Help me please!!!!!!!

Stephanie Adkins · #1 (**permalink**) 04-14-2012, 05:43 PM

Ford F-150 1991 302 motor 4 wheel drive truck will start then will die straight out got fuel pressure tested and it was low so put a new fuel filter in it and it is still doing it any ideas on how to fix this problem any and all suggestion will be appreciated!!!!

Ddaybc · #2 (**permalink**) 04-14-2012, 07:08 PM

Quote:

Originally Posted by Stephanie Adkins

Ford F-150 1991 302 motor 4 wheel drive truck will start then will die straight out got fuel pressure tested and it was low so put a new fuel filter in it and it is still doing it any ideas on how to fix this problem any and all suggestion will be appreciated!!!!

Stephanie if ur truck has dual tanks make sure ur switch is set on the tank with fuel in it. I know as I had the same symptoms nd mine was on the wrong tank. Also, re-test ur fuel pressure with the new pump. Some of our trucks come with a low pressure pump (in the tank) and then a high pressure one at the fuel rails. However I don't know when that was started by Ford. I think ur 91 only had the tank pump(s) but I am not sure. I hope someone else can clarify for u. I hope this gives u a place to start. My knowledge is pretty limited.

subford · #3 (**permalink**) 04-14-2012, 07:23 PM

Low fuel pressure most of the time would mean that you have a bad high pressure check valve in the other tank then the one you are running on. This would also mean the the tank that you are not running on is filling with fuel.
You do have two tanks yes, no?
Are you only using one tank if you have two?

Who check the fuel pressure and how did they check it?

Yes a 1991 F-series only has the high pressure pump in the tank and none on the frame.

Stephanie Adkins · #4 (**permalink**) 04-15-2012, 12:56 PM

it just has one tank, we have checked the coil its good we have replaced the module also so it is good and it still won't fire what could it be now !!!!!!

subford · #5 (**permalink**) 04-15-2012, 01:09 PM

I have my doughs on the low fuel pressure.
Who checked the fuel pressure and how did they check it?

When these fuel pumps run they will put out about 100psi into a closed head.
The Fuel Pressure Regulator (FPR) will reduce it down to around 30-34psi at idle and 40-45psi at full throttle. The spring in it will hold the pressure at 45psi but with the engine running vacuum is supplied to counter the spring and at idle the vacuum is enough to reduce the pressure down to 30-34psi depending on the vacuum reading.

The spring could be weak in the FPR but other than that and the fuel filter there just is not anything else that could do it other than a pinched fuel line from the tank to the fuel rail or low voltage.