Doesn't start (fire) at all
 

97 V6 4.2L 55k miles
This has been used a few times a month for 4-5 years. Last time (last month) it started only after the battery was fully charged. Now it doesn't start. Last tune up was about 4-5 years ago (about 1-2 thousand miles ago). I was going to replace the spark plugs first and pulled one. It was clean without any erosion/soot (no surprise). Gap was 0.54". No change. So I put it back.

I need to check if the engine is getting GAS, SPARK, and AIR. It's been a while since I worked on this pickup. Please kindly help me with diagnosis. Thank you.

1. How do I check spark without damaging ignition coil? I know I have to disabel fuel pump first. Where do I disconnect the fuel?

2. How do I check for GAS? I remember checking fuel pressure with a rental tool from AutoZone. Where do I make the connection? By the way, I always had to crank fuel pump a few seconds first, shut off ignition, and re-crank in order to start the engine. Apparently, fuel is losing pressure in the line after overnight parking. It's been this way about a year.

3. Last time I used the pickup, there was no error code (no yellow light on the dashboard). I have a scanner.

Thanks.

Air. Crack the throttle 1/4 way. This bypasses the IAC valve which might be gummed up and staying closed.

LISTEN for the fuel pump to run for 2-3 seconds when the key is first turned from OFF to RUN (not START). If you have to, take off the fuel cap and put your ear close to the filler neck and have an assistant turn the key. If the fuel pump does not run, neither will the engine.

Shortcut for fuel and spark: Squirt a shot of starting fluid into the throttle body and see if it fires. Use sparingly. If it fires, you have spark but no fuel.

The fuel pump test port is on the fuel rail. Looks like a tire valve stem.

Once you know which key element is missing, you can more readily diagnose and correct the fault.

Verify the CEL comes on when the key is turned to RUN from OFF. If it doesn't, the PCM may not be getting its power which, of course, is a prerequisite for the whole system to operate.

Thanks. Tomorrow I will try squirting starting fluid into the throttle and report back. Thanks.

Go look at the CEL first. If it doesn't come on during bulb proveout, the rest is moot.

I forgot to mention it. All lights come on including the yellow check engine light. Thanks.

By the way, I now remember that I didn't have service engine soon light for a while just because the bulb was out. When I pulled out the dashboard for another repair need and replaced all light bulbs, the service engine soon light finally came on. Hooked scanner and had to repair MAF wire. It was damaged by air filter housing rubbing on it for years.

The starting fluid worked. The engine is running fine. No error code yet except P0100, diagnosis hasn't been completed yet. This is puzzling since I have never disconnected battery. I will keep driving the pickup for a few more days and post results here again. Thanks a lot.

What did you figure out? I have same issue.

Okay, quit posting in every thread that resembles your situation. Do some digging first, then some testing and observation.

This is my only thread by the way.

I now know I have a fuel related problem. Potential culprits are fuel filter, injector clogging (old fuel), and fuel pump. This is what I am going to do:
1. Fuel filter: This weekend I am gonig to replace fuel filter and see if engine starts without starting fluid. If problem persists, I will use starting fluid again and ...
2. Fuel pump: I will measure fuel pump duty cycle. If this checks out okay, then
3. Fuel injector clogging

But I will continue to post what I find here to get expert advice. Thanks for helping me out in advance.

So you start it on the can, and it runs fine with normal power and acceleration. You shut it off and it wont start up again on its own?

What is "starting on the can"? Do you mean starting fluid? Yes, I can start with starting fluid. Once starting fluid is used and engine is warmed, it starts on its own. But once parked overnight, it wouldn't start on its own.

Aha!


1. so its either a 'cold start issue'
or
2. there is a leak in your fuel system allowing air to enter the lines as the vehicle sits overnight, making for a very hard self start without priming.


cycling the pump a few times and maybe even checking for fuel pressure in between should rule out the air in the line possibility.

Sorry, what was intended for the thread hijacker. I should have quoted.....


In any event. it does sound like the pressure is getting lost too quickly. The pressure gauge would tell the story quickly. If it's leaking down, the normal culprits are leaky injectors or the check valve function in the pump assembly.

If that's the case, multiple consecutive priming cycles usually will usually you to start it.

BTW, the duty cycle of the fuel pump is either 0% or 100%. The 97 didn't use PWM to control fuel pressure.

Borrowed fuel pressure gauge from AutoZone. Ignition ON. Zero pressure. And I realized the familiar fuel pump priming sound was absent.

Fuel pump fuse: Looked okay. No melting or damage
Fuel pump relay: I don't know how to test a relay. So I swapped pump relay with horn relay. Still no pump priming sound.

I am going to check if 12V reaches fuel pump connector. Will report back soon.

PS: When is the horn to work? At all times or only when engine is running? Or ignition on but engine not running? Thanks.

You'll probably find it easier to check at the inertia switch first (which should be checked to make sure it isn't tripped). Don't forget, you'll only have power for 2-3 seconds when the key switch is turned from OFF to RUN. After that, any reading is invalid.

The horn should always work, regardless of the ignition switch state. It's on an "ALWAYS HOT" circuit.