Bmusick11

So I have a 96 f150 4.9l y. Automatic 60k 4wd. So it runs and drives great until you drive it until it warms up and let it set for 20 mins and then try to start. Acts like it is going to crank. Starts shaking and dies. Usually take 4 or 5 times to finally get it running and then does fine. Or u can let it set until it fully cools off and starts with no issues. Have Changed the following. Distributor. Plugs and wires. Crank shaft position sensor. Fuel filter. Throttle position sensor. Engine coolant sensor. Injectors. The injectors has been the last thing I changed and since then the truck don't have to really get hot like it did to have the same issue. Now it does it if it has been sitting over night. About 2 months ago I drove the truck for 2 weeks straight and it never had an issue. But it has started again. That is why the injectors was changed but still have same issue now. Please help! Have tried everything and don't wanna keep throwing money into truck that isn't helping issue

Matthew Burr

have you pulled codes?

Bmusick11

Yes. It has pulled p0171 and p0174. And also p0301 p0385

Manuellabour247

Fuel pump and o2 sensors been changed? Also, check all of your ground cables.They cause gremlins like no other.

Bmusick11

Haven't changed the fuel pump yet. Is there anyway to test it before replacement?

Manuellabour247

2 ways, you can volumn check the flow by disconnecting the fuel line and measuring the amount that flows into it in a specified time. That's really for old school set ups though. The main way that people check on fuel injected vehicles is putting a gauge on your fuel rail and recording the pressure. There are a few threads on here that have the readings you should be getting with KOEO (Key on Engine off) and KOER (Key on Engine running).

I still would check the ground wires first though. It's simple enough to do. Make sure there is very minimal corrosion on the connections. Use dielectric grease on the connections when you go back together with it. That will help prevent future corrosion.

Bmusick11

Took truck to ford dealership to have it looked at. They said the throttle position sensor was bad. Replaced it again. Still have same issues tho. Pulling codes p0385, p0171,p0174, p1150, p1151. Any ideas ?

Chris_1

iTrader: (1)

Don't throw any more money at it until you have checked the fuel pressure. Your own gauge will cost you about $60 and you get to keep the gauge after. Mine has been a very good investment.
A 96 4.9 runs between 30 to 45 psi and does not run below 30 psi. There is a schrader valve on the fuel rail (where the injectors are). You screw the gauge on there and turn your key to on.
You should be looking at about 42 psi minimum. It should hold that pressure for a good 3 to 5 minutes at least.
Now you start the truck. At idle it should drop about 5 to 8 lbs. maximum. While it is idling, disconnect the vacuum line from the fuel pressure regulator (also on the fuel rail). Pressure should climb back up and then drop again when you plug the vacuum line back in. You can also smell that vacuum line to see if it has a fuel smell, which would indicate a leak in the diaphragm in the fpr.
You could be dealing with a low pressure, hydrolock, or flooding situation. You need to do these tests to determine that.
If the fuel system checks out ok, then you can move on to other possibilities. Until you test the fuel system, you're just throwing money at the truck, hoping it works.

Bmusick11

Ok thanks. What kind of gauge should I get? Can you send me a link to one that'll work for my truck?

Bmusick11

Got a fuel pressure tester and hooked it up to truck. When truck is on running about 40-42 psi. When rev truck up fuel pressure drops? Shouldn't revving the truck increase the psi? And also one turn off truck and start back up fuel pressure decreases low sometimes under 20 psi then once it seems to pick up fuel pressure increases back to 40. What could this be? Bad fuel pump or what ? Please help