Dakotas: Return vs Returnless fuel systems

Hey Terry

Does your 92 have a fuel pressure regulator on the fuel rails and two lines or no regulator and one line?


Regulator on the rails and two lines.
Why for you want to know? :slight_smile:

Thanks Terry

2000 Ram and the 1994 Dakota doesn’t. I looked at the timing adjustment video and it look’s like Chris’s '92 and mine does . Just wondering if one system does better or if you can even tell a difference. I think you and Wayne have run both types.


Hey Marvin and Terry ,

I have had 9 dodges 92-95 and seems they were all like Chris’s truck with the single fuel rail.

Wayne, Terry

Just trying to figure out the difference between these two (or possibly more) setups.

The first picture shows the 1992 Dakota regulator in the middle. The two lines are hard to see but go down over the transmission and it has a fuel filter on the frame rail. Automatic truck.

The second picture shows a 1994 Dakota’s fuel rail with a single line. The regulator/filter is suppose to be on the fuel tank. Have not seen it yet. 5 speed truck.

About 1:17 into the construction video on timing you can see the regulator I think but can’t see the lines good. Maybe Chris could check for us.

Not sure if it would make any difference on wood/hybrid driving or not.


Hello Marvin ,

I have a 92 here in the yard . Will take a picture and post in the morning . I almost positive it is the same as your second picture .


My truck looks like your first picture. Appears to be a regulator with two lines. Photo attached, but yours is exactly the same in better light.

I was under the impression that all these Dakotas were single returnless fuel lines.

EDIT: OK, from what I’m reading the 92-93 trucks had return systems, and 94+ went to returnless lines. Very interesting!

I’ve always thought just from how it operates that the Dakota will “stay put” as I turn down the pump for a while… then it loses pressure real quick. Now it makes a lot more sense!

Thanks Wayne,

I was just saying on the hangout last night that I wondered if the Dodge computers could handle the fuel side of things better than Ford or Chevys since the Dodge regulators kept a constant pressure and the others changed with vacuum. It seems like the Dodges would have to have a wider adjustment range through the computer. Makes me wonder why they swapped.


Couple links to what I’m reading…

'94 Dakota: Returnless to return fuel system conversion


This from here: http://www.dakota-durango.com/forum/showpost.php?p=2947828&postcount=57

“The year of the motor matters because the fuel rails on the motor also differ, depending on whether it’s a return-type or return-less type. Return-type has the fuel pressure regulator on the rail, the returnless has it in the tank module. Another thing is the fuel lines themselves. This is sort of obvious but return-less systems have only one line, while return-type have two. While it might work OK, your ’88’s TBI return-type fuel lines aren’t really designed for the additional fuel pressure of the EFI return-type. I believe the older lines are also 5/16’s versus 3/8’s for the EFI (I might be a little off on this).”

Thanks Chris

I tried looking at the construction videos with the bed off but couldn’t tell anything for sure. I would think a returnless system would have two lines (one being a vent to the charcoal canister) and a return system would have three.


Moved to new thread. I think the charcoal canister is off of the air breather? But I could be wrong. It can’t be connected to the fuel system under pressure, there’s no reason to vent it. There should also be a line from the gas tank to the canister.

Good reading on the why’s of this change to returnless fuel systems: http://www.underhoodservice.com/Article/46468/point_of_no_return_returnless_fuel_injection_systems.aspx

Chris do know if this is what you are looking for but on the GM the TBI fuel pressure is 35 psi and on the EFI it is 65 psi . Don’t know about the dodge fuel psi. But it mite be the same as the GM


From what I’ve read 43.5 psi on the returnless systems, Not sure on the other.


That’s what I was meaning. Both should have an extra line running to the tank. probly hard black plastic, not under pressure.

This quote from the article you linked to might explain why they swapped over since the Dakotas don’t have a mass air flow system.

"Actually, there are two different types of returnless EFI systems in use: mechanical and electronic. In the mechanical systems, a mechanical regulator is mounted on the fuel pump module to provide a more or less constant fuel pressure to the engine. This type of setup works well with a speed-density EFI system that uses throttle position, intake manifold pressure and engine rpm to determine engine load rather than an airflow sensor. "


I think they basically wanted to quit heating up the fuel by pumping it to the engine. So they put the whole system under regulated pressure… which would make for a very long critical vacuum line to control the regulator. So you have two choices - control the fuel pump electronically (PWM) or just deal with a constant output. Dodge chose the latter. Many others chose the PWM - even Dodge in later years.

