How Much is Too Much?

2004 Dodge Dakota 4.7l v8
Quad cab 4x4

I'm not looking for repair advice, just questioning some specifications, so I figured this would be the appropriate section.

Double digit negative fuel trims on both banks under all conditions.

Fuel pressure checks at 60psi
Published spec. is 49 + or - 2.

Mechanical returnless system with fuel pump mounted regulator and filter.
Description and operation states that when pressure exceeds 50psi, fuel is returned to the tank via integrated regulator.

Swapped out the sending unit with a used one, 60 psi.

I feel like I was lead down the wrong path by the service info
I have noticed on many occasions pressure specifications not matching up with real world conditions, but it never tricked me so bad that I pulled a tank over it, lol.
I trust my gauge, it's not a cheap one by any stretch.

High fuel pressure is probably pretty low on the drivability problems list, but how much would be too much for the PCM to compensate for?
Obviously 10 psi over isn't an issue for this Dodge, so where do you plant the red flag?

Thanks for reading, as always, looking forward to discussion.

For reference, how negative are the double digits? 10, 20? I dunno if I'd sweat - 12, but certainly - 20 would be a problem.

Is this why the truck came to you?

My experience is that fuel pressure has to be off more than that to show strong fuel trim changes. So, if the trims are your problem, I might dig more into the MAP or an engine mechanical issue.

working on a 2004 grand cherokee 4.7 liter today! i have -19 and -23 on both banks. fuel pressure is bouncing between 60 and 65. p0303 p0304 p0300. checked engine vacuum it was 16 inches steady at brake booster. checked all injectors. (used injector balance tester) swapped coils/plugs. still missing on cylinder 3. coolant temo reads right. tps reads right. any more ideas??

Thanks for the quick reply
-11 to -14 ltft with negative corrections still being made in stft.
B2 was always at least -14 ltft, with b1 trending closer to -10.
It is a used car I was asked to go over before it goes up for sale with an engine light. p0300 was the code with a slightly perceptable miss at idle. Misfire counters heavier on b2 (where I discovered cyl. #2 injector flowing more fuel than the rest).
Baro is spot on for my location, so I moved away from the MAP, but will have a closer look when it comes back in for a radiator later this week.
After replacing the suspect injector and clearing the fuel adaptive, trims seem normal. Not sure why an injector on one bank would effect the trims on both banks though...

Maybe I should bounce this over to the repair questions section.

Jumped timing? 4.7 can't stand being in mechanical time. :lol: They do everything they can to skip.

cheryl hartkorn wrote: working on a 2004 grand cherokee 4.7 liter today! i have -19 and -23 on both banks. fuel pressure is bouncing between 60 and 65. p0303 p0304 p0300. checked engine vacuum it was 16 inches steady at brake booster. checked all injectors. (used injector balance tester) swapped coils/plugs. still missing on cylinder 3. coolant temo reads right. tps reads right. any more ideas??

Wow, I thought my pressure was high!
I would pull the tank, but you see where that got me, lol
Vacuum seems on the low side as well (at least steady though). How much of a PITA is it to verify timing on these?

kinda thinking that. does anyone have a known good cam/crank waveform??

Tyler wrote: Jumped timing? 4.7 can't stand being in mechanical time. :lol: They do everything they can to skip.

Truth! Seems like anything with a _.7 can't wait to bend valves.

checked iatn. couldnt find anything on there.

just a quick question. can do you remember the drop rate on the injectors? mine is starting at 52 down to 40-41. key on engine off.

cheryl hartkorn wrote: kinda thinking that. does anyone have a known good cam/crank waveform??

I can scope mine tomorrow if you like.

cheryl hartkorn wrote: just a quick question. can do you remember the drop rate on the injectors? mine is starting at 52 down to 40-41. key on engine off.

mine settled at 57 ish koeo and all dropped to 50 except for #2 which dropped to 46.

My all sun pulse tool has 3 settings, i was using setting 2.

yea i think im going to change the fuel filter/regulator. supposedly the regulator and filter are built in together bolted externally to the tank. should be quick and easy to get the fuel pressure closer to spec. looked on oreileys website looks like the dakota is different, which sucks

I just put a tank skid plate in an 04 Grand Cherokee today too.
Hope you don't work in the rust belt!
I lifted the Jeep and the tank stayed on the floor of the shop!
Trailer hitch adds a degree of difficulty...
But yeah, the Jeep filter isn't on the sending unit like the Dakota

cheryl hartkorn wrote: checked iatn. couldnt find anything on there.

How about one from an '05 Dakota? I'm assuming they're all the same. :silly:

members.iatn.net/file/view/?id=46462&detailed=1

Lemme know if that link doesn't work.

Before pulling the tank it might be an option to run the engine on a regulated, alternative fuel source like a fuel injector cleaner kit....

That way you'll know hoch much effect - if any - the higher pump pressure does have on the fuel trim and if it's worth to pull the pump.

Thank you Juergen!
That's an interesting idea, I don't have access to a tool like that though.
I have thought of maybe rigging an adjustable fuel pressure regulator inline with my gauge set to see how the trims are effected with pressure changes, but I don't know if that's a realistic idea...