Hey guys;

Last night my son's '90 F150 351 wouldn't start. We checked the module on the distributer, it was OK. Then we put a little gas in the throtle body intake and it fired right up then stopped when it used that fuel. The fuel pump runs all the time, but the truck won't start. Before we go through the hernia operation of changing the pump, is there anything else we might check?

Are we possible talking about the "sock problem"?

If a pump change is in order, how hard it is to just lift off the bed to gain access to the pump?

Thanks in advance, you guys are great.

Frank

 

I lift the bed off to get to the pomp on my 92 F150. 6 nuts, the gas tank filler hose, two brake connectors and you are ready to go. I have a 45 gal gas tank so this is much easier.

 

How do you deal with the wiring for the tail lights when you remove the bed? I have to get to my front fuel tank and would rather not drop it.

 

you unplug the harness from the bed, behind the rear bumper if you folow the wires there is a plug, unplug it, its the same spot where you plug in for trailer lights. i think its a gray connector, and the wires are covered in a black coragated stuff.

 

I'm going to try it. Thanks, DCC

 

Check to see if you have fuel pressure on the rail first. I am thinking that it may be a clogged fuel filter or possibly a fuel pressure regulator. If the filter has not been changed in a while that would be the first thing that I would try.

 

I think it is not the fuel system at all. Turn your key from off to on. Do not attempt to start. You should hear the electric fuel pump come on, then shut off after two seconds. If instead, it keeps running and running and running, there is a good chance the engine control computer (ECM aka PCM) is dead. One way to check this is to attempt to run a KOEO test. If you cannot get codes (pass or fail) out of the ECM, it is not going to run your fuel injectors.

The ignition system can run independently of the computer, especially during start. It is quite possible for the engine to run on fuel dumped into the throttle body, and spark generated by the TFI, with a dead ECM. It will act like a "fuel problem", but the reason fuel isn't reaching the engine is that the fuel injectors are not being opened.

Before going to all the work and expense to change the fuel pump, you should buy a $40 fuel pressure guage and check your fuel pressure. If the fuel pressure is 40 PSI or thereabouts, the starting problem is not being caused by the fuel pump. For that matter, you can do a $0.00 check just by pressing in on the stem of the Shrader valve on the fuel rail. If you get a good piddle of fuel, there should be enough pressure to get at least a pop out of the engine.

If, indeed, it is a non-responsive ECM, the first thing to check is the ECM power relay, the grounds, and the big 60 pin connector.

 

Could you elaborate on the KOEO test?

Thanks

Frank

 

You can find descriptions on how to run the test here:

http://www.dalidesign.com/hbook/eectest.html

or here:

http://www.troublecodes.net/Ford/

or here:

http://fordfuelinjection.com/index.php?p=13

Basically, all you need to do is find STI and ground it (or hook to SIGRTN).
You do not need to hook up to STO, the MIL lamp on the dash is less work.

In your case, you are not so much interested in specific trouble codes, but whether the computer will talk to you at all.

 

Thanks I will check that out. I got a fuel pressure regulator and will throw that at it first. It is only 20 bucks, so I can gamble that much. If that doesn't fix it it is time to "call the man". I can't start throwing $100+ parts at the problem.

Thanks

Frank

 

Well, I ran the KOEO test and got many codes. They were telling me that various sensors signals were out of the usable range. I am assuming that that is because the engine was cold. Since I did get codes, I guess the computer is OK. While we were running the KOEO test the fuel pump stopped. After the test we tried to fire it. It started after much trying. I am thinking the fuel pressure regulator is not holding pressure after shutdown, I am going to change the regulator tomorrow. We'll see what happens then.

Frank