1990 Furd

grouch

Full Access Member
Joined
Jan 23, 2019
Posts
491
Reaction score
800
I've got a 1990 Ford F150 with starting issues. It acts like it wants to start, but won't quite. To help you help me, I'll run down what the truck is and what I've done to it.

It started running rough so the previous owner got rid of it. He said it started running rogh after he replaced the valve cover gaskets. The intake plenum has to be removed to do this. While he was at it, he broke a bunch of vacuum lines, which he repaired.

It kept running worse and worse once I got it and I heard a LOT of noise out of the timing chain area. I tore it down and replaced the timing chain first thing. It had a lot of slop so a new chain went in. The water pump looked iffy so a new one went on, just so I wouldn't have to do it later. The alternator tested out bad so a new one of those went on. I had pulled the distributor out to work on the front of the engine. New cap and rotor went on.

When I wired it, it wouldn't hit a lick. It turned out the engine was a 1994 or later engine which has a different firing order. Wired the plugs for a '94 and it started and ran. Not very well but it ran. The shaft had some wobble so I replaced the distributor too. It ran the about the same but had less mechanical rattles.

A fuel pressure check showed it would pressure up, but drop off fast. Great, bad fuel pump. Replaced the pump and it now gets and holds pressure like it should. I suspect the pump was the original start of the problems.

While running, it has massive fuel consumption. You could almost see the gauge dropping. Pulled the plenum again and checked the injectors. They were shot. Some wouldn't work at all, some worked fairly well and some would stick open. New set of flow matched injectors went in. The pressure regulator is working fine so it's not replaced.

I had replaced the plugs before I found the injector problem with Autolite plugs. I believe #25. (Not sure and don't care) I figured they may be like Champions and work fine until they get flooded. Replaced those with NGK Copper Plus plugs. Autozone said to gap them at .54 inches. The engine will crank and act like it wants to start, but just can't quite get going. Looking in an old Haynes manual, it says to gap plugs at .44 inches. I'll be doing that as soon as I get momma's rider mower back together after belt replacement.

I rotated the engine so the timing mark is lined up with the indicator tab. The distributor is dead nuts on #1 cylinder. The battery is fully charged. The coil was bench tested and is good. Fuel pressure is good. It is a later, 1994 or later, engine in a 1990 truck.

Does anybody have any ideas if regapping the plugs doesn't help?
 

exp500

Full Access Member
Joined
May 14, 2017
Posts
1,430
Reaction score
1,071
Did you verify TDC compression stroke on #1? Valves closed or finger in hole while turning?
If you are sure about ignition, Sniff some quick start as you may have vacumn leaks. Look for a big one.
Also verify CPS output/ spark test.
 
OP
OP
grouch

grouch

Full Access Member
Joined
Jan 23, 2019
Posts
491
Reaction score
800
Did you verify TDC compression stroke on #1? Valves closed or finger in hole while turning?
If you are sure about ignition, Sniff some quick start as you may have vacumn leaks. Look for a big one.
Also verify CPS output/ spark test.


I verified TDC. One thing I'm trying to find is how the injectors are activated. Being a later engine with a different firing pattern on the ignition. I'm wondering if the injectors are pulsing correctly. I was very careful putting the timing chain in to get everything right.

The engine was running but getting worse before the fuel pump replacement. It has proper pressure and holds it just fine. No bleed off on the injectors so they aren't stuck open.
 

exp500

Full Access Member
Joined
May 14, 2017
Posts
1,430
Reaction score
1,071
CPS is main sensor for injection, any sparks on distributor spark test that don't happen may also be happening to fuel.. Also look at /test engine grounds.
 
Joined
Apr 11, 2018
Posts
4,127
Reaction score
6,476
Location
St. Louis
Hope you meant 0.054 and 0.044 for the plug gaps and not 0.54 and 0.44

Also, what engine? I know you said the truck is a '90 but the engine is ' 94 or later. They had either the 4.9 straight 6, the 5.0, and 5.8 but started putting the 3.8, 4.2, and 4.6 in for '97
 
Last edited:

exp500

Full Access Member
Joined
May 14, 2017
Posts
1,430
Reaction score
1,071
Re-reading this thing again, Makes me wonder if it ever ran right. I think you need to pull up some interchange info on the fuel injection box. How to identify what you have, and what box(es) the 94 used. My bet is the connectors are different too. This could be a problem child unless you know where the donor 94 truck is. To complete the swap with the right boxes then wireing the truck FI/IGN supply wires to match. Good luck,keep us updated. Will help if we can.

On second thought, maybe it would be easier to swap injector ground wires around to the proper cylinders. Try to talk to original Swapper if possible to save time/money. What did you Do?
 
Last edited:

TollKeeper

Full Access Member
Joined
Feb 21, 2010
Posts
1,198
Reaction score
1,697
Location
Brighton, CO
You said 90, but with a 94, firing orders changed, and various other problems.. This is bigger than the seller let on..
 

Forum statistics

Threads
118,233
Posts
1,624,545
Members
79,246
Latest member
Restmam2k

Latest posts

Top