Fuel light flicker fix - Diesel Forum

waterdude · 07-05-2005, 02:36 AM

A couple of weeks ago, my Fuel Light started flickering at start up.

I'm going on a long trip next weekend, so any suggestions would be great.

--Hugh

pnose · 07-05-2005, 12:05 PM

How old is your fuel filter,thats what i would start with.

cdnsarguy · 07-05-2005, 02:26 PM

Do a pressure and volume test on the Lift Pump.....the flickering light indicates a vacuum in the filter header. Like PNOSE said either filter plugged, lift pump dieing or tank pickup could be broken if the fuel level in that tank is around 1/4 full.

Do pressure and flow test on the fuel pump at the Schrader valve on the filter (FSS- fuel shutoff solenoid disconnected). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.

If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.

tim94f250 · 07-05-2005, 02:27 PM

If it was just the fuel filter light, then replace it. If it was the water in fuel filter light, then drain the water out of the drain.

waterdude · 07-06-2005, 10:56 AM

Thanks for the suggestions...

My Motorcraft fuel filter is 1 year old (4,000 miles).

It isn't the Water in Fuel light (below the Wait to Start light), but the Fuel Filter light (next to the Brake light).

From what I've been reading in the archives, lots of other 7.3L owners with similar age and mileage are seeing the same symptoms. Also, if more people would post the results of their testing, others would have more knowledge of what the fixs are.

I'll drain any water from the filter and then do Pete's testing procedure.

Thanks a million,

Hugh [img]/ubbthreads/images/graemlins/smokin.gif[/img]

waterdude · 07-08-2005, 12:31 AM

Ok, I'm feeling lame as I can't find the location of the fuel pump. I bought a new one and I want to change it out.

1. Where the heck is the fuel pump?

2. How do I nudge the starter to get the fuel pump cam lobe into the low position? How do I know when it is in the low position?

Thanks much,

Hugh

cdnsarguy · 07-08-2005, 08:34 AM

Location is front pax corner of the lower block, you can use a socket/ratchet on the crankshaft bolt 15/16 I believe.

To ensure that the cam is at low position, it is necessary to use a mirror. Observe the cam through the mounting port and bump the engine around until a one (1) inch wide machine surface is observed. This is low position of the cam. Now complete normal fuel pump installation. Point is put the pump arm in straight so the pump flange contacts the block flat "not ****eyed then try to pull it flat with the bolts".

waterdude · 07-19-2005, 02:31 AM

I bought a 5/8" flare nut wrench tonight, so I'm almost reading to roll.

I have to get this done by the weekend and I've never attempted a fuel pump before.

1. should I remove the vacuum pump to get at the fuel pump mounting bolts? Or just work from underneath?

2. I still don't understand when I know that my motor is in the low cam position? I should loosen the mounting bolts and then bump the engine around and wait until it feels loose?

Thanks much, Hugh

cdnsarguy · 07-19-2005, 02:51 AM

Just work from underneath, read the insructions above ...via the mirror and light, I use a 15/16 socket and ratchet/bar to rotate the crank clockwise.

icanfixall · 07-19-2005, 01:03 PM

Years ago when I replaced my mechanical I worked from the top. I removed the vacuum pump for more room. I may have even removed the alternator but its long ago. I now have an electric Holley Red pump and it sure works nice.... [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

waterdude · 07-21-2005, 10:43 AM

Last night I did it [img]/ubbthreads/images/graemlins/smile.gif[/img]

The fuel pump removal was the easy part. 5/8" flare nut wrench with a small extension for leverage made removing the brass fuel line easy. I didn't want to bust a knuckle to begin the job. The old fuel pump came out easy, didn't matter where the cam lobe was sitting (now I know what the low position looks like too).

Installation was a different story [img]/ubbthreads/images/graemlins/frown.gif[/img] I thought that I was going to quit as I couldn't get the bolts to start on both sides and I thought I might ruin the new gasket. Instead of quitting, I removed the vacuum pump and trying installing from above. That worked fine, it took me just under two hours working at a snail's pace. Now that I've done it, I should be able to do it next time in about one hour.

The TDS advice/help is awesome, I could not do it without all of your help. A special thanks to Pete for his consistant helpful posting to advise the newbie.

Hugh [img]/ubbthreads/images/graemlins/cool.gif[/img]

waterdude · 07-26-2005, 09:08 PM

arrrrgggghhh [img]/ubbthreads/images/graemlins/frown.gif[/img] the fuel filter light is flickering again after I replaced the fuel pump. What do I do now?

I don't mind that I have a nice new fuel pump, but I still have a problem to solve.

Thanks,

Hugh

--well, I just read cdnsarguy 1st reply above, I guess I already have things to check [img]/ubbthreads/images/graemlins/crazy.gif[/img]

Gibson · 07-27-2005, 12:45 PM

try switchin tanks. the rpoblem might be in one tank adn not the other. good luck.........Gibson

DLSF350 · 07-28-2005, 10:39 AM

If it is flickering more when you first start it, start looking for air or vacuum leaks. I changed 2 filters and eventually a pinhole leak in the front tank sending unit made the truck run rough. I temporarily installed a piece of clear plastic tubing between the lift pump to the filter to see the air bubbles being pulled in. It took about 6 months/6000 miles between the flickering @ startup to get bad enough to affect the truck idle.