Cheers everyone,

I am still having some issues with my 5,7 HEMI when running on petrol only (car also has a LPG system).
Getting a P0300 from time to time, but not consistent.
Together with that, I also have a problem with the fuel gauge dropping to "complete empty", giving the warning chime, then going back to the correct value again within a fraction of a second.
Now could it be that these two problems are related? Would a corroded/damaged connector at the fuel pump and thus the pump not pumping properly give a P0300 maybe?
Will have to inspect it, but it's so damn cold outside at the moment that I will have to wait for some warmer days.

Thanks for any help guys!

 

Low fuel pressure, (wonky pump) Should also give you a code for the system running lean..... What plugs are in it? If you have a scanner, what do fuel trims look like?

 

There are NGK copper plugs in it, the "normal" ones, about 15k miles "old".
Fuel trim looks good, BUT: when the engine starts hesitating the fuel trim goes up (Short Term on bank 1 goes up +20/+30 when it was wandering around like -5/+5 before).
Once engine is running normal again the trims are back to normal, too.

 

That's weird..... How old are the O2 sensors? Connectors clean, and look good? Something is causing the engine to think it is running excessively lean.... or, getting a lot more air than it really is.... So, MAP, or O2's?? What does MAP sensor do when the problem happens? Can you graph it?

 

I think I can rule that all out, as with the car running on LPG instead of petrol fuel it is running totally fine. The LPG also uses O2 and MAP information.
So it is down to fuel delivery and that led me to the thing with the fuel pump.
I recently checked all the wiring to the injectors and they were looking fine, but replaced the +12V supply wires as they were badly done by the installer of the LPG system.

It was snowing here today and it is still cold so will have to wait until I can check the fuel pump plug without freezing my fingers to death

 

I too have the issue where it randomly drops to empty and comes right back up.

 

Damn, so seems to be like a common problem?
I had no time checking it today, was busy with the rear leaf spring bushings. Once I have that sorted I will check for the wiring there.
I bet that there is corrosion or something, last time I pressure washed my truck and also cleaned between the cab and the bed, the issue was a lot more present, but went away after 2 days in the sun. So seems like moisture is getting somewhere?!

 

When I had my truck I noticed that the fuel guage wasn't always accurate. I just assumed it was the fuel sending unit.

 

Yeah, accuracy is always a thing with fuel gauges. Bot it is very unlikely that the fuel level drops to "zero" within a second and then gets back to half filled in a second again

 

Sometimes after gassing up it'll click up to the new level, other times it's a slow crawl up to the new level. All my dodge trucks have done that though.

I'd assume if it was a loose connection I'd experience a fuel deprivation misfire too but the issue seems isolated to the sending unit. Come back with an update if you ever figure it out.