mattbarron94

Hey guys it’s been a while since I posted but I am stuck and I need some help. I drive a 1994 f150 with the 4.9 straight six and it’s not starting.

About a week ago I got off work and got in my truck and no start, it was cranking but it didn’t start. So I hoped back in the work truck and drove home.

Now I have my work truck (13 f150) to drive fortunately so I decided to tackle this one myself instead of taking it to a shop.

i knew my front fuel pump was on its last leg so I immediately jumped to that. I replaced the whole fuel pump assembly with a spectra premium fuel pump and also replaced the fuel filter. No good.

I then replaced the TPS, Fuel pressure regulator, and the distributor cap (All cheap parts so I said the heck with it, can’t hurt it) still no good.

i did some research and found that aftermarket fuel pumps tended to be a nightmare and decided to return the spectra and order a motorcraft fuel pump. Tonight I installed the new motorcraft fuel pump, and double and triple checked to make sure I wired it up right. Still not starting.

I cant seem to get a fuel pressure reading, I’m assuming because you can only get one when the truck is running? I’m at a loss, I still have a couple weeks to figure it out before the work truck has to go back, so I’m determined to get it started without bringing it to a mechanic. Any help would be greatly appreciated.

p.s. I’m no master mechanic, but I can sure as hell turn a wrench and I’m not afraid to get dirty

Eric Fullerton

A couple of things to check, the relay under the hood, the inertia switch in the passenger kick panel. Does the pump prime when you turn the key on (the few second buzz).

mattbarron94

I checked the fuse and the relay, I have not checked the inertia switch, and I have not heard the pump prime, but I havent really listened for it either.

Chris_1

iTrader: (1)

You should see close to 45 psi fuel pressure as soon as you turn the key to on.
Make sure it's quiet, but then you should hear the pump prime for 1 or 2 seconds every time you turn the key off and back on.
If you've already checked the fuse and relay, then the inertia switch behind the passenger kick panel could be tripped - the red button should be pushed down. You can use a test light to check for power on both sides of that.
The dash switch is also in that circuit.
You'll also want to check for spark in case all this has nothing to do with fuel pressure.

mattbarron94

Ok, so check inertia switch first, then check for spark. So what causes the inertia switch to flip during normal operation?

88xlt

The inertia switch should not trip unless something bumps into the truck or the truck bumps into something. It's possible another vehicle bumped into your truck while it was sitting in the parking lot, not likely but possible. So a good idea to check the inertia switch if you don't hear the fuel pump for a second when you turn the key to the run position.

Phil48315

You need to check for fuel pressure.
Spark
And fuel injector pulse.

Go to you-tube and look for videos that show what to do to test.

Chris_1

iTrader: (1)

You can also do the "starting fluid test" to try to narrow it down to fuel or spark.

Pull the intake hoses off the throttle body. With the throttle plates wide open, fire a 3 second burst of starting fluid straight in. Then turn the key. If it fires for a few seconds and dies, you likely have a fuel issue.
If it doesn't fire, you likely have a spark (or timing) issue.
My son said brakleen works as starting fluid, but I haven't tried it.

Phil48315

Yes it does.

mattbarron94

Ok, so checked inertia switch, it was pushed down in the correct position (am I right?)

checked the fuses and relay again. All good.

listened to hear the fuel pump prime, nothing. I hear a click or two and that’s it.

So ive gone aftermarket and motorcraft fuel pump and neither are working? I know it’s wired up correctly because I read correct fuel level on my fuel gauge.... I’m so lost lol