I have tried everything I know of. Help!

[Bgunner]

It wouldnt even start on 2 cylinders.

This is exactly what has me confused. But with the given information it suggests the only cylinders constantly firing are 2 and 4. The key word here is constantly.

@OP at night in. Dark area pop the hood and run the engine. Look for skark leak through all plug wires down sides of plugs and across the top of the cap. At night you will be better able to see it spark jump and see the blue arc run across things.

It is always possible to have 4 injectors getting plugged and limiting fuel delivery but you need to be sure there is no spark issue first before going this far and either testing or replacing them. So again double and triple check under the cap for ground traces after the night test. The traces will look like a light pencil line leading to a grounded surface. These can run in between plug posts also or even down the rotor to the distributor shaft.

 

[rusty ol ranger]

Id go pick up some 5 dollar inline spark testers from harbor freight, hook them on the offending cylinders and wait for a nice night.

Could be some sort of weird TFI issue. Have you pulled codes?

 

[Trevorrudai]

 

[Trevorrudai]

This is the test I was referring to Ron. It's in my Sun Tune up/Testing equipment kit. I just did the compression test again results are, Cylinder:
1.150
2. 145
3. 150
4. 150
5.147
6. 150.
My spark plugs look to be in good condition with the exception of cylinder 2 which had some, but not an exceptional amount of carbon. I used a spark tester last night when I ran the spark test consistent spark from each plug. Replaced in tank fuel pump about a month ago, in line fuel filter about 3 weeks before that. I can't find a screw on adapter to go from fuel pressure gauge to valve stem of Schrader valve so I used a hose with 2 clamps on end but no reading registering. Positive gauge works already tested that possibility, also positive there is quite the fuel pressure being delivered to fuel rail because when I depress the schrader valve it appears to come out at the rate it has always since I bought it.

 

[Bgunner]

So the only "uniform" cylinders were 2 and 4?

if so this would seem to suggest the others are misfiring at times but not others. From experience it is unusual for 4 injectors to plug at the same time but not unseen from someone driving with an issue for long periods. This is why I recommended to double and triple check spark to be sure.

You must not have a tack in the dash because the same could be done with a factory tach.

Just FYI if this was a single cylinder or maybe 2 it could be done by ear but missing on 4 cylinders I can see your troubles finding it.

 

[RonD]

Compression looks fine, nothing stands out

With no load on the engine you may notice a misfire but may not as well
On a V6 a cylinder is firing every 120deg, so 3 times per 1 RPM

so its fairly smooth, even with a misfire

Cylinders 2 and 4 don't really have anything in common
The match pairs are 1/5, 2/6, 3/4 each pair is at TDC at the same time to balance the engine

3.0l Vulcan Firing order is 1-4-2-5-3-6
seen here: https://ricksfreeautorepairadvice.com/wp-content/uploads/2009/09/Ford-3_0.distributor.jpg

so 2 and 4 do share adjacent connections on the cap

Just FYI, match pairs can be determined by firing order, 1-4-2-5-3-6, just split it in half and put one half below the other
1-4-2-
5-3-6

Those are the matched pairs used to balance this engine

Can't really explain your results on the RPM test


As for fuel injectors
If possible look at the injector wiring on one side
All will have a RED wire, see what color the other wire is on the 3 injectors on one side
If you see 3 different colors then you have sequential fuel injection
If just 2 separate colors then you have Batch Fire injection, 3 injectors open at the same time, 2 on one side and one on the other, then the other 3 open on the next RPM, this keeps the lower intaske full of air/fuel mix and cylinder just suck in what they need, so wouldn't be injector issue if there was a steady misfire

 

[adsm08]

Cylinders 2 and 4 don't really have anything in common

Not quite. I know around here we like to refer to the early non-sequential EFI systems as "bank fire" but they are really more accurately termed "batch fire".

