3.0 flex fuel to 4.0ohv

cowboycowboy91 · Dec 6, 2016

I have a question, what is needed to swap out a 3.0 flex fuel with a early 90s model ranger 4.0 ohv engine? Could I just swap throttle bodies and fuel rail/injectors out and make it work? would the crank sensor and cps work with the computer of the 3.0 flex fuel? I know I have swapped parts from a 3.0 flex fuel with my brothers older 4.0 ohv engine and it ran still, but what about the electronics from the 3.0 being compatible? Someone told me that the flex fuel 3.0 uses 4.0 injectors...if that's true, then wouldn't the fuel ratio be the same?

RonD · Dec 6, 2016

Not understanding what you are doing?

Putting a 4.0l OHV engine and transmission into a 2000 3.0l ranger?
But using 3.0l wiring and computer

3.0l Computer would be hard pressed to deal with the extra air the 4.0l would be pulling in, 4.0l would be pulling in 1 liter more air, 33% increase
Engine computers are programmed for engine displacement so they know the weight of the air being used every 2RPM(4 stroke engine)
3 liter used 3 liters of air, 4 liter uses 4 liters of air, every 2 RPM, depending on throttle position, which the computer also "knows".
Computer bases 14.7:1 air:fuel ratio for gasoline on RPMs and throttle position
MAF(mass air flow) sensor does aid in adjusting that
Then O2 sensors are used to trim air:fuel mix for best Oxygen level in the exhaust

Flex Fuel computers have a wider latitude for fuel ratios, but I think 2000 models needed a fuel sensor on the fuel line to allow them to lower the ratio, ethanol has 9:1 air:fuel ratio

Later model Flex Fuel computers didn't need the fuel line sensor.

Crank sensor is the same, VR sensor, and firing order is the same, 3.0l/4.0l

CPS was changed in the late 1990's on most Ford engines, 3 wire hall effect sensor was used in 1990s, and then changed to a 2 wire VR sensor, they are not interchangeable and there is no "wiring mod", computer needs software for Hall Effect or VR to understand that type of sensor.
So if you have a 2 wire CPS on the 3.0l then you would need to get a 2 wire CPS for the 4.0l

cowboycowboy91 · Dec 6, 2016

Hey Ron,
Yeah, what I was wanting to know is how big of a pain it is to put in a 4.0 ohv vs a 4.0 sohc to replace my 3.0 flex fuel. I am just sick and tired of these 3.0 flex fuels. I have replaced the engine 2 times now and it keeps having trouble with the valves and the first spun a rod bearing. I love the 4.0 ohv engine in my brothers 1992 ranger. I just got to thinking about it and started wondering if those engines would run off of all the electronics already in my truck for a 3.0 flex fuel. I didn't think about the extra air intake causing it to confuse the 3.0 computer and causing it to run lean. The cam syncronizer wiring is another issue I didn't think about. I have a 2 wire, so I would need to put one on the 4.0. It sounds like the 4.0 ohv would be about the same as a 4.0 sohc swap. I would probably be better off just changing everything from the donor over to mine and making it easy to just plug in and go. I found a 1992 automatic 4x4 ford explorer with a 4.0 in it and low miles. I was debating on buying it. They only wanted $1100 for it, which seemed like a cheap fix to my truck, but I don't really need another lawn ornament. I would love to put in a 4bt cummins swap, but that swap sounds even more complicated. I love my truck, but I need more power and less problems.

RonD · Dec 6, 2016

IMO a 5.0l swap would be better all around, same labor, a bit more in parts cost.
V8 Ranger has some value
Frankenstein 4.0l OHV or SOHC doesn't have much value

You can go out and buy a Stock 4.0l OHV or SOHC Ranger, but not a V8 Ranger

The 3.0l Vulcan engine was used in literally millions of Ford cars and trucks, 1986 to 2008.
It has a very good track record for reliability, not for power though, lol.
Surprised you are having those issues.

2002 to 2004 3.0l heads did have exhaust valve issues
Flex Fuel had a different chamber shape in the head and larger injectors but those were the only differences in the engine.
There has never been a one or the other reliability issue between FF or Gas Only 3.0ls

I would either do the V8 swap or fix the 3.0l and sell that Ranger to buy a Ranger with 4.0l OHV, 4.0l SOHC needs to be 2005 or newer Ranger, earlier had the timing chain problems

4bt swap would be great except for the cost, lol

stmitch · Dec 7, 2016

RonD said:
I would either do the V8 swap or fix the 3.0l and sell that Ranger to buy a Ranger with 4.0l OHV

This. Trying to get an OBD1 4.0 to run properly using OBDII 3.0 electronics sounds like an unnecessary nightmare to me. Just buy a Ranger with the engine you want. They made millions of them, and used Rangers are cheap.

3.0 flex fuel to 4.0ohv

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