1990 Ford Ranger 5.0 efi issues

[RangerRedneck5.0]

Hi everyone, I started this project about 6 months ago. I had a 1990 ford ranger 2.9l 2wd and I started off by putting a 4x4 front axle off of a bronco II and then I put the 5.0 and tranny in from a 1991 ford f150. I then painted it and polished it and put it all back together. The wiring harness from the f150 had the wires in different spots on the cab connection where the engine bay hooks up to the cab had the wires in different spots than the ranger so I messed around and got the motor to turn over and the fuel pump and most of the lights to work with the key on. It still wont start. I dont know the issue if you guys could maybe give me some things to check that would be prefect! Thanks!

 

[Elutheros]

Are you using the ECU from the F150? Is it carb or EFI? Did you test to see if you have spark?

 

[RangerRedneck5.0]

Yes I am using the ECU from the f150 and it is efi it has spark as well as fuel

 

[RonD]

If it has spark and fuel then it will start, unless there is no compression

Only way to check for spark, at the right time, is to spray fuel into the intake and then turn over the engine, 50/50 test
Been used since the first spark plug engines in late 1800's,

If you manually add fuel then there are two results:
Engine starts and dies, spark is OK but no fuel is getting into the engine
Engine doesn't start, spark is not working or not timed correctly(assumes compression is OK)

So do 50/50 test so you can get on the right track, spark or fuel issue

I think 1991 F-150 5.0l still used a distributor so it can be mistimed, 180degrees off
There were also 2 firing orders depending on the cam that was used, but even with wrong firing order a few cylinders would fire if timing is correct

Fuel pressure doesn't mean fuel is getting into the engine
You can crank engine over a few times and pull out a spark plug to see if its tip is WET, if not then injectors are not opening

Fuel injectors all have a Red wire, that red wire should have 12volts with key on
The computer Grounds each injector to open it
So test if Red wire has 12v with key on
You can't really test Ground wire on injectors, it happens too fast to see on a volt meter, you can hook up a NOID light between injector and wiring harness, and it will flash if computer is pulsing the ground on that injector while cranking engine over

The computer has a few Ground wires, they are not shared inside, so each ground wire needs to be grounded.

And metal in a vehicle is NOT a good ground because its metal
Engine should have the larger negative battery cable connected to it, for starter motor and alternator grounds.
But engine and trans sit on rubber mounts so don't transfer ground to frame or body
And body parts are all painted FIRST and then assembled, so no reliable ground transfers between body parts
There needs to be a ground strap from engine to Cab Firewall
A ground from engine to frame
A ground from engine(or battery) to inner fender and Rad support
Computer needs to be grounded to cab or inner fender

 

[RangerRedneck5.0]

I'm pretty sure my grounds are correct I've done my best to time it multiple times and even put fuel in. The spark plugs are wet when I pull them out so the injectors are working. The only thing that happens is when I turn it over it sounds like one cylinder is firing or something so maybe it could be out if time but I've messed around with it for a while and still no luck....there is no exhaust system yet only open headers, would that cause any issues?

 

[lvwill]

What cam is in the engine and what firing order are you using? The f150 engine and the 5.0 h.o. Engine use different firing orders

 

[RonD]

Exhaust pipes won't effect startup, on or off

Distributor rotates Counter Clockwise
Ford numbers cylinders like this:
4 8
3 7
2 6
1 5
front

Most likely firing order is 1-5-4-2-6-3-7-8

So arrange the wires in that order on the cap, counter clockwise
Put crank timing mark on TDC
Rotor in distributor should be pointed at #1 on cap, lift distributor and reset rotor if it isn't
Try to start engine

If it doesn't start you will lift distributor and turn rotor 180degs then put it back down.
Then try to start again


A distributor turns at Half the RPMs as the crank, so crank must complete TWO rotations for each ONE rotation of the distributor

On the distributor cap #1 and #6 are opposite, 180deg difference
So when crank is at TDC mark rotor should be pointed at #1 or #6 but only #1 or #6
One will be correct timing the other 180deg off, so those are the only two positions you need to try, no guessing needed, 50% chance it will be right the first time
100% chance its right the second time, lol

If it still doesn't start then compression is under 100psi



5.0l HO or 351W used a different Cam so used firing order 1-3-7-2-6-5-4-8
#1 and #6 are the same so those 2 would fire
As are #2 and #8, so 4 of the 8 cylinders would fire correctly, it would be a poor start up but it would start

 

[Ranger850]

So ....
Much ....
Info ...
Brain.... Can't..... Take it

 

[RangerRedneck5.0]

Thank you ron d, that was some good information, is there any sensors or anything that is really important to it starting that I should double check to make sure that I rigged all the wires right? I tried my best I'm 18 and my only prior knowledge is basic maintenance and working on tractors. I've been trying to get it running for about 4months now. I think the vacume lines are correct. I took all the injectors out and cleaned them and made sure they were spraying good. I just dont know what it could be besides the timing maybe or a sensor or something dumb. Thanks for all the input! Keep it coming!

 

[RonD]

Only sensor that can cause a No Start on pretty much any computer controlled engine is the Crank Sensor, which you don't have specifically.

Crank sensors were used on distributorless engines, before that the Distributor module would send the "timing pulse" to the computer so it could time the injectors.
Electronic distributors are self contained for Start Up, they don't "need" the computer.
The distributor does have a Hall Effect sensor under the rotor that generates the timing pulse for coil to spark, if you have tested spark and are getting multiple sparks on one spark plug wire then that sensor is working.

The computers in these years were for the fuel injection system for the most part, so they needed the timing pulse for the injectors.
And in some years the computers were used as the "Vacuum Advance" for Spark timing, instead of having that on the distributor, but vacuum Advance is not used at Start Up.


You need 3 things for any gas engine to start up
Spark, at the right time
Fuel, in the right mix with air
Compression, above 120psi

Gasoline can't be ignited by a spark, yes the movie guys take liberties, lol
Only gasoline Vapor can be ignited by a spark, that's what the Compression is for.
Compression causes the gasoline Liquid to heat up, and some of it will turn into a Vapor as its heated, more heat more vapor, so high compression = more heat, lower= less heat.
You need 30% vapor in a cylinder for a spark to ignite it reliably.
Cold engine and cold gasoline means less vapor, that's why cold engines need to be Choked, even fuel injected engines.
Choke just means to add more gasoline than "normal" to get higher Vapor level until engine and gasoline warm up

Ether(Quick Start) is good to use because it has a lower vapor point than gasoline, so a spark(at the right time) can ignite an ether/air mix easier than a gasoline air mix
Often used in Cold Climates to start Cold engines

If possible test your compression on at least 3 cylinders, all would be better, just to take compression off the table, or find out that it IS the problem so you don't waste time on "non-fixes"
302/5.0l should run minimum 150psi in each cylinder, but would expect 155-165psi

 

[RangerRedneck5.0]

Thanks I'll check my compression on them hopefully I can find the issue soon so I can drive!

 

[Josh B]

Good luck with it RR5, I think you'll be a fine mechanic