put the filter back in and check the fuel pressure with a stick style gauge. If the engine won't start you should still see about 20 PSI cranking. If it will start and idle, you should see about 50-65 PSI at idle. This is a simple test to help you determine whether you're on the right path or not.

Have you tried this on both tanks? Are they both over half full? If not a 5 gallon can of diesel in one of the tanks is an easy thing to try. Some guys have had the pickup tubes crack or the shower head comes off the end of them and they won't pick up fuel toward the bottom of the tank.

Be forewarned, changing the pump is probably a 3-4 hour job if you're handy with a wrench. The pump isn't easy to reach. You'll need a 1 1/4" combination wrench for the banjo bolt too. Aside from that, you will need basic tools and a metric socket set (12 or 13mm and a long extension) to remove the pump and fuel filter housing. Removing the filter bowl isn't absolutely necessary but loosening it will make it easier to get the hoses started onto the pump.

If you want to do the smart thing, replace the hoses and clamps while you're in there.

This is a pretty good writeup that shows the hoses and has pictures of everything.
https://www.ford-trucks.com/forums/8...-write-up.html

What he doesn't detail is replacing the pump itself. To do that you need to remove the banjo bolt in the back of the pump (that's where you need the big wrench) and it is a pain. Then pull the two bolts that hold the pump down and turn the negine over until the pump rises up off the engine a little. That will ensure that the tappet doesn't fall out of the pump and down into the engine when you pull the pump. Then pull the pump straight out the top of the engine, and reinstall the new one.

 

Thanks! I have tried it on both tanks and both tanks are over 3/4 full. Each time i pull the filter, the bowl is only about 1/4 full. Reading more, it looks like i should have about half a bowl of fuel with the filter out.

Thanks for the warning and info. The banjo bolt sounds tough. I think i can manage the rest hopefully.

When you mention removing the banjo bolt and other 2 bolts holding the pump down, then have someone turn the motor so the pump rises....how many cranks/turns of the motor does it usually take for the pump to rise a little? I'm scared of that tappet falling off and want to make sure i do it right since i'm doing this myself. It really sounds like it's the pump to me even though it's not leaking/weeping anywhere in the valley. Pump is only about a year and a half old and looks like the lines were replaced then as they look new.

 

At most, you'll have to turn the motor no more than two turns (two turns of the crank = 1 turn of the cam). The banjo bolt is tucked up under the web of the turbo pedestal; some fellas have bent the end of a box-end wrench just to fit it in there.

But if the pump is that new, I'd def. check the pressure at the schrader valve first.

 

^^ Agreed. Check the pressure first as this is a lot of work to go through if this isn't the issue.

Does the gauge change between the tanks? Ie. are you sure the valve is switching and isn't stuck in between tanks?

You want to turn the engine over by hand to push the pump up off its seat. You can do so with a socket on the crank pulley (harmonic balancer) bolt.

 

The fuel gauge does change in between tanks - the front tank is just at the full line and the back tank is about 3/4 full.

If I check the Schrader valve and don't get 20 psi on cranking or the 50-60 psi range upon idle, does that tell me I have a fuel pump issue?

Agree that I want to do the simple test first and if that tells me I have a fuel pump issue, then i'll change it. Going back to the island on Sunday to work on it again.

If I get a no-start however and do have 20 psi on cranking, what does that tell me? fuel supply issue somewhere? see no leaks anywhere and the switch seems to work between tanks -- maybe a suction issue?

also never tried to turn the motor manually, have replaced the serpentine before - what size socket does it take to turn that? i'm guessing it's not easy to turn either? thanks much guys

 

If you get 20 PSI cranking then I would wager to say that your issue is not a fuel supply issue at all, but something else. If, on the other hand you don't get 20 PSI cranking, then the troublesome thing is that you won't know for sure whether you have a dead pump or a blockage in the lines somewhere else. I suppose if you wanted to go "loaded for bear" you could take a section of 3/8 fuel line with you and a can of diesel. With those supplies you can do a couple of things.

One is that if needed, you can disconnect the selector valve and run the suction line into the can of fuel. That will eliminate the possibility that the lines are clogged somewhere between the valve and the tank, or that the valve itself is bad.

The other thing you can do is to test the theory that the fuel pump is bad by filling the fuel bowl about half way and then closing it back up and trying it. The pump is a 2 stage pump with a low pressure diaphragm side and a high pressure piston side. The low pressure side pulls the fuel from the tanks and pushes it through the filter, then the fuel returns to the pump and goes through the high pressure side where it is pumped to the fuel galleries in the heads. If the bowl is running empty as a result of a failed pump, the low pressure side is likely to blame. If that's the case, filling the bowl with fuel, closing it up, and trying to crank it should net you with either a (briefly) running truck, or at least 20PSI cranking pressure.

If someone else doesn't chime in with the crank bolt size I will go crawl under my truck tomorrow and get the size for you. I want to say it's around 22mm but it's been a while and my memory may be off a millimeter or two, lol.

If you're going "to the island" to work on the truck, I don't want to leave you guessing and unprepared. Where exactly is this truck, lol?

 

On a 99 7.3, you have to have 40 or better to crank

 

That would be the case with a SD truck with an electric fuel pump. Since the OBS has a mechanical fuel pump it doesn't make very good pressure unless the engine is running. Just cranking, it doesn't spin fast enough to make full pressure.

 

OK guys, will the fuel bowl actually fill up cranking with the filter out? I thought the fuel filter needed to contact a pin in the bottom of the bowl to allow fuel to enter, don't know really but read that somewhere. Maybe I'm out in left field.

To the OP you indicated when draining the water almost nothing came out. To me that indicates a clogged drain hose or fuel bowl because turning that valve on should drain the entire filter canister.

What style fuel filter did you put on, the one with attached lid or the older style where filter is separate and lid is separate?

You indicated this does not occur unless the truck is HOT + 10 - 15 minutes. Define HOT, fully up to temperature or what?