4.0
Thread Starter
|
Elder User
Joined: Sep 2004
Posts: 500
Likes: 0
From: midwest
4.0
hi guys. my buddy has a 90 ranger with a 4.0. he recently did some head work and reassembled the motor only to find it wont run. he said it ran on a few cylinders for awhile but now wont even fire when cranking. compression is good, fuel pressure is 40 psi and it seem to have spark according to him. the fuel pump seems to run continueosly when turning the key foward, is this normal? what should he check? im not to familiar with this motor.
Elder User
Joined: Aug 2006
Posts: 761
Likes: 0
From: Southeast MI
Could it be leaking from a loose fitting or gasket? Sounds like its not able to fully pressurize along the line somewhere. Of course, you said it was ok on some for a while... Check the fuel injectors for leaks.
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Well if he as fuel pressure & compression, look to a spark problem.
You can use a inductive type timing light to safely determine if it has spark & if the spark timing is right.
Is he sure that the plug wires are in good condition, routed as the factory had them & they are tight on the right plug????
Is the distributor cap & rotor in good condition, no cracks, mosture, or carbon tracks inside.
Are the distributor shaft bearings good & tight & did he get it installed right? The timing light would tell you if the spark timing is off.
Are the distributor trigger module & spark coil ok????
He can test the coil with a ohmmeter & most autoparts stores can bench check the distributor module.
You can use a inductive type timing light to safely determine if it has spark & if the spark timing is right.
Is he sure that the plug wires are in good condition, routed as the factory had them & they are tight on the right plug????
Is the distributor cap & rotor in good condition, no cracks, mosture, or carbon tracks inside.
Are the distributor shaft bearings good & tight & did he get it installed right? The timing light would tell you if the spark timing is off.
Are the distributor trigger module & spark coil ok????
He can test the coil with a ohmmeter & most autoparts stores can bench check the distributor module.
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Are you sure about the fuel pump? It should only run a couple of seconds and then stop until the motor starts. This is controlled by the PCM
You might check to see if somehow the wiring to the PCM got hosed. I think that there's a fuse and relay in the power circuit to the PCM.
If the fuel pump isn't really constantly running, then what the other guys said.
You might check to see if somehow the wiring to the PCM got hosed. I think that there's a fuse and relay in the power circuit to the PCM.
If the fuel pump isn't really constantly running, then what the other guys said.
Thread Starter
|
Elder User
Joined: Sep 2004
Posts: 500
Likes: 0
From: midwest
yeah hes sure its wired right. the pump does keep running with the key on. it never shuts off. it doesnt have a distr. its a coil pack.
Trending Topics
Lead Driver
Joined: Jul 2007
Posts: 7,868
Likes: 9
From: Rhode Island
He needs to rent an injector noid light from autozone, and make sure the injectors are firing, and perhaps an OBD-I reader as well
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Well then have him check the crank sensors electrical connetor & electrical output, if it's corrupt, or has no output to the computer, he'll have spark problems.
I know you said he had it wired right, but their are only 3 coils in the coilpack to fire the 6 plugs, so they are fired in pairs, one plug on it's compression stroke, the other one when it's on the exhaust stroke, so coil pack plug wire connections & routing must be right.
Does he have a CEL lit???? If so have him pull & post ALL the trouble code numbers, as they could offer up some good clues.
Are the dash warning lights lit when he turns the key on, before he cranks the engine????
If not, have him swap out the under hood computer power relay with the A/C relay.
Normally the fuel pump runs for about 2 seconds & turns off before cranking the engine.
You say he has fuel pressure & spark, so if it won't fire, either the spark timing is off, or the fuel injectors aren't getting B+ to them, or a ground pulse from the computer. So check for B+ at the injectors connector at KOER, if ok then check for a ground pulse from the computer.
