friend is having problems with his 300

88 F150, Tried starting it up and it usually starts up right away. This time it just kept cranking but never started. Finally it started and the rpms were all over the place and then settled down back to normal after a few seconds. I was thinking it could be a fuel pump issue or maybe a censor. Any thought? Thanks

As for noises it sounds like its trying to start but it just doesn't start. Almost like when a vehicle would vapor-lock

 

Yes, it's VERY likely that it's the fuel pump(s). Get a gauge & check the pressure at the test port on the rail. It's inside the intake cage, and you might have to pull out the blower hose to get at it. Refer to the chart at the bottom of this diagram:

(Note that his fuel pumps are VERY different from the top of that diagram, so disregard it.)

If that's good, get a Haynes manual & a cheap digital multimeter, and test the ignition system.



If that's all good, read this:

 

I had the exact same problem, I mean exact. My RPMs would rev way up then drop to the floor along with my voltage while the engine felt like it would shake the car apart. Many times, I had to turn off the radio and fan and take my foot off the brake pedal (lights) just to keep it started until I could gas it. I tried myself and then had to ask around and came up with a list of things you might try, most helped but only one knocked it out completely (hint: IAC).

1. New PCV Grommet: My PCV was flopping around loose with no grommet. Somebody suggested fixing this could be it. (WTF?)
Plus: Air actually runs through the air filter.
Fixed Idle/Start: Nope (Duh)

2. Fuel System Treatment: Truck driven hard and then neglected in my pop's driveway, hadn't had a treatment in years.
Fixed Idle/Start: Improved. Slightly smoother at running and idle speeds, still experienced major RPM and voltage fluctuations.

3. Replace Plugs & Wires: Lord knows when these were changed.
Fixed Idle/Start: Much improved. Much quicker start. Still experienced RPM and voltage fluctuations BUT these were delayed and did not start immediately on idle any more.

4. Clean Fuel Injector Plates: Good idea anyway.
Fixed Idle/Start: Improved. Noticeable improvement in RPM and voltage fluctuations.

5. IAC (Idle Air Control) Valve: Mechanic strongly suggested it, shop owner had his doubts. It's worth noting, the shop owner thought the engine needed an overhaul to fix the idle, but that he strongly suggested I just learn to ignore it since this was my only engine concern.
Fixed Idle/Start: Bingo! Right up on the top, in arm's reach, with just two little bolts and a dinky little wiring harness. Replaced in 5 minutes in the driveway at a whopping $58. Keep the battery disconnected for a couple minutes more to make sure the computer resets.

It was just a little crudded out, but a new IAC made all the difference. At low RPMs, combustion isn't complete when the IAC is not able to permit maximum air flow. Power dips, and the engine begins to lose life while RPMs hit the floor and so then does voltage, and then the engine revs way up to compensate. Think nodding off on a long road trip and waking up when you slip onto the shoulder.

I really think that this could be it for you and items 2-4 wouldn't be bad either. Good luck.

 

I mispoke about the PCV valve. The doohicky I'm talking about is the P-something-something coming out of the oil cap to the air filter box for recirculation and combustion. Some hippy contraption. Anyway, it was a dumb repair but worth the laugh.

 

That's the fresh-air INtake for the PCV system.

 

That's the ticket.

 

Had the same problem with my 87 f150 I6 IAC valve stuck and would stall going around corners and down shifting

took it off and cleaned with carb cleaner, never had anymore issue's with it