Question about 1988 Ford F 350

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Glow-plug relay

Why would the wire attahed to the big terminal on the control board get hot and smoke when ignition is first turned on and after cranking engine,but then cool

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To much power trace it back and make shure it is right size and not geting 24 volts it only needs 12 to convert to 9

Posted on Feb 03, 2009


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1983 Chevy Silverado, Glow plug light will not come on, Truck will turn over but not start, fuse panel has no blown fuses, I suspect the Glow Plug Relat but I don't know how to verify it is bad.

With most relays, you have 4 wires. One is power to the component the relay controls, one is a ground to the relay magnet, one is power to the magnet, and the fourth goes to the component, in this case the glow plugs. The ground usually comes from the computer.
With the key on you should have power to two terminals and you would jumper the hot terminal to the glow plug terminal. Or use a test light or meter to check for power on the glow plug circuit.

Sep 19, 2012 | 1983 Chevrolet Silverado

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1988 Ford Econoline E350, 7.3 L Diesel does start only by using the starter fluid. but ones it is warm, it will start by itself. however it smokes a lot.

Sounds like a glowplug problem to me. The most common problem I've had is the relay on the glow plug controller failing. I have had several where one lug actually burned through the plastic case on the relay. The controller is located on top of the engine. The relay I'm referring to looks like a typical ford starter selenod. Does the wait to start light come on when you first turn the ign on? If not you definitley have a controller issue. If it does come on, you may still have a controller issue but it is probably just the relay itself, not the whole controller.

You can test the relay with a test light. With the key off you should have +12v on only one of the big lugs. When the wait to start light is on after you first turn on the key you should have +12V on both of the bug lugs. You should also hear the relay click when you turn on the key. If you don't get +12V on both big lugs you should change the relay. I have found them quite a bit cheaper($30-40) at International truck dealers than anywhere else, and I have not had good luck with anything other than Ford or International name relays(the 7.3 is actually an International engine). You may need to take the old relay with you to get the correct one. If you change the relay but still don't get +12V on both lugs you will probably need to change the whole controller(you can return the relay if you need the whole controller because it will come with a relay already installed).

If you get +12v at both big lugs on the relay and the wait to start light comes on like it should but the engine still doesn't start like it should you mave have some glow plugs burned out. If you look on the intake side of the heads you should see the glow plugs, there will be 4 wired together on each side of the engine. If you can't find them you can trace the wiring harness back from the controller. They should be lined up 4 in a row. To test the glow plugs disconnect the wire from the plug, check continuity with an ohmmeter from the terminal to ground(any where on the steel part of the engine). If the meter gives you an ohm reading the plug is fine. If the meter reads open the plug is bad. I would also buy the glowplugs at either international or ford, and take an old one with you to make sure you get the right one as they made several different plugs for the same engine. (I bought some parts store brand plugs once and they didn't last two days!) Plugs run around $20-25 each, so if you find only one or two bad I would change only the one or two.

One note - take it easy on the ether! If any of the glow plugs are working the ether can cause a hot spot in the cylinder which can burn a hole in a piston! I've seen the results of this and it ain't pretty.
Since you haven't had this happen yet I'm guessing the relay or controller are probably the problem, but you may change one of them and find a couple of bad glow plugs as well. The last time I changed anything on my rig I had to change the controller and all eight plugs(the parts guy said the failed plugs probably caused the controller to fail). It is worth the time to troubleshoot if you can save on a few plugs.

Feb 16, 2011 | Ford Econoline Cars & Trucks

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7.3 Liter Diesel starts hard in morning, ok if not left more than 8 hours. How to check the Glow Plugs?

Your glow plug relay is located on the top of the engine on the right side toward the front. Some models there are 2 solenoids. A large one toward the front and a smaller one right behind it. The glow plug relay is the smaller one toward the rear. The larger front one is the intkae heater relay. To test the glow plug relay turn engine to on. dont start it. both of the large terminals should have power with key on. then turn engine off. only one large terminal should have power. If when you turn engine to on you only have power on one side then go to this test. Turn engine on and test smaller wire. it should have power. If it does replace the relay. If the smaller wire does not have power you have an ignition problem or power (wiring) problem to the relay. Also note the engine needs to be cold. If temp of engine is over 130 the computer will not turn the glow plug circut on! Most of th time this is what fails and not your glow plugs.

Oct 27, 2010 | 1996 Ford F350 Crew Cab

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Where is the glow plug controller located on 7.3 f250

Your glow plug relay is located on the top of the engine on the right side toward the front. Some models there are 2 solenoids. A large one toward the front and a smaller one right behind it. The glow plug relay is the smaller one toward the rear. The larger front one is the intkae heater relay. To test the glow plug relay turn engine to on. dont start it. both of the large terminals should have power with key on. then turn engine off. only one large terminal should have power. If when you turn engione to on you only have power on one side then go to this test. Turn engine on and test smaller wire. it should have power. If it does replace the relay. If the smaller wire does not have power you have an ignition problem or power (wiring) problem to the relay.

