Still need halp

[Mark towery]

I’m still having trouble with my 2000 k3500 6.5.
Accelerates good but when I get to about 2500 rpms and start to back off it hiccups and jerks until I get back in it.
I have replaced lp, throttle sensor, pmd, ops, cleaned grounds, put clear hose on and no air bubbles. Also replaced hoses that run from pump to filter. 8# with lp and5# when running. Any advice welcome

 

[JayTheCPA]

Description looks like the PMD to me. Sometimes even new PMDs are bad.

If possible, locate a known working PMD and use that one to help isolate.

 

[Mark towery]

Ok. The old one was doing the exact same thing?

 

[jrsavoie]

Trying a known good PMD and resistor will narrow things down just a tiny.
It doesn't sound like a PMD issue to me. But you need to eliminate that possibility.

Have you been using the same resistor with each PMD?

 

[Mark towery]

Trying a known good PMD and resistor will narrow things down just a tiny.
It doesn't sound like a PMD issue to me. But you need to eliminate that possibility.

Have you been using the same resistor with each PMD?

I’m not sure what resister ?

 

[Mark towery]

I’m not sure what resister ?

Sorry. I put a new one in on this one

 

[dbrannon79]

Do you have the clear hose on the return of the IP? you might need to have a helper video it while you put the truck under a load, but it might be getting air and fish biting under a load

 

[Mark towery]

I do. What would cause that?

 

[dbrannon79]

getting air when under load means you have a leak in the fuel lines behind the LP going back to the tank. if your running the factory style LP, check the o-rings on the fittings. Now if you have a pressure gauge and see the system loose pressure below 0 under load. this may also be another issue

 

[Mark towery]

I’ll see if I can check those things

 

[Mark towery]

getting air when under load means you have a leak in the fuel lines behind the LP going back to the tank. if your running the factory style LP, check the o-rings on the fittings. Now if you have a pressure gauge and see the system loose pressure below 0 under load. this may also be another issue

Ok no bubbles in line at 1600 rpm. I hold 4 psi at 1600 rpm’s truck does idle a little rough though.

 

[ak diesel driver]

Is that under load?

 

[Mark towery]

That’s just setting in driveway idling. It up to 1600 rpm’s

 

[Mark towery]

Is that under load?

Excuse the ignorance but how would I do what yall are talking about.

 

[ak diesel driver]

You need to be able to see the gauge under load to truly see what the fuel pressure is. Temporarily tape a gauge to your wiper blade......

 

[Mark towery]

Ok

 

[jrsavoie]

Or install a permanent fuel pressure gauge

 

[dbrannon79]

You can get away with a light load by dropping it into gear, holding the brake and romping on the pedal so long as you don't run over anything. but again that will only put the engine under about a 30% load even at WOT.

have the pressure gauge on a long enough hose so that you can afix it to your wiper blade in such a way you can watch the pressure as you drive down the road. go find a steep hill and feed it the onions while keeping one eye on the gauge.

 

[Mark towery]

Ok unable to go for a drive BUT holding brake and mashing on it I have 4#
No bubbles in line UNTIL I kill it then there are air bubbles

 

[dbrannon79]

Ok unable to go for a drive BUT holding brake and mashing on it I have 4#
No bubbles in line UNTIL I kill it then there are air bubbles

Pictures or a video please.

seeing a single bubble is normal after shutting down the engine, but multiple, there is an issue.