Could this be the solution?

[Bart F-350]

The only one I know of would be where the nylon and steel lines coming from the tank go to the lift pump, and that I will be checking out soon as the weather clears.

 

[KansasIDI]

This might be way off base, but could you be collapsing a fuel supply hose at high rpm?

Yes. That little hose between the metal line and the lift pump loves to collapse. Idk if Bart replaced it or not though

 

[Bart F-350]

not yet, could you imagine, This whole story started in January 2023!
I know, a lot of things are happened since then, but imagine, in the end (If so) a bit of fuel hose preventing me getting my truck registered due to "impossible" to drive....

 

[Booyah45828]

Glad to see you're testing this. Since no one else answered it.

Red arrow is pre-filter
Green and violet arrows are post-filter

Shouldn't matter though, as unless the filter is plugged, the pressure should be the same on all 3.

As said by others, anything less then 4-5 psig is low and shows fuel starvation issues. Next step would be to route pump inlet into 5 gallon bucket and see how pressure reacts.

IDK if your ambulance has a selector valve, but that being stuck between tanks could also cause fuel starvation.

 

[Bart F-350]

It has, but I don't think it's stuck, because about two or three months ago I all cleaned very thoroughly, and I'm not using the midships tank for the moment,and he's still dry, so no return diesel there either.

 

[Bart F-350]

Shouldn't matter though, as unless the filter is plugged, the pressure should be the same on all 3.

Would be fun to test before and after the filter at the same time, helas I'm not equipped to do so, I can call myself lucky to have at least 1 (one) such a vacuum-gage to use! to measure the pressure drop over such (and eventually New) filter.

If I manage to "tee" in my gage before the lift pump, what could I expect to measure pulling from the tanks? anyone an Idea?

Oh, one more thing, the part of the ignition switch is difficult to turn, It keeps the starter turning, (I guess not used? ) what can I use to free this up? Kind of a spray?

 

[Booyah45828]

Ideally you want as little vacuum as possible. Ford manual specs no more then 6 in/hg vac pre lift pump. The fact that you had 10 in/hg post lift pump, tells me you'll have at least that pre-lift pump, unless the lift pump is the restriction.

 

[Booyah45828]

There's an actuator on the end of the cylinder that gets sticky with age. You'll have to remove the steering wheel and clean it and then regrease it with some light lube, like silicone spray. I typically see them broke, because guys won't fix it until it is broken and no longer moves.

xc_hide_links_from_guests_guests_error_hide_media

 

[SIKPUP]

I really need help with a weird no start

I have seen a couple act similar to this. One was a collapsing fuel line before the pump, the other was a restricted/blocked return back to the tank. Was caused by tank valve. That's what i was hoping the problem was. I ran a new line straight from a fuel jug to the filter head and I'm still...

www.oilburners.net

Did you replace the internal filter in the injection pump ?

Transfer Filter Screen 28986 for Most Stanadyne DB2 DB4 Pumps

Stanadyne Transfer Filter Screen 28986 replaces Stanadyne part number 28986. This only fits DB2 and DB4 Pumps ( and not all of them). Please see all Photos!

dieselitems.com

I'm not sure on this filter above , but thats what I'd try ?
I've had that one clogged from contamination !

 

[Bart F-350]

I really need help with a weird no start

I have seen a couple act similar to this. One was a collapsing fuel line before the pump, the other was a restricted/blocked return back to the tank. Was caused by tank valve. That's what i was hoping the problem was. I ran a new line straight from a fuel jug to the filter head and I'm still...

www.oilburners.net

Did you replace the internal filter in the injection pump ?

Transfer Filter Screen 28986 for Most Stanadyne DB2 DB4 Pumps

Stanadyne Transfer Filter Screen 28986 replaces Stanadyne part number 28986. This only fits DB2 and DB4 Pumps ( and not all of them). Please see all Photos!

dieselitems.com

I'm not sure on this filter above , but thats what I'd try ?
I've had that one clogged from contamination !

HHmmm, I'm not sure about that, could be? but would (if this one is contaminated) this pump still pull a vacuum at the filterhead? I'm not sure?

 

[Bart F-350]

There's an actuator on the end of the cylinder that gets sticky with age. You'll have to remove the steering wheel and clean it and then regrease it with some light lube, like silicone spray. I typically see them broke, because guys won't fix it until it is broken and no longer moves.

xc_hide_links_from_guests_guests_error_hide_media

would this be the same for lift or non lift colums?
I couldn't find that hole where he was poking in with that screwdriver?
mine is a non lifting column.

 

[Rdnck84_03]

You will just have to look around the molded part of the column where the lock cylinder slides in. It is around the bottom half somewhere.

Once you find it use an ice pick or similar tool to push on the pin while turning the key to the run position, once in the run position gently wiggle the lock cylinder while pulling out. It should slide rite out.

I would recommend unhooking the batteries before you start since the ignition will be on until you put the cylinder back in to turn it off.

James

 

[Bart F-350]

BTW, I found a video which very clearly explains the different functions from the fuel filter manifold, I hope it's ok if I link that here?
7.3 idi fuel filter manifold how it functions?

 

[Bart F-350]

Busy making some gadgets to measure some pressures and flow volumes.
all your fault, motivating me to see how everything is as close to spec's or not?
see if it works.

Btw, what makes the filter heater to start heating the fuel?

 

[Booyah45828]

Turning the key on gives them power, then as they heat up, they are supposed to be self regulating so as not to burn out. All of them that I've found have been unplugged, and most leak and have been removed, or smeared over with sealant.

In theory the heater was to melt wax and ice crystals that might be in the fuel, so that they don't plug up the filter. I'm not sure how well they worked in the real world even when new. It's better to use a fuel additive when it's cold out.