May 01, 2010 | 2002 Ford F250 Super Duty SuperCab

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Glow plugs stopped working on a pajero 2.8td 1994 model, plugs and buzz bar are ok.

My glow rail would come on for a very short time, then turn off (less than 1 second).
Replaced the control wire for the glow relay, with a test lead from battery to relay control terminal - relay was working fine (relay is between batteries).

Checked the engine temperature sensor (located on top of the housing where the top radiator hose attaches to the engine).
Take out and test in a pot of water (need a 19mm deep socket to remove).
At 0 deg C should be 8.6K ohms
At 20 deg C should be 3.25K ohms
At 40 deg C should be 1.5 K ohms
At 80 deg C should be 300 ohms
I replaced the temperature sensor with a 8.2K ohm resistor (engine cold).
Then tried with a 1.2K ohm resistor (engine hot).
Each time I tested the glow rail at the relay (with a multimeter) it would turn off after about 12-14 seconds, which is normal, to protect the glow plugs and battery drain (they come on again when engine is starting).

When I put the temperature sensor back in, the glow rail was working fine again - only thing I can think of is that the contact between the sensor and the plug, may have had a oxide formed and caused a high resistance or open circuit, indicating to the glow controller that the engine was hot and did not need glow activation.
So try taking the plug off the temperature sensor, and reattaching it again it might be all it needs, to clean its contacts.

Feb 01, 2010 | 1994 Mitsubishi Montero

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The glow plug relay is responsible for the duration of glow plugs, this needs to be the starting point. You should get a 12v out for so many seconds when ignition is switched on.
I have taken the cover off relays in the past, cleaned up the internals, sprayed with circuit cleaner and got plenty more years out of them, worth a try.

Nov 21, 2009 | 1997 Volkswagen Jetta

1 Answer

Kia rio 1500 diesel 2006

This would appear to be the start of GLOW PLUG failure. Raise the hood and Swich On the Ignition.
With a volt meter,... test the supply voltage on the Glow Plug supply terminal connection. If this is GOOD, Switch Off the ignition and remove the Key.
Remove the Glow Plugs with a Long shank socket.
Make up a length of 14/16 gauge wire, stripped about 1 inch from each end. Attach 1 end to the Battery Pos.+ Terminal,and holding the other end, take each Glow Plug in turn,and hold the PLUG BODY onto the Neg.- Terminal, and TOUCH and HOLD the wire to the Plug TERMINAL CONTACT. If the Plug is GOOD it will SMOKE and GET HOT. If more than 2 Plugs do not react then JUNK them ALL, and replace them. If only 1, then just replace it solely. Make sure on re-installation, that the PLUG, is FIRM and SNUG in the receiver. Disconnect your Supply from the Battery, and attempt Start Up procedure.
Let me know how you get along.

Aug 26, 2009 | 2006 Kia Rio

1 Answer

Car doesn't start when the glow plugs don't work

In most cases it is not the relay, although the Glow plugs operate on a reduced voltage, that is where to start checking.
Glow plugs are installed just like Spark Plugs in a Gasoline Engine, use a Long Shank removal socket to extract them, ease them out and make sure they are a snug tight fit on installation
Remove ALL Glow plugs. Set up a 12 or 14 guage wire bared at both ends, that will be long enough to connect to the Positive terminal of the battery, to the opposite Negative.
With the Positive end of the wire connected, take a Golw plug and Press it against the Negative Terminal of the Battery, and at the same time touch the Pos. Wire on to the Center Power terminal of the Glow Plug. If the Plug is GOOD it will start to SMOKE in 3-4 seconds and get HOT. Repeat the procedure with the other 3. If the failure rate is more than 2 out of 4 discard all plugs and install new. If less, replace only the junk ones. If all plugs are Good replace the Power Timer relay on the Vehicle. It is cost effective to check the Plugs first. But at the same time with a Volt Meter check the Power reading at the Glow plug Connection terminal.

Best of luck in your endevours.

Aug 24, 2009 | Volkswagen Jetta Cars & Trucks

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Glow plugs causing starting problem

if you need connectors and terminals for the glow plug connections under the valve cover, Ford sells then so you don't need a whole $600 harness.

info for your use

Section 03-07B: Glow Plug System 1996 F-250, F-350, F-Super Duty Equipped with 7.3L Diesel Engines Workshop Manual
DESCRIPTION AND OPERATION Glow Plug System The 7.3L diesel engine uses a glow plug system which preheats air in the combustion chamber to improve cold engine starting. The system consists of eight glow plugs, the glow plug control module (12B533), powertrain control module (PCM) (12A650), engine oil temperature (EOT) sensor and barometric pressure sensor (BARO sensor) (12A644). The glow plug system is electronically controlled by the powertrain control module. The powertrain control module energizes the glow plugs immediately after the key is placed in the ON position and then determines how long the glow plugs will be on according to the engine oil temperature and the barometric pressure. The required time for the glow plugs to be energized decreases as the engine oil temperature and barometric pressure increase. The glow plugs are self-regulating, and the powertrain control module controls relay ON time. The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.

