I've got an 89 F250 with a 7.3. The problem I'm having with it is that when driving the fuel filter light comes on and I loose power. I slow down / stop, the light goes out, it idles normally. The kicker is that I've replaced the fuel filter 3 times in the last 1k miles. The first time I cut the filter open and it was black and a little slimy. The last 2 times however the filter really hasn't looked plugged at all. At first I figured a few filter changes isn't a bad price to pay for driving a truck that has been parked 97% of it's life, after 20 years of sitting it probably should have plenty of sediment / growing things in the tanks. But since the filters don't look clogged and the last one tripped the light and bogged the truck with less than 50 miles on it I suspect that throwing $50 filters at it is not the right solution and I should be looking elsewhere. I've spent about the last 5 hours scouring these forums for help, and I've learned a lot. I'm just not any closer to picking up a wrench. Long story short, can anybody point me in the right direction?

Oh it's also got air infiltration problems, after about 30min of sitting there is almost no fuel left in the filter. Takes 2 people to start it easily. One to turn the key and one to hold the schrader valve open until fuel flows nicely. Then it just runs rough instead of dying followed by 45 sec of cranking to get fuel to the IP.

I think I've gathered enough info to solve the air problem from previous threads; but I'm not sure if I've looked in the right place or applied the right searches for the power loss / filter problem. Again, any direction would be appreciated.

Thanks,
Joe

 

I have an 88' that had a similar problem. What it was is the rubber hose that connects the fuel line to the lift pump had a crack in it. Could get started, died less than a mile down the road. There should only be one rubber hose down there, I'd suggest to check it out. Otherwise check the pressure of your lift pump, it may be worn. They are pretty cheap to replace.

On a side note, I have an 89' that SOMEBODY (PO) cut the fuel line that goes over the crossmember under the motor and replaced it with a rubber line... check for any of that juryrigged stuff too. Most of the lines are fairly easy to see.

 

The black slime may be degraded rubber lines. You could have a weak lift pump or chunks of your fuel pickup blocking a line. Do your tanks go clear to empty? A previous post stated the fuel filter light will come on if it senses a restriction based on ? I think he said vacuum.

 

I checked out the rubber hose going to the lift pump it looks to be okay. The back tank goes clear to empty. So I'm assuming the cone of doom hasn't rotted off of the sending unit yet. The front tank hasn't been used in 12 years. The fuel selector switch stopped working either the switch or valve is bad. I've just never fixed it because it feels better at the pump when you only have to pay for one tank of fuel. The truck has less than 20,000 original miles on it. So 90% of its problems are probably due to it being stored improperly for nearly 20 years. It’s never really seen road salt, sun, snow, or any kind of weather at all; even as a Minnesota truck.

As I understand it I can check pressure / flow at the schrader valve on the filter housing. And I know I've read what I should see for numbers at that point. I just can't seem to find them now. My head is telling me 4-7 psi and about a pint a minute at idle; does this even sound right? Even if the lift pump is cheap I have a lot more time than money at the moment (starving college kid), so I'd rather run some tests and identify my problem and only fix what needs to be done for now. Someday when I have a great job, the economy is awesome, and Chuck Norris cry's I'd like to turn this truck into a mechanical monster. Until then I'll be happy to keep it on the road.

Although I’m thinking, the truck runs fine at idle; so maybe I will see normal pressure and flow even if I test it (at idle). So is there a way for me to test it under load? And if a lift pump is going bad will it be capable of supplying enough fuel at idle but then fail to deliver at hwy speed?

Sorry the post got long, I’ve been thinking while I type.

 

I must say I enjoyed reading your tale of a long post, and I am in the same position as you lol drove 1300 miles to go to college and no job, but anyways... The lift pump runs off of a lobe from the crankshaft. When it is at idle it may supply enough fuel to keep it running fine then, but as soon as you rev it up, if the pump is bad it will not supply the motor with sufficient fuel. The pump is roughly $30 and extraordinarily easy to install, I personally would suggest to replace the rubber hoses while you are down there to be sure they don't break on you later. As for the tank selector valve... The switch itself is easy enough to test with just a voltmeter, just set it to a continuity test and test it between front and rear. Chances are the actuator to switch between the front and rear tank snapped off, and the motor is still fine. But, the part itself is around $350 from the stealership, I bought one roughly three weeks ago, but it was also smack in the middle of my 1300 mile trip. So if you can get by on just one tank, I'd suggest that.

Something else I just thought of, when was the last time the fuel filter was changed at the engine? If you haven't changed it recently... unscrew it, how full of fluid is it? If it is low, means you have poor flow through your filter or a leak. Those are roughly $30-$40 depending on where you go.

I'll end my rant now, I love these trucks. Guess that's why I have two of them

 

So it took me three months to finally have the "time" to work on the old beast again. The future misses has been stealing all of my weekends for wedding planning ordeals. Went to Oriely's bought a lift pump. Pulled the vacuum pump, pulled the old lift pump, turned engine over with a socket and breaking bar until the oddly shaped cam was positioned right. Installed new pump. Reattached curly rubber hose. 15 min; I think I'm doing well. I thought wrong New pumps fitting for the metal line is about 1/2 inch further from the ground than the old one. One hate filled hour later I finally got smart (maybe), unbolted the filter housing, attached the line and forced the housing back in place. If it breaks or starts leaking at the fittings It'll be a good excuse to block off the pump hole and go electric.

Then the fun stuff happened, I decided that since I tried one bad idea already, I might try for two. Instead of messing with cranking cycles, and paying my jerkoff roommate to come turn the key for me while I bleed the system (He's so lazy he won't walk out to the garage and help for 5 min without monetary incentive). I decided to jump the starter relay without turning the key on first to bleed the system. My idea being that if the fuel shutoff valve is closed while it's cranking it can't get any air in the injector lines. So I pulled the shraeder valve, and jumped it, filter was half full when I started. 10 sec later there is fuel shooting everywhere! Awesome! Right? Yes.... Valve, re-installed, key in ignition, glowplugs cycled, turn key to start. Nothing. What!? Plug little wire back into the relay. Key in ignition, glowplugs cycled, turn key to start. Bam! Started right up And stayed running. Drove her to Target to get some milk for breakfast tomorrow. I'll probably drive'r to work 'morrow just 'cause I can.

So the take away from all this is thanks Nero and airdale for the help . My truck thanks you, I thank you, the future misses will thank you. (after she gets over the fact that I skipped calling cake vendors in favor of fixing my truck ). The truck will after all eventually move all her crap to our new place, then she'll appreciate it too

 

Glad to hear you have it running again! Just as word of advice when bleeding air be careful not to crank too long, and allow starter to cool so you don't burn it up! I made that mistake ONCE. Enjoy your wedding day, I'm looking forward to mine!