7.3 idi stalling while on load

[Eds toy]

Hi there im new to the forum, I have a 1993 F350 idi that i purchased about 4 years ago with 112k miles on it. I installed a factory turbo system of another 7.3 idi right after i got the truck and it has been working beautiful for the past 3 1/2 years until around 8 months ago. The truck started to act a bit crazy the fuel filter light will come on and then the truck will stalls out and wont start again. I can let it sit for a few hours and i will start again but a mile down the road cuts off again. I have install 2 new fuel filters on it and it does the same thing. It has a new tank maybe a year old and that is the only tank I ever use, I dropped the tank twice already and its clean and I blew the lines around 10 times already with my air compressor and they are clear, the sending unit is clear and clean. The truck will sit at idle all day long and if I put it on jack stands and run it I can take it up to 80pmh steady with no problems at all. Now as soon as I put it back on the ground and take off not even a mile down the road will cut off again. Any ideas on what maybe causing it to do this??

Thanks for the help in advance

 

[chillman88]

Have you ever changed your lift pump? Could be going bad and not keeping up with demand.

 

[CBRF3]

might want to rig up a pressure gauge on the filter head fairly easily done if eliminate the return to filter line from the injector just under the filter ( i like to use a boost vacuum gauge cheap on ebay for like $15 ) and watch it as you load the engine this will tell you if you get a plugged filter or have a bad lift pump also these trucks fuel tanks often have the plastic piece break apart in tank and stop up the outlet tube inside the tank for your fuel feed from fuel tank to rest of fuel system or you got trash in the tank doing same thing.

I will say this also on rare occasion have seen air intrusion do this also get under load and it would suck hard and get enough air in the lines to bog the motor a bit second you let off it picks right back up and goes on its merry way till you stand in it again.

 

[Eds toy]

Hi there
NO i have never replaced the lift pump, tis truck was a county truck that i got at an auction that is why it had such low miles on it, im sure they service the truck on the regular but since ive had it i never did much to the motor besides the turbo system. I really dont drive it much I got it with 112k miles 4 years ago and it has 130k now. Im not much of a diesel mechanic but do this lift pumps go bad like that? meaning with such low miles on the truck? you would think with it being a diesel it would take around 200k to start breaking parts especially on this old bullet proof 7.3s

the tank is clean when I pull the filter is clean too..

 

[Vern]

A lot of fuel should come out of the filter while cranking if you remove the injection pump supply line. Have someone crank it for you while you watch it should really spurt out!

 

[Eds toy]

well i think im getting enough fuel because like i said before when is up on jack stands i can get it up to around 80mph and keep it running steady for a good 10 to 15 min with no problems at all. What doesnt make sense to me is when i put it back on the road (under load) it dies and cuts off not even 1/2 mile down the road. Is like its starving for fuel in my opinion once it has to actually work. hahaha

 

[CBRF3]

well i think im getting enough fuel because like i said before when is up on jack stands i can get it up to around 80mph and keep it running steady for a good 10 to 15 min with no problems at all. What doesnt make sense to me is when i put it back on the road (under load) it dies and cuts off not even 1/2 mile down the road. Is like its starving for fuel in my opinion once it has to actually work. hahaha

that means nothing there is no load when you load our setups the injection pump then increase the fuel delivery to try to hold that speed / rpm or accelerate we have almost a tractor governor system in ours not like most diesel trucks our injection pumps were used in alot of equipment / tractors and such hince why ours are a International harvester / navistar diesel motor not just a navistar look up a roosa master injection pump
https://www.asme.org/about-asme/eng...s/131-roosa-master-diesel-fuel-injection-pump

without a load the injection pump will not give it the fuel like it would going down the road or up a hill on jack stands free revving it to 80mph means absolutely nothing.

 

[CBRF3]

A lot of fuel should come out of the filter while cranking if you remove the injection pump supply line. Have someone crank it for you while you watch it should really spurt out!

well yes and no on that testing procedure the reason being running vs cranking on fuel flow is a big difference our lift pumps often pump well on low RPM but taper off as soon as the motor fires up if is failing also if are cranking it without starting it which I advise you to disconnect the run solenoid on the injection pump otherwise if it starts with your method will fill the injection pump full of air and this is not good for the injection pump doing the gauge setup as i advised before is the best option or can find a old bicycle air pump end and attach it to schrader valve on filter head and hook that to a low pressure gauge.

 

[Eds toy]

Any other suggestions before I go spend 6 to $700 on a lift pump? its just so odd to me that a truck that only has 130k miles on it would mess up that pump. Im just trying to be sure thats it before I go broke this Christmas.

 

[CBRF3]

Any other suggestions before I go spend 6 to $700 on a lift pump? its just so odd to me that a truck that only has 130k miles on it would mess up that pump. Im just trying to be sure thats it before I go broke this Christmas.

a lift pump is like $30 https://www.amazon.com/Carter-M6027...3490---2-685--7-1&vehicleName=1986+Ford+F-350 its 2 bolts and 2 fuel lines one fuel line is a hose clamp so where is this $600-$700 coming from man someone is really gouging you if that is the price you were quoted.

I want to point out usually if our motors got a bad injection pump theyre are a pain to start or once warm they refuse to start if it starts easily and quickly your injection pump is most likely not bad.

 

[frankenwrench]

Any other suggestions before I go spend 6 to $700 on a lift pump? its just so odd to me that a truck that only has 130k miles on it would mess up that pump. Im just trying to be sure thats it before I go broke this Christmas.

The lift pump is on the front bottom of the passenger side of the block. Depending on your area shouldn't be more than 50 bucks. Local parts store to me in tx charged me 35 for one. 700 bucks is more like the injection pump on top of the block price.

 

[frankenwrench]

@CBRF3 you beat me to it. Lol

 

[CBRF3]

@CBRF3 you beat me to it. Lol

sorry seen the price and was LIKE what the you know what I wanted to make sure a shop wasn't trying to get him lol our engines are very simple to work on a very simple design and meant for reliability / simplicity.

 

[chillman88]

Exactly, LIFT pump, not injection pump. You'd most likely have bigger problems if the injection pump was bad. Top center of the engine is the INJECTION pump. I was talking about the LIFT pump on the side of the block.

 

[Eds toy]

ok got you now I was a lil confused on the 2 pumps and looked up the wrong part. hope i dont ever have to replace the injection pump cus that would really hurt looking at the price they go for. Well imma get the LIFT PUMP and start with that, thanks to all of ya for the advice!!! I will post back the results