Question about 2003 Ford F350 Super Duty DRW SuperCab

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Hard starting change glowplugs now runs rough and sluggish

I have been having trouble stating 01 ford 7.3L diesel so i replaced glow plugs and relay. now starts right up but runs really rough it wont get up and go like it did before i changed them i checked electical wires that i took off and alson checked vacuume lines. what now. can a dealer hook it up to a computer and tell what is wrong like which cylinder is misfiring.

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  • Anonymous Jan 17, 2009

    that engine has the wiring for the injectors built into the
    valve cover gasket and the connectors do get brittle
    unfortunately the gasket it $60.00+
    so find out which cylinder bank is not firing first



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Well first off i would change the fuel filter if that has not been done also check the air filter if this does not work sounds like ya got a bad injector most any shop that works on diesel and has a scan tool can tell you what clynder is causing you the problem. They are a bullet proof engine most the problems i see are fuel leaks glow plugs and the relay that go bad but the injectors also go bad every now and then.

Posted on Jan 08, 2009


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My hiace turbo turns over ..but is very sluggish until it heats up a bit..then seems to run thinking glowplugs..

not sure of what you mean
glow plugs are there to assist the instant start of the diesel engine
it will wind over well without the plugs operating but takes longer to heat the compressed air in the cylinders to fire the diesel being sprayed in
if it starts and is still sluggish to respond to the accelerator , that is a different problem to the glow plugs
I'm thinking low fuel pressure if common rail diesel and bad injectors squirting and not atomizing
have a proper diagnosis done by an accredited professional diesel repair shop

Apr 18, 2017 | Cars & Trucks

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This is not to hard to solve. The outside airtemp determines how long the Glowplug timer works for absolute cold starts. Starting a warm engine is affected by underhood temps.

The Timer Relay will pulse power to the glowplugs. If the glowplugs are good, it is enough to preheat the cylinder for firing.

To tell if a glowplug is good is a matter of comparision between a new glowplug and a worn glowplug. YOU CAN MELT A GLOWPLUG WITH THIS TEST, but you remove the glowplugs, get a set of battery jumper cables and place one jumper to the base of the glowplug USING CARE not to ruin the threads on the glowplug.

You do not want to arc the spark on the glowplug threads. You want your fixed jumper connector locked on the base of the glowplug. The other battery cable jumper is touched to the top of the glowplug where the arcing occurs. This will not hurt the contact point if done properly.

You compare the "glow" of the old glowplug to the "glow" of the new glowplug. Bad glowplugs stay dark or operate at a darker color.

The Timer Relay gives you pulses and that is all the glowplugs get to heat up. This is what you simulate in your test. If a glowplug operates in a dull or dark condition, it is bad and throw it away. You want all glowplugs to readily light up when power is applied.

The other 2 parts to the system are the Timer Relay and the Power Relay. The timer gets its power from the Power Relay and the Power Relay is like a starter solenoid. The Power relay gets a tickler charge when the keyswitch is held to Start.

There are sometimes extreme cold Timers that hold the power longer tothe glowplugs. I do not have the Specs to tell you if your Timer is kicking out to soon.

I hope my solution helps. I have told you how to test your glowplugs. The timers are affected by air temperature and that makes it difficult to say if it is working long enough. If you know the glowplugs are good, and the timer shuts off before the glowplugs heat up, then you need a new or different type of timer.

Sep 26, 2012 | Cars & Trucks

1 Answer


Hello, The diesel engine relies on Glowplugs for the first start in the Morning or a cold start at anytime.

The Glowplugs themselves can be bad, but there is a Timer which determines how long the Glowplugs will stay on. Before the Timer is a Glowplug Relay which gives the Timer its power to operate. The Ignition switch provides power to the Glowplug Relay.

You disconnect a Glowplug wire, put on a test instrument (either a testlight or Voltmeter) and look to see what happens when you initiate a start. If the testlight lights and cycles a few times like a pulse, then the power supply is good. If not inspect the Timer and Glowplug Relay for continuity

If all the pulses seem to reach the Glowplugs, then most likely the Glowplugs are worn out. Test by removing then and connecting battery jumpers. Briefly touch the top terminal of the Glowplug with the Hot cable after grounding the negative cable on the base of the Glowplug, avoiding the threads.

You can melt a Glowplug. But if you find the Glowplug staying dark, then it is bad. Do this for all the Glowplugs and replace the bad ones. Remember the Glowplug only has the amount of time the Timer gives it to work. So if a few pulses do not make it Glow, then replace it. This should fix you up.

Aug 24, 2011 | 2005 Ford Expedition

1 Answer

1987 Ford f-250 6.9 liter diesel. Glow plugs are good, Relay is new, glow plugs don't work... is there a glow plug relay controller or timer that can be replaced, and what is the part's proper name?

Check for fuses first. The Glowplug timer is the proper name for the part that responds to Temperature when starting your engine. When the engine is cold, of course it is on longer and can cycle making a click and intermittently dimming the lights on your truck. When the engine is warm, your gowplugs may not even fire as the engine is using compression alone to fire up.

Also, Ford did make a Severe Weather model that kept the glowplugs on longer. If you stay in Alaska or a climate with consistent subzero temperatures you may need it.

Nov 16, 2010 | 1987 Ford F 250

1 Answer


some of the glow plug have had it, rough idle ,andsmoking after a hard start is typical symptom of some of the glow plugs not working.what happens then,is because you keep trying to start it,the remaining glowplugs get over heated with continuous heating up so they toss it in then it gets to the point where it wont start squirt some starter fluid ,or aerostart into th air cleaner and you will probablyfind it will start strait away if so anew set of glow plugs is in order ----"youdoit"

Oct 28, 2009 | Ford F-350 Cars & Trucks

1 Answer

I have a 1999 Ford F450 super duty diesel. It

Replace the glowplug relay.Its faulty.The glow plugs stay on until engine warms up.The engine temp switch then activates the relay to switch off.So it could be the temp switch also faulty.

Jul 17, 2009 | 1999 Ford Super Duty F 450

1 Answer

Glow plug problem

This may not person to your question. A friend familiar with diesels takes out the automatic electric timed feed to the glowplugs, installs a manual momentary switch to energize the glow plug warm up power. His theory is timer problems, to eliminate the timer and use the glow plug manually.

Oct 01, 2017 | Ford E-350 Cars & Trucks

1 Answer

2004 F450 super duty, very hard to start, must use either.

Check the glow plug relay, wires and glow plugs, could be that or an injector stiction problem. If you have an in range coolant sensor, intake air, or manifold air temperature fault the engine could think it is already warm when it starts and does not compensate for the cold start condition, however this is pretty rare anymore. If you need help with the glowplugs let me know.The stiction problem is going to require dealer tools unless you have a high dollar tool like a genisys which can do a scuff test and the knowladge of how to take the info to figure that the injectors are sticking. If you have a scan tool you can also look at all the temp sensors at start up to see if they are all normal.

Apr 09, 2009 | 2008 Ford F 450 Super Duty

1 Answer

Starting trouble

Suspect the glow plugs or timer not working proper. You could plug your truck in keep the engine warm so it starts easier. Or you could have the glow plugs tested and replaced if faulty. Your engine has 8 glowplugs and even a couple faulty glowplugs will cause problems starting. You could have injector or injection pump problems as well but harder to diagnos yourself.

Feb 26, 2009 | 1995 Chevrolet K2500

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