I would be interested to see the difference in turning down the pump pressure on a 92 vs a 94. What exactly does the pressure curve look like?

I might be tempted to play with the vacuum line to my regulator. If I can increase vacuum (less fuel) at higher RPMs I may get better hybrid driving. Only an option on 92-93 trucks though.

Steve, here’s a good reference on fuel pressures: http://jameshalderman.com/links/book_adv_eng_perf_5/s_and_c/Fuel_Pressure_Specifications.pdf

Rest PSI
Reg. PSI
Deadhead PSI

3.9L, 5.2L
31 approx.
39-41 approx

3.9L, 5.2L, 8.0L

45 min.

3.9L, 5.2L, 8.0L
54 min.

My RAM is a 97 it has a single line.
The timing seemed to be the same.
It backfired lots! I’m thinking I was probably advancing to far, like I was initially with the Dakota.

I stand corrected on the above statement about the 92 -95 being the same.

Pic 1 and 2 are a 92 and 93 , 318 . Appears to be the same with a return fuel line.

Pic 3 and 4 are a 94 and 95 , 318 Appears to be the same with NO return fuel line .

Pic 5 is a 95 , V-10 Can’t see from the picture but I think it has NO return fuel line .

Well I have read this all including the put up links.
I lived through this Chysler/Dodge/Jeep two line Return type, to single line Returnless types transition phase.
I can tell you what they were telling us in the factory training classes.

“We’ve found that the long fuel chains being top of engine heated then squeezed past the hot top of engine pressure regulator metal slit is breaking down leading to DEPOSITS building up at the fuel injectors.” " Injector deposites lead to poor spray patters and shut off fuel dribbling" “Single line returnless helps much with mandated stable 80,000 miles emissions compliance.”

That was the official fed out line.
Candidly at coffee breaks the Auburn Hills trained insructors, also humans, engine lovers, and most weekend hot-rodders would say:
Less parts means more profits.
Less parts means less to go wrong. Less warrantee issues.

And they did not see going returnless as a bad thing.
On service work, I did see less top of engine fuel “problems” like after Intake R&R’s, after service fuel leaks. Sucker IS right above the ignition distributor!
Returnless then never ever did have a metal diaphragm in a fuel pressure regulator hairline crack and have the fuel milage and emissions go to hell with ungoverned fuel going into the intake via the vacuum control line. Any top of engine fuel pressure regulator system becomes a Must-Do physical check with performance issues to vacuum control line pull and check for gasoline fuel. ANY seen. Bad fuel persure regulator. Just like the “oil leaking out the wires on my oil pressure sender” Blown diaphragm - REPLACE IT OUT.

I never once saw a Chrysler/Dodoge/Jeep with an engine vacumn line going back to the returnless systems in the tank fuel pressure regulator. DID see some in-the tank fuel pump modual pressure regulators go bad. Stuck open regulator would bleed off supposed to be held system fuel pressure leading to extended cranking starting up.
At the dealerships the WHOLE fuel pump module assembly was replaced. A New regulator/pump/plastic coiled fuel inner lines/inner wiring&connectors/sock pick-up filter/fuel level sender ALL renewed every time. Less time. Less liability. Less come-backs for “IT was-just-in-serviced! now it . . .!!” In the independent shops each of these were replaced individually. NO extra pay for the extra module disassembly/reassembly work and tech’s personal liability sweating. Sweat the internal module details like old hardened disturbed plastic coil lines and wiring insulations or that no-charge, do-over, come-back tank dropping was all out of your own pocket including the vehicle tow-back.

