I was thinking some of the younger truck owners may not be familiar with older vehicle issues, and issues that are also "Ford specific". I was compiling the things I could remember for my grandson, and I thought maybe some of the posters here could see if I missed anything. I'm somewhat experienced, but still learning, and also new to my 1994 F150, 300/4.9L, manual trans, EFI

ENGINE DOES NOT TURN OVER, "NO CRANK"

- Turn on headlights to see if battery has power. Bright lights mean full power, dim lights should still cause the starter-solenoid to rattle. No lights = dead battery

- Battery posts. If battery has power. Post-clamps can be loose (try to wiggle them), or may have built up corrosion, which makes a poor connection. Clean and tighten post-clamps

- Turn on interior light, then try to start engine. If interior lights dim, high amps are going to the starter, but its not spinning. This means the ignition switch is working.

- Solenoid sticking. Tap solenoid while someone else turns the key. Solenoid may be sticking, and the starter will not spin without solenoid cycling.

- Short the starter post to solenoid power with the metal tip of a screwdriver while someone turns the key. This verifies that the starter motor still works, but solenoid is not engaging.

- Starting safety switch. The clutch must be depressed, OR auto trans must be in park/neutral for starter circuit to work. Safety switch may be worn.

ENGINE TURNS OVER, DOESNT FIRE

The engine needs compression, fuel, and spark. Compression lowers over time from wear, and that happens gradually. Low compression is typically found on very old engines with 150K miles or more. It is rare for compression to be the problem, and it is rare for no-fuel and no-spark to happen at the same time as each other. If the engine turns over well, the most common no-start problem is either no-fuel OR no-spark.

- First test is...if you have two fuel tanks, switch to the other tank to see if that fixes the no-start. It is possible to have a bad switch, and also a bad fuel pump at the same time, meaning you cannot switch to the good fuel pump.

- Fuel gauge not working. Take off the gas cap on the tank. rock the truck and listen for splashing. Alternately, tap on the side of the fuel tank(s), Tank may be empty even when the fuel gauge shows 1/4 tank remaining.

NO-SPARK

- Test spark. I have pulled a spark plug wire, and held it a quarter-inch away from the spark plug while the engine is turning over, I could see the spark jump through the air. A blue spark is good, a red spark is weak, and no spark reveals the suspect. This may be difficult to do in the daytime when it's sunny. Try it first on a running car at night to see what a normal spark looks like. Wear some type of glove, or you may get a shock.

- Distributor cap and rotor. Spark plug wires are cotton fibers infused with carbon powder, and they actually do wear out,. However, wire failures are gradual rather than sudden. That being said, the distributor cap and rotor present a single point of failure, and are a prime suspect. The current pathways involve sparks flying through the air inside the cap, and the metal tips experience erosion. Heat-expansion when running can change the air-gap distance, and after being parked, a cold distributor may have too much air-gap. After swapping-in a new cap and rotor, if this does not solve the no-start, save the old parts as a back-up since they may be working fine.

- Coil. The 1987-96 F150 model range has a single coil to serve all the spark-plugs. I don't have a good test for a stock coil, but they are easy to swap-out. Again, if swapping-in a new coil does not fix the no-start, save the old one for using as a back-up.

- Ignition Control Module / ICM. Its a small "black box" on the drivers side fender, attached to a finned aluminum heat sink. I don't have a good test for these, but the ICM is attached to the required heat-sink by two bolts with a 5.5mm hex head. These can be drilled out and replaced with common hardware-store 8-32 screws. I used 2-inch long screws with one-inch long steel sleeves so the hex-nut is located above the deep pocket. The ICM is a single-point of failure, and dies with no warning. I suggest that they be replaced at your convenience while it is working, and the old one one carried as a spare.

Here is a good "NO SPARK" diagnostic video (1994 F50 300/4.9L)

NO-FUEL

- Smell the exhaust. If you have turned over the engine quite a few times and it hasn't started, sniff the exhaust, and if it doesn't smell like gasoline, it is likely a no-fuel problem. If you smell gas, it's likely a no-spark.

- Fuel Pump. Turn the key to "ON" but do not turn the engine over. Crawl under the bed and listen to the gas tank to see if it is humming. The fuel pump should make a humming noise. You should familiarize yourself with this sound when the truck has been running well. The fuel pump motor may be work, and have a "bad spot" on the commutator when it comes to a stop. With the key in the "RUN" position, bang on the underside of the fuel tank with a soft-faced mallet. If this works and the pump starts to hum, be aware it will happen again soon at random times. Plan on replacing the fuel pump soon.

- Relay / Fuel pump. In the fuse-box inside the engine compartment on the driver-side fender there are several cubes in a row, and these are relays. Test the horn, and then swap the working horn relay into the fuel-pump relay position, and re-test the start.

- Fuse / Fuel pump, If you find a burned fuse for the fuel-pump, swap-in a new one. If the new one burns, do not install a higher-amp fuse, because there is a short in the fuel-pump wires.

- Inertia Switch / Fuel pump. If you are involved in a collision, the inertia switch senses this and stops fuel from pumping, since the fuel lines may be torn open. It can be re-set, and its located behind the passengers knee panel.

