Dodge guy NEEDs Help with a 01 7.3,

[mattpopp]

I am not even sure where to start on this truck. As I only know what my brother in law has told me about and the 4 hours I spent on it last night trying to get it to run. First off its a 2001 7.3 with about 40,000 miles on it. The truck is mint accept it has a Veggy Oil kit on it. Not a fan of those after seeing how dirty the fuel system can get.

Last week he had a issue with the truck losing power when running on Diesel. So he changed the fuel filter and everything was fine. Yesterday he had a issue with it lossing power again running on Diesel going to work. ON his way home he started it on Diesel and then switched to Veggy Oil after it was up to temp. Before he gets home he has to switch back to Diesel to get the Veggy Oil out of the system. After he switched to Diesel the truck started to lose power again with in a Minute and then died. He had to get a buddy to drag him home.

Now here is where I need to describe the Fuel system as it has changed due to the Veggy Oil kit. It has a soleniod valve kit under the hood for switching, Diesel or Oil. They removed the lift pump from under the truck. and mounted it after the Valve Pack. So now the Lift pump does not push diesel to the stock fuel filter but sucks it threw the filter. The diesel fuel route from the fuel tank runs to the filter, then to the Valve pack and to the Lift Pump. I pulled off the soleniods to clean them and free them up a bit. They where some what dirty. I pulled some of the lines off to see if they where blocked. I notice that the line coming from the Fuel Filter felt blocked. I could not suck or blow threw it. This I believed to be the issue. I pull the filter out and that black tube run up along with the heating element out of it. It seemed that that spring loaded valve inside was stuck. Heres something I need yall to describe to me. When you pull the filter lid off that valve should shut to keep fuel from draining back, correct?. Then when you put the lid back on the tit sticking down form the lid should open that valve to let fuel in when there is a demand for it, correct?

With the fuel filter back together and if you try to suck fuel through the line if almost feels like I am sucking air but if you try really hard you will get a mouth full of diesel (taste great), so I am torn between, is it sucking air from some place, is something jacked up inside of the filter housing or is it a bad lift pump.


The truck wants to start but there is no fuel there to get it going, If by chance there is enough fuel it has that loud knock but I can only imagine that is it straving for fuel.

Another thing I did bypass the valve pack all together and run the fuel line from the filter to the Lift Pump to see if that made a difference. Nope.

Anyhelp would be great guys. If any of you know a good 7.3 PSD mechanic in the Humble Tx. area this would be very helpful. Please no Ford acronyms, you will lose past PSD.

[Justin M]

i would say its a bad pump. We have a few SD powerstrokes at work and they all lost power, like you said, and we changed the pump and it was back to normal.

[MrJohnWayne]

I'm gonna have to say the fuel pump is going weak. We all should know that pumps are designed to push fuel not pull it. If it has to pull fuel through all that line it has probably gone weak.

you are correct about the filter opening and closing the valve in that tube though.

you can rig up a pressure gauge to the drain valve on the back of the filter housing to test fuel pressure.

[mattpopp]

Originally Posted by MrJohnWayne

I'm gonna have to say the fuel pump is going weak. We all should know that pumps are designed to push fuel not pull it. If it has to pull fuel through all that line it has probably gone weak.

you are correct about the filter opening and closing the valve in that tube though.

you can rig up a pressure gauge to the drain valve on the back of the filter housing to test fuel pressure.

I don't like the Sucking effect as it is set up either.

I tried all sorts of stuff yesterday with the fuel pump. at the best it would just spit fuel out, maybe enough to run a single cylinder 5hp diesel engine. You could hold your finger over the OUT side of the pump and you could feel it build a very small amount of pressure, all air though.

[Justin M]

that pump is shot. Is it the stock fuel pump on the truck , just relocated

[mattpopp]

Originally Posted by Justin M

that pump is shot. Is it the stock fuel pump on the truck , just relocated

Yes sir, he said it was from under the truck and they relocated it.

I was not sure if yalls Lift Pump was like a Dodge where it was in the fuel tank or not. But I guess its on the frame rail, or was in this trucks case.

[MrJohnWayne]

7.3's don't use a "lift" pump. that one pump is it. provides all the pressure for the fuel system.

if you can hold your finger over the outlet and it not blow it off or atleast squirt out I would say it is not building enough pressure. 7.3's operate at 50-55 psi stock...

[mattpopp]

Originally Posted by MrJohnWayne

7.3's don't use a "lift" pump. that one pump is it. provides all the pressure for the fuel system.

if you can hold your finger over the outlet and it not blow it off or atleast squirt out I would say it is not building enough pressure. 7.3's operate at 50-55 psi stock...

If the pump was good and was not able to pull a prime or was taking in air due to a bad line or seal somewheres. Can that pump, pump enough air to push your finger off of the pressure out port of it.

[MrJohnWayne]

I doubt it would build any type of significant air pressure. Whereabouts around humble are you? If you have time this afternoon or tomorrow I can run out there and give you a hand. I have an old pump that we can use to test the fuel system. It is weak as well but would still run my truck expect at high rpm..

Plus I have auto enginuity that we can plug into it to see if there are any other problems.

[mattpopp]

It was not the pump. I just got a call from him and he put a new pump on and still the same issue.

Well we are going to play with it some more this afternoon and go from there.