• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

2.3L ('83-'97) SOLVED 97 intermitent hard starting


Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Howdy yall, I bought me a 97 supercab 2.3 5 speed the other day. I runs great.... when it actually starts... Its gonna need a new flywheel and possibly a starter but thats for another story.

So sometimes it will fire right up, and sometimes it takes forever! Hot or cold, doesn't matter. New ECT, new plugs/wires, good fuel pressure. Timing is 10 BTDC. My dad and I believe it is a problem with wiring to the primary coil When cranking it backfires through the intake. . If the front coil is unplugged, the thing runs like crap, however with the back coil unplugged and the front coil plugged in, barely noticeable change in the way it runs. We swapped them around to no change in the way it starts. We read that the front one doesn't start working until 400 RPM, so we think this explains the hard starting yet great running. Checked grounds, and checked resistance between coil plug and eec connector. One prong had some resistance but the other 2 did not. Do you guys have any suggestions for what the problem is?
 

Attachments



Rock Auto 5% Discount Code: 7FA902352B4C01: April 5th, 2021
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
We are pulling the timing cover off to check to make sure it is in time. The PO put a new timing belt on and may not have timed it correctly. Will report back here with what we find.
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
18,517
Reaction score
2,993
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
1997 2.3l should run OK with either coil pack unplugged, these engines used 4 spark plugs(and distributor) from 1974 to 1988 and did just fine
The 4 extra spark plugs were added to get extra power, same as with the Dodge Hemi, at the time, 1989, it was easier to do with distributorless engine than 4 valves in each cylinder(which is a better use of head space)
There is no alternating of spark, both spark plugs in a cylinder fire at the same time or there would be no point, no extra power

So you have some bad spark plugs or wires on the one coil pack if it doesn't run smooth on the one coil pack

Its possible the computer has a bad "spark driver" for that one coil pack, there are 2 "drivers" for each coil pack, so 4 total in the computer, but its a LONG SHOT, never even read about one failing

Each coil pack has just 2 coils inside, not 4, each coil sparks 2 cylinders at the same time, 1/4 and 2/3 are the paired cylinders on each coil pack
Its called a Waste Spark system since one spark is wasted each time a coil sparks
Waste spark is used because its reliable, simple and was the first spark system ever used back in the late 1800's
Your lawn mower uses it, lol, pretty much any single cylinder gasoline engine uses it
Crank timed spark instead of cam timed spark

So figure out why that one coil pack and set of spark plugs are not working


That could be the reason for the slow startup, but.............
Could be you are losing fuel pressure at the injectors when engine is off
Try cycling the key on and off 3 times, and then try to start the engine

The fuel pump only runs for 2 seconds with key on, and if pressure was 0psi that only adds 10psi of pressure
Engine runs with 30-40psi pressure when fuel pump is on full time, after startup
So 3 on and off gets 30psi again


Also all gasoline engines need to be choked on COLD start, and need the choke applied until coolant temp gets above 140degF
On cold start idle should be high, say 1,000rpm, and then slowly drop over the next few minutes as engine warms up
This means Choke Mode is working, its a computer program
If not then replace ECT(engine coolant temp) sensor, this sets "the choke" if it shows temp under 140degF
 
Last edited:
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
RonD thanks for the reply.

We have good fuel pressure. It doesn't leak down after sitting, and no matter how many times you prime the pump it makes no difference to the way it starts.
The choke mode is working, and the ECT sensor is brand new.

I find it very weird that with the primary (exhaust side) coil unplugged it runs crappy. Brand new plugs and wires. Perhaps the spark driver is bad.... If the timing isn't off then we will check that next. Speaking of checking it, how would you do that?
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
18,517
Reaction score
2,993
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Crank/cam timing is not off or it wouldn't run smoothly on the other coil pack
You can use a vacuum gauge on idling engine, 17-20 inches would mean timing belt is OK

If you have a timing light you can test if each spark plug wire on that coil pack is sparking and steadily
Make sure the spark plug wires at the coil are in correct Matched Pairs, 1/4 and 2/3, they can be 4/1 and 3/2 as well, doesn't matter
Each pair of spark plugs are wired in series so if one wire or spark plug is not working that can cause BOTH spark plugs to not work on that coil
So pulling off spark plug wires on a running engine to test them is not a good idea with waste spark systems


"Primary" coil pack was the designation for the exhaust side coil pack for 1989-1994 2.3l when they used external spark module, and when cranking this was the only coil pack used, there was a spark inhibitor put on "secondary" coil pack, when cranking engine over
1995 and up used both coil packs all the time, even on startup
Just FYI
They kept the names just as a convenience, because there is no "primary" coil pack after 1994, just exhaust side and intake side
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Plugs 1 and 4 on exhaust coil are the not working and there is no change when swapping the two coils around.
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
And also, if both coils were used on startup it should fire up no problem I assume.
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
18,517
Reaction score
2,993
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
I would guess the ground wire for the 1/4 coil is either bad or its the computer

You can unplug the computer connector on firewall and look for corrosion and then test that wire with OHM meter

Coils are numbered 1 to 4
1 is a tan/white wire goes to pin 26 on computer
2 is a tan/orange wire to pin 52
3 is a tan/blue wire to pin 78
4 is a tan/green wire to pin 104

Google: Ford PCM pin numbers
Should see a few diagrams
These OBD2 Computer connectors have 104 "pins" total so find the tan/green wire at one corner of connector, that will tell you the rest of the numbers, the orientation

It could be coil driver in the computer, but wire issue is the far more likely of the two
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
There are only 3 wires at the plug going into the coil. We checked resistance values on them and 2 were fine but one was a little questionable.
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
18,517
Reaction score
2,993
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Yes, 2 ground wires(tan/???) and a red/green 12volt with key on wire, on each coil pack, so 3 wires on each coil pack
Ford numbers the 4 ground wires 1 to 4

I didn't know which wire was the problem so I listed all 4 ground wires from the computer, one of them is not working, since cylinders 1/4 spark plugs are not sparking after testing that wire on both coil packs
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Gotcha, I got confused.
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Little update for those who care.

Checked the timing. It was 1 tooth off on the cam. Put it in time. We had the plug wires off so we could swap the coil. Put the plug wires back on and then realized they were wrong. Whoever had the truck before me put the rear coil plug wires on wrong.

So let this be a lesson. Don't assume. Always always check the little things.
 
Joined
Jun 6, 2019
Messages
69
Reaction score
12
Points
8
Location
Maud, Texas
Vehicle Year
90
Make / Model
Ford Bronco II
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
And thank you RonD for all the information. It really got my head thinking and I was prepared to test everything when we got the timing cover back on.
 


Top