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Ok, this is as far as I've gotten. What other items can be the cause of a "no start"? (all corrections to wrong info above is appreciated).

Engine Control Unit / ECU?
Relay to the ECU?
Mass Air Flow / MAF?
Manifold Absolute Pressure / MAP?
Crankshaft Position Sensor / CPS?
Throttle Position Sensor / TPS?
Fuel Pressure Regulator / FPR?
Coolant Temperature Sensor?
"X"?

 

Seems like a lot of your methods to fix something is swapnostics. Very poor way of trying to fix something and will cost more. I'd suggest adding test procedures to everything you said and not just "swap out this part and if it doesn't work, keep it as a backup". For example on a coil, you need to check resistance on the primary and secondary coils. Although that doesn't always prove a good or bad coil as a coil can fail at operation temp but work when cold. If you don't know the specific methods of testing what you will bring up in a document, or if you have to look everything up, perhaps it would be best for someone else to. As teaching swapnostics is the worst diagnostics to use.

 

I would include a sort discussion on the differences between carburetion and fuel injection - specifically how to test for a no-fuel situation. Try the fuel pressure test point on the FI rail and using a fuel-pressure gauge to see how much pressure is generated at-starting and how it holds up after stopping cranking, and what pressure is needed for the vehicle involved. Also, how to test the carburetor for presence of gas (without starting a fire).

 

Thanks jwitty and Josiewales. I appreciate the input.

I have to agree with you on "swapnostics" for most vehicles (that's a great word!). If a truck is not old or doesn't have a ton of miles, it makes sense to find the problem through better diagnostics, rather than throwing parts at it. However, I have owned many older vehicles, and there have been consistent trends. For instance, when I recently bought my 1994 F150, I immediately changed the fuel filter, even though it drove fine all the way home from the purchase. A couple weeks later I even bought a second fuel filter simply because there have been times when the local parts store didn't have my model in stock on the day my truck stopped running.

Another example is that the fan-belt looked old, but "it was running fine". Of course when the fan-belt finally dies, no diagnostics are needed, the cause of the problem is very obvious. I installed a new one even though the old fan-belt worked fine. One area I mentioned above is the spark-plug wires. I have not replaced them, and I may keep them till next summer. When they go bad, its gradual and they don't all go bad at once. This means that with a rough idle, I can still drive it home, instead of getting towed.

I haven't replaced my coil yet, but just looking at it...the old coil is clearly the original 30-year old unit. If the coil was ten years old, I would diagnose any issues and I would verify the coil is working because I would not suspect it of having failed. The problem with a 30-year-old coil is that...even if it is not todays problem, I have verified enough old coils as having failed that I now feel it is a waste of time. It may be good today, but it will die soon, and at the worst possible moment.

The fuel pressure port test is good advice, I need to get a gauge. Not expensive, and it answers several questions quickly..

Thanks again

 

Is there spark from the coil wire at the distributor?

The ICM is not the little black box on the fender. The ICM on my truck is mounted to the distributor. Somewhere on here you should be able to find the procedure to test the module. There is no need to drill out the bolts and replace with some hardware store bolts if you use the special thin walled socket to remove the screws. It will run you about the same price as a regular socket.

 

If I am not mistaken, the ICM on the 1991 and older Ford fuel injected pickup trucks is mounted on the distributor. On the 1992 and newer Ford pickups(up to 1996 or 1997) the ICM is located near the driver side fenderwall.

 

Thank you My4Fordtrucks and 88n94. I am starting to find all the minor differences between all the various models. I recently saw on wikipedia that the switch to EFI from a carburetor was added to the 302 in 1986, then added to the 300/4.9L in '87, and finally to the 351/5.8L and 460/7.5L in 1988. The 1987-91 body style (3x4 grille) is the 8th generation, and the 1992-97 (3x3 grille) is the 9th generation. The 8th and 9th generation body styles (1987-97) are considered the "Old Body Style" / OBS

Thanks for pointing out your ICM is mounted on the distributor on earlier years. If I was a professional mechanic, I would certainly buy the 5.5mm deep thin-wall socket, so any repair would look stock. That being said, I have a newly installed ICM on my recently-purchased 30-year old F150, and the old (working) ICM is now a spare. I can now switch it out when I am far from home, using a common 7/16 socket. I have been accused of "swap-nostics" and I must confess I am guilty as charged. Young vehicles may be better diagnosed with proper testing (a 2023 tail-light assembly can be $330!), but my experiences have urged me to replace certain items on a 30-year-old vehicle before they go bad.

For instance, the truck was running fine when I bought it, and yet I immediately replaced the fuel filter, ICM, and fan belt (among others)...

 

The ‘92-96/7 is what some call the “Old Body Style.” The ‘87-91 body is called the “Bricknose.”

At least you kept the old ICM. Unless you replaced it with a Motorcraft part you will probably be replacing it sooner than later. There is nothing wrong with replacing wear items like filters but if you think that replacing the ICM or sensors “just because “ is a good idea you will end up causing more problems. New parts are a crap shoot right out of the box. More than one person has done the diagnostic testing then replaced the part only to have the same issue due to the new part being bad.

 

Thanks for the reply, you have given me a lot to think about.