I know that this topic has been addressed in other posts, but the answers do not quite answer my problem. Maybe someone has the "simple solution" for me. I have a 2002 F350 w/7.3. I do not drive it during the colder months since it is pretty much used to haul summer toys. Last fall it was beginning to start harder and harder. I do start it periodically during the winter and leave it run for a while, but other than that, it lives in the barn tucked away for the Wisconsin winters. I am trying to avoid having to pull the rocker covers to replace the glow plugs if they don't need replacing. Here are my questions. Is there a way to test the plugs without removing the rocker covers? Is there a way to test the relay? Are there any other tests I can perform before actually removing the rocker covers? One other bit of info. When I check the voltage on the down stream side of the relay (mine has 4 terminals) I only read a little over 10 volts. I bought the truck 5 years ago, and I am pretty sure the batteries are the originals. I stopped at a local WalMart and had them load test the batteries. One showed marginal, and they could not get a good connection on the other. I cleaned the terminals, so I know the connections are good. Is it possible my whole problem is just low voltage? Much below 60 degrees, the engine won't start. Any ideas would be appreciated.

 

I would change the batteries first. Next thing would be the Glow Plug Relay. I would doubt it would need new glow plugs. They last a long time. You could also plug it in and see if it starts easier.

 

That might be the problem. Diesels don't like to be started and shut off cold. Unless you drive the truck for at least 20 miles, the engine will be better left alone for the months you are not using it. Just pull the battery clamps off and recharge the batteries every 6 months.
The 7.3 l will be always hard to start since it needs to build up oil pressure to open injectors. Mine other diesels start on the first or second cylinder even after sitting for few months, the 7.3 will take at least full turn even restarted after a minute.

 

Moved to the 1999 - 2003 7.3L Power Stroke Diesel forum.

 

Thanks for sending it down this way John.

To the OP. For future reference, post your 7.3 engine questions down here. Odds are if you're showing only 10 volts when the key is turned on then your issue is voltage since the glow plug system is what is drawing your voltage down so low. What happens is when you crank the engine, voltage is dropping off so much that the IDM is not firing the injectors. To test this, turn the key on and watch your meter while it's reading 10 volts. Keep watching until the glow plugs cycle off (up to 2 minutes) and see if the voltage doesn't come back up to around 12 volts. Then without turning the key back off, turn the key to start and see if the truck will start up.

To answer your questions about testing, the GPR has 2 large posts and 2 small posts. One large post has a rubber boot on it and should show 12volts at all time. The other large post (down stream) should only show voltage right after the key is turned on (for up to 2 mins). If you've got voltage coming out of the GPR and it's very close to the voltage reading of the power coming into the GPR, then the relay is good.

To test glow plugs, locate the flat wiring connector that plugs into the inboard side of each valve cover. Unplug the connector and you will see 9 flat pins inside the connector at the valve cover gasket. Grab a multi-meter and set it to read ohms. Place the black lead on battery ground and touch the red lead to the forward 2 and rearward 2 pins at each valve cover. These pins are connected to your glow plugs. Good glow plugs should read less than 2 ohms (usually we see around 0.6)

If you replace batteries, be sure to replace both of them at the same time.

 

Thanks for the help folks! I tested the batteries with a hydrometer, and found several low and one dead cell. I put in two new batteries and my voltage is now constant across the controller. Engine cranks like it hasn't for years. I tried it when it was around 60 degrees outside and it started after about 5 seconds. Looks like everything you guys told me is accurate. Hopefully it is still several months away before I can try it in below freezing temps. Sure is nice to know how to test the plugs without tearing everything apart to do it. Thanks again for everyones help!