Injectors 1,2 and 4 fire together. So if 1,2 and 4 work but 3,5, and 6 are dead that could indicate a wiring or computer issue.

 

[RonD]

Yes, +1 ^^^

But a 1994 3.0l would for sure have 2 upstream O2 sensors, one on each bank/side
So even if only 1 injector was working on one side, with Batch Fire, computer would just leave it open longer to get O2 sensor on that side showing good voltage and should turn on the CEL

 

[rusty ol ranger]

Yes, +1 ^^^

But a 1994 3.0l would for sure have 2 upstream O2 sensors, one on each bank/side
So even if only 1 injector was working on one side, with Batch Fire, computer would just leave it open longer to get O2 sensor on that side showing good voltage and should turn on the CEL

But we are talking about a 2.9....

 

[RonD]

But we are talking about a 2.9....

OOPS

nevermind, lol

 

[franklin2]

I am thinking some of these very difficult efi issues with these older engines ends up being a wiring problem, which is very difficult to find. Some of the problems we have on these old Rangers and Broncos seems to be inflicted by Ford. There a lot of wiring plugs over on the driver's side inner fender, and the ignition coil also, and there is a large open hole at the bottom of the inner fender. If you turn the wheel a certain way, and it's wet outside, it throws all that moisture off the tire up into the engine compartment all over the coil and the wiring on the driver's side inner fender. I have found corrosion problems over there on my little ranger, that is why the electronic 4x4 would not work.

On both of these vehicles I had owned, I had added a piece of rubber hanging down onto the steering hoses to block this and keep it clean. It's really scary when you are driving in the snow and they put salt on the roads, and you see all that white salt up on all your wiring over there.

 

[91stranger]

A hose clamped to the Schrader valve isn't gonna give you a reading because you have to have something pressing on the stem inside the valve.... You're not gonna be able to make one of these and you'll just have to pay the $20 to get an actual fuel pressure gauge for the schrader valve.... Easy way to check without a gauge is see how high the gas flies when you press the stem inside the Schrader valve. The gas should go about 2 feet in the air. If it barely comes out or only a few inches then you have no fuel pressure.

 

[franklin2]

A hose clamped to the Schrader valve isn't gonna give you a reading because you have to have something pressing on the stem inside the valve.... You're not gonna be able to make one of these and you'll just have to pay the $20 to get an actual fuel pressure gauge for the schrader valve.... Easy way to check without a gauge is see how high the gas flies when you press the stem inside the Schrader valve. The gas should go about 2 feet in the air. If it barely comes out or only a few inches then you have no fuel pressure.

It would be nice to have the correct gauge, but I am cheap. What I do is relieve the pressure on the fuel rail by pressing the schrader valve with a rag around it, and then I take the same tool you use for tires, and unscrew the guts out of the schrader on the fuel rail. I then slip a hose over it with a hose clamp, and run the hose through the back of the hood and tape it to the windshield for testing.

 

[rusty ol ranger]

It would be nice to have the correct gauge, but I am cheap. What I do is relieve the pressure on the fuel rail by pressing the schrader valve with a rag around it, and then I take the same tool you use for tires, and unscrew the guts out of the schrader on the fuel rail. I then slip a hose over it with a hose clamp, and run the hose through the back of the hood and tape it to the windshield for testing.

You can buy a actual fuel pressure gauge at harbor freight for like 20 bucks.

 

[franklin2]

You can buy a actual fuel pressure gauge at harbor freight for like 20 bucks.

This must be what you are talking about. https://www.harborfreight.com/fuel-injection-pump-tester-62623.html

I notice the hose is not very long. You can't max out the fuel system by revving the engine in the driveway. You have to get out on the road and find a long hill to pull. The reason I tape the gauge to the windshield.

Probably could modify the above with a longer hose. You can take those brass crimps on those fittings and grind them down carefully on a grinder and pull the hose off and you are left with a nice barbed fitting that you can put a new hose on and use a hose clamp.