Possible Causes: Insufficient glow plug ON time will not allow enough heat to accumulate in the combustion chamber to easily facilitate starting. If the glow plug system ON time does not meet any of the specifications in the accompanying chart the problem is most likely a faulty wire harness connection, ground connections or glow plug relay.

If the glow plug resistance to ground is high, the most likely causes are an open UVC (under valve cover) harness or open glow plug.
Relay Operation
Install a DVOM on the glow plug feed side of the glow plug relay (large stud with two wires connected). Turn the ignition key to the ON position but do not attempt to start. Note the time in seconds from when the key is turned on and the glow plug relay energizes until the glow plug relay de-energizes. The glow plug relay makes a loud click noise which is easily heard when it energizes and de-energizes. The dome light will dim and the dash voltmeter will dip when the glow plugs are drawing current from the battery. Compare the times measured to the table (time will be affected by engine temperature, battery condition and vehicle altitude). The voltage at the glow plug feed terminal may vary from 9 to 12 volts depending upon battery condition.

If battery voltage not present check for B+ at power supply terminal (terminal with single large wire). Power for glow plug power supply is supplied from starter relay through two fusible links at solenoid.
Glow Plug Operation
Disconnect all of the glow plug/injector harness connectors from the valve cover gaskets. With the pigtail installed, measure glow plug resistance to ground (preferably B-). A resistance measurement of .1 to 6 ohms indicates a good glow plug.

Glow Plug Harness Continuity
Measure for continuity from the connector harness to the glow plug feed terminal on the glow plug relay. Resistance should be less than 5 ohms.
Incorrect measurements will result if all glow plug/injector connectors to valve cover are not disconnected.

Glow Plug Relay The glow plug relay (12A343) has a plastic base and two mounting bolts. It is operated by the powertrain control module (PCM) (12A650) which senses engine oil temperature, PCM voltage and barometric pressure. When the engine oil temperature or the barometric pressure is low, the PCM activates the glow plug relay and the glow plugs. If the PCM voltage is too high, the powertrain control module deactivates the glow plug relay and the glow plugs immediately energize for a shorter duration, decreasing the modulation of the duty cycle.
Glow Plug Removal
    Remove valve cover (6582). Refer to Section 03-01D .
  1. Disconnect glow plug electrical connector using a pair of pliers.
  1. Remove glow plug using 10mm socket.
  1. Clean and inspect glow plug tip for damage. Replace if damaged.
  1. Install glow plug and tighten to 19 Nm (14 lb-ft).
  1. Connect glow plug electrical connector. Make sure glow plug wiring is routed to avoid moving parts.
Glow Plug Control Glow plugs are used to warm the cylinders to improve cold-engine starting. The PCM uses the engine oil temperature (EOT) sensor and barometric pressure (BARO) sensor to determine how long the glow plugs will be on. The PCM energizes the glow plugs longer if the engine is very cold or if the barometric pressure is low at high altitudes.
The PCM controls the relay that supplies power to the glow plugs with the glow plug control (GPC) signal. When the GPC signal is grounded by the PCM the relay closes, turning the glow plugs on.
The glow plugs are controlled by the following sequence:
  1. PCM energizes the glow plugs.
  1. The PCM energizes the glow plugs immediately after the ignition is placed in the ON position.
  1. The PCM then determines how long glow plugs will be on based on EOT sensor and the BARO sensor. The required time to warm up the cylinder decreases the engine oil temperature and barometric pressure increases at low altitudes.
Glow Plug Lamp Control The glow plug lamp (GPL) signal controls the WAIT TO START light located on the instrument panel. This light is used to indicate when to start the engine. The cylinders are being warmed by the glow plugs during and after this light is lit. The PCM energizes the glow plug lamp longer if the engine is very cold or if the barometric pressure is low.
When the GPL signal is brought low, the "Wait to Start" lamp is turned on.
The glow plug lamp is controlled by the following sequence:
  1. PCM lights the WAIT TO START light after a key on reset occurs.
The PCM determines the glow plug lamp activation time based on engine oil temperature, barometric pressure and battery voltage.
  1. PCM turns off the WAIT TO START light.
The glow plug lamp is turned off when the timer counts to the number of seconds specified by the PCM. The glow plugs will normally remain on longer than the "Wait to Start" lamp.

Mar 14, 2009 | 2004 Ford F350

1 Answer

I just replaced the glow plug relay dur to hard starting


Jan 17, 2009 | 1992 Ford F250

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