I have a '91 F-350, crew cab, 5 sp., 460, with flatbed & two fuel tanks.

The problem is some times it won't start right off when the key is turned to start. When I first turn the key I can hear the wirring sound in the dash. But when turned to the start position it doesn't alway start. Acts like lack of fuel. Most the time this happens after the rig has been run & warm, but also has done this a time or two after sitting all night & cold. It doesn't matter which tank it is on. After start I'm getting plenty of fuel from either tank. I've pulled hellish loads in high heat up 10 to 18 percent grades (dirt mountain roads) in over 90 degree heat, never misses a beat, just winds out as pretty as can be! So I don't think this is a pump or selector switch issue.

Some times I have to try starting it 8, 10 times before it starts. As soon as it starts never misses a beat. Could this be a relay or some thing? You guys have always bailed me out in the past so here I am again. Thanks in advance for your responses!!

 

Can't think of anything right now but figured I'd post and get you back to the top.

I originally thought check valve in pump. Or regulator. Or iffy high pressure fuel pump.
Maybe fuel pump relay is acting weird.
But you say it runs great... Which it wouldn't if any of those were starting to fail. The check valve is only an issue if you turn key to run and then wait too long before cranking. Or of you are inpatient to let pump prime first and all pressure has bled down.

Back to top. Hope someone can throw in some ideas.

 

How long does the "wirring sound" last if you do turn the key to start?
One second?
OR does it make the "wirring sound" all the time the key is in the on position when it does not start?

 

When I turn the key from off to on it makes a wirring sound. It only lasts 1 or 2 seconds then stops by its self, fuel prime or something? I've always turned the key farther to start after the sound quit. Most the time it fires up quick. lately it has taken 8, 10 tries like this to fire. When it does fire it never skips a beat. Any ideas?

 

Ok. Lets start from beginning.
When was last time you had plugs wires and coil changed.
Next, you need a fuel pressure gauge to see if you're actually at 38-40psi when it doesn't start correctly.

Fuel pressure is as simple as using a spare oil pressure gauge on the fuel rail. It's a 1/16 npt fitting in the rail you can use. Then duck tape gauge to windshield wiper so you can see it.

 

Try turning the key just to on and then back to off. Do this four times before you try to start it and see if it starts right up that way.
If it does then you have a bad check valve in the fuel system, fuel pressure regulator or a leaking injector.
To check the regulator just pull the vacuum hose of the nipple on top and turn on the key with a cold engine. If any fuel comes out of the nipple you have a bad fuel pressure regulator.

 

UNTAMD
I haven't changed plug wires or coil. Bought this truck used, never had any problems. Good gas mileage for what it is & how it is used. I really put a load on these trucks & people don't understand the kind of dirt mountain roads I run on. No high or low rpm misses, just really purrs right a long. Just the start up thing every once in a while. At this point I really don't think it is plugs, wires or coil. I have a fuel pressure gauge at home but I need to get off the mountain to get it. All this week I only had the start up problem once.

subford
I tried pulling the vacum line off of the regulator this morning with a cold engine, no fuel, so I guess the regulator is not suspect at this time. I haven't had the start up problem since I read your post. Will try the 4 time key trick the next time it acts up. Some more questions now. Where would a check valve be in the fuel system? In each pump? Any others? If not it seems weird to me that I would have pump problems starting at the same time in two different tanks. When I get off the mountain I'm going to put a new fuel filter on. I really don't think that will fix this but there will a new one installed going into winter. I have a '89 460 donor enginge. The fuel inectors in that don't have 5,000 miles on them. Will they work in this 91?

Thanks to the both of you for giving me your thoughts on this!! If you think of anything else please let me know.

I'm real curious what my fuel pressure will be with a gauge hooked up when it acts up. Trying to figure out a way I can hook it up & drive with it before it acts up. That way I cold see what it was doing right then.

Thanks again guys!!

 

The shrader valve in the fuel rail is where you hook the gauge up. You can unscrew it and most oil pressure gauge kits come with a 1/16 fitting that will screw right in. I don't suggest you put the gauge inside because if anything happens you'll have fuel in the cab.

Check valves are in the top of each pump

Blue top injectors in the 89 are the same as in the 91.