Could this be the solution?

[Bart F-350]

dang! guys! you and this forum are sssoooooo ggoooooddd!
we have a saying here, "messen ist wissen" "meten is weten" or "measure is knowing" and again, that's king!

It will be more difficult if you don't have the right tools for the job, but.........

Anyway, I found how to measure the fuel pressure, and what do you think?
engine running stationary warm, 2,5-3 Psi.
When accelerating a bit the needle plummets to below 1 Psi.
hence the filter restrict light comes up every time running higher Rpm's, the IP is pulling fuel through the lift pump right?

 

[gnathv]

Now run a fuel line from the fuel pump inlet to a bucket of fuel and see what your fuel pressure is.

 

[Bart F-350]

Now run a fuel line from the fuel pump inlet to a bucket of fuel and see what your fuel pressure is.

Isn't that a bit difficult? the fuel going into a bucket instead of the IP? I think the test could be over quickly? if there is no motor to activate the fuel pump?

 

[Brian VT]

...fuel from a bucket into the fuel pump, rather than from your fuel tank.

 

[Bart F-350]

Ok, but what difference would that make? I.e. what goal you have in mind by doing so?

 

[Rdnck84_03]

To make sure there isn't a restriction in something before the pump causing it to not draw enough fuel.

James

 

[Bart F-350]

well I was busy typing such a thing... you overtook me

That will be for tomorrow when we have daylight again, and no rain I hope.

 

[Bart F-350]

Now run a fuel line from the fuel pump inlet to a bucket of fuel and see what your fuel pressure is.

When I read this I thought: undo the fuel line after the lift pump, and see how much diesel you get in the bucket in let's say one minute or so, thinking further, with no diesel to the IP the engine will not run and so on!

 

[Bart F-350]

well, I was reading through Dieselmanns pages, and I stumbled upon this, it's from his page, and when you mention where it comes from you are allowed to use it, so herby:


Fuel system
Next check for fuel delivery through the fuel filter. On 6.9 engines this is checked at the 3/16" hose barb on the fuel filter outlet elbow, and on 7.3 at the fuel filter orifice/return line fitting or restricted filter sensor port. If checking either at the filter return line fitting, plug the return hose. Fuel pressure here should be 1 psi minimum at idle. Lift pump pressure is taken at the fuel filter bleed schrader port and should be 2 psi minimum at idle. Fuel volume is taken at the same point and should be at least one pint in 30 seconds at idle. Inspect the fuel taken during the volume test for signs of water or contamination.
If the engine won't start, these specs may be lower as idle speed is 675 RPM and cranking speed will be less.



I think I see pressures indicated here, which I thought (with the general info that I knew of Fuel pressure at schrader valve 5 Psi?)While Dieselmann speaks about 2 or even 1 Psi.

I have a hard time to determine who to believe?
If I believe Dieselmann, pressurewise I have no problem on my truck. If I believe the general knowledge (5Psi)I do have a problem on my truck.

Yes, I should still measure the capacity test here described, as well as the pressures taken at the lift pump and fuel retour.
didn't do it as it rained the whole day yesterday.



__________________

 

[Cant Write]

Did you try the jug of diesel feeding the lift pump test yet?

 

[The_Josh_Bear]

well, I was reading through Dieselmanns pages, and I stumbled upon this, it's from his page, and when you mention where it comes from you are allowed to use it, so herby:


Fuel system
Next check for fuel delivery through the fuel filter. On 6.9 engines this is checked at the 3/16" hose barb on the fuel filter outlet elbow, and on 7.3 at the fuel filter orifice/return line fitting or restricted filter sensor port. If checking either at the filter return line fitting, plug the return hose. Fuel pressure here should be 1 psi minimum at idle. Lift pump pressure is taken at the fuel filter bleed schrader port and should be 2 psi minimum at idle. Fuel volume is taken at the same point and should be at least one pint in 30 seconds at idle. Inspect the fuel taken during the volume test for signs of water or contamination.
If the engine won't start, these specs may be lower as idle speed is 675 RPM and cranking speed will be less.



I think I see pressures indicated here, which I thought (with the general info that I knew of Fuel pressure at schrader valve 5 Psi?)While Dieselmann speaks about 2 or even 1 Psi.

I have a hard time to determine who to believe?
If I believe Dieselmann, pressurewise I have no problem on my truck. If I believe the general knowledge (5Psi)I do have a problem on my truck.

Yes, I should still measure the capacity test here described, as well as the pressures taken at the lift pump and fuel retour.
didn't do it as it rained the whole day yesterday.



__________________

5psi input is what these IP's are calibrated for, according to the guys that actually rebuild them, which I why we say 5psi.
1 psi is acceptable, but not ideal. You have a problem that you're pulling a vacuum at higher RPM's-- that's a problem. Whoever you believe, you still need pressure at 3000k rpms and you're not getting that. So you have a plugged up filter, weak lift pump, or other restriction, perhaps at the tank. Doing the bucket trick is a great way to narrow down the variables.

If you can get a gauge for that filter header that's great, the best spot is the vacuum switch port, 1/8" NPT. Probably not standard in France... But that's what it is. If you measure at the Schrader valve port you're measuring BEFORE the filter and won't have an accurate reading. Because what you need is AFTER the filter to know how much pressure is getting to the IP.

Even better if you can get that gauge out where you can see it while driving. Then you'll know all sorts of fun info while driving around.

 

[Bart F-350]

Nice from you all to help me so well.
No, I did not yet do the bucket test, we have really bad weather here now, and I'm working outside.
I did the test with the compound gage and used not the schrader valve port, but the one next to it where the brass valve thingie is in which also connects to the fuel retour line, (which isn't connected;the retour line that is)
I think I wil do this test with the compound meter also on the vacuum switch port, and do the 1 pint in 30 sec. test. as weather permits.
we'll see.

 

[Bart F-350]

Does anyone of you know if I still can get, and so where? the Airtex mechanical lift pump for these engines?
I was told these have less issues then the Carter ones.

 

[Bart F-350]

Image of filterhead; Am I right in assuming that Red and Green flash are BEFORE filter? and Violet flash is AFTER filter?
with my test I used the green connection, because I couldn't get the vacuum switch out without destroying it, didn't feel too much for doing that :-(

My test, as said on the green connection: warming up the engine on stationairy, had a pressure of 2,5 - 2.8 Psig light green flash on the image.

running the engine up to 3000 Rpm for two minutes, pressure dropped to -10 Inch/Hg vac.

Then released pedal, Rpm's back to stationary, pressure came up, but did not depass 2 Psig.

then weather declined and was too bad to continue.

 

[Cant Write]

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