1989 F-250 300 inline 6 W/N start

[Austin8214]

I have a 300 fule injected inline 6 that will start but only run for a few seconds. It seems to be getting fule but i am not sure of the pressure. I pulled the plug on the mass air flow sensor and it ran for a bit longer but still stalled out. I pulled a plug but it seems to be dry, can smell fule on it but it is not wet. Spark seems to be strong at the plug. do you have any ideas for me? any help would be great thanks in advance.

[daveward]

Originally Posted by Austin8214

pulled the plug on the mass air flow sensor and it ran for a bit longer but still stalled out. I pulled a plug but it seems to be dry.

Austin8214...I've had similar symptoms that turned out to be a malfunctioning AirFlow sensor itself. In effect, the sensor has a door, through which all the air must pass as it gets sucked in. As more air volume tries to get through the door, it opens wider til fully open. The mechanism is prone to gunk build-up and then the dreaded sticky-door syndrome. If the door won't open...or won't open enough, or won't close, or close enough, that's all bad. That's because the "sensor" evaluates the door's position and reports the corresponding airflow to the computer...but if the airflow "number" reported is not consistent with other information the computer has (like throttle position), then the computer can't make sense of the data...and nothing good happens then.

For example, if the door is stuck closed, but the throttle position is wide-open-throttle, the computer will try to send loads of fuel into the intake manifold but there will be no air there to mate with. Engine acts like it's flooded and dies.

As for the fix, mechanics seem to want to replace the thing rather than clean it up and renew it. The logic seems to be since they have to take it out to clean it, they just put a "new" one in and it'll already be clean. I haven't had the "opportunity" to try to clean one up so I can't advise you on this aspect.

Dave

[FORDTRACMAN]

You need to check fuel pressure, 2or3 pounds will squirt you in the face from the shrader valve,but won't start engine.Check.
Report back.

[Austin8214]

OK i have low fuel pressure only about 10 psi. Where would i locate the high pressure pump on this truck? Or is there just the one in the tank?

[FORDTRACMAN]

I believe you need about 50 pounds of pressure.I am assuming you don't have dual tanks.Have you checked fuel pressure regulator,fuel filter?
Try a shot of starting fluid to see if it fires.

[Austin8214]

it will fire on starting fluid. I am getting good flow out of the Scharder valve on the fuel rail so i assume the filter is fine. Do you know if this truck has a high pressure fuel pump or is there just the one in the tank. I can hear the one in the tank run when i turn the key on. Also where would i locate the fuel pressure regulator at?

[FORDTRACMAN]

If it runs on starting fluid you have eliminated ignition.According to my book you should have 50 to 60 pounds of fuel pressure,[not running].I'm not sure about high pressure fuel pump.Try to follow the line.

[Austin8214]

Ok thanks for your help.