Back to woodgasifng effects.
Use what you got.
Both returned types and return-less types are initially engineered to have pumping over capacity. This was to compensate for variable out in the world conditions. This was to compensate for inevitable pump motor and the actual pumping pieces wear.
Having a pressure regulator with a vacuum control type than by all means you can play with this line to reduce the pressure/volume of to the injector gasoline delivery. How much?? Donno’ - maybe 20-30%.
Remember it takes MORE to the regulator CONTINUOUS vacumn suppied to reduce this gasoline fuel delivery. This system was suppose to help enlean at part trottle cruise for fuel stretching. Help enrich at floored mashed trottle high engine loads for more power. Fuel system Pressure bases were to follow the actual intake vacumn.
Retunless they learned they could do all of this with software, higher flow capable, yet better low flow spray patterning injectors. All what they need anyhow to be able to certify for E-10 up to E85 alchol bended fuels. It was Chrysler/Dodge FIRST onto this years before Ford “Green Leaf” and GM “flex-Fuel”. Not altruism here. Money. They were able to then tap into Clinton/EPA era “clean fuels” money, and earlier g.H.Bush/DOE ‘Amercan Energy Independence’ per vehicle manufactured credits.
For an “alternate” not so engine effected vacuum source you could add a tap into the vacumn brake booster. Or add in a FORD #10 soupcan vacumn reservoir.

SAFER TO PLAY WITH THE UNDER HOOD VACUUM LINE THAN ANY HIGH PRESSURE FUEL LINES trying to valve down or rail test port bleed off gasoline fuel delivery that way. Summer’s here now. Passing highway vehicle underhood fires: burn those visuals into your memory banks. You do not want to be one of these from playing hot underhood gasoline fuel dink’ing games.

Yes there is a fuel vapor recovery line all of the way from the fuel tank up to the engine compartment vapor recovery charcoal canister in these pick-ups. This IS for fuel tank filling displaced out tank vapors recovery too. Even IF like on PT Cruises and mini-vans the charcoal storage canister is in the back - STILL will be a back to up to the front engine mounted vapor line, needed. Realize that the running engine is THE time and volume controlled fed-in vapor eater upper.
Yep Fedral mandated Evaporative Emissions Systems leakage capabilities standards did march down a game from a 1st 0.060" to 0.040" to a very, very hard to achieve and maintain 0.020" standard 1996 to ~2007. I did a lot of EVAP warrantee working after that last tiered level was imposed.
This EVAP hard factor, CAN buss and a bunch of other reasons why I am saying that post 2003 vehicles are going to be woodgas conversion “interesing”.
You, younger, bright new shiny penny boys and girls get to figure out these newer ones. ChrisKY, IanA. and others.

For woodgas system gasoline fuel moderating I do think that the PWM fuel pump electric suppling add ons will prove out the trick way. Watching with interest how the fellows using the newer electronic trailer brake controllers are faring now with great interest.
Radio Shack, and airplane modeler hobbiest versions leave me cold though.

Mt woodgasing ain’t no hobby but a keep the lights on darn serious passion.

For hobbies I read. I go lakes canoeing with my wife. Up the hobby danger game; and I go-to-the-limits handload up for my different bang-go-booms. 16,000 to 65,000 PSI pressure duration pulses. Self-loader bang-go-booms are boring, needing always conservative mid-range loadings. Or stuck cases, blow-ups and jams, jams, jams.

Steve Unruh

Terry-Thanks for looking.

Chris/Wayne- Can the 92 dial the fuel out be itself like Wayne describes? Leave the fuel full on and then pull on the gasifier, computer will cut the fuel out? Not sure what year Dakota he is running now.

Wayne- Thanks for the pictures. Pretty handy having a few Dakotas all in one place to check. I figured as many as you have done it wouldn’t be an issue either way but wanted to check.

Steve- 6000 miles on the Ford with the brake controller. No sign of problem with it. When I figure out how I like to try to add a rheostat remote mounted for it.
Thanks for the info on the fuel systems. Sheds a lot of light on things. I do know the Ford cannot handle the adjustments on the fuel side as well as people are describing the Dodge doing.
What about EGR vs nonEGR? Did they change the cam profile to do away with it, computer tuning, something else?

Pictures 1-5 non egr
Pictures 6-9 egr


My truck will do the hybrid thing, but it doesn’t like it much. If you adjust the throttle by more than a couple degrees, it will flood and quit. I think the returnless may do a hair better - but I can’t